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  • Chemical Engineering  (954)
  • 1985-1989
  • 1980-1984  (524)
  • 1975-1979  (430)
  • 1925-1929
  • 1982  (524)
  • 1979  (430)
Collection
Keywords
Publisher
Years
  • 1985-1989
  • 1980-1984  (524)
  • 1975-1979  (430)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Fiber-foam: A rheological phenomenon and a novel product (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 12-17 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: When certain molten thermoplastics containing glass fibers up to 20 mm in length are extruded through an orifice, the extrudate has a frothy texture and solidifies into an irregular open-cell structure. The effect is apparently caused by the recovery of the fibers from distortions arising in the region of converging flow near the entry to the orifice. The effect is particularly pronounced in systems with melt viscosities between 50 and 500 Ns/m2. Polypropylene, as an example, containing weight fractions of about 0.25 of glass fibers can be extruded through a zero-length die 2 mm in diameter to give “ropes” that can be readily formed into flat sheets or three-dimensional shapes because of adhesion between the still molten polymer in the newly extruded rope. Such sheets can then be bonded to other materials to make a variety of laminates. A range of bonding techniques is available and the rough surface texture of the ropes provides a useful mechanical key for bonding with grossly dissimilar materials. Fiber-foam is highly resistant to fracture and has a modulus in the range expected by a simple model for the foam.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190103
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  • 2
    Electronic Resource
    Electronic Resource
    Aspects of the yield behavior in poly(ethylene terephthalate) fibers (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 18-23 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The yield behavior during cold drawing of commercially spun poly(ethylene terephthalate) (PET) filament yarn was investigated. Microscopic examination revealed the presence of inherent flaws within the spun filaments; these act as points for localized stress concentration. These inhomogeneities appear to be either internal cracks or crazes developed during the fiber melt spinning process. During elongation, stress magnification at these flaws results in shear band formation, indicating the onset of inhomogeneous yielding. At the yield bend in the load-elongation curve a circumferential crack propagates within these shear band regions. This yield crack develops into the classical neck geometry which further localizes additional plastic deformation within the sample at the neck.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190104
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  • 3
    Electronic Resource
    Electronic Resource
    Application of small system thermodynamics to polymer molecules. I. The entropy barrier between liquid and crystalline state (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 40-44 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The methods of small systems thermodynamics have been applied to the calculation of the entropy barrier to the growth of polymer crystals. The height of this barrier at the equilibrium melting point of polyethylene molecules of typical lengths (X = 4,000 to 10,000 segments) is estimated to be of the order of 4 to 5 Kcal per molecule. This barrier increases linearly with ln X if the crystal is very large but retains the approximate values mentioned for crystals with the lamella thicknesses usually found. This entropy change causes the free energy to go through a maximum as in a nucleation phenomena but no new surface formation is involved. The existence of such a barrier explains why crystallization (or melting) never occurs at the equilibrium melting temperature.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190107
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  • 4
    Electronic Resource
    Electronic Resource
    Application of small system thermodynamics to polymer molecules. II. Secondary nucleation (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 45-50 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Statistical mechanical methods can be used to relate not only structure and thermodynamics but also structure and kinetics. Methods are developed for calculating the crystal growth rate kinetic models. When the usual macroscopic thermodynamics are applied, the resulting surface energies, σ and σe extracted from the experimental growth rates are quite comparable to those obtained from kinetic models. However, when one applies small system thermodynamics, a substantially smaller σ is obtained. This latter assumption has the advantage of explaining why extended chain seed crystals do not promote crystal growth and why folded chain crystals grow on such seeds. The statistical mechanical methods in both of these cases predict the observed decrease in the rate constant, Kg with decreasing molecular length without the necessity of a separate theory for varying σe with molecular length.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190108
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  • 5
    Electronic Resource
    Electronic Resource
    Introductory remarks (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 65-65 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190202
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  • 6
    Electronic Resource
    Electronic Resource
    An anomaly in the necking behavior of polyethylene (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 77-81 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Tensile creep measurements at constant load on nonoriented polyethylene have shown a marked transition at a certain stress level from a neck formation followed by instantaneous fracture to the formation of a neck which resists fracture for a considerable time. The transition, which shifts towards shorter time and higher nominal stress with increasing molecular weight, has been studied for 16 polyethylenes of different molecular weights, degrees of branching and crystalline structures. The marked. transition has only been observed for high density polyethylene of high molecular weight. Deformation measurements show a more distinct necking for the high density than for the medium density polyethylenes. This is consistent with current molecular deformation theories. A hypothesis for the transition is proposed based on the distinctness of the neck process in the high density polyethylene and the large difference in strength between the spherulitic structure and the fibrillar structure. The dependence of the transition on molecular weight is expected since the number of tic chains incrcrtses with increasing molecular weight.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190204
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  • 7
    Electronic Resource
    Electronic Resource
    Influence of crosslinking on the tensile strength and fractography of poly(methyl methacrylate) (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 95-98 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Glassy crosslinked networks were prepared by copolymerization of methyl methacrylate with up to 4.7 mole-percent ethylene dimethacrylate. These networks were degraded by exposure to γ-rays and the solubilized fraction estimated by benzene extraction using the analysis of A. R. Schultz. The efficiency of the Crosslinking agent was found to be 0.5 and this value was used to calculate the molecular weight between crosslinks. The molecular weight of the primary molecules in the network, M, was estimatfrom the radiation dose using the known fact that one fracture requires an energy deposition of 59 ev. Crosslinking was found to have little influence on the tensile strength of networks of primary molecular weight 〉 105. In contrast. crosslinking raised, the strength of polymers of M 〈 105 to, a value approaching that of a high molecular weight linear polymer (ca. 70MN/m2). Crosslinking was found to have only a small influence on the gross morphology of fracture surfaces.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190207
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  • 8
    Electronic Resource
    Electronic Resource
    Masthead (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190301
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  • 9
    Electronic Resource
    Electronic Resource
    A method for the determination of the internal particle structure of poly(vinyl chloride) suspension resins by analyses of vinyl chloride desorption rate data (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 181-189 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method has been developed for analyzing the vinyl chloride desorption rate data from poly(vinyl chloride) resins. This technique, based on Fickean diffusion kinetics already demonstrated for this system, yields fundamental internal particle morphology information, which is in agreement with that determined by other methods. The approach detailed in this manuscript can be applied to other particle-penetrant systems for which the nature of the diffusion kinetics is known.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190304
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of mandrel rotation on power consumption in polypropylene extrusion (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 198-202 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Improved properties of thermoplastic pipes may be achieved by rotating the core of the extrusion die, to produce orientation in the tangential direction. It has been suggested that a further advantage of mandrel rotation is an increased output rate for a given power input. The flow of a “power law” fluid through a rotating die is analyzed, and the power consumption and throughput are investigated. Experimental results for polypropylene melt are presented, which illustrate the effect of rotation on the die characteristics. It is found that the output is increased, but the savings are minimal in view of the power which must be introduced via the rotating mandrel.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190306
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  • 11
    Electronic Resource
    Electronic Resource
    The effects of eccentricities on the fracture of off-axis fiber composites (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 337-341 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Finite element analyses were performed to investigate theoretically the effects of in-plane and out-of-plane eccentricities, bending or twisting, and thickness nonuniformity on the axial stress and strain variations across the width of off-axis specimens. The results are compared with measured data and are also used to assess the effects of these eccentricities on the fracture stress of off-axis fiber composites. Guidelines for detecting and minimizing the presence of eccentricities are described.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190503
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  • 12
    Electronic Resource
    Electronic Resource
    Some corrosion mechanisms in attack of resin and resin-glass laminates (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 329-336 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In contrast to metallic corrosion where electrochemical corrosion mechanisms are dominant, a variety of mechanisms play a role in degradation of fiber reinforced plastic (FRP) structures. Attack may occur by physical or chemical means or by a combination of both. Although some actions of particular attacking species may be quite specific, there are a number of general corrosion mechanisms and broad guidelines that can be established in order to choose a resin suitable for a particular service. Corrosion mechanisms are illustrated by interactions of environments with vinyl ester resins. Attack in non-aqueous media is often related to chemical similarity between attacking specie and the resin. Among chemically similar resins, the extent of this type of attack is often influenced by the crosslink density of the resin. It is shown that the solubility parameter of the attacking specie is useful in predicting suitability of a resin for service, if the resin has been evaluated by a test sequence in organic media of varying solubility parameters. In aqueous media it is found that physical attack can occur by means of an osmotic permeation of the resin by water. Degradation by pure water is often more severe than that caused by ionic solutions. Such physical attack can cause delamination and blistering of laminates and must be regarded as a potentially serious corrosive mechanism, although not primarily chemical in nature. In addition to physical attack, chemical attack can occur. Saponification by sodium hydroxide and oxidation by sodium hypochlorite are discussed in some detail as examples. It is shown that in both these cases the chemical corrosive process may be inhibited by controlling the physical corrosion process due to water.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190502
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  • 13
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    A study of chain-addition polymerizations with temperature variations. IV. Copolymerizations - Experiments with styrene-acrylonitrile (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 190-197 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Free-radical copolymerizations were studied under nonisothermal conditions with emphasis on their thermal runaway and ignition behavior. Computational models are presented in generalized form and compared with experiments on the system styrene-acrylonitrile. A new, useful method is proposed for the evaluation of runaway parameters from scant kinetic data.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190305
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  • 14
    Electronic Resource
    Electronic Resource
    Finite element analysis of polymer melt flow in cable-covering crossheads (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 203-209 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A finite element method is presented for the analysis of isothermal non-Newtonian polymer melt flow in narrow channels of complex shape. The particular application considered is flow in cable-covering crossheads. The geometric flexibility of the finite element method allows a mesh of triangular elements to be constructed to suit the shape of the flow channel. Computed results obtainable from the analysis include the distribution of polymer layer thickness on the finished cable, together with the extrusion pressure required to maintain a given flow rate of melt. Some typical thickness distribution results are presented as an introduction to experimental verification of the method and its application to crosshead design.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190307
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  • 15
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    Processability of raw elastomers and its relation to deformational and failure behaviorPresented at the US-Japan Joint Semina on Elastorners at the Institute of Polymer Science, The University of Akron, Akron, Ohio (October 17-21, 1977). (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 215-222 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method was proposed for a scientific description of processability of raw elastomers involving a master curve representing deformation behavior and a failure envelope representing the ultimate properties. When a specific machine is given, the mechanical and environmental conditions may be defined from the geometry and operating condition of the machine. Matching these conditions, specific information on processability may be extracted from the master curve and failure envelope. In constructing the master curve, we have proposed to use the strain-time correspondence principle including the behavior at both small and large deformation. The necessary measurements may be considerably simplified; for example, the Rheovibron and the Mooney rheometer provide necessary data over the entire range of the rubbery behavior. The latter instrument may be operated at a slow speed, i.e., 0.05 RPM and the torque-rise curve is used. With the rotational viscometer, the stress often reaches a maximum before reaching steady state, particularly with rubbers. We have shown that the curve leading to the peak is the shear stress-strain curve. The maximum was found to correspond to the failure point in the tensile deformation. The stress-time correspondence principle is not applicable to some rubbers. In these cases, the same calculation may still be conducted to evaluate the deviation from the master curve. Then, the extent of deviation may be used to represent the degree of long chain branching.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190309
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  • 16
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    Stress-strain isotherms for polymer networks at very high elongations (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 254-259 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Some polymer networks show an anomalous increase in the modulus or reduced stress at very high elongations. This behavior has now been investigated definitively by determining stress-strain isotherms for both crystallizable and noncrystallizable networks, prepared using several curing techniques (carried out so as to yield a wide range in degree of cross-linking). The networks were studied unfilled at a number of temperatures, and at several degrees of swelling. The results clearly implicate strain-induced crystallization as the origin of the upturn in the modulus, and thus demonstrate that the wide spread interpretation of this upturn in terms of limited chain extensibility is incorrect.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190405
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  • 17
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    The classification of solvents for bis-phenol-a polycarbonate (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 625-637 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A procedure is described which permits the classification of solvents according to their effect on polycarbonate (PC):Class I - dissolve amorphous or crystalline PCClass II - dissolve only amorphous PCClass III - convert amorphous PC to crystalline PCClass IV - none of the above.This classification is achieved by comparing solvents to CH2Cl2 with respect to the exotherm and rate of crystallization observed when the solvents are brought into contact with PC under controlled conditions.
    Additional Material: 20 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190906
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  • 18
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    Introductory remarks (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 661-661 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760191002
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  • 19
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    The torsion pendulum in the investigation of polymer (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 664-675 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The early history of the use of the torsion pendulum in the investigation of polymers is described together with the development of dynamic mechanical testing at TNO. Examples are listed of studies of structure-property relationships by means of the torsion pendulum. Techniques using supported. Samples are compared with those using unsupported samples, particular attention being paid to the advantages and restrictions of torsional braid analysis (TBA). The comprehensive application of TBA by Professor Gillham is reviewed; a few TBA results are compared with our torsion pendulum measurements. A rheologist's view on the so-called liquid-liquid transition (Tn) in polymer melts, as observed by TBA, is presented.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191004
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  • 20
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    Factors affecting the formation of hard elastic fibersWork done at Celanessse Ressearch Company, Summit, New Jerssey 07901. (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 427-432 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Factors affecting the formation of hard elastic polypropylene and nylon 6,6 are described. In the case of polypropylene, it is shown that the morphology of the stress spin-oriented fibers depends on the molecular weight, the molecular weight distribution, and the cooling rate. Narrow molecular weight distribution and/or fast cooling rate can lead to a smectic, essentially fibrillar morphology in contrast to the normally observed crystalline, essentially lamellar structure. Hard elastic nylon 6,6 fibers are produced by drawing regularly spun nylon 6,6 yarn to draw ratios in the range of 1.6-3 and annealing the resulting fibers in phenol solutions (cone. 1-5 percent). By this method, a highly increased crystalline order is created, simultaneously transforming the original morphology to a lamellare one or superimposing a lamellar morphology on the poorly organized fibrillar base. Some tensile and elastic characteristics of polypropylene and nylon 6,6 yarns as. functions of spinning and annealing variables are presented.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190611
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  • 21
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    Monodisperse polyethylenes: Crystallization kinetics (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 436-440 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Crystallization kinetics of hydrogenated monodisperse polybutadienes have been measured using hot-stage microscopy, and the data have been analyzed in terms of crystallization half-time and Avrami exponent. Results obtained from hydrogenated polybutadienes having M̄w's in the range 5,100 to 340,000 were compared with what was obtained from several commercial polyethylenes. A four-branch star hydrogenated polybutadiene was also included in this study. Crystallization half-time at constant undercooling was found to go through a minimum when expressed as a function of M̄w; such behavior is consistent with polyethylene data already reported in the literature. It was found that crystallization half-times for all polyethylene homopolymers studied (hydrogenated polybutadienes as well as commercial polyethylenes with their broad molecular weight distributions) exhibit similar exponential dependences on undercooling.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190613
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  • 22
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    Scaleup factors of tubular emulsion polymerization reactorsPresented at the 70th Annual Meeting of AIChE, New York, N. Y. (november 13-17, 1997). (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 482-487 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper examines the important dimensionless numbers that control emulsion polymerization in a tubular reactor. It was found that the activation energy of polymerization was of major importance, while the role of monomer diffusion was not very significant. By selecting certain combinations of the dimensionless numbers, changes occurring during scaleup from a small tubular diameter to a larger diameter can be approximated.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190704
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    Young's modulus of uniform density thermoplastic foam (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 493-499 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A comparison of experimental data for zero strain Young's modulus of uniform density thermoplastic foam for short times has been made with several theoretical and empirical correlations. An analysis of the variance of the data with the predicted values from the many models indicated that the simplistic density squared relationship adequately described the modulus of the foam for basic engineering calculations.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190706
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    Fatigue crack propagation in, graphite fiber reinforced nylon 66 (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 512-518 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The rate of fatigue crack propagation in graphite fiber reinforced nylon 66 was measured. A model of the form å = β [Kmax1-γ ΔKγ]r was used to correlate the rate of crack propagation å with the maximum stress intensity Kmax and the amplitude of the stress intensity ΔK experienced by the notched specimen during the fatigue test. The quantities β, γ and r were constant at fixed temperature and frequency of the test. It was also found that there exists both an upper and a lower threshold of stress intensity for the slow ropagation of damage during fatigue. The mechanism of crack propagation in the short graphite fiber reinforced nylon was found to be similar to the growth and fracture of crazes in thermoplastics. The propagation of damage at the crack tip is controlled by matrix deformation, cavitation, fiber breakage and fiber pullout. Damage can propagate in the absence of crack growth until a critical point is reached at which time the material fractures catastrophically.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190709
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    Compatible glassy polyblends based upon poly(2,6-dimethyl-1,4-phenylene oxide): Tensile modulus studies (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 519-524 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical behavior of compatible glassy polyblends based upon poly(2.6-dimethyl- 1,4-phe nylene oxide) (PPO) was investigated. In particular, the influence of composition, molecular weight, and molecular weight distribution upon the tensile modulus of the blend was assessed. Various possible correlations between the experimentally determined moduli and theory are considered. Included are correlations with density, packing density, composite theory, and lattice fluid theory. The modeling of the properties of mixtures via Simplex lattice design is also presented. Finally, attention is given to the development of compatibility criteria based upon tensile modulus and density measurements.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190710
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    Time constants for moisture diffusion through a permeable barrier into an airspace (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 525-529 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper arose from a study of the use of polymeric materials to protect humidity-sensitive items from damp ambient conditions. A one-dimensional model for the Fickian diffusion of moisture through a permeable wall into a volume of air is considered. The humidity in the airspace asymptotically approaches equilibrium with the exterior, and the time constant is defined as the time to reach 1-1/e of its ultimate value. Exact and approximate solutions are considered. Depending on the system geometry and properties, the time constant is either permeability-controlled or diffusivity-controlled, or somewhere in between. Under certain conditions, there exists an optimum combination of airspace depth and wall thickness that maximizes the time constant.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190711
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    Physiochemical quality assurance methods for composite matrix resins (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 545-551 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fiber reinforced composite structures have gained a significant position as materials of construction for the aerospace industry. It thus follows that large expenditures of funds and human lives are dependent on the reliability of these products. An important step in gaining confidence in a part is knowing that the starting prepreg has the same chemical formulation in each lot of material and that each lot has been processed in the same manner. This can be accomplished by physiochemical characterization. The techniques described herein were developed for 177°C (350°F) epoxy matrix systems. However, the methods form a basis for developing similar procedures for other types of matrices.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190804
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    Orientation in injection molded polystyrene (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 558-563 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The ultimate properties of injection-molded thermoplastics articles are controlled to a large extent by flow and heat transfer phenomena that take place during the injection-molding process. In fact, the thermo-mechanical history of the melt during the molding process leads to a non-uniform distribution of many of the critical properties of the molding. Birefringence has been employed as an indirect measure of the distribution of frozen stresses or strains in amorphous polymers. The present study employs birefringence to study the development of frozen stresses in injection-molded polystyrene. In general, orientation in the flow direction is much greater than the orientation in the transverse direction of the moldings. In the vicinity, of the gate, where mold filling is characterized by spreading radial flow of the melt, the hoop stresses (planar deformation) at the melt front give rise to high orientation in the transverse direction. It appears that relaxation phenomena are not very important during the filling stage; however, they become more, important in the packing and pressure holding stages. With the aid of the appropriate rheo-optical relationship, it is shown that the distribution of frozen-in orientation in injection-molded polystyrene may be estimated on the basis of data relating to pressure variations during the filling stage.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190806
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    Glass transitions of organic compounds. III. Cellulose substrate technique and aliphatic alcohols (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 716-721 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The cellulose blotter/torsion pendulum technique used for the determination of relaxations that occur in low molecular weight compounds, oligomeric materials, and amorphous polymers is discussed. The glass transition temperature of a number of aliphatic alcohols and hydrocarbons have been determined and correlated with a method proposed by Gorskii in 1934. The glass transition temperature and molecular weight of these compounds follow the relationship Tg = BMa rather than Tg = Tg(∞) - K/M. Although differences exist between the primary, secondary, and tertiary alcohols, they appear to follow a similar general pattern. In contrast, the hydrocarbons investigated have markedly different behavior.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191011
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    The influence of drawing, twisting, heat setting and untwisting on the structure and mechanical properties of melt spun polypropylene filament (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 761-773 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The changes in structure and mechanical properties of melt spun polypropylene filaments were determined as the filaments were successively (i) drawn, (ii) twisted, (iii) annealed, and (iv) untwisted. Filaments spun to two different melt draw down levels were studied. The effects of draw temperature and draw ratio, extent of twist, annealing temperature, and the extent of untwisting were examined. Melt spun and twisted filaments (draw ratio of 1) were also considered. Structural characterization techniques used in this study include wide angle (WAXS) and small angle (SAXS) diffraction, scanning electron microscopy (SEM), birefringence and density measurement. Drawing increased crystalline orientation and at low temperatures disrupted the monoclinic unit. cell existing in the melt spun fibers. The drawing produced considerable fibrillation under all conditions even when carried out at 120°C. The fibrillation quid void formation due to low temperature drawing was more pronounced. The variation of WAXS patterns and mechanical properties of twisted drawn filaments was interpreted by presuming that the fibrils act in a manner analogous to that of the filaments in a continuous filament twisted yarn. In the case of incompletely drawn filaments the effect of additional drawing occurring during twistin must be considered. Twisted fibers annealed at 150°C sowed a drastic reduction in tensile properties, while those annealed at 125°C did not set the twist and caused the fibers to tend to untwist. Annealing at 140°C appeared to give satisfactory heat setting. Annealing of cold drawn and cold drawn and twisted fibers increased the density, removed many defects and reformed a well defined monoclinic crystal structure and a lamellar morphology. Untwisting of heat set filaments tended to give back the properties of hot drawn fibers. In some cases, however, the opening of cracks was noted.
    Additional Material: 30 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191102
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    A new technique for determining the oxidative stability of molten polymers (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 805-809 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A new method and apparatus for determining the oxidative stability of molten polymers, especially polyolefins, is described. The apparatus consists of a laboratory scale mixer modified to allow for the continuous determination of the oxygen absorbed by the polymer. The oxygen uptake curve observed for polyolefins is of the type normally associated with the autocatalytic oxidation of hydrocarbons and yields an induction period - a traditional measure of stability. Typical results from experiments concerning the antioxidant type, antioxidant level and temperature on polyethylene stabilization are presented to illustrate the usefulness of the technique in both quality control and research applications.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191108
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    Viscosities and normal stress coefficients of high impact polystyrene-mineral oil mixtures (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 815-817 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Measured melt viscosities and primary normal stress coefficients are presented for a well-characterized, rubbermodified polystyrene as a function of shear rate and mineral oil diluent concentration. The logarithmic blending relationship accurately predicts the observed data. Melt relaxation times and shear compliance data are also calculated. The compliance numbers are consistent with molecular models based on a simple dumbbell (appropriately modified for rubber and mineral oil addition).
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191110
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    Chemiluminescence of incompatible polymer mixtures (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 841-844 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chemiluminescence of an incompatible mixture of polystyrene and cis-1, 4-polybutadiene was studied. The luminescence characteristics of the component polymers are preserved in the incompatible blend and the intensity for the blend can be represented as the surface-area-average of the individual intensities.
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    URL: http://dx.doi.org/10.1002/pen.760191205
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    Equation of state of cis-1,4-polybutadiene melt (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 845-848 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Recent equation of state data are analyzed in terms of the hole theory of polymer melts. The good agreement between experimental and theoretical volume-temperature curves at atmospheric pressure, observed previously for a number of amorphous and crystallizable polymers, is again confirmed. Similarly, satisfactory theoretical results for the isotherms ensue, with deviations however becoming noticeable at elevated pressures and low temperatures. The linearity of the isochores observed experimentally is confirmed by the theory, however with somewhat different slopes. Departures of maximally 10 percent from the thermal pressure coefficients derived from the experimental PVT data are noted. Significant differences between theory and experiment apper only in the third derivatives of the partition function, as has also been observed with other pollymers. The characteristic scaling parameters of volume, temperature and pressure show the expected similarity with hevea rubber. Earlier correlations for scaling entropy and segmental volume with scaling temperature are found to be valid within the scatter of these relations. Finally, the applicability of the empirical Tait equation in the form applied to the equation of state in other polymer melts is confirmed. Although the resulting thermal pressure coefficient exhibits an explicit even if smal dependence on temperature, in disagreement with experiment or theory, the Tait equation remains a useful relation for the representation of PVT information.
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    Cavity temperature - an important parameter in the injection molding process (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 893-899 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The paper stresses the importance of cavity temperature in the injection molding process of thermoplastics. From the study of the temperature field in the mold, it follows that there is no such thing as a uniform mold temperature. The heat balance equation for the injection mold is discussed in detail. It shows that the sum of the heat exchanges during the cycle equals zero. There is an extensive explanation of the heat transfer from the melt to the mold, the heat exchange with the environment, and between the heat exchange medium and the mold. New criteria are given for the cavity material selections. The cavity temperature is a complex function of static and dynamic parameters and should be kept constant in the equal parts of the cycle. This demands a new way of regulating the temperature.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191303
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    Heat transfer in blow molding operations (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 910-916 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A one-dimensional model of unsteady state heat conduction has been applied to the cooling and solidification of a polymer in a blow molding process. The approach includes a temperature-dependent specific heat term to account for latent heat effects during the phase change. The model is used to predict temperature profiles in a thick-walled component of high-density polyethylene. These profiles lead to a clearer understanding of the heat transfer process. It is further shown that these temperature distributions can be used to study the influence of the major process variables upon the cooling of the molded component.
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    URL: http://dx.doi.org/10.1002/pen.760191306
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    The effect of moisture on the mechanical behavior of a nylon-epoxy adhesive (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 940-945 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of a commercial nylon-epoxy resin have been studied using a sensitive creep apparatus which employs a frictionless levitation magnetic bearing. Isothermal creep measurements over a temperature range of 30-170°C and covering a time scale of five decades were made on the wet and dry state of the material. Following the usual time-temperature reduction scheme, master curves for each state were constructed from the experimental data. The effect of moisture was found to be more than that of a simple plasticizer. The steepness of the reduced curves in the transition region was determined and the distribution function of retardation times of the two states of the sample were calculated. The problem of predicting the physical state of the bulk adhesive at higher temperatures was found to be complicated, possibly due to the presence of nylon crystallites.
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    URL: http://dx.doi.org/10.1002/pen.760191310
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    Rheo-optical studies on the deformation mechanism of semicrystalline polymers. VIII. Dynamic x-ray diffraction of a high-density polyethylene film having row-structure of C-axis orientationPresented in part at the ACS San Francisco Meeting, August, 1976, and in part at the 26th IUPAC Congress, Tokyo, September, 1977. (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 929-939 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dynamic x-ray diffraction is employed to scrutinize the structural origin of the α mechanical dispersion of a highdensity polyethylene having preferentially oriented rownucleated cylindritic texture around the machine direction (MD). Results indicate that the α1 dispersion is associated with two kinds of orientation processes of crystallites: (1) the orientation process involving the rotation of crystallites around the crystal b-axis (lamellar axis) dominates in the MD specimen; (2) the other process accompanying the rotation of crystallites or lamellar segments around their crystal a-axis dominates in the TD (transverse direction) specimen. The complex apparent crystal lattice compliances show no frequency dependence in the real component and no appreciable value in the imaginary component, indicating that the α1 process is definitely associated with the intercrystalline process, but not relavent to the intracrystal process. However, at elevated temperatures, the complex lattice compliances exhibit a remarkable frequency dependence, suggesting that the α2 dispersion concomitant to intracrystalline nature takes place in this time scale. The α2 dispersion was found to be more pronounced upon stretching along the lamellar axis (TD) than normal to it (MD).
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    Determination of the structure of the noncrystalline regions in isotropic and oriented poly(ethylene terephthalate) (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 966-974 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of polymers are influenced strongly by the structure of the noncrystalline regions. The different methods for characterization of these regions are reported and the results obtained on polyethylene terephthalate, are discussed. The orientation function of the noncrystalline chains can be determined by measurements of the X-ray scattering and the birefringence. The fraction of taut noncrystalline chains is obtained from NMR measurements combined with a determination of the degree of crystallinity. For a further evaluation of the results it is also necessary to use calculations of the NMR- line-width and the birefringence of chains with fixeu ends. With help of such calculations the end-to-end distance of the taut and mobile non-crystalline chains can be determined, It is also possible to distinguish between tie molecules and loops. With increasing orientation, the amount of taut noncrystalline chains increases. The taut chains are tie molecule rather than taut loops. The end-to-end distances increase with increasing crystallization temperature.
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    URL: http://dx.doi.org/10.1002/pen.760191404
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    The role of inter- and intra-links in the transformation of folded chain lamellae into microfibrils (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 1017-1022 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this study we investigate the effect of crystallization rate on the extensibility (draw ratio) of spherulitic polyethylene film uniaxially deformed at room temperature. Draw ratios for deformed films increased with increasing crystallization temperature. Transmission electron microscopy of the microfibrillar structures revealed and interconnected network of fibrils. The degree of connectivity between microfibrils was found to decrease with increasing-crystallization temperature. A model of the deformation process is developed in which inter- and intra-link (extended chain fibers formed during crystallization) distribute the applied stress, initiate the micronecking process and influence the amount of chain unfolding during drawing.
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    A dielectric study of the crystal and amorphous fractions in oriented polyethylenes (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 1023-1028 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Polyethylenes have relaxation processes separately assignable to the crystal and amorphous components. The possibility thus presents itself for studying the interaction between the two phases by investigating the anisotropy of the separate relaxation processes induced by overall orientation of the material. Such a study was carried out here by the dielectric method on samples rendered dielectrically active by the introduction of a few carbonyl groups by oxidation. In addition to the usual advantage of ease of frequency variation, the dielectric method in this case has a very great advantage in interpretation resulting from the similarity of dielectric constants of the two phases. In specimens oriented by solid-state extrusion, it was found that the crystalline relaxation process (α) develops the expected anisotropy resulting from dipoles normal to C-axis alignment in the extrusion direction. In branched polyethylene (BPE) no accompanying anisotropy of the amorphous β and γ processes was observed. Since the extrusion was carried out well above the glass temperature of the amorphous component, this indicates that constraints from the crystal phase are not sufficient to prevent dissipation of amorphous orientation by segmental motion. However in linear polyethylene (LPE) (where there is no well-developed β process) some anisotropy of the γ process was observed. It is proposed that a higher degree of constraint of the amorphous component by the crystals in LPE results in suppression of the glass-rubber (β) relaxation and permits amorphous orientation to accompany crystal orientation.
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    Modeling of polymeric film-blowing processesPresented at the 52nf Annual Meeting, Society of Rheology, February 1981. (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 172-181 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Industrial film-blowing processes are characterized by large deformation rates, rapid changes of temperature and high stress levels. A pilot scale process was set up to simulate these variables. The pivotal element in modeling the process is a rheological constitutive equation which describes the fluid properties accurately over the entire range of conditions encountered; it was found that contributions to the stress in the material which arise out of the changing thermal history of a fluid element were a significant fraction of the total. When the deforming film is subjected to stretching but to little or no blowing, the axial stresses in the film are predicted excellently by the model under both isothermal and non-isothermal processing conditions. With rapid blowing and major deviations from uniaxial extension, the axial stresses are predicted less well, but still satisfactorily, under the conditions used. In no case are the circumferential stresses predicted accurately: i.e. unequal biaxial extensional deformations represent complications which have not been resolved.
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    URL: http://dx.doi.org/10.1002/pen.760220307
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    A dynamic mechanical study of the curing reaction of an unsaturated polyester (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 254-259 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing process of an unsaturated polyester was followed by employing the dynamic spring analysis (DSA) technique attached to the Rheovibron viscoelastometer. The storage and loss moduli and the gel times of the resin with various concentrations of initiator (methyl ethyl ketone peroxide) were determined at several temperatures. The activation energy for the curing process studied was about 40 kJ/mol. Temperature effects on films partially cured below the ultimate glassy transition temperature (Tg) were studied similarly using the tensile mode on the Rheovibron from room temperature to 120°C. Two modulus peaks were observed upon heating and these were independent of precure conditions. The lower temperature peak was the result of continued curing and the higher temperature peak was attributed to the glassy relaxation of the cured product. The DSA technique were found to be useful for characterization of the curing process and the results showed good qualitative agreement with those obtained by tensile measurements using cast films when the shapes of the curves were compared.
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    Property-morphology relationships of polymethylmethacrylate/polyvinylidenefluoride blends (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 234-240 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation was conducted to establish property-morphology relationships in polymethylmethacrylate/polyvinylidenefluoride (PMMA/PVDF) blends. All blends were compounded in a twin-screw extruder and then processed by injection molding Mechanical properties of blends of various compositions were studied by dynamic mechanical and impact strength measurements. The presence of crystalline regions in blends was determined by Differential Scanning Calorimetry (DSC). Morphology of fracture surfaces of blends was studied by Spinning Electron Microscopy (SEM). PMMA/PVDF blends were found to form compatible mixtures over a wide range of blend composition. Changes in dynamic mechanical properties upon annealing were found to be a direct function of blond morphology. Electron microscopic evidence showed no signs of phase separation. DSC measurements detected crystalline regions in all blends containing 40 percent or more (by weight) PVDF.
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    URL: http://dx.doi.org/10.1002/pen.760220404
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    The limiting pressure-velocity (PV) of plastics under unlubricated sliding (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 248-253 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The limiting pressure-velocity (PV) of plastics materials under normal contacting pressure P and sliding velocity V when the sliding goes on continuously unlubricated has been discussed theoretically in this study. The sliding friction tests between the rotating edge of a hollow cylinder against a stationary metal surface were carried out in room air and when the metals were cooled with circulating water.The results obtained were as follows: The relation between PVmax and the critical temperature τbmax of the surface above which ordinary frictional conditions are not maintained may be represented by the following formula, \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm PV}_{max} = C(\tau _{bmax } - \tau _a)} & {(1)} \\ \end{array} $$\end{document} Where C = Hn/μk, and H is the mean total heat conductivity between materials and environment in cal/cm2. °C · s, n the area ratio of heat radiation surface to frictional surface, μ the kinetic frictional coefficient, k the thermal equivalent of frictional work in cal/kg · cm · s, and τa the cooling or environment temperature.The value of C ranges from 1 to 10 in cal/kg · cm s · °C, and the value of PVmax from 45 to 750 in kg/cm2 · cm/s under prevailing room temperature air cooling in this experiment, however, the value of C has been increased about 2.3 times as much as those values by circulating water of 2°C around the lower side of the test piece.
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    Solid-phase backward extrusion of thermoplastics (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 269-279 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The backward extrusion process was studied as a means of forming projections and ribs on flat sections of thermoplastic parts. The simplified, open-die axisymmetric and plane-strain extrusion cases were mainly considered. The results were applied to the development of a continuous solid-phase-forming process. Commercial-grade polycarbonate (PC), polypropylene (PP), and polystyrene (PS) were used in the investigation. The projection height and extrusion loads in the unconstrained extrusion were measured as a function of the initial temperature of the material, the load hold time, and geometric variables. Cold dies were used in the experiments, and the samples were kept below their melt temperatures. The dimensional recovery of the flange section of the formed samples was also measured as a function of the hold time for given initial temperature and geometric variables. The slab and the upper-bound methods-in plasticity analysis were used to theoretically derive the projection heights and forming loads. The degree of correlation between the predictions and the experimental results depended on the estimates used for the frictional factors at the interfaces between the deforming material and the dies.
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    Effect of compaction rate during the cold forming of polymeric powders (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 300-306 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: During many plastics processing methods, both conventional and novel, plastic powders or granules are subjected to pressure. The pressure transmissibility through the powder has an important effect on the success and efficiency of the process, and so it is desirable to be able to predict the pressure at any point from a knowledge of the applied pressure and the geometry of the system. To examine this pressure transmissibility effect, poly(vinylidene chloride) powder has been compacted in a metal die under different rates using either load or displacement control. It has been found that rate effects are particularly important for loading rates greater than 8 MPa/s and displacement rates greater than 7.5 mm/s. The ratio of transmitted pressure (P2) to applied pressure (P1) has been measured for a range of compact geometries, and it has been found that the ratio is approximately constant during the latter stages of the compaction process. Various laws for predicting the transmitted pressure have been studied, but it has been found that the simplest equation that agrees with the data is of the form \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{P_2 }}{{P_1 }} = e^{- \alpha \mu ch/D} $$\end{document}
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    Molecular weight distribution of polyethylene terephthalate in homogeneous, continuous-flow-stirred tank reactors (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 314-323 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(ethylene terephthalate) (PET) formation in homogeneous, continuous-flow-stirred tank reactors (HCSTRs) operating at steady state has been simulated. The feed to the reactor is assumed to consist of the monomer bis-(hydroxyethyl) terephthalate and monofunctional compound (MF1) cetyl alcohol. The overall polymerization is assumed to consist of the polycondensation, reaction with monofunctional compounds, redistribution, and cyclization reactions. At a given time, the reaction mass consists of polyester molecules (Pn), polyester molecules with an ending of molecules of monofunctional compound (MFn), and cyclic polymers (Cn). A mass balance for each of these species in the reactor gives rise to a set of algebraic equations to be solved simultaneously. The MWD calculations show that the redistribution reaction plays a major role and cannot be ignored, This result is in contrast lo the observation for semi-batch reactors, for which redistribution becomes important when the cyclization reaction is included. For the same residence times of semi-batch and HCSTRs, the latter gives considerably lower-number average molecular weight, Nav, and polydispersity index, ρ. However, for the same conversions, the ρ for CSTR is higher. The concentration of the monofurctional compound, [MF1]0, in the feed and the reactor temperature both influence ρ, but the effect is small within the range studied.
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    An improved lattice-fluid equation of state for pure component polymeric fluids (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 345-348 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The Fluid-Lattice Theory (Ising Fluid), recently tested by Lacombe and Sanchez, has been modified by introducing the typical Flory's surface-to-volume ratio of the characteristic-segment of a polymeric liquid. This surface-to-volume ratio is not an adjustable parameter. It is obtained from Bondi's tabulations. The resulting new equation of state has three adjustable parameters per component and it represents a definite improvement for the fitting of P-V-T data for polymeric liquids. Extension to mixtures is not tested in this work but, in principle, it can be done by well-established methods.
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    URL: http://dx.doi.org/10.1002/pen.760220603
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    Capillary and slit flow behavior of concentrated solutions of a rod-like polymer (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 521-527 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper is concerned with the flow behavior of isotropic solutions of the rod-like polymer, poly(p-phenyleneterephthalamide) (PPT), in 100 percent sulfuric acid. Studies include entry flow visualization in a slit die and solution fracture, and die swell in capillaries and a slit die. It was observed that solutions of PPT exhibit nearly negligible die swell, a slip-stick type of fracture that disappears at high shear rates, and radial entry flow patterns similar to Newtonian fluids. Fracture was associated with the plateau in the shear stress vs shear rate curve. Because values of the wall shear stress (τw.) obtained from capillary measurements were in good agreement with those obtained from a cone-and-plate rheometer and values of the loss modulus (G″) obtained from small-strain dynamic oscillatory measurements, it is believed that the rheological properties lead to the flow instability. These results are in agreement with the predictions of a recent theory by Doi and Edwards for concentrated solutions of rod-like molecules. Data are also presented for a flexible chain polyamide, nylon 6,6, in 100 percent H2SO4 for the purpose of comparing the flow characteristics of rigid and flexible chain polymers.
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    URL: http://dx.doi.org/10.1002/pen.760220902
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    The elastic change of volume in pressurized bottles made from polymeric materials (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 472-477 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The relations describing the elastic change of volume of thermoplastic cylindrical pressurized containers are presented. Discussions have been made on various cases including isotropic (i.e., un-oriented), uniaxially, and biaxially oriented materials. These relations are expected to be helpful for selecting the optimum processing conditions (i.e., draw ratio) in order to achieve the desired properties of polymeric pressurized containers.
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    The hydrolytic stability of some commercially available polycarbonates (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 370-375 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A number of commercially available polycarbonates, including formulations made flame retardant by two different modifications, have been exposed to conditions producing moderately rapid hydrolysis. Hydrolysis rates were calculated from molecular weight data determined by gel permeation chromatography and, in some cases, from melt flow rate data. The rates calculated by the two methods are in good agreement. In general, the standard formulations containing minimal additive packages are the most hydrolytically stable. Although one relatively new flame retardant polycarbonate demonstrates generally good resistance to hydrolysis, most of the flame retardant formulations appear to be quite susceptible to hydrolytic degradation. For these materials, hydrolysis under conditions encountered in use could cause significant decreases in impact strength within a few years.
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    URL: http://dx.doi.org/10.1002/pen.760220608
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    Low temperature thermal aging of ethylene vinyl alcohol copolymers (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 382-387 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The crystallites of semicrystalline polymers formed at low temperatures are subject to partial partial melting and recrystallization resulting in a systematic increase in the size and perfection of the nascent crystallites. Differential scanning calorimetry (DSC) and x-ray studies suggest that ethylene-vinyl alcohol copolymers (EVOH), in particular, may undergo these secondary crystallization processes upon storage at temperatures far below Tm. DSC scans have been run on “as received” and quenched samples; the mole percent of vinyl alcohol in the copolymers studied was 0, 62, 70, 72, 82 and 100 percent. Tests on secondary crystallization kinetics, performed at different temperatures, further confirm the hypothesis of an increased degree of perfection (lamellar thickening) of the bulk crystallites achieved upon long term storage at temperature between Tg and Tm.
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    Rheology of polymer blends: Simultaneous slippage and entrance pressure loss in the ethylene-propylene-diene (EPDM)/viton system (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 507-511 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Because the exact nature of the mechanism governing the marked viscosity reduction in the highly incompatible EPDM/“Viton” fluoroelastomer system is not fully understood, a study was undertaken to shed more light on the phenomenon. Interracial. Slippage in the blend has been suggested as the mechanism by which a substantial reduction in the melt viscosities of either component takes place upon addition of a small amount of the other, In the present investigation, a Mooney slip analysis demonstrated wall slippage in the EPDM/Viton system over the shear stress range of 40 kPa to 160 kPa. The capillary surface was examined for evidence of coating by the minor component of the blend (Viton), and 9-fold enrichment was found by elemental analysis. However, on no occasion was pure Viton found. In other experiments, the dynamic linear viscoelastic properties and the transient squeezing flow response of the blend were found to be no different from those of the neat elastomer. In addition, the slip velocity in a capillary (and consequently, the viscosity-lowering effect) was reduced by a factor of 2 to 3 in capillaries with a 90° included entrance angle. It is postulated that the reduction in the flow resistance for the blend is unique to the sharp-entry capillary geometry and results from removal of Viton from the melt in the recirculating flow at the entrance. This material then feeds along the capillary wall, disrupting the already tenuous adhesion of the elastomer to the metal surface.
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    Unsaturated polyesters from 2,2-dimethyl-1,3-propanediol (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 556-559 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series unsaturated polyesters were made from 2,2-di-methyl-l,3-propanediol, propylene glycol, fumaric acid, and isophthalic acid by a two-step fusion process. The effect of catalyst, conversion, composition, unsaturation, and styrene content were studied, and the relationship between composition and properties was established.
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    URL: http://dx.doi.org/10.1002/pen.760220907
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    Effect of the addition of ethylene-propylene random copolymers on the properties of high-density polyethylene/isotactic polypropylene blends: Part 1 - morphology and impact behavior of molded samples (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 536-544 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Two random commercial ethylene-propylene copolymers (EPM) with different ethylene content have been added to binary isotactic polypropylene (iPP)/high density polyethylene (HDPE) blends by melt mixing in a Brabender-like apparatus. Impact Izod tests and a morphological analysis on the fractured surfaces of broken specimens have been performed and discussed, in order to improve the deficiency in toughness of the binary HDPE/iPP mixtures. The results show that the impact performance of both homopolymers and HDPE/iPP binary blends is strongly improved by the addition of the EPM copolymers. Such an effect is related to the fact that the overall morphology, as well as the mechanism and mode of fracture, are greatly modified by the presence of such additives. The extent is dependent on factors such as the nature of the matrix (HDPE or iPP), the composition, and the chemical structure and/or the molecular mass of the added copolymer.
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    Masthead (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982) 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221001
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    Estimation of injection pressure during mold fillingPresented in part at the “Second World Congress of Chemical Engineering,” Montreal, Canada, Oct, 4-9, 1981.This paper is a corrected reprint of the paper that originally appeared in POLYMER ENGINEERING AND SCIENCE, Mid-April, 1982, Vol, 22, No. 5. (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 589-593 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Dimensionless diagrams for estimating the bulk temperature of the flow front and injection pressure in the limit of small viscous generation are obtained. Also, a criterion for neglecting viscous generation is identified, The diagrams, based on the Lord and Williams model, refer to rectangular geometry and amorphous materials. A satisfactory comparison is obtained with literature data taken on polystyrene. A reasonable estimate of polyethylene injection pressure was obtained by roughly accounting for latent heat of crystallization through modified thermal diffusivity.
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    The relationship of carbon black dispersion to electrical resistivity and vulcanizate physical properties (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 601-609 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The degree of dispersion of carbon black in rubber is known to be a determining factor in the physical properties of the composite. It is important, therefore, to have a reliable, quantitative technique for assessing carbon black dispersion. It has been known for some time that the degree of dispersion of carbon black is reflected in its electrical resistivity. A resistivity instrument, developed by B. Boonstra, has been redesigned and constructed for use in this study. Factors that influence resistivity (i.e., black type, volume loading, and mixing time) are examined. Physical property and dynamic mechanical measurements are made, and their relationship to black dispersion is investigated. Light microscopy is also used to evaluate dispersion, and these data are compared to the resistivity results.
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    On the dynamics and control of a plasticating extruder (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1095-1106 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In recent years, there have been many papers published on the application of process control to plasticating extruders. Much of the literature concentrates on the more classical control techniques. However, recent research has studied the application of stochastic identification techniques for building transfer function models for the extruder. In particular, the relationship of screw speed to die pressure and temperature has been studied. In the present work, both step tests and pseudorandom binary sequence tests were used to study the process dynamics of a 38 mm Killion extruder having a Iength-to-diameter ratio of 24:1. This study concentrates on the regulation of the extruder pressure in the face of its inherent surging characteristics. Variations in the quality of the feed plastic were studied through pulse and step changes in input polymer composition. Significant control problems resulted from measurement noise, which appeared at the same frequency as the screw rotation speed. Various mathematical filters to reduce the effect of this noise on the control variables were studied.
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    Siloxane-poly(Methylmethacrylate) amphoteric blends (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1123-1126 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly([4-(methacryloyloxy) butyl]pentamethyldisiloxane), PMBPD, has been prepared for the first time. At the weight average molecular weight of 55,900, it is a clear, viscous liquid with a glass transition temperature, Tg, of 236K. Copolymers with methylmethacrylate have also been prepared. The homo-and copolymers, all of which have methacrylate backbones with pendant siloxane groups, were blended with poly(methyl-methacrylate), PMMA. Using the existence of a single Tg as a definition of miscibility, it was found that blends of either PMMA or PMBPD with random copolymers are miscible. However, in spite of a clear appearance, the blend of the two horriopolymers were found to have two distinct Tgs.
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    Recent advances in interpenetrating polymer networks (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1143-1152 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We review the synthesis, morphology, and physical and mechanical properties of IFNs as well as the related pseudo-IPNs, in which only one of the polymers is crossliriked. Recent studies have shown that the degree of phase separation achieved in these materials is strongly dependent on the compatibility of blends of the linear polymer constituents of the IPN components as well as the kinetics of chain extension and the presence of grafting between component polymers. We illustrate this by a series of IPNs consisting of a polyurethane and an acrylic copolymer. The acrylic is a typical automotive enamel. An enhancement in properties results, which is dependent on the amount of grafting and the kinetics of polymerization. Also discussed are IPNs of a polyurethane and an epoxy, which exhibit a synergism in adhesive properties, and IPNs of a RIM polyurethane with several epoxies and unsaturated polyesters. In addition, also reported are the preliminary studies on the first successful preparation of a three-component IPN, consisting of a polyurethane, an epoxy, and an acrylic.
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    Development of industrial polyolefin blends using melt rheology data (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1153-1165 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The review of current knowledge of the composition dependence of polymer-blend processability and morphology shows that development of industrial blends requires use of a semiempirical approach, based on the particular rheological composition (PRC) concept. Selecting blend composition in the close proximity to PRC and employing factorial experiments for the mixing process allows the development of successful industrial polyethylene/polypropylene blends designed for film and blow-molding applications.
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    Composition and processing effects on the properties of one-component polyurethanesPresented at Second World Congress of Chemical Engineering, Montral, Canada, October 4-9, 1981. (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1177-1183 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A polyurethane consisting of a poly(propylene oxide) soft segment and a diphenylmethane diisocyanate - hydroquinone di-(b̃-hydroxyethyl) ether (HQEE) hard block has been characterized over the composition range of 30 to 60 percent hard block. The flexural modulus varied from 60 to 900 MPa over this composition range. The elongation was approximately 250 percent at the lower hard block contents but fell below 100 percent at 60 percent hard block. Differential scanning calorirnetric measurements showed that the crystallinity associated with the hard phase increased with increasing hard block content but decreased with increasing cure temperature. The heat sag was found to decrease with increasing hardblock and increase with increasing cure temperature. A material with properties comparable to current fascia materials had a significantly better heat sag resistance than a current RIM (reaction injection molding) polyurethane. The combination of the solid chain extender, HQEE, and a solid catalyst, zinc stearate, lowing it to be processed as a one-component resin having a pot life of greater than 8 h at 20°C al-injection molding machines. The one-component nature of the resin has made it possible to use a continuous in-line mexer and to reduce the amount of scrap by using cold runner molds. In addition, any scrap that is generated can be used as regrind in the system.
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    Fractography of polyethylene glycol dimethacrylate doped with polymethyl methacrylate (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1199-1204 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The presence of polymethyl methacrylate (PMMA) can greatly affect the properties of materials made by polymerization of ethylene glycol dimethacrylate (EGDM). Fracture surfaces, examined by scanning electron microscopy, show a much wider range of morphologies in mist regions than observed in previous work on PEGDM alone. These morphologies are attributed to the moderation of brittle fracture by localized plastic deformation. It is suggested that the effect of PMMA is due to its segregation around clusters of highly cross-linked particles of PEGDM that, as a result, become more discrete and, hence, more susceptible to interparticle displacements during fracture. In agreement With this suggestion, the mist regions usually exhibit a particulate microstructure.
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    Studies of epoxy resin systems: Part D: Fracture toughness of an epoxy resin: A study of the effect of crosslinking and sub-Tg aging (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1228-1236 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The fracture toughness of an epoxy resin system, diglycidyl ether of butanediol, DGEB, cured with 4-4′ diaminodiphenyl sulphone, DDS, has been studied by varying the crosslinking density and state of aging. A stable, but rough, crack propagation was observed with specimens that were 99 percent cured and quenched. When the extent of curing was less than 99 percent or the material was aged for more than 20 min at 62°C, crack propagation was of the unstable stick-slip nature. Aging was found to decrease the initiation fracture toughness dramatically, but the arrest fracture toughness was almost unchanged. This result was associated with a change of relaxation strength of the primary, a, transition with aging. An increase of crosslinking density was found initially to reduce the fracture toughness of this epoxy resin, but the fracture toughness increased after 87 percent of curing. The initial decrease of the fracture toughness was attributed to a decrease of relaxation strength of the primary transition (i.e., the area under the α-relaxation peak), while the increase of the fracture toughness after 87 percent curing was explained by the onset of the stablerough crack propagation, Micrographs taken by scanning electron microscopy-showed possible existence of blunting during crack propagation and a decrease of blunting with the extent of aging.
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    Mathematical modeling of the blow-molding process (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1075-1083 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A mathematical simulation of the blow-molding cycle has been developed by combining general conservation principles along with appropriate constitutive relations for the material. A model of the parison formation stage has been devised by considering the competing effects due to swell and drawdown. A more rigorous numerical analysis of parison formation is also discussed. A theoretical treatment of parison inflation is described for both inelastic and viscoelastic materials by assuming uniform radial growth, Comparisons are made with experimental data for all phases of the molding cycle. The mathematical model is in reasonable quantitative agreement with experimental results and is capable of elucidating the influence of material properties and process conditions on the dynamics and performance of the blow-molding process.
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    Editor's note (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1107-1107 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760221708
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    13C NMR characterization of intermolecular interactions for polymers. Part 3. Solvent effect on the blend compatibility of poly(vinyl methyl ether) and polystyrene (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1109-1116 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The solvent has an influence on the homogeneity of the poly(vinyl methyl ether)-polystyrene, PVME-PS blends Prepared by drying cosolutions. This influence has been analyzed in terms of the competition among polymer-polymer and polymer-solvent interactions. Model solutions have been prepared in which intermoleeular interactions correspond to the interactions in this blend and in some of the cosolutions. These interactions in the model solutions have been detected and identified by applying Rummens' method. The 13C NMR spectra have been determined for PVME and for styrene oligomer dissolved in n-alkanes, cyclohexane, diethyl ether, isopropyl methyl ether, diisopropyl ether, and chloroform, and for PVME dissolved in benzene, toluene, and cumene. The chemical shifts have been plotted against the parameter g2 = [(n22 - 1)/(n22 + 1)]2, where n2 is the refractive index of the solvent. If the structural segment represented by certain carbon and some solvent has an interaction that is stronger than dispersive, the chemical shift for this carbon will deviate from the line formed by its shifts in n-alkane solutions, these deviations indicate characters and intensities of the intermoleeular interactions. Results indicate that cyclohexane exhibits weak interactions with both of the polymers and does not interfere with their mutual interaction, leading to a compatible blend. Results also suggest that benzene and toluene interact in the PVME in the same manner as PS. This leads to a gradual increase of the number of polymer-polymer interactions as the concentration of the polymers is increased by solvent removal, resulting in a compatible blend. Chloroform apparently interacts more strongly with PVME than with PS but interacts strongly enough with both to restrict interaction among the two polymers. As the concentration of polymers in the cosolution is increased, PS forms a separate phase. This leads to an inhomogeneous blend when the solvent is evaporated.
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    Fracture toughness (KQ) testing with a mini-compact tension (CT) specimen (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1190-1198 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A testing method using the Rheometrics Mechanical Spectrometer as the loading instrument to measure the fracture toughness KQ, which is related to a specific sample geometry and dimensions (half-inch compact tension) is reported. The small sample size requirement makes it attractive to do fracture toughness testing on newly synthesized material for preliminary material study and comparison purposes. Commercially available epoxy resins were used to check the procedure at different temperatures (-150° to 250°C). An empirical crack length averaging method was used that appears to give constant KQ values independent of the a/W ratio values. The fracture surfaces were studied using scanning electron microscopy.
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    Studies of epoxy resin systems: Part A: A study of the origins of the secondary relaxations of epoxy resins by thermally stimulated depolarization (1982)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 22 (1982), S. 1205-1212 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The relaxation behavior of several epoxy resin systems, which have systematic structural differences, has been studied by the thermally stimulated discharge (TSD) technique. Two TSD peaks centered at about 115°K (β peak) and 185°K (β peak) were found for epoxy resins cured with a diamine. Structural change, either in the epoxy resin molecule or the amine molecule, did not seem to affect those two peaks. The TSD thermogram of the DGEBA (diglycidyl ether of disphenol A) epoxy resin part only showed a small new peak at 160°K instead of the ft peak at 185°K. This result, together with the fact that postcuring increased β peak height, leads to the conclusion that the ft peak is most likely due to the newly-created molecular segment during the curing reaction. The peak at 160°K was assigned to the epoxy group. This assignment was based on the fact that the 160°K peak of an epoxy homopolymer, which has fewer epoxy groups, was smaller than that of the parent DGEBA. The β and γ peaks were found to be of distributed characteristics, and the distribution of activation energy was studied by the partial heating method.
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    The influence of structure on the failure of isotactic polypropylene films (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 66-76 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The failure behavior of uniaxially-oriented isotactic polypropylene films has been examined over a wide range of rates and temperatures. Above the glass transition temperature the failure behavior is observed to be a direct function of the initial noncrystalline orientation state of the film. Below the glass transition temperature (-80°C, -196°C), both the crystalline and noncrystalline regions contribute to the failure.
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    An instability leading to failure of polyethylene in uniaxial creep (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 104-107 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Based on a continuum model, a point of instability is predicted for the uniaxial creep of high density polyethylene. From dead load experiments it has been found that the instability occurs for linear polyethylene at around 10-12 percent strain, depending upon molecular weight and molecular weight distribution. It is shown that in the range of applied stresses for which the specimens neck during uniaxial creep, the time required to reach the critical point is related by a constant factor to the time at which the neck appears. A synopsis of theoretical considerations, as well as experimental work in support of this idea, is given.
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    High speed electron spin resonance techniques applied to polymer fracture (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 112-113 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Mechanical fracture of nylon 6 produces free radicals as a direct result of bond-breaking; these initial free radicals rapidly decay into secondary free radicals at room temperature. Aromatic nitro-compounds react with the initial, but not the secondary, free radicals. The rate of reaction is sufficiently fast to compete with the usual initial radical decay process, even at room temperature. Considerations involved in applying high speed (microsecond) electron spin resonance techniques are discussed.
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    A slender-body theory for interfacial failure in unidirectional fiber-reinforced composites (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 125-130 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Based on asymtotic techniques which have been recently developed for the mechanics of linear continuous media containing slender inclusions, a theory is presented for the nonlinear problem of interfacial failure in a fiber-reinforced composite. Based on the lowest order slender-body theory, and a correspondingly simple model of interfacial slip or plastic yielding, a constitutive equation is, derived for unidirectional, dilute-fiber composites. This equation provides a tensile stress-strain relation which exhibits microscopic, ductile yield arising from the microscopic failure process. Approximate formulae are proposed to account for fiber interactions among closely-spaced parallel fibers and for interfacial slip with sliding friction. It is shown that all the results can be represented in terms of a “reduced-variable” plot, which suggests that experirniental data for various fiber aspect ratios and concentrations might he reducible to a single curve, depending only on tine mode of interfacial failure.
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    Origin, extent, and effect of molecular stress concentration in fibrillar structures (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 140-144 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Electron spin resonance and infrared spectroscopy investigations of the deformation of oriented polymers have given insight into the loading and rupture of chain segments. Whereas there is agreement on the phenomenology of chain scission, fiber deformation, and stress relaxation, quite controversial interpretations have been given of the observed phenomena. Particularly disputed have been the extent of interfibrillar slip, the effect of chain scission on macroscopic stress-strain behavior, and the cause of microcrack formation. Dealing with polyamide-6 fibers it is shown that the microfibrils do not unload through slippage and that the lateral rigidity of the crystal blocks within the sandwich-structured microfibrils must be large enough so as to permit the build-up of large stress concentrations. The extent of molecular stress concentration is calculated. The qualitative agreement between the slopes of stress-strain and free radical-strain curves is analyzed. Unless this agreement is coincidental, it can be sought in an amplification effect accompanying the rapid release of stored elastic energy. The ensuing local temperature rise will facilitate the extension of kinked chains tinder annihilation of kinks. This is practically equivalent to unloading those chains without breaking them. The formation of submicrocracks is not related to the breakage of chains. The direct influence of submicrocracks as potential stress concentrators is weak and ineffective with regard to accelerating chain scission.
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    Polymer applications in three dimensional linear fracture mechanics analysis (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 108-111 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A discussion is given of three types of experimental techniques which make use of polymers for the verification of theoretical solutions to three-dimensional linear fracture mechanics problems. The three techniques discussed are designated as the fatigue method, the photoelastic stress-freezing method and the static fracture method. These techniques employ poly(methyl methacrylate) sheets which are cut into appropriate fracture mechanics specimen geometries or castable epoxies which may be cast into flat plates or other appropriate shapes for investigation. The suitability of these materials for linear fracture mechanics testing is discussed and the quality of results obtained is described.
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    Elastic modulus and strength of fibrous material (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 118-124 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: As a rule, the large increase of elastic modulus with increasing draw ratio obtainable in highly-drawn or extruded semicrystalline polymers is not reflected in a similarly large increase of strength. This is closely connected with the wellknown fact that with increasing plastic deformation one obtains fibrous material with decreasing strain to break. The axial elastic modulus is mainly caused by the taut tie molecules which bridge the amorphous layers between consecutive crystal blocks and thus provide an efficient axial force transmission through the sample. The defects at the ends of microfibrils interrupt this transmission because they contain few if any taut tie molecules connecting the end of microfibril with adjacent fibrillar elements. As a consequence of the small number of such ends, they only marginally reduce the elastic modulus. But as the mechanically weakest areas of the fibrous material, they drastically depress the strength. They fail as soon as the strain concentration upon them reaches their strain to break. The growth and coalescence of resulting microcracks finally lead to bulk fracture as the growing crack reaches critical dimensions.
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    Failure sensitivity of high density polyethylene in compressionWork performed in conjunction with Stanford University, Department of Materias Science, Stanford, CA. (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 136-139 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: As part of an investigation of the compressive mechanical behavior of high density polyethylene between room temperature and the crystalline melting temperature, the strain-to-failure as a function of temperature and strain rate was studied. The two resins studied in applied-strain-rate tests were found prone to fail, as judged by decreased strain-to-failure, at temperatures from 70 to 88°C. The strain-to-failure decreased as the temperature was increased or as the strain rate was decreased. This behavior is opposite to that observed in tension at lower temperatures. At temperatures just below melting, the strain-to-failure apparently began to increase again. By analogy to the results of tearing experiments on polyethylene and other thermoplastics, the findings are explained in terms of the influence of the α relaxation in polyethylene. Differences in the behavior of the two polyethylene resins were also examined.
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    Effect of molecular weight distribution on fatigue crack propagation in poly(methyl methacrylate) (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 145-150 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: It is well established that both molecular weight (M) and its distribution (MD) affect many polymer properties such as mechanical behavior. Thus studies have shown that fatigue life is enhanced by increases in M. Research here has shown that with notched specimens fatigue crack propagation (FCP) rates are dramatically decreased by increasing M, even when the M is high enough that the static fraeture energy has essentially reached its asymptotic limit. In this study, specimens of poly(methyl methacrylate) containing either high- or low-M tails were prepared and characterized. The earlier finding that FCP rates are inversely related to average M was confirmed, but specific effects of M distribution were observed. At constant Mn, a low-M tail had little effect on FCP resistance, while a high-M tail improved FCP resistance of polymers whose average M was too low for effective entanglements. Thus with high-M tails, it was possible to test specimens whose average M's were too low to permit machining. It is proposed that the effects noted are due to relative stabilization or destabilization of crazes ahead of the crack.
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    Masthead (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979) 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190101
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    Thermochemical characterization of some thermally stable thermoplastic and thermoset polymers (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 24-29 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The thermochemical and flammability properties of some thermally stable polymers considered for use in aircraft interiors are described. The properties studied include: (a) thermomechanical properties such as glass transition and melt temperature; (b) dynamic thermogravimetric analysis in anaerobic environment; (c) flammability properties such as oxygen index, flame spread and smoke evolution; and (d) selected physical properties. The thermoplastic polymers evaluated included polyphenylene sulfide, polyaryl sulfone, 9,9-bis(4-hydroxyphenyl)-fluorene polycarbonate-poly(dimethylsiloxane) and polyether sulfone. The thermoset polymers evaluated included epoxy, bismaleimide, a modified phenolic and polyaromatic melamine resin. These resins were primarily used in the fabrication of glass reinforced prepregs for the construction of experimental panels. Test results and relative rankings of some of the flammability parameters are presented and the relationship of the molecular structure, char yield, and flammability properties of these polymers are discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190105
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    Viscoelastic measurements of PVC plastisol during gelation and fusion (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 210-214 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This work is concerned with the change of viscoelastic properties of poly(vinyl chloride) (PVC) plastisol during heating. The system changes from a suspension of solid particles in a liquid medium to a swollen gel and further to a fused state as the temperature is raised. The Rheometrics mechanical spectrometer was used in the oscillatory mode at 0.1 Hz. The temperature of the sample was raised in a controlled manner to 195°C. During gelation, the viscosity increased rapidly about three decades. There was a similar increase of the elastic modulus. After reaching a maximum, both viscosity and elastic modulus decreased rapidly with the progress of fusion. The viscoelastic properties depended somewhat on the heating rate. At 170-195°C, it took a few minutes for the moduli to reach steady values. Continued heating, for several minutes at 195°C, did not change the moduli any further. The temperature range of the decomposition of a blowing agent in the plastisol foam formulation was determined. Over this temperature range, the viscoelastic properties change very rapidly. Quantitative estimates were made for the decrease of moduli during this period.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190308
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    Radical formation and deformation in poly-p-(2-hydroxyethoxy) benzoic acid fibers (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 89-94 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Radical generation during tensile deformation of poly-p-(2-hydroxyethoxy) benzoic acid (PEOB) fibers was studied by electron spin resonance techniques under various stretching conditions. Primary phenoxy radicals were detected at room temperature, indicating main-chain rupture during mechanical loading. The kinetics of phenoxy radical formation were observed at constant strain, constant load, constant strain-rate, and in constant load rate experiments. The effect of strain rate on the radical formation was found to be larger in this sample than was observed in Nylon 6. These results coupled with other experimental observations have yielded information on a basic structural model and improved insight into the basic molecular mechanism responsible for deformation and fracture.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190206
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    Creep failure and fracture of polyethylene in uniaxial extension (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 99-103 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is shown that under conditions of uniaxial creep the fracture of high density polyethylene can be categorized as one of three types, depending upon the magnitude of the applied load, molecular architecture, and environment. When subjected to relatively large loads, the specimens neck and then fracture almost immediately. At the other extreme of very small initial loadings, the specimens fracture in a brittle fashion through crack formation and growth. In the intermediate range of loadings the specimens neck and, depending upon the molecular weight and molecular weight distribution, may then elongate substantially before fracture. It is shown that the uniaxial creep behavior for the region where drawing occurs, when plotted in terms of isochrones, represents a type of phase diagram, one boundary of which describes the fracture enelope. In addition, experiments employing different constant rate of loading histories are described and an additivity of damage criterion used to predict the time to failure under constant load conditions, and visa versa.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190208
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    Role of bond thickness on adhesive failure (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 114-117 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An analytical, numerical and experimental program is described which establishes the basic fracture mechanics properties of an adhesive joint. A finite element analysis of a homogeneous finite tapered double cantilever beam is first presented and the results compared with elasticity and strength of materials solutions. Using analytical results developed in another paper, a finite bond line thickness correction factor is introduced to determine the crack tip stress intensity factor as a function of crack length. An experimental program is described wherein the crack tip stress intensity factor for the cantilever beam adhesive joint is measured by the compliance method and the results compared with those obtained by analytical and numerical methods. Finally, the critical value of the adhesive crack tip stress intensity factor is determined using the analytical and experimental techniques presented.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190212
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    Carbon fiber structure and stability studies (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 342-349 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study has been made of the thermal-oxidative stability of several commercially available carbon fibers. Significant differences in the weight loss behavior were observed in air aging studies run on the bare fibers at 600°F (589 K). The stability of high temperature laminates, such as those based on NR-150 polyimide precursor solutions, was found to be directly affected by the stability of the reinforcing carbon fibers. In studies carried out to determine the reasons for carbon fiber instability, residual sodium sulfate was found to be the principle destabilizing factor. A mechanism whereby the sodium sulfate promotes the oxidation of carbon in the presence of air is proposed.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190504
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    Evaluation of resin-glass fiber interface under environmental stress (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 350-352 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A test method has been developed to evaluate resin-glass composite materials for their resistance to environmental, thermal and hydrolytic stresses, humidity, radiation, and immersion in aggressive fluids. The advantages this method offers are ease of specimen preparation, small specimen size, and maximum exposure of resin, glass and interface to the test environment.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190505
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    Origin of moisture effects on crack propagation in composites (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 353-358 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study has been made of the origin of unexpected moisture effects on crack extension in fiberglass laminates. Water immersion has been found to greatly reduce the rate of crack growth under constant loading while increasing the rate under cyclic loading, the latter effect being the expected one. Observations were made of the extension of the stable damage zone at the tip of precut notches in wet and dry environments. The damage zone size is postulated as a critical element in the relaxation of high stress concentrations in composites, such as those at notch or crack tips. Under constant load, moisture is shown to greatly expand the interply delamination region in the damage zone, thus reducing the local fiber stresses and increasing crack resistance. Under cyclic loading moisture has little effect on the delamination region, which is large even for dry environments, and the only effect is weakening of the material and acceleration of cracks. Severe hygrothermal conditions can so weaken the material that the crack resistance is reduced under constant loading as well.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190506
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    Moisture effects upon the dimensional stability of an S-glass/epoxy composite (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 359-364 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental investigation is described of the effects of moisture and a polar solvent upon the changes in the axial dimensions of composite tubes fabricated with S-glass and an epoxy resin. Test parameters included different axial stress levels, sorption variations, and changes in the short-beam shear strength with moisture variations. Several wetting and drying cycles were used to establish the reproducibility and reversible characteristics of the observed dimensional changes. Test results are compared and discussed with findings reported by other investigators.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190507
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    The thermal expansion of reinforced nylon-6 composites through the matrix glass transition temperature (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 365-372 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The coefficient of thermal expansion (CTE) of nylon-6 reinforced with particulate filler, short glass fibers, and long-to-continuous glass fibers was measured between -30 and 170°C. As the reinforcement level, the reinforcement aspect ratio, or degree of orientation increases, the linear CTE decreases. The Tg range for the composite system is equal to the Tg for the pure nylon-6 matrix. An unexpected result is observed when the nylon-6 is reinforced with long or continuous glass fibers in random planar orientation and the weight fraction of reinforcement exceeds 10 percent. In this case, the longitudinal linear CTE (parallel to the plane of the fibers) above the Tg is lower than the longitudinal linear CTE below the Tg. Analysis of the mathematical descriptions of composite thermal behavior indicates that an extremely low composite modulus in the transverse direction above the Tg may be a cause for this low CTE. The differences in CTE between short fiber and long fiber reinforced compositions indicate that the critical fiber length for thermal stress transfer may be higher than the critical fiber length for mechanical stress transfer.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190508
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    An ultrasonic-acoustic technique for nondestructive evaluation of fiber composite quality (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 373-376 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This report describes an ultrasonic-acoustic technique used to measure a “stress wave factor” in order to nondestructively assess the quality of composite structures. In a prior study this factor was found effective in evaluating the interlaminar shear strength of fiber-reinforced composites. Details of the method used to measure the stress wave factor are described. In addition, frequency spectra of the stress waves are analyzed in order to indicate the nature of the wave phenomena involved. The stress wave factor can be measured with simple contact probes requiring only one-side access to a part. This is beneficial in nondestructive evaluations because the waves can run parallel to fiber directions and thus, in many cases, measure material properties in directions assumed by actual loads. Moreover, the technique can be applied where conventional through transmission techniques are impractical or where more quantitative data are required. The stress wave factor was measured for a series of graphite polyimide composite panels and results obtained are compared with through transmission immersion ultrasonic scans.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190509
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    Masthead (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979) 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190601
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    Determination of fiberglass lengths: Sample preparation and automatic image analysis (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 377-382 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The optimization of end product properties of fiberglass reinforced engineering thermoplastics must be based upon knowledge of the constituents, including the fiber length distribution. This paper presents the techniques developed for the recovery, dispersal and length distribution analysis of glass fibers recovered from filled engineering resins. An automatic image analyzing computer system is used for the determination. The tedious manual method of measurement from optical photomicrographs is replaced by a rapid, quantitative and reproducible analysis.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760190510
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    Fracture toughness testing of dental biomaterialsPresented at the 175th meeting of the American Chemical Society, Division of Organic Coatings and Plastics Chemistry, Anaheim, California (March 1978). (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 607-608 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The adaptation of a cylindrical geometry fracture toughness test specimen to testing of polymeric dental biomaterials is demonstrated. The specimen configuration facilitates the fabrication of small specimens and simplifies the experimental study of environmental effects on properties of dental biomaterials. The test method is used to measure critical stress intensity factor, KIC for poly (methyl methacrylate) (PMMA), particulate composite restorative materials, and dental polymers. Values obtained are in agreement with data reported for other specimen configurations.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/pen.760190903
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    On the conformational behavior and solid-state extrudability of crystalline polymers (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 450-455 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Extrusion experiments on thirteen polymers in our laboratory and extrusion and forging studies on nine polymers in other laboratories reveal that solid-state extrusion and malleability occur in semi-crystalline polymers that have a crystalline relaxation, αc at the temperature Tαc, and do not occur in semicrystalline polymers devoid of αc. The solid-state extrusion takes place in the temperature range of Tαc ≤ T 〈 Tm with Tm being the melting point. In this temperature, range, the polymeric crystals show a measure of disorder, observed by several techniques and by small heats and entropies of fusion. A survey of the literature indicates that, in general, polymers which have a αc and are solid-state extrudable have shallow and broad bottoms to the energy-wells describing their most stable crystalline conformations, and polymers showing no αc have steep-walled energy-wells for the same conformations.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190615
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    Interaction of water with macromolecules by dynamic mechanical analysis (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 722-727 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dynamic mechanical relaxation of macromolecules is found to be very sensitive to the presence of water which is strongly associated with the macromolecule. Polymers with the amide group exhibit a characteristic loss process (β or β2) in the region of 200K which is associated with the amide-water complex. Changes in the relaxation parameters with water content permit the stoichiometry of the interaction to be determined. Polymers with ionic groups on the side chain exhibit a higher temperature relaxation (β1) associated with side chain motion. This relaxation is also affected by the presence of water. Analysis of the effect of water on the loss parameters of the β2 and β1 processes has provided insight into the nature of the interaction of water with complex biological macromolecules.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191012
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    Investigation of the Tu(〉Tg) relaxation in homopolymers and block copolymers of styrene by torsional braid analysis (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 749-755 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Investigation of the Tu (〉Tg) relaxation in amorphous polymers of styrene by the technique of torsional braid analysis is reviewed. For the most part the relaxation behaves like the glass transition (Tg) in its dependence on molecular weight, on average molecular weight in binary polystyrene blends, and on composition in a polystyrene homogeneously plasticized throughout the range of composition. Diblock and triblock copolymers also display a T 〉 Tg relaxation above the Tg, of the polystyrene phase. Two results in particular suggest that the Tu relaxation is molecularly based. (1) The Tu temperature is determined by the number average molecular weight for binary blends of polystyrene when both components have molecular weights below Mc. (the critical molecular weight for chain entanglements). (2) Homopolymers, and diblock and triblock copolymers of styrene, have a T 〉 Tg relaxation at approximately the same temperature when the molecular weight of the styrene block is equal to that of the homopolymer.
    Additional Material: 18 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191015
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    Effect of cure cycle on mechanical properties of thick section fiber-reinforced poly/thermoset moldings (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 774-778 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: One of the major factors of concern in compression molding of fiber-reinforced thermosets is the mold cycle time which directly affects the processing cost. An ideal system would be the one which cures in a relatively short time resulting in excellent mechanical and physical properties. However, in practice, a compromise has to be made between the mold cycle time and ultimate property requirements. The effects of cure cycle time, temperature, preheating and post-cooling on mechanical properties of continuous as well as chopped glass fiber reinforced polyester and vinyl ester systems involving 1/4 to 1 in thick sections have been studied. Mold cycle time is strongly influenced by the part thickness and mold temperature. Internal heat generation due to curing reaction causes high thermal gradients across the thickness. Preheating offers advantages of reducing both the mold cycle time and the thermal gradient. The flexural and interlaminar shear strengths are strongly dependent or, the mold cycle time. Maximum strengths are obtained when the mold is opened at the instant when there is no thermal gradient across the thickness.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191103
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    Viscoelastic properties of epoxy polymer concrete (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 795-799 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The viscoelastic nature of polymer concrete was investigated utilizing an epichlorohydrin/bisphenol A-type epoxy resinaggregate system. Compression specimens were tested for linearity of viscoelastic behavior, the effect of size of mass on creep, and for determination of the specific creep compliance and the associated elastic modulus. The creep compliance was determined by least squares curve fitting of the experimental creep data. Collocation, a numerical Laplace transform inversion routine, was used to develop the equation for the relaxation modulus.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760191106
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