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  • Articles  (279)
  • Chemical Engineering  (279)
  • 2015-2019
  • 1980-1984  (279)
  • 1981  (279)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (279)
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  • Articles  (279)
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  • 2015-2019
  • 1980-1984  (279)
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  • 1
    Electronic Resource
    Electronic Resource
    Rheological and mechanical properties of plasticized poly(vinyl chloride) (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1037-1045 
    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 dependence of rheological properties of a plasticized, filled poly(vinyl chloride) compound on three different methods of thermomechanical treatments has been studied. These three different states of the compound are the dry blend mixed at a maximum temperature of 93°C, the two-roll milled sample prepared at 150°C from the dry blend and the molded sample pressed at 170°C from the previously milled material. At 150°C the viscosity and elasticity of the molded sample are considerably higher than those of the dry blend and the milled sample. At higher temperatures, although their flow curves more or less merge, extrudate swell, extrudate appearance and extrudate tensile properties of the three samples vary. The mechanical and Theological properties of the quenched and annealed molded samples and those of the same compound without filler have also been investigated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211510
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on physico-mechanical properties of some new light weight engineering materials (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1085-1091 
    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, agricultural, and naturally occurring waste materials in conjunction with liquid epoxy resin, silica and asbestos were employed to make light weight engineering composite materials. To bring down the cost of the expensive resin, additives such as linseed oil and urea formaldehyde were added to replace the bulk of epoxy resin. Various physico-mechanical properties of these composites were studied. In comparison with ordinary cement concrete, properties such as water absorption and fire resistance improved substantially for the majority of mixes, whereas other physico-mechanical properties did not improve greatly in many cases. Such composites, which are similar to (and in some cases better than) ordinary cement concrete can be of use in building technology because of substantially lower prices.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211607
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  • 3
    Electronic Resource
    Electronic Resource
    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760211701
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  • 4
    Electronic Resource
    Electronic Resource
    Optimal thermal design of compression molds for chopped-fiber compositesPresented at the second world Congress of Chemical Engineering, Montreal (October 1981). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1139-1148 
    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: Because heat is convected by the motion of material in the cavity of a compression mold, the time-averaged heating load on the cavity surface is nonuniform. In rapid production of large, thin parts, this can lead to large variations in cavity surface temperature when the mold is heated by the usual uniform distribution of heating lines. In this paper, a new method is developed for optimizing the mold heating design so that this nonuniform heating requirement can be satisfied with a minimum variation in cavity surface temperature. Oil heating is considered specifically, but the method can also be used for stream or electric heat. The optimal position and power supply for each heating line in the mold is determined by combining mathematical programming techniques with an analysis of the steady temperature field in the mold. The nonuniform heating load on the cavity surface is represented by a time-averaged steady heat transfer coefficient calculated from the transient temperature distribution in a polyester sheet molding compound as it fills the mold cavity. The design method is applied to an example mold for a large flat panel. At a one-minute cycle, the optimal heating design dramatically reduces nonuniformity in cavity surface temperature compared with a conventional distribution of heating lines. The optimal design is remarkably simple, uses only conventional equipment, and involves only half the customary number of heating lines. Nevertheless, it still has sufficient flexibility to adjust for changes in cycle time without sacrificing uniformity in cavity surface temperature.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211705
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  • 5
    Electronic Resource
    Electronic Resource
    Pressure development in the melting zone of a single-screw extruder (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1162-1166 
    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 analysis is given of the pressure generation mechanism in the tapered channel of a single-screw extruder. It is shown that when increasing the throughput the pressure build-up capacity of the melting zone tends to decrease. As a result, severe pressure drops may occur in the tapered sections. A relationship between the pressure profile and the melting mechanism (solid bed/melt pool configuration) is described in terms of the cross-channel melt circulation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211708
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  • 6
    Electronic Resource
    Electronic Resource
    Sintering rheology of amorphous polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1167-1170 
    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 activation energy for sintering of poly(methyl methacrylate) particle pairs is shown to be similar to their activation energy for Newtonian flow. Sintering progress with time is in good agreement with the Frenkel's coalescence theory. Typical sintering shear rates are shown to be very low and potential energy change (two particles) is small in comparison with the surface energy change. These results lead to the conclusion that the coalescence sintering mechanism of amorphous polymers above their glass transition temperature is essentially a Newtonian viscous flow mechanism where surface tension is the major driving force. A periodical phenomenon associated with sintering progress with time is reported and a supporting mechanism is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211709
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  • 7
    Electronic Resource
    Electronic Resource
    A theoretical analysis of non-isothermal flow in wire-coating co-extrusion dies (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1128-1138 
    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 theoretical study of non-isothermal superimposed flow of two polymer melts in wire coating co-extrusion dies has been carried out. Numerical methods have been employed to solve the coupled momentum- and energy-balance equations. Various combinations of three polymers - namely, high density polyethylene (HDPE), polystyrene (PS) and low density polyethylene (LDPE) have been studied and least squares curve fitted quadratic polynomials have been used for constitutive equations for all three polymers in non-Newtonian high shear rate regions. A multitude of thermal and mechanical boundary conditions can be treated by this algorithm. It was found that temperature and velocity profiles in the die depend significantly on the arrangement of the polymers. Maximum temperature rise has been noted to increase sharply with wire velocity but it can be reduced by increasing the die radius. When the thickness of the outer layer is increased from zero, the shear stress at the wall undergoes a dramatic change (if the viscosities of the polymers are different) at small values of the flow rate ratio and it reaches an asymptotic value at large values of flow rate ratio. It was also found that viscosity ratio at the interface can be reduced by changing the initial temperatures of the liquids. It was observed in some cases that large errors in the calculation of rheological and thermal variables for this problem can be made if temperature rise due to viscous dissipation is not considered.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211704
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  • 8
    Electronic Resource
    Electronic Resource
    Weld line structures and properties in injection molded polypropylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1149-1155 
    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: Weld regions are formed wherever polymer flow fronts meet. The present study examines the effects of melt temperature, mold temperature, mold cooling conditions, injection speed and annealing on the tensile properties and morphological structure of weld regions in four commercially available polypropylene resins. One of the resins contained nucleation particles. Scanning electron micrographs of the weld region revealed a wide range of morphologies from very strong welds which formed part of a stable neck to brittle failures at low elongation caused by the presence of large nucleation particles in the weld region. The melt temperature, mold temperature, and annealing had the greatest effect on the weld region's tensile properties.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211706
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  • 9
    Electronic Resource
    Electronic Resource
    The viscosity of fiber suspensions at low fiber volume fractions (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1171-1172 
    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 viscosities of suspensions of glass fibers in an aqueous solution of sucrose have been studied by use of a capillary viscometer. In the aligned condition in the capillary, the viscosity depends little on shear rate within the range studied or on fiber length, but increases with increasing volume fraction of the fibers. The entrance effect was found to depend strongly on fiber volume fraction and fiber length: this indicates that the suspensions are relatively resistant to flow during the initial stages while alignment takes place.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211710
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  • 10
    Electronic Resource
    Electronic Resource
    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760211801
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  • 11
    Electronic Resource
    Electronic Resource
    New model of curing process kinetics of diurethane crosslinked natural rubber (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1188-1193 
    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 model for the curing kinetics of diurethane crosslinked natural rubber is elaborated. On the basis of rheometric data, calculation of rate constants of both formation and degradation of the following bond types: urea-urea, urethane-urethane, and urea-urethane, was enabled and thermal activation energies of these processes were determined. Activation energy values for formation of the bonds above are: 61.5 kJ/ mole, 187.6 kJ/mole, and 28.9 kJ/mole, respectively. For degradation, activation energies are: 293.9 kJ/mole, 195.5 kJ/mole, and 163.3 kJ/mole, respectively. An algorithm for carrying out of these calculations on a computer was developed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211803
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  • 12
    Electronic Resource
    Electronic Resource
    The effect of annealing on the thermal properties of reaction injection molded urethane elastomers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1210-1217 
    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: Reaction injection molded (RIM) polyurethanes, especially reinforced RIM polyurethanes, are promising candidates to replace metal exterior body panels on automobiles. One of the most important performance properties which these RIM parts must possess is thermal dimensional stability. Thermal dimensional stability is defined as the ability of a part to withstand distortion or change in size during thermal cycles. This property is important for two reasons. First, during paint operations parts are exposed to high paint bake temperatures. Second, parts may be exposed to relatively high temperatures in use. Thermal dimensional stability is mostly controlled by formulation and post-treatment. Formulation can change the structure of the polymer leading to different thermal properties. Posttreatment such as annealing can change (a) the degree of hard segment phase order, (b) the degree of phase separation and (c) the relative continuity of the phases. Experimental evidence is given to support all these factors.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211806
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  • 13
    Electronic Resource
    Electronic Resource
    Molecular weight distribution in novolac-type polymerization in homogeneous, continuous-flow stirred tank reactors (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1218-1227 
    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 kinetic model for irreversible novolac type phenol formaldehyde polymerization and equations governing the molecular weight distribution (MWD) of the polymer formed in homogeneous continuous-flow stirred tank reactors (HCSTR) have been derived. The set of algebraic equations involves three reaction parameters R1, R2, and R3 and have been solved using Brown's algorithm which was found to be more efficient than the Gauss-Jordon technique of solution. A sensitivity analysis of different reaction parameters has been carried out and the reactivity of the para position was found to be an important factor affecting the MWD. In view of the fact that parameters R1 and R2 have a negligible effect on MWD, the phenomenon of molecular shielding described by Drumm et al. (1) can be neglected. The novolac formation can then be equivalently described by assuming R1 = 1 and R2 = R3 and the kinetic description so obtained is completely based on the experimentally observed different reactivities of ortho and para sites. The results for HCSTR have been compared with those for batch reactors and the former is found to give polymer of lower average molecular weights having higher polydispersity index.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211807
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  • 14
    Electronic Resource
    Electronic Resource
    Dependence of mechanical properties in polyolefin blends on shear and thermal history (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 433-438 
    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: Variously dispersed two-component blends of linear polyethylene and a thermoplastic rubber were subjected to different thermal histories after compression molding and their properties were evaluated. It has been shown that ultimate properties of the blends are not defined by the composition, but vary greatly with degree of dispersion and thermal history. Stronger materials failing in a ductile manner were produced under shock cool conditions and in, finely-dispersed blends. Brittle failures and weaker materials were favored by annealing procedures and in blends subjected to brief and/or lowshear dispersion procedures. Time and temperature dependent changes in properties of blends prepared under standard conditions have been observed and activation energies for the aging process calculated. Data interpretation was based on a hypothesis of domain morphology in the blends, and on the existence of “tie molecules” which help to determine the cohesive strength of domain boundaries.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210710
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  • 15
    Electronic Resource
    Electronic Resource
    The development of C-10 phthalocyanine for composite matrix applications (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 441-448 
    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: Thermomechanical analysis was carried out for various phthalocyanine resins. The polymer based on the C-10 diamide resin was then chosen for evaluation as a potential composite matrix material. Prepregs with Thornel 300 graphite reinforcements were successfully prepared using a hot-melt technique. The processability of this material was studied by employing instrumental techniques including differential scanning calorimetry, thermal gravimetric analysis and dynamic dielectric analysis. A cure cycle was developed for the fabrication of angle-ply laminate using the conventional vacuum-bag technique in a hydraulic press. Laminate mechanical properties both in tension and in flexure were determined. The results for the C-10/T-300 samples were shown to be similar to those of an epoxy/graphite and a polyimide/graphite composite system.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210802
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  • 16
    Electronic Resource
    Electronic Resource
    The effect of molecular orientation on the mechanical properties of fiber-filled amorphous polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 449-456 
    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 technology of using glass fibers to increase the modulus and the strength of polymeric systems is well-developed. Much less widely exploited has been the enhancement of properties by orienting the molecules of the polymer itself. The purpose here was to look for a synergistic combination of these two strategies: using glass fiber-filled polystyrene and introducing molecular orientation into the polystyrene matrix. For rheological reasons it is not possible to introduce large stretch ratios in the rubbery state and thus the amount of molecular orientation that can be frozen into the quenched glassy composite is small. Even so, however, the rubbery elongation (which we associate with subsequent molecular orientation) has a very significant effect on the final (room temperature) mechanical properties. Analysis of these properties was made in terms of various theoretical models (those of Brody and Ward, Smallwood-Guth, and Russel and Acrivos for the Young's modulus; and that of Kelly and Tyson, as modified by Lees, for the tensile strength). These comparisons showed that the brittleness of unoriented polystyrene is such that the matrix does not effectively distribute the stress along the length of the fiber and thus the benefit of the length is not realized; whereas the higher ductility of oriented polystyrene allows such transfer and a consequent improvement of properties.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760210803
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  • 17
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    Characterization of the interlaminar shear fatigue properties of SMC R-50Owens Corning Fiberglas. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 461-466 
    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 interlaminar shear fatigue behavior of the sheet molding compound SMC-R50 has been studied. A thick-laminate, short beam shear test was employed to characterize S-N behavior for the material at 21 and 90°C. The shear modulus (Gxy) was determined at 21 and 90°C and the effect of fatigue on modulus at both test temperatures is discussed. Scanning electron microscope (SEM) and optical photomicrographs of pristine and post test specimens were studied to assess the relationship between material microstructure and the observed fatigue results for strength and modulus. The experimental evidence suggests that the fatigue life for this material is determined by a single flaw growth mechanism, rather than a global “wear out” process.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210805
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  • 18
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    A comparison of impact tests for assessment of fiberglass reinforced plastic toughnessPresented at the 35th Annual Technical Conference, Reinforced Plastics/Composites Institute, The Society of the Plastics Industry, Inc., New Orleans (1980). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 467-473 
    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: All measures of impact resistance have shortcomings. The ASTM tests, Izod, Charpy, and drop-dart, measure impact at a single velocity. Furthermore, the Izod and Charpy tests impose an unrealistic unidimensional stress on the test specimen. Indirect gauges of impact toughness, such as the area under the tensile stress-strain curve (tensile work), flexural modulus, or resin cracking in mandrel bend tests, are normally conducted at unrealistically low straining rates. Variable-rate impact testers have been developed to overcome these shortcomings. In this paper, results obtained from a variable-rate tester are compared with those from other methods for assessing composite toughness. Data are reported for flexible and brittle low profile press molding resins, tested as SMC (sheet molding compound) moldings by Izod, drop-dart and variable-rate impact. Indirect measures of impact resistance, mandrel bend and flexural modulus, are also discussed. The effects of resin flexibility and the composite glass content are demonstrated. The glass content affects the ultimate failure strength of the composite but not the failure of the resin matrix. The resin flexibility affects the initial stages of failure.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210806
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  • 19
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    Effect of aging and moisture on the reactivity of a graphite epoxy prepreg (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 474-482 
    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 effect of moisture on the curing reaction of Hercules 3501-6/AS graphite-epoxy prepreg was investigated. Test samples of prepreg were aged under humid conditions, while control samples were aged under identical temperature conditions but with negligible humidity. Determinations of the amounts of moisture absorbed and desorbed fom the samples were accomplished gravimetrically. Dielectric analysis was used to monitor the relative reaction rates and overall activation energies of the prepreg after various aging periods. Changes taking place in monomer concentrations were observed using high performance liquid chromatography (HPLC). As aging continued, samples aged under humid conditions displayed, significant decrease in the overall activation energy accompanied by increased reaction rates. This change did not occur in the control samples. Samples aged in high humidity showed increased conversion of monomers to polymer when compared to dry aged samples. The aging time required before the above changes became apparent was temperature dependent; the higher the aging temperature, the sooner the changes in reactivity occurred.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210807
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  • 20
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    Effect of carriers on the performance of aluminum alloy joints bonded with a structural film adhesive (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 797-803 
    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 effect of polyester and nylon carriers on the durability of metal joints bonded with the modified epoxide adhesive BSL 312 has been examined. Joints have been exposed to air at 50°C and 100 percent RH for periods of up to 10,000 h. Some joints were under tensile stress and this seems to have no effect on durability. Carriers cause a slight lowering of the strength of dry joints, but they appear to have negligible effect on joint durability. An analysis of water distribution in exposed joints implies that the rate of strength loss is dependent upon the rate at which water enters joints by diffusion.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211210
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  • 21
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    Specification of biaxial orientation in amorphous and crystalline polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 859-868 
    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 fundamental concepts for specifying orientation in amorphous and crystalline polymers are reviewed. A new set of orientation factors is proposed to represent the second moments of biaxial orientation. The factors are defined both for the chain axis and for three crystallographic axes of an orthorhombic (or pseudo-orthorhombic) crystal structure. The orientation factors are defined in terms of the angles between the crystallographic axes and Cartesian coordinate reference axes defining the machine, transverse and thickness directions of films. This makes the orientation factors symmetric with respect to the machine and transverse directions unlike the Stein-Nomura-Kawai orientation factors which are defined in terms of Euler's angles. A graphical procedure for representing the state of orientation as a point inside an isoceles triangle is described. Methods of measuring the orientation factors are also reviewed. The paper concludes with examples of the application of these concepts to orientation in amorphous polystyrene films fabricated in our laboratories and to crystalline polyethylene samples discussed in the literature.
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    Tensile properties of polyethylene blends (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 869-872 
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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: Binary and ternary blends were prepared from low, medium, and high density polyethylene. The tensile properties of these materials indicated that the blends formed either compatible or semi-compatible mixtures. One of the ternary blends exhibited a slight synergism in properties which could be partially attributed to an enhancement in crystallinity. Such blends may have practical utility by yielding materials having a combination of strength, stiffness, and toughness.
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    URL: http://dx.doi.org/10.1002/pen.760211310
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    Introductory remarks (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 873-873 
    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.760211402
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    Crazing and acoustic emission in poly(methyl methacrylate)/acetone and polystyrene/methanol systems (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 854-858 
    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: Craze initiation and growth in the poly(methyl methacrylate)/acetone and polystyrene/methanol systems was studied using photographic and acoustic emission techniques. The poly(methyl methacrylate) system was the only one that produced detectable acoustic emission; however, it was found that craze initiation occurs predominantly in the first half of a sample's lifetime while acoustic emission is detected predominantly in the second half. The detected acoustic emission in the poly(methyl methacrylate) system is believed to be due to the rupture of craze fibrils. Craze initiation in both polymer systems was found to be dependent on stress and time with higher stresses initiating more crazes at earlier times. Although the craze growth rate in both systems exhibited extreme variability, the average growth rate tended to increase with craze size and applied stress. In the poly(methyl methacrylate) system, craze velocity was independent of time but in the polystyrene system it decreased with time. None of the existing craze growth theories were capable of explaining these results.
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    An overview of the nonequilibrium behavior of polymer glasses (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 874-895 
    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
    Additional Material: 38 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211403
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    Prediction of solubilities for volatile hydrocarbons in low-density polyethylene using UNIFAC-FV model (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1015-1018 
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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 UNIFAC-FV model has been applied to predict the weight-fraction Henry's constant of n-hexane, n-octane, benzene, and toluene in low-density polyethylene in the region 124 to 250°C. By adjusting the number of external degrees of freedom per hydrocarbon molecule, the weight-fraction Henry's constant was correlated with good agreement by the model. Namely, the solubilities of hydrocarbons in the polymer can be obtained correctly from the model at low pressures, less than 2 atm. Although the model is very useful, its applicability is limited to the subcritical temperature range of a volatile hydrocarbon.
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760211601
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    Electrical properties of carbon black filled crosslinked polyethylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1049-1054 
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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 electrical resistivity of peroxide and radiation crosslinked polyethylene/carbon black compounds was studied as a function of black concentration and, temperature in heating/cooling cycles. Different carbon blacks in compounds with polyethylene responded differently, regarding electrical resistivity, to the effect of crosslinking. In one case (fine black) the resistivity and PTC (positive temperature coefficient) effect did not significantly change, whereas in another case (coarse black) the effect of crosslinking-was to significantly increase the resistivity and reduce the PTC effect. The main advantages of crosslinking were to give compounds having good electrical reproducibility and to practically eliminate the NTC (negative temperature coefficient) effect in compounds containing fine, coarse, or mixtures of carbon blacks. Crosslinked compounds containing mixtures of carbon blacks have shown good conductivity, electrical reproducibility, and switching properties.
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    Mass transfer and depolymerization of styrene in polystyreneThis paper was presented at the 73rd Annual Meeting of the American Institute of Chemical Engineers, Chicago, Illinois (November 20, 1980). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1055-1062 
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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 work shows how laboratory experiments may provide parameters which are useful in modeling a commercial process of polystyrene devolatilization. Such processes often occur at temperatures where depolymerization of polystyrene to monomer may be significant. Polystyrene devolatilizers function by forming thin films of the polymer, with styrene loss by flashing and diffusion and styrene generation by depolymerization. The modeling parameters of importance are: depolymerization rate constant, monomer diffusivity, and thermodynamic equilibrium polymer-vapor partition coefficient. Typical levels of styrene in polystyrene in the last stage of devolatilization are 100 to 1000 ppm. Pressures and temperatures in the devolatilizer are often less than 10 torr and greater than 200°C. For styrene-polystyrene the desired parameters have not been reported, nor apparently measured, at the concentration, pressure and temperature levels of interest.
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    Nylon-6 containing metal halides II: Tensile properties (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 223-226 
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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: Following the reported pronounced effects of metal halides incorporated into nylon-6 on its glass transition temperature, melting temperature, melt viscosity, crystallization rate and final crystallinity, the tensile mechanical properties and crystallinity of nylon-6 as affected by the absorption of metal halides were studied. At low salt content, some of the mechanical properties are substantially altered and at higher salt concentrations the ductile polymer becomes brittle. There is no marked difference between the salts studied (CuCl2, CuBr2, FeCl3) regarding their effects on the polymer mechanical properties. In the concentration range studied, absorbed Cu salts do not significantly change the polymer's degree of crystallinity, whereas absorbed FeCl3 results in a pronounced reduction, indicating its effect also on the crystalline phase.
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    Experiments in extensive mixing in laminar flow. I. Simple illustrations (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 212-217 
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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: Simple quantitative mixing experiments in well-defined deformations clearly demonstrate the validity of previously derived equations relating deformation and mixing. A simple mixture of black and white polyethylene is studied by direct measure of striation thickness. The well-known linear relationship in simple shear is demonstrated. By using a simple method for uniform reorientation, the second power relationship in shear once interrupted, the third power relationship in shear twice interrupted and the fourth power relationship in shear interrupted three times are demonstrated. In uniaxial elongational mixing of a silicone fluid, exponential dependence of mixing on strain is demonstrated.
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    Correction (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 248-248 
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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.760210411
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    A biaxial extensiometer for molten plasticsPresented in part at a national meeting of the A.I.Ch.E. in Miami in November of 1978. Experimental data presented in this paper are taken from the doctoral thesis of J. Rhi-Sausi. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 227-232 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: While biaxial stretching plays a central role in several polymer processes, there has been no technique suitable for laboratory study of controlled biaxial stretching of molten thermoplastics at typical melt processing temperatures. The sheet inflation technique, which has been used previously to study rubbers and very high viscosity melts, has been adapted for use with molten thermoplastics by the use of oil as an inflation medium. Problems encountered in the use of the first prototype were eliminated in a second model, which is thought to produce reliable results. Stress growth data are presented for a low density polyethylene and for a polystyrene. A basic limitation of the technique is that the maximum achievable strain is in the range of 1.3 to 1.7, and this is often insufficient to bring out the nonlinear viscoelastic behavior of the melt.
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    Design and application of an instrumented falling weight impact tester (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 313-324 
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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: Within the past decade, instrumented impact testers have become important tools for characterizing the response of polymers to short term loads. Unlike conventional test equipment which yield only the fracture energy, the instrumented devices are capable of providing detailed force vs time plots of the impact process. An instrumented falling weight impact tester is described which is equipped with an accelerometer which permits direct observation of the weight's deceleration as it strikes and pierces the test specimen. Integration of the resulting acceleration vs time curve provides the velocity change upon impact from which the fracture energy can he calculated. The impact tester is capable of accepting a wide range of specimen shapes and sizes and is especially useful where small amounts of material are at hand. To date, it has proved its utility in characterizing thin plastic sheets as well as fiber-reinforced laminates.
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    Measurement and calculation of parison dimensions and bottle thickness distribution during blow molding (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 331-338 
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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: Experimental data are reported regarding the dynamics of the blow molding process, including parison formation, growth, and inflation. These data have been obtained with the aid of high speed cinematography and pinch mold experiments, in conjunction with two commercial blow molding polyethylene resins. It is shown that pinch mold experiments alone do not yield accurate data regarding thickness and diameter swell. Furthermore, the inflation process involves decreasing rates of inflation with time, as a result of the rise in viscosity due to the cooling of the parison during inflation. Mathematical procedures are proposed for a first-order estimation of parison length and swell as a function of time and the inflation behavior after clamping. In the absence of more dependable basic procedures, the proposed treatment is employed to estimate the effective transient swell functions for the parison using experimental data obtained under the specified conditions. The mathematical treatment is extended to determine the thickness distribution of the bottle. Good agreement is obtained between experimental and calculated results.
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    The melting performance of single screw extruders (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 352-359 
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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 recent screw designs is analyzed for melting performance, using a simple analytical approach based on Tadmor's original work. The melting length for a screw with constant depth channel is used as reference. An ideal compression screw will have a melting length of one-half the melting length of the reference screw. The Maillefer melt separation principle is discussed. The Maillefer screw melts in 2/3 of the length of the reference screw. Screws by Barr, by Dray and Lawrence and by Kim are shown to approach the ideal compression screw. A new design screw, using ideal compression and multiple channels and having a very large screw pitch, is shown to be a considerably more efficient melting device than any of the other, screws discussed.
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    Crosslinking of hydroxyl-terminated liquid rubber with divalent metal salts of mono(hydroxyethyl) phthalate, anhydrides, and bisepoxide (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 360-365 
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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: Crosslinking of hydroxyl-terminated liquid rubber with divalent metal salts of mono(hydroxyethyl) phthalate, anhydrides and bisepoxide was investigated by the diols-anhydridesbisepoxide, reactions. As the anhydride, succinic anhydride and hexahydrophthalic anhydride were used, and bisphenol A diglycidyl ether was the bisepoxide used. The metal carboxylate groups of these metal salts catalyzed the crosslinking reactions and, further, the Mg salt showed higher catalytic activities than the Ca salt. As for the physical properties of the metal-containing cured rubbers obtained, tensile strength and Shore A hardness increased with increase in the metal salt content. In addition, the rubbers containing Mg showed better physical properties than those containing Ca. Meanwhile, elongation showed a maximum with increase in the metal salt content. Resistance; to water and chemical attack, thermal behavior, and stress relaxation are also discussed.
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760210701
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    Processing history in extrusion dies and its influence on the state of the polymer extrudate at the die exitPresented at the VIII Int Congr. Rheology, Naples 1980 (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 366-374 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A method is proposed to describe the processing history in extrusion dies and its influence on the state of the polymer after processing. The approach differs from conventional processing analysis, which uses the shear viscosity function to calculate pressure drop vs flow rate relations. The approach also differs from heuristic analysis which tries to find empirical correlations between rheological observations and processing behavior. The method is applied to the flow in annular extrusion dies. An integral constitutive equation is chosen to calculate the flow and to describe the flow history at the die exit as memorized. In the analysis, the kinematics are locally approximated by isothermal steady shear flow. The velocity and the velocity gradient are used to determine the Finger strain tensor, the path lines, and the residence times of the deforming material elements. Measures of the state of the polymer at the die exit are chosen to be the stress ratio N1/2τ12 and the free recovery. The free recovery calculations presume that the extrudate is chopped into small volumes of homogeneous flow history. The results of the calculations show the polymer very sensitively reacts to small changes of the die geometry. Important applications of this analysis are film blowing and blow molding, where the extensional behavior during the blowing process outside the die depends greatly on the preceding shaping process inside the die.
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    Correction (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 375-375 
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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
    Additional Material: 1 Ill.
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    Limiting regimes of deformation of polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 339-351 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The relaxation transition of polymers under the influence of deformation from the fluid to the forced high-elastic (rubbery) and leathery states has been studied. It has been shown that the investigation of the polymers in question under the conditions of uniaxial extension allows one to estimate the properties of polymers at deformation rates exceeding by 4-5 decades the rates of deformation at which simple shear can be realized. A set of critical parameters has been found for the polymers investigated which determines the regimes of their transition from the fluid to the forced rubbery and leathery states and also their fracture properties. These parameters are subdivided into two groups. The parameters of the first group refer to critical values of stress and deformation. They are invariant to temperature and molecular mass. For different polymer-homologous series the critical stresses vary by more than 10-20 times; as regards the values of strains, they vary by more than several times. The parameters of the second group define the rates of strain which bear a simple relation to the initial viscosity and can be changed within many decades. This determines the success of the procedure of reduction of fracture properties to temperature and molecular mass.
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    The effect of degree of polymerization on glass-transition temperatures (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 377-380 
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    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Finite-molecular-mass homopolymers are modeled as binary random mixtures of high polymers and oligomers or chain ends, in proportions determined by the number-average degree of polymerization. This leads directly to an entropic equation for the effect of molecular mass on Tq in terms of the glass-transition temperatures and transition increments of heat capacity of these two components. Predictions of the theory are found to be in satisfactory agreement with calorimetric measurements of Tg over a wide range of molecular mass.
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    Mold release agents. I. Fatty acids and selected fluorinated compounds as releasants for polyurethane from cold rolled steel (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 381-384 
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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 effect of saturated aliphatic fatty acids and a number of fluorinated polar organic compounds on the release of polyurethane foam from cold rolled steel has been investigated. Little release was observed with aliphatic acids of less than 10 carbons or with the organic compounds. Release behavior increased with aliphatic chain length from C12 to C18. Stearic acid release increased only marginally above 0.034 μ g/cm2. Infrared studies of demolded eluted surfaces indicated that stcaric acid at levels of up to 178 μ g/cm2 was apparently removed from the surface by foam.
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    Outgassing of high temperature-resistant organic polymeric materials (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 385-389 
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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: Four polymeric materials, polyphenylene oxide, polyquinoline, acetylene substituted polyimide, and polybenzimidazole, reported to possess high-temperature resistance, were investigated in order. to determine their outgassing characteristics as related to their suitability for high temperature applications in confined structures. The materials were sequentially exposed to 150, 250 and 450°C for 3 h periods and the types and amounts of their outgassed products were determined. The amounts of outgassed- products were small from polyquinoline, acetylene substituted polyimide, and polybenzimidazole. It was concluded that those materials would be suitable for use in applications where high-temperature resistance (up to 450°C) is required, providing that normal ventilation is available. The quantity of outgassed products from polyphenylene oxide was too great to consider that material suitable for shipboard or other confined structure applications requiring high-temperature resistance.
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    URL: http://dx.doi.org/10.1002/pen.760210704
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    Experimental study on cold press workability of aluminum-polyethylene sandwich laminates (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 398-405 
    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 cold press workability of aluminum-polyethylene sandwich laminates is experimentally investigated by a deep drawing process with a conical die. “Planium” of 2 mm thickness, in which the core layer, high density polyethylene, is sandwich-laminated between two aluminum sheets, is used as a test specimen. Soybean oil is employed as a lubricant. The dimensions of the drawing die set are determined for a circular, blank so that the tensile fracture of the drawn.cup occurs at the top corner of the punch. The limiting draw ratio (LDR) is experimentally explored by using many blanks of various initial diameters. In general the maximum punch load in successful drawing increases linearly with increasing draw ratio. Because of the sandwich structure, the fracture of the drawn cup occurs twice. The initial fracture (LDRs) corresponds to a fine bending fracture at the aluminum surface. The second fracture (LDRB) is the complete fracture of the whole laminate. The effect of punch corner radius, working velocity and thickness fraction of aluminum and polyethylene on LDRS and LDRB are studied. The strain distributions of deep drawn cup in three orthogonal directions are analyzed experimentally.
    Additional Material: 19 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210706
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    Molecular weight distribution control in continuous “living” polymerizations through periodic operation of the monomer feed (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 415-423 
    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 main objective of the work is to explore the problem of producing polymers of any desired molecular weight distribution (MWD) in isothermal, solution, “living”, anionic polymerizations carried out in continuous tubular reactors. For this purpose, a novel control scheme was designed and implemented, which involves the periodic operation, of the monomer solution flow rate, with the flow profile automatically derived from the required MWD and other data. For experimental validation, a polymerization rig was especially built that included a process computer and an automatic gel permeation chromatograph. The chromatograph permitted the measurement of the MWD of the reactor effluent in a matter of minutes and the process computer was employed to implement the control policies and to perform the chromatograph data acquisition and reduction. In spite of the practical problems encountered, experiments showed at least a semi-quantitative validity of the method.
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    URL: http://dx.doi.org/10.1002/pen.760210708
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    Torsion impregnated cloth analysis (TICA): A forced torsion technique to study resins supported by inert substratePart of the results included were presented at the american chemical society national meeting (september 1979). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 390-397 
    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: Torsion Impregnated Cloth Analysis (TICA) uses fiber glass cloth as support for polymeric resins and measures the clothresin composite's in-phase and out-of-phase dynamic mechanical responses with a Rheometrics mechanical spectrometer. The TICA thermoscan results of a thermoplastic were compared with that of the neat material. A similar comparison was made between the isothermal curing results of a thermosetting resin and the corresponding parallel plate and TBA measurements. The peaks associated with the vitrification were verified to correspond to those in the glass transition region. Conventional thermoscans of partially cured specimens with known Tg were shown under certain conditions to give erroneous results about the glass transition temperatures. A reduced parameter (T-Tg) was introduced to describe the response of a specimen undergoing additional cure while being subjected to a thermoscan. Examples using this parameter to understand seemingly complex experimental results are given.
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    Effects of composition and polymerization mechanism on the mechanical properties of uv-cured crosslinked polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 406-414 
    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 effect of compositional variables on the mechanical properties of a UV-cured coating was investigated. The coating contains two monomers, 2-ethoxyethoxyethylacrylate (EEEA) and N-vinyl-pyrrolidone (NVP), and a higher molecular weight resin (MW ∼1000) which is a commercial urethane diacrylate. In addition, a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, was present at a constant concentration. It was found that the mechanical properties of the cured films depend mainly on the concentration of 2-ethoxyethoxyethylacrylate (EEEA). Spectroscopic analysis. showed that EEEA undergoes both homopolymerization as well as an addition reaction with the photoinitiator and is thus not incorporated in the crosslinked matrix but rather acts similar to a compatible plasticizer. Kinetic analysis of the reactions of the single components and mixtures showed widely diverging reactivities of the components with homopolymerization of EEEA being a favored reaction path. A speculative conclusion is that, to avoid homopolymerization and monomeric reactions, optimized coating formulations (coatings with mechanical properties that are not affected by small compositional variations) should be based on monomers and oligomers with similar reactivities.
    Additional Material: 13 Ill.
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    Circular couette flow of a polymerizing fluid (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 424-432 
    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: Flow of a polymerizing fluid between rotating concentric cylinders has been analyzed theoretically. A solution has been obtained employing a finite difference method. Using a RIMtype (reaction injection molding) urethane system as an example, the velocity, temperature, and NCO group concentration fields have been described as functions of time. A numerical example is given to demonstrate the applicability of the present analysis to reactive processing and viscometry. The mixing characteristics and the flow rate associated with circular drag flows involved, e.g., in reactive extrusion, have been shown to depend strongly on the operating conditions. It has also been demonstrated that the range of applicability of Couette viscometers to fast curing systems may be limited by the interfering time-dependent temperature gradients involved. It has been concluded that analysis of the. present nature provides a useful design and evaluation tool applicable to Couette flow problems in reactive processing and viscometry.
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    URL: http://dx.doi.org/10.1002/pen.760210709
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760210801
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    A study of the structural integrity of graphite composite structure subjected to low velocity impactPresented at the 35th Annual Technical Conference, 1980 Reinforced Plastics/Composites Institute, the Society of the Plastics Industry, Inc. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 493-498 
    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 analysis for the transient deflections, bending strains, and interlaminar shear stresses in a simply supported laminated composite plate subject to low velocity impact has been obtained using a series solution of the plate governing equations. Results are presented showing the effect of plate geometry and impact location on damage mode. Computed stresses and strain are compared with impact test data to verify, the analysis.
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760210901
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    Compatibility and physical properties of a new polyester blend (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 513-517 
    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 compatible nature of a new polyester blend, polybutylene-terephthalate (PBT) and a copolyester of bisphenol-A-neopentyl glycol-terephthalate (CP-350), has been inferred from the single Tg by DSC and dynamic mechanical studies. Compatibility is further confirmed from the progressive melting point depression of PBT, and the increasingly coarse and open spherulitic morphology of the blends as the weight percent of CP-350 increases. At and above 40 weight percent of CP-350, crystallization of PBT is impeded by the presence of high concentrations of CP-350 which results in a low degree of PBT crystallinity (0-8 percent) in such blends. The melt viscosity as a function of blend composition shows a good fit to the Hayashida model.
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    Numerical determination of internal stress and viscoelastic parameters for xerographic papers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 538-541 
    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 computerized method has been developed for determining, from one experimentally obtained loading curve for a paper sample: (a) the viscoelastic parameters for predicting paper deformation, and (b) the internal or residual stress level in the paper. The loading curve comprises a stress-time curve obtained at a constant straining rate, followed by a stress relaxation curve at a constant strain level. The paper deformation is modeled by the Halsey, White, and Eyring model and a nonlinear viscoelastic model.
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    Internal stress levels in xerographic papers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 534-537 
    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 stress relaxation method for determining internal stress levels in polymers has been used to estimate internal stress levels in certain fine papers typical of those used in xerographic processing. The effects of stress relief, obtained by wetting and redrying a sheet without restraint, strain rate, initial stress and sheet anisotropy on the results were examined.
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    Studies on structural foam processing. IV. Bubble growth during mold filling (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 518-533 
    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 and theoretical study was carried out to achieve a better understanding of bubble growth during the filling of gas-charged molten polymers into a rectangular mold cavity. For the experimental study, a rectangular mold cavity (15.24 × 4.55 × 0.64 cm) was constructed, with glass windows on both sides to permit recording on a movie film of the growth of gas bubbles in the mold cavity as a molten polymer containing inert gas was injected into it. Sodium bicarbonate (generating carbon dioxide) was used as a chemical blowing agent, and the polymer used was a general purpose clear polystyrene. All experimental runs were made at isothermal molding conditions, and the injection rate was varied. It was found that, at and above a certain injection rate, little bubble formation was observed in the mold cavity during injection except at and near the moving melt front. For the theoretical study, the growth of a single gas bubble in a viscoelastic medium (represented by the DeWitt model), subjected to high injection rates, was considered by including the effects of diffusion from the liquid phase to the gas phase, interfacial tension between the liquid and the gas phases, and stress relaxation of the melt upon ejection. It was found that the level of stresses, built up in the met during injection, has a profound influence on the formation and growth of gas bubbles during the initial stage of mold filling. Also, a multichannel mold cavity was employed in order to observe the effect of processing variables on the cell size and its distribution in molded specimens. A uniform cell structure was obtained at higher injection pressures, at an optimum injection melt temperature, and with an optimum combination of blowing agent and nucleating agent concentrations.
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    Plane strain fracture toughness testing of high density polyethylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1019-1026 
    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 concepts of linear elastic fracture mechanics (LEFM) are applied to three grades of high density polyethylene in an attempt to determine their fracture behavior in terms of a linear elastic fracture toughness, Kc. The effect of specimen size (thickness and width), crack length and the mode of loading on Kc has been investigated in order to determine the plane strain fracture toughness, KIc, of these materials. The effect of temperature (between +23 and -180°C) on their fracture behavior has also been investigated and compared in terms of their plane strain fracture toughness values.
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    Properties of polyether-polyurethane zwitterionomers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1027-1036 
    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: Polyether polyurethanes based on 4,4′-diphenylmethane diisocyanate (MDI), N-methyl diethanolamine (MDEA), and polytetraniethylene oxide (PTMO) were synthesized with varying levels of hard segment content. The tertiary amine of MDEA was sulfonated with γ-propane sultone thereby converting the polyether polyurethane to a polymeric zwitterion. The effect of the chemical composition and the degree of ammonium sulfonation on the extent of phase segregation, and physical properties were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis and tensile testing. It was found that the MDEA chain extender inhibits microphase separation of the polymer in the solid state. As the degree of ammonium sulfonation increases in the zwitterionomers, an improvement of phase separation and domain structure was observed. In addition the tensile properties change dramatically with increasing sulfonate content going from properties characteristic of soft, weak gum rubbers to those of hard, strong thermoplastic elastomers.
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    The relationship between mechanical properties and structure in rolled polypropylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1063-1071 
    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 relationship between mechanical properties and fine structure has been studied in polypropylene rolled both unidirectionally and biaxially (cross rolled). In unidirectionally rolled samples, a complex dependence with cold work is observed with a substantial change being observed at about 50 percent cold work. At 70 percent cold work, the yield strength and tensile strength increase substantially in the roll direction as compared with the starting billet but decrease only slightly in the transverse direction. Above 50 percent cold work, Young's modulus increases rapidly in the roll direction with a smaller increase in the transverse direction. The elongation to freak decreases in the roll direction but increases in the transverse direction. A striking feature is the large increase in ductility due to a small amount of cold work (ca., 10-20 percent). Analogous property changes are observed for cross rolled samples although no significant variation with direction in the sheet was found. The complex property changes are accompanied by complex changes in the molecular orientation as observed by wide angle X-ray pole figures and by changes in the morphology as observed with small angle x-ray scattering. These changes are interpreted in terms of a model incorporating tilting both of lamellae and of chain stems within the lamellae at early stages of rolling followed by breakup of lamellae and molecular rearrangement at later stages.
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    Extrudate swell and extrusion pressure loss of polymer melts flowing through rectangular and trapezoidal dies (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1101-1107 
    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 theoretical and experimental study of pressure losses and extrudate swell of flow through dies with complex crosssections is presented. The range of utility of models based on one-dimensional shearing on pressure loss-extrusion rate behavior is indicated. A procedure to predict extrudate profiles emerging from complex dies is developed. This is based on consideration of the idea of unconstrained elastic recovery from long dies. The theoretical predictions are contrasted with experiments on polystyrene and polypropylene.
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    Rheology of diallyl phthalate polymers below the gel point (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1108-1112 
    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 analysis of molding operations for thermosetting polymers requires information on the reaction rates and rheology of the materials. The purpose of this research was to measure kinetic and rheological data on diallyl phthalate resins and to develop models describing the flow behavior. The rheological data were measured with a mechanical spectrometer equipped with eccentric rotating discs. For the region below the gel point of the polymer, the elastic modulus and viscosity were correlated with molecular weight, temperature and shear rate through fairly simple models. By combining kinetic and rheological correlations, the viscosity of a reacting thermoset can be predicted as a function of time, temperature and shear rate.
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    Residence time distribution in a real single screw extruder (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1194-1202 
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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 residence time distribution in an industrial single screw extruder was investigated experimentally in the case of melt and plasticating extrusion. The investigations performed proved that the extrusion parameters influence strongly the residence time distribution in the extruder. It was found that the resistance to flow through the die-head of the extruder is very important from this point of view, as well as other parameters like rotational speed of the screw and the screw channel depth. Variation of these parameters can change the residence time distribution over a broad range between the extreme idealized cases of plug flow and flow with perfect mixing. In order to obtain quantitative dependences three moduli were used and a correlation equation was obtained. This equation enables an estimation of residence time distribution on the basis of experimental characteristics of the extruder and the actual extrusion parameters.
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    Temperature rise in a thermoplastic under completely reversed bending stresses (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1203-1209 
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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: When a thermoplastic specimen is tested in flexural fatigue, the viscoelastic behavior of the material combines with the heat dissipation mechanism to generate an equilibrium temperature distribution. In order to locate the starting point of an eventual fatigue crack in the most stressed section of a particular geometry, it is important to know where the temperature reaches its maximum value. A first mathematical model has been proposed to evaluate the temperature distribution across the thickness of the specimen. Solutions have been obtained analytically and by a finite difference method. A comparison of the solutions enabled us to optimize the mesh size, the relaxation factor and the convergence criterion in the finite difference scheme in order to get results within a chosen accuracy. Preliminary test results are given and compared with the theoretical temperature distribution for two thermoplastics, nylon 66 and acetal homopolymer.
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    Simulation of cavity filling and curing in reaction injection moldingPresented in part at the First International Conference on Reactive Polymer Processing, pittsburgh, Pennsylvania (October 28-30, 1980) and at the 1981 Spring Meeting of the American Chemical Society, Division of Organic Coatings and Plastics Chemistry, Microsymposium on Fast Polymerization Reaction Injection Molding, Georgia (March 30-April 3, 1981). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1234-1243 
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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 report describes a procedure to stimulate the reaction injection molding process. The analysis considers the conversion that occurs during cavity filling with reactive fluids and the subsequent cure in the mold based on initial conditions derived from the filling analysis. Extensive conversion can occur during cavity filling when highly reactive resins are used. High conversion material with attendant high viscosity can be found in the cavity during filling without flow seizure because the conversion is non-uniform. The overall cycle time can be decreased by promoting conversion during cavity filling as long as flow seizure is avoided. Temperature and conversion profiles during cure in the mold elucidate thermal runaway and its importance in reaction injection molding. The simulation can be used to explore material and process parameter sensitivity, predict the cycle time and the maximum exotherm temperature, and evaluate moldability.
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    Effects of residual stress and orientation on the fatigue of injection molded polysulfone (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1173-1180 
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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 tensile fatigue behavior of unnotched injection molded polysulfone specimens has been investigated. The effects of orientation and residual stress were studied by comparing asmolded specimens with annealed or annealed and quenched specimens with a known residual stress pattern. The treatments are shown to have differing effects at high stresses, where failure is by shear yielding and necking, and at intermediate stresses, where failure is by fatigue crack propagation. The geometries of fatigue cracks are described for each case. An attempt is made to separate the effects of crack and craze initiation from crack propagation, and cyclic loading from cumulative time under load.
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    URL: http://dx.doi.org/10.1002/pen.760211711
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    Non-equilibrium processes in poly(vinyl chloride) glasses vitrified at elevated pressures (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1181-1187 
    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 conformational and enthalpic changes that occur in poly(vinyl chloride) (PVC) glasses that have been vitrified from the melt under pressure have been examined by Fourier transform infrared spectroscopy and quantitative differential scanning calorimetry. It is shown that these pressures freeze in the high energy states that are characteristic of the vitrification temperature and increase the apparent glass transition temperature of the polymer. In addition, pressures in excess of the vitrification pressure, cause intermolecular effects that can be relaxed out below Tg. Both of these processes create characteristic endothermic and exothermic changes in the apparent heat capacity of the glass that appear over a period of time and are sensitive functions of the glass formation processes as well as the subsequent annealing history. The endothermic events are interpreted as the stress perturbed volumetric relaxation process white the exotherms are associated withh the release of the frozen in stresses.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211802
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    Charpy impact fracture testing - a precise measure of ductile-brittle transition in a filled polymeric system (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1228-1233 
    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 fracture toughness of a filled nitrile rubber/phenolic polymeric system was assessed by means of ductile-to-brittle transition temperature (DBTT) as measured by the Charpy impact method to search for sampling location dependencies of toughness in structures. This investigation established the relationship between the Charpy DBTT and exposure to selected relative humidity (RH) for the filled polymer from the three lots. Charpy fracture tests of specimens subjected to a low RH environment (15 percent) had higher DBTTs than their counterparts exposed to a high RH condition (70 to 75 percent). Charpy specimens of this material exhibited a 9 to 22°F change in DBTT which depended upon the manufacturer and the conditioning period for a corresponding change of 60 percent RH. The change in DBTT with relative humidity was found to be reversible; initial fracture behavior could be restored to samples from the low RH (15 percent) station by equilibrating at a high RH (75 percent) level.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211808
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    Flow of carbon black loaded styrene-butadiene (SBR)-cis-polybutadiene blends through capillary dies - influence of mixing and the location of carbon blackBased on a paper presented at the Society of Rheology 50th Annual Meeting in Boston, Massachusetts (October 28-November 1, 1979). (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 294-300 
    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 flow behavior of carbon black loaded styrene-butadiene (SBR)-cis-polybutadiene (BR) is investigated as a function of mixing and the location of carbon black. The blends consist of an 80:20 weight ratio of SBR and BR with the incorporation of 20 phr carbon black via three different schemes to control the location of carbon black in the individual rubber phases. These are: (A) free black mixing of the three components, (B) mixing of SBR-black masterbatch with BR, and (C) mixing of BR-black masterbatch with SBR. Dynamic Mechanical Analysis (DMA) was used to characterize carbon black distribution. The damping characteristics indicate that when carbon black is masterbatched into either one of the rubbers, it continues to remain incorporated in that particular rubber phase upon blending with the second rubber. The flow behavior is measured with an Instron capillary rheometer. The results indicate that the viscosity function of these blends is not sensitive to the mixing conditions. However, the elasticity is always, dependent on mixing. Elasticity is expressed as ΔPe/σ, where ΔPe is the entrance pressure drop from the Bagley plot and σ the shear stress. In general, ΔPe/σ of the blend decreases with increasing mixing.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210507
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760210601
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    Determination of capillary entrance pressure losses and first normal stress difference in polystyrene and high impact polystyrene melts (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 307-311 
    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 industrial polymer processing, polymeric melts give rise to shear stresses above 105 dynes/cm2. For the determination of rheological properties and particularly melt elasticity, only the capillary type instrument is applicable to this range. In this paper, a comparative experimental study of the first normal stress difference, obtained from end pressure losses, entrance pressure losses and die swell is reported for polystyrene and high impact polystyrene. Good agreement between results from the three methods of measurement was obtained. The results are in accordance with literature data obtained using a capillary rheometer. It is seen that the values of first normal stress difference are greater in polystyrene than in high impact polystyrene.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210509
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    Physical aging studies of styrene-butadiene and carbonate-siloxane block copolymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 325-330 
    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 physical aging process in styrene-butadiene and carbonate-siloxane block copolymers has been studied by monitoring the time dependent changes in mechanical and thermal properties. Specifically, stress-strain, stress relaxation and differential scanning calorimetry experiments were utilized. For the styrene-butadiene systems, it was found that the rate of physical aging increases with decreasing glassy content between 50 and 100 percent glass. However, the rate must decrease to zero when the percent glass reaches zero. The occurrence of physical aging was also noted in the carbonatesiloxane block copolymer investigated. The data are discussed in light of the practical ramification of utilizing these block copolymers in material applications.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210603
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    Heat transfer in polymer composites containing thermally active fillers: Mathematical modeling (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 457-460 
    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 heat transfer data recently presented by Migliaresi, et al. are used as the basis for developing two models of the coupled heat transfer-phase transition phenomena in polymeric composites containing thermally active fillers. Both models represent an extension to heat transfer of ideas which have originated in the analysis of mass transfer phenomena in polymeric materials. The second model is able to correlate all the available data within 0.5°C.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210804
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    Rheological characterization of unsaturated polyester resin sheet molding compoundPresented at 35th Annul Conference: SPI Reinforced Plastics/Composites Institute, New Orleans, Louisiana. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 499-506 
    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 presents a theoretical and experimental analysis of the rheological behavior of sheet molding compound (SMC). The work analyses the squeeze flow in a parallel plate plastometer of SMC discs which contain 25 percent of fiber glass by weight. This method of flow characterization gives a good insight into the basic rheological behavior of SMC for the compression molding process when producing flat parts. The theoretical analysis applies to thickened and matured SMC at room temperature. The analysis treats SMC as a viscoelastic material having an equation of state with viscous, elastic and yield elements. The time variation of compressive force when squeezing SMC discs between two parallel plates (one fixed and one mobile) has been derived from the equation of state. The values of the viscous, elastic and yield parameters were determined by using a least squares method of curve fitting to the experimental results. There are two aspects to the reported experimental work. One aspect is concerned with showing that the three element model for the equation of state provides a realistic mathematical basis for characterizing the rheological behavior of SMC at room temperature. The other shows how the parallel plate plastometer can be used to give data which characterize SMC flow behavior under conditions similar to those of the actual compression molding process.
    Additional Material: 16 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210810
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    Sorption and diffusion of alcohols in amorphous polymers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 542-547 
    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 effects of polymer composition and penetrant molecular size on the solubility and diffusivity of alcohol vapors in a series of well characterized isoprene-methyl methacrylate copolymers and their corresponding homopolymers has been investigated at room temperature. The rate of sorption behavior changes progressively from Fickian to non-Fickian, to Case II to “Super Case II” transport with increasing methyl methacrylate (MMA) content in the polymers. The equilibrium solubility of the alcohols increases linearly with increasing penetrant molecular size for polymers which are above their glass transition temperature and decreases for polymers which are below their Tg. The solubility also initially increases as an approximately linear function of MMA content in the copolymers. At about 55 mole percent MMA, the sorbed concentration either levels off or passes through a maximum depending on the size of the penetrant. The apparent “diffusion coefficients” (D) decrease with increasing molecular volume of the penetrants. An exponential dependence was found between these two variables for PMMA. These “diffusion coefficients” also decrease exponentially with increasing MMA content in these polymers. However, at 55 mole percent MMA the copolymer undergoes a rubber to glass transition at the temperature of the experiments. On this basis, it is suggested that the hindered chain segmental motion contributes to the sorption process in addition to strictly thermodynamic considerations. Free volume theory can be used to explain the mechanism of diffusion through the rubbery polymers while the “hole” theory can be applied to explain the transport of the penetrants through the glassy polymers.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210906
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    Dynamic properties of crosslinked epoxy resin at large cyclic and static deformation (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 566-570 
    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: Measurement of dynamic properties of crosslinked epoxy resin have been performed under torsional cyclic deformation with different amplitudes and frequencies and with extensional creep under different loads. It is found in both cases that the dynamic modulus decreases above a certain critical value of deformation. Truncation of the glassy state region and shifting of the transition zone to lower temperatures and higher frequencies have been observed as effects of large amplitude deformation. The maximum reduction in the modulus value and the minimum in the critical amplitude both occur in the region of Tg Shear fatigue of the material has been observed in the glassy state with a frequency- and temperature-dependent fatigue life. It is found that the loss modulus under extensional creep depends upon the values of the deformation and stress whereas the storage modulus depends solely upon the deformation. The ratio of energy expended during static and cyclic deformations is shown to depend only upon the extensional deformation.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760210909
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760211001
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    Effect of thermal aging on impact strength acrylonitrile-butadiene-styrene (ABS) terpolymer (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 571-575 
    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 high speed puncture impact apparatus was used to measure impact loss in thermally aged ABS (acrylonitrilebutadiene-styrene) as a function of time and temperature. Impact energy values decreased to a low level and degraded surface layer thickness increased as a function of aging time at three aging temperatures. Systematic removal of surface layers from thermally aged samples progressively increased impact energy values to control levels. Infrared spectroscopy, differential scanning calorimetry and molecular weight data indicate that degradation occurs in the rubber, graft and rigid phases at different times during the thermal aging period. Microscopy results show a critical degraded layer thickness which causes brittle failure of the entire sample.
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    URL: http://dx.doi.org/10.1002/pen.760210910
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    Effect of long term humid aging on plastics (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 557-565 
    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 warm humidity resistance of more than thirty plastic formulations has been evaluated in a program which aged specimens for periods ranging from 10 months to 3 years. Both thermoset and thermoplastic products were included in this study. All of these materials can be used in high humidity at moderate temperatures for short periods of time except where water absorption lowers the glass transition temperature enough to cause distortion. Several of these commercial products exhibit good long term resistance to humidity at temperatures approaching 100°C. However, some are degraded by long term exposure to warm humidity. This hydrolysis effect can result in useful lifetimes which are considerably shorter than would be expected from projections which are based on conventional dry oven aging tests. This broad data base provides a basis for selecting plastics for use in warm, humid environments.
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    URL: http://dx.doi.org/10.1002/pen.760210908
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    Dimensional variations of two spherical polymeric particles during sintering (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 582-585 
    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 quantitative “Round Neck” (RN) model based upon volume balances and considerations of surface tension phenomena is proposed for simulation of coalescence of two spherical polymeric particles; during sintering. This model and an early model developed by Frenkel are compared and evaluated against experimental data to show their suitability to simulate geometrical variations of a particle pair during sintering.
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    URL: http://dx.doi.org/10.1002/pen.760211003
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    Viscoelastic dissipations in the fracture of glassy polymers near their glass transition temperature (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 577-581 
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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 viscoelastic energy dissipations within the bulk of the test specimen are not taken into account by classical fracture mechanics. In this study it is shown that on approaching the glass transition temperature, the amount of energy dissipated in the bulk of the specimen relative to that required to create two new surfaces can be substantial, and it may be estimated from measurements carried out on specimens with different gauge lengths. Furthermore stress relaxations can take place at the crack tip, even in absence of yielding. These can be sufficiently pronounced to eliminate stress intensification and give rise to constant fracture stress conditions.
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    URL: http://dx.doi.org/10.1002/pen.760211002
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    The effects of processing parameters on the tensile properties of weld lines in injection molded thermoplastics (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 586-593 
    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: Weld or knit lines result wherever two or more polymer flow fronts unite. This results in a region of a different level of molecular entanglements than the bulk material. Consequently, weld regions have been observed to have inferior mechanical properties compared to the bulk. Although this phenomenon occurs in almost all the commercially important polymer processes, there has been little systematic investigation. The effects of melt temperature, mold temperature, injection speed and injection pressure on the tensile properties of commercial grades of polystyrene (GPS), high impact polystyrene (HIPS) and polypropylene (PP) are examined. The most important processing parameters seemed to be melt and mold temperature; injection speed and pressure had little effect on the tensile properties of any of the samples. A higher melt temperature increased both the strain and stress at break considerably in GPS. In HIPS increased melt temperature increased only the elongation to break substantially. Increased mold temperature improved the stress and elongation to break in GPS but not as much as melt temperature. Polypropylene showed improved weld yield strength with increased mold temperature. Under the conditions examined, injection pressure and injection speed showed no effect on the tensile properties of any of the materials investigated.
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    Die drawing: Solid phase drawing of polymers through a converging die (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 612-618 
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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: Die drawing, a new process for the production of oriented thermoplastic rods with an ultrahigh modulus of elasticity, involves drawing an isotropic workpiece through a converging die at temperatures below the polymer melting point. Die drawing of polypropylene is described, but the process is applicable to any polymer which can be drawn by conventional means. The considerable advantages of die drawing compared with conventional tensile drawing and hydrostatic or ram extrusion are discussed.
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    Structural changes in the surface layer of plastic as a result of sliding friction in a metal-thermoplastic system (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 594-602 
    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: Studies on structural changes in the surface layer of plastics during internal sliding friction (friction upon seizing) of metalthermoplastic systems have been carried out. These structural changes were carried out by means of polarized light microscopy, density measurements, X-ray diffraction and IR absorption spectroscopy (ATR). They were carried out for high density polyethylene (HDPE), polypropylene (PP) and nylon 6 (PA6). As a result it was found that the formation of completely different structures was caused by internal sliding friction.
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    The fracture toughness of polypropylene containing poly(ethylene terephthalate) fibers (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 603-611 
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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 polypropylene was increased tenfold by the addition of 30 volume percent of chopped poly(ethylene terephthalate) rovings without any appreciable sacrifice in strength or modulus. The resulting fracture toughness was independent of temperature to -40°C. For maximum effectiveness the rovings must be integrated so that the component filaments cannot disperse during the processing and injection molding stages. The three different methods employed to measure fracture toughness showed good correlation with each other and confirmed the general utility of the Izod test (with slight modification) as a measure of fracture energy. The increased toughness was attributed almost entirely to frictional energy losses during fiber pullout. Polyester fibers can be useful additives for increasing the fracture toughness of brittle resins where processing temperatures do not preclude their use.
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    Viscoelastic behavior of suspensions of particles in polymer solutions (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 619-623 
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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: Suspensions, consisting of glass beads about 1 μm in diameter and a 20 wt percent polystyrene solution in diethyl phthalate, were prepared at concentrations up to 13 vol percent. The viscoelastic properties were measured by means of a conventional dynamic method and by the raised cosine pulse method. The relaxation intensity and relaxation times of suspensions increased with increasing particle concentration. However, at concentrations 〉 13 vol percent, the stress against the raised cosine pulse strain did not approach zero. It was found that concentrated suspensions were complicated by a combination of viscous, elastic, and plastic effects. The experimental results have been qualitatively explained on the base of the network structure of particles.
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    Masthead (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981) 
    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.760211101
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    Environmental stress cracking in impact polystyrene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 624-633 
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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: Environmental stress cracking (ESC) measurements for various impact polystyrenes were performed using a constant load technique with the specimens in contact with a 50/50 solution of cotton seed oil and oleic acid. It was shown that ESC in impact polystyrene is controlled by the transport of the aggressive liquid through a pre-established dry craze structure where capillary pressure is the driving force. At moderate stress levels just above the critical stress for environmental cracking, there is an apparent incubation time for the dry craze formation. The craze incubation time is strongly influenced by thermal stresses induced by the gel particles. As a consequence, ESC is two-stage process involving both an incubation time and actual crack growth. Control of the craze structure to maximize fibril content is essential for good ESC resistance. The craze fibril content can be altered by variables such as gel particle size, matrix molecular weight, plasticizer content, and rubber content.
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    URL: http://dx.doi.org/10.1002/pen.760211009
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    Mitchel C. Shen. 1938-1979 (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 641-642 
    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.760211102
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    The effects of hydrogen on the plasma polymerization of tetrafluoroethylene (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 643-649 
    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 was made of the effects of hydrogen containing additives on the polymerization of tetrafluoroethylene in a radiofrequency low pressure plasma. The addition of ethylene and molecular hydrogen were found, under certain circumstances, to significantly increase the rate of polymer deposition. This effect is ascribed to the release of hydrogen atoms from the additive, which enhance the formation of fluorocarbon-free radicals and scavenges fluorine atoms. ESCA (electron spectroscopy for chemical analysis) spectra of the deposited films show that upon addition of hydrogen to the monomer, the F/C ratio of the film decreases and the H/C ratio rises. Hydrogen addition also influences the extent of crosslinking - a decrease being observed at low discharge power and an increase being observed at high discharge power.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211103
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    The flow of thermosets through the nozzle of an injection molding machine (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 634-640 
    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 conservation equations of momentum, energy, and mass are numerically solved for the flow of thermosets through the nozzle of an injection molding machine. The following working hypotheses are stated: perfect mixing of reactants, validity of the lubrication approximation, steady state (based on previous results for thermoplastic materials), negligible diffusional mass transfer, adiabatic boundary condition, and wall slip. Numerical results for a particular case-show that the value of the slip friction coefficient is very important for defining the process feasibility. The apparent viscosity of the material is also relevant to the process. Materials of low viscosity gel at the wall of the nozzle inlet section; high viscosity materials may gel at the outlet section, requiring great pressure gradients and showing high wall temperatures at the exit. These high temperatures may cause degradation or undesirable side reactions.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211010
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    Plasma polymerization of hexamethyldisiloxane in the gas phase. I. Polymerization studiesThis paper is dedicated to the memory of late Prof. Dr. M. Shen. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 658-661 
    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
    Notes: Hexamethyldisiloxane (HMDS) was r.f. plasma polymerized (PP) in the gas phase by use of a tubular reactor with inner electrodes, at 13.56 MHz. The film obtained under all conditions tested was highly crosslinked and did not oxidize in air after aging. Time dependence of p.p. HMDS deposition, overall deposition rate as a function of monomer flow rate at different power levels, as well as interrelation between deposition rate, monomer flow rate and r.f. power were examined and results are discussed. Infrared spectra of the products obtained at different conditions were similar, excepting for the differences due to crosslink densities and background absorptions.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211105
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    Water vapor resistance of plasma-polymerized coatings on potassium bromide windowsPresented at the Second Chemical Congress of the North American Continent, Las Vegas, Nevada (August 24-29)We came to know Mitch through our mutual interest in moisture protective coatings for infrared windows. Although our acquaintance was short in duration, it was a very fruitful one. His untimely passing shocked us and we hope that our contribution to this symposium proceedings will be a small tribute to Mitch. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 650-657 
    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: Plasma-polyme rized (PP) coatings of chlorotrifluoroethylene (CTFE), tetraluoroethylene (TFE), and ethylene were deposited in a capacitively-coupled 13.56-MHz radio-frequency glow discharge on potassium bromide (KBr) infrared windows for moisture protection. The PPTFE coatings deposited slightly downstream of the internal plasma reactor electrodes provided the best moisture protection for the KBr windows. The PPTFE-coated windows tolerated an upper limit relative humidity of about 80 percent at 297°K without visible damage occurring to either window or coating within 24 h (86.4 ks). It appeared from environmental tests that some of the coatings failed to protect the KBr windows from moisture because of defects in the coatings (pinholes, cracks); others failed because of their high water permeability. Elemental analysis of the bulk and photoelectron spectroscopy (ESCA) of the surface of PPTFE coatings deposited downstream of the electrodes revealed that these samples contained less oxygen (from the atmosphere) than coatings deposited between the electrodes. The lower oxygen content of the coatings deposited downstream may have accounted for the improved moisture resistance of these coatings. The PPTFE coatings were posttreated by heating and by cross-linking with activated species of inert gases (CASING). Neither post-treatment technique was effective in improving the moisture resistance of the PPTFE coatings.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211104
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    Plasma polymerization of hexamethyldisiloxane in the gas phase. II. Formulation of various selected parameters affecting rate of polymerization and their optimization (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 662-663 
    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: Formulation of three selected operational parameters (flow rate of monomer, radio frequency power applied, and reactor tube pressure) affecting rate of polymerization of HMDS by plasma at 13.56 MHz is made by use of rotatable central composite (RCC) statistical design. The flow rate is found to be the most important parameter in determining deposition rate, followed by power and pressure; optimum values of these three to yield maximum deposition rate are also evaluated.
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    URL: http://dx.doi.org/10.1002/pen.760211106
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    Thermal and mechanical properties of linear segmented polyurethanes with butadiene soft segments (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 668-674 
    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 series of segmented polyurethanes based on a hydroxyl terminated polybutadiene soft segment (HTPBD) have been prepared with varying hard segment content between 20 and 60 weight percent. These materials are linear and amorphous and have no potential for hydrogen bonding between the “hard” and “soft” segments. The existence of two-phase morphology was deduced from dynamic mechanical behavior and thermal analysis. Both techniques showed a soft segment glass transition temperature, Tgs, at -56°C and hard segment transitions between 20 and 100°C, depending on the urethane content. The low value of Tg, only 8° higher than the Tg of free HTPBD and independent of hard segment concentration indicated nearly complete phase segregation. Depending on the nature of the continuous and dispersed phases, the urethanes behaved as elastomers below 40 weight percent hard segment or as glasslike materials at higher hard segment contents. The effect of thermal history on transitions of the HTPBDurethanes was also investigated and the results suggest that the absence of hydrogen bonding to the soft segment must account for the extraordinary insensitivity to thermal history in dynamic mechanical, thermal and stress-strain behavior. Comparisons are made to the more common polyurethanes containing polyether and polyester soft segments.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211108
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    Some studies on plasma polymerization of benzene and cyclohexane in the gas phaseI feel really lucky in knowing Mitch since the year of 1964 (Princeton, N.J.), although there was a big ten years gap until we got together for the second time, in Berkeley, California. I feel lucky, because personally I always have learned something from him, from his colorful personality, from his way of approaching problems, and his open mind in science. In addition to his international scientific reputation, he personally had a number of friends abroad, and he was really international in that respect. Three years ago, I remember him being in Ankara to give us a talk. While he was sitting in my room at METU for a rest, he steadily kept looking at a Chinese proverb on the wall, written in Chinese: “When planning for a year, sow corn - when planning for a decade, plant trees - when planning for life, train and educate men”. When I began to think that he liked it, he said, “Thanks for putting that thing over there for me, but please next time be careful not to hang it upside down”. That “thing,” since then has remained in the right position now, like our memories and respects always for Mitch. Dr. Güneri Akovali (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 664-667 
    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 glow discharge polymerization benzene and cyclohexane at 13.56 mHz, and 60 watts, in a plug flow reactor with inner electrodes was studied. Film powder and oily polymeric products were obtained from benzene, and only films were produced from cyclohexane. Polymers produced were analyzed by infrared and their characteristic maps demonstrating the correlation between various physical forms of polymer and reaction conditions were prepared. Excepting oily products, all others are found highly crosslinked and contained free radicals. Contrary to the plasma polymerization (PP) oil of benzene, all others showed no aromatic character.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211107
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    Analysis of the tensile stress-strain behavior of elastomers at constant strain rates. I. Criteria for separability of the time and strain effectsIn 1979, I (S. D. Hong) had the good fortune of working with the late Professor Mitchel Shen, as his research associate, at the University of California in Berkeley. This professional association, though only for one year, proved to be very productive in terms of research accomplishments. We proposed and developed, in collaboration with Dr. David R. Hansen Professor Michael C. Williams, and Professor David S. Soong, the transient network model for modeling the viscoelatic behaviour of entangled polymers. We also studied and published papers, jointly with Professor Richard S. Stein, Dr. Thomas P. Russell, and Mr. C. F. Jasso, on the morphological changes of deformed SBS copolymers and the mechanical behavior of gradient polymer. We cintinued our research corporation until his untimely death.More importantly for myself as my own career was starting, I came to appreciate that Professor Shen was an outstanding scientist as well as a wonderful person. He was always eager to explore new scientific frontiers and he possessed a marvelous intuition for tackling a new problem. He was extremely dedicated and has an intense drive for accomplishment. He was also a person of unique warmth and cheerfulness. He had that certain quality which made it natural and easy for him to provide inspiration, guidance as well as encouragement to his associates. I shall value our professional association, and cherish our personal friendship. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 688-695 
    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: Considering the case where the relaxation time spectrum is preserved at finite deformations, a theoretical analysis of the tensile stress-strain relation of elastomers at constant strain rates has been carried out. The finite strain effect is taken into account by replacing the Cauchy strain by a general strain function, ƒ(∊), in the Boltzmann superposition integral. The analysis shows that there are two cases where the time and strain effects are separable when: (1) the segment of the stress relaxation modulus which coincides with the experimental time of stretching can be represented by a single power law; and (2) the general strain function, ƒ(∊), is linearly proportional to the Cauchy strain. Separability of the time and strain effects, therefore, can be achieved by adjusting the stretching time (or strain) and temperature, if the relaxation time spectrum remains unchanged by the deformation. The tensile stress-strain relations derived from the theoretical analysis were applied to analyze data on a crosslinked styrene butadiene rubber obtained in the temperature range -40 to 60°C. Γ(∊), which describes the strain dependence of tensile stress, B∊, the ratio of isochronal stresses at different strains, and ai, slope of a segment of the relaxation modulus Ei(t) on log t plot, were obtained directly from the experiment. Values of Γ(∊), B∊ and ai obtained at -40°C are quite different from those obtained at -30°C or higher. Results obtained from our analysis are generally in agreement with those obtained by an empirical method for analyzing the experimental data.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211110
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    Poly(n-Butyl acrylate)/polystyrene interpenetrating polymer networks and related materials. II. Aspects of molecular mixing via modulus-temperature studiesWhen I joined Prof. A. V. Tobolsky's laboratory in July, 1965 as a Postdoctoral Research Associate, I had the pleasure of sitting in the exact chair that Mitch had vacated a few days earlier. While the other students in the laboratory told me of mitch's outstanding capabilities, I did not meet him personally until a few years later.Two areas of Mitch's research particularly attracted my attention. The first was his study of the thermodynamics of rubber elesticity, which contributed enormously to our understanding of the front factor and ƒe/ƒ, the internal energy contrubution to the retractive force.Later, Mitch became interested in gradient polymers, or gradient interpernetrating polymer networks. Some of his compositions were amazingly tough plastics. The science of IPN's will surely be hurt by the incomplete nature of these experiments caused his premature death. L. H.S (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 696-702 
    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 glass transition, rubbery modulus, and tensile behavior of poly(n-butyl acrylate)/polystyrene interpenetrating polymer networks (IPN's), semi-1 IPN's, and their corresponding random copolymer networks were studied as a function of both composition ratio and crosslink density. Two temperatures were selected for analysis: 25°C, halfway between the two transition temperatures, and at 160°C., in the rubbery plateau region. The modulus data at 25°C were compared with wellknown composite models. The moduli of the IPN's and semi-1 IPN's lie close to the Davies model in the polymer II rich region but follow the Budiansky model in the polymer I rich region. In one interpretation of the Coran-Patel model, a phase inversion takes place around φ2 = 0.8, which is higher than the composition at which the phase connectivity of polymer II begins to appear, φ = 0.5, via electron microscopy studies. The rubbery modulus behavior of the full and semi-1 IPN's follow the equation of Siegfried, et al. reasonably well, which considers the deformation effect of polymer I in terms of the rubber elasticity front factor.The stress-strain behavior of both the full and semi-1 IPN's was similar to that of toughened plastics at polymer II rich compositions, and to that of reinforced elastomers at polymer I rich compositions.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211111
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    Relaxation of damped debye lattices: Poly(methyl methacrylate)This paper is dedicated to the memory of Mitchel Shen. He was a friend and outstanding scientific colleague. He is sorely missed. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 703-706 
    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 damped Debye lattice model has been helpful in structuring molecular interpretations of viscoelastic relaxation in the primary transition region. Here, this model has been applied to the viscoelastic behavior of plasticized poly(methyl methacrylate) PMMA samples in the primary transition region. More than 25 samples using 11 different plasticizer systems were studied. The steepness indices of these samples remain experimentally indistinguishable from 1.0 inspite of the fact that substantial changes in characteristic temperatures were observed. These results on diluted PMMA lead to the conclusion that intermolecular interactions are dominant in these systems. If this is true, the model clearly predicts that further plasticization will be accompanied by a very distinctive variation of steepness index with plasticizer concentration.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211112
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    Pretransitional effects in the isotropic phase of a lyotropic polymer liquid crystal (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 717-720 
    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: Consolidation of chiral orientational ordering in concentrated solutions of poly(benzylglutamates) has been investigated by polarization microscopy, measurements of birefringence and optical rotatory dispersion. A pretransitional region was examined where the temperature and concentration of polymer are held just below critical conditions for phase separation of anisotropic, liquid crystal spherulites. Optical rotations observed in this visually isotropic region are considerably in excess of those found in dilute solution of the polymer and exhibit a strong temperature dependence. This critical enhancement of optical activity is attributable to short-range chiral ordering of the long axes of macromolecules in the isotropic phase.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/pen.760211115
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    Semi-stiff chain aromatic polyamides: New candidates for thermotropic liquid crystalline polymersWe would like to dedicate this paper to the memory of the late Mitchel Shen. He was a personal friend of the Institute, visited us on numerous occasions here in Lyngby and was our gracious host in California. We think that he would have enjoyed reading this paper about liquid crystalline polymers as it typifies the new areas of polymer science in which he was interested. Mitchel was, however, more than a scientific colleague. He was a good friend and we will remember fondly the pleasant afternoons at the coast north of Copenhagen as well as the exciting evenings in San Francisco. We will miss him. (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 712-716 
    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 spectrum of newly synthesized polyamides have been characterized with the intent of elucidating crystalline and possible liquid crystalline behavior. The different polymers contained various rotatable linkages in the main chain as well as substituent methyl groups in some cases. These were deemed as important variables for controlling the propensity to form ordered morphologies in these polymers. Methods of characterization included: X-ray diffraction analysis, differential scanning calorimetry, and optical birefringence.
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    URL: http://dx.doi.org/10.1002/pen.760211114
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