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  • Articles  (7,592)
  • Chemistry  (7,542)
  • 72.20  (30)
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  • 1985-1989  (6,504)
  • 1950-1954  (1,088)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (7,592)
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  • Articles  (7,592)
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  • 101
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    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 403-403 
    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
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  • 102
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 429-433 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A method for estimating the polymer melt extrudate temperature fluctuation in the single screw extrusion process is proposed. Predictions of the melt temperature fluctuation is feasible if the extrusion process parameters are known. The method is superior to these in the literature because it incorporates effects of the melting process on the temperature fluctuation. The method has been verified experimentally.
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  • 103
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 453-459 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation was undertaken to study the extrusion behavior of composite systems. A compound made up of approximately 50 percent ceramic particulates by volume dispersed in a high molecular weight thermoplastic polymer was characterized by measuring the shear viscosity on an Instron capillary viscometer. The experimental data indicated that the ceramic composite exhibited an apparent yield stress. As a result, an expression that was previously shown to provide flexibility for describing a yield stress at low rates of deformation could explain the viscosity of the ceramic composite. The expression was then applied to the flow analysis of both a “rod” and a “slit” die in an extrusion process, and the derived equations adequately correlated experimental volumetric flow rate us. Pressure drop data obtained on a laboratory extruder.
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  • 104
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 485-490 
    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 model for the molding by reactive injection of reinforced plastics for systems in which fiber glass reinforcements are placed into the molds, is proposed. It allows for the determination of processing parameters and their influence on dependent variables: conversion, temperature, and pressure. Moldability areas, where premature gelling is avoided, are defined. Operating conditions are selected to reduce cycle time, produce small load losses, and provide a fairly uniform curing stage throughout the product.
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  • 105
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 510-516 
    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: For linear copolymer molecules, the refractive index increment depends on the chemical composition of the molecules. However, the polydispersity in chemical composition of the sample introduces a great complexity in the data analysis in order to obtain a true molecular weight distribution. Even when the mean chemical composition does not depend on the molecular weight, a correction has to be applied when the output of an instrument depends quadratically on the refractive index Increment of the sample, such as in a light-scattering measurement. For that purpose, the light-scattering expressions are written in terms of polydispersity in chemical composition, which in turn is modeled using linear copolymerization equations. The microstructure effects, which are related to the order in which two different kinds of monomers appear along the chain, are not as yet taken into account in this approach.
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  • 106
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 506-509 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this work, creep induced buckling was studied for a number of thermoplastic materials. The effect was observed by monitoring top displacements of thermoplastic bars as a function of time under static loading conditions. The recorded times to failure were averaged and correlated with the applied loads. The experiments, conducted for different materials, established an exponential dependence between the critical time and the load. The evolution of the buckling eigenvalues was modeled numerically. The simulations of eccentric columns behavior under compressive loads were coupled with the eigenvalue analyses. The correlation of the time-load predictions obtained from the numerical simulations followed the experimental results within acceptable limits. The observed phenomenon of creep induced buckling was explained by damage accumulation leading to an effective reduction of the load carrying capability.
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  • 107
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 334-338 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: As a result of increased interest from industry in using dielectric cure monitoring, a need has arisen for simplifying frequency, cure, and temperature dependent data so that control decisions can be readily made. Techniques utilizing data covering several decades of frequency now exist for separating ionic conduction levels from dipole and electrode polarization responses. Ionic conduction levels are particularly useful since they can be correlated to both viscosity and extent of cure. In addition to being a function of extent of cure, dielectric properties are also influenced by temperature. This dependence often makes the dielectric response more difficult to interpret. This paper investigates two methods for overcoming the temperature dependence of the dielectric response during nonisothermal cure. The first method utilizes recent WLF modeling techniques and extends them with the end result of extracting Tg in real time during cure. The second technique involves measuring the temperature dependence of uncured and cured material. Utilizing the correlation between log ionic conductivity and extent of cure, which has been noted by previous researchers, the normalized conductivity can be converted to a cure index. Several examples including epoxy, polyurethane, and a UV cured photoresist are presented, showing data before normalization and after both Tg and cure index determination.
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  • 108
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 359-365 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(ethylene terephthalate) (PET) and bisphenol-a-polycarbonate (PC) are known to form a miscible blend whereas ternary blends of PET, PC, and polypropylene (PP) form two phases. This is based on the considerations of various chemical events which may occur in these systems. The role of ester-carbonate interchange reactions during melt mixing and fabricating is found to be unimportant. Differential scanning calorimetric analysis of the ternary blends shows that there appears to occur an exothermic transition in the heating mode of the instrument. This exothermic event was found to be suppressed considerably by incorporating suitable additives into the system. Degradation reactions studied by thermogravimetric analysis and a dilute solution viscometric technique reveal that there exists some kind of interaction among the components even with the immiscible PP component.
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  • 109
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 397-404 
    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: Interpenetrating polymer networks of polyurethane and unsaturated polyester were prepared by reaction injection molding (RIM) and transfer molding. The structures of the molded samples were analyzed by electron microscopy and dynamic mechanical analysis. It was found that polymer morphology and dynamic mechanical properties depend strongly on the molding temperature, reaction rate and reaction sequence. Simplified structure models based on Takayanagi's model and sample morphology can predict the storage modulus reasonably well but not the tanδ.
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  • 110
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 432-432 
    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
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  • 111
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 448-455 
    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 plasticating or melting behavior of polymer pellets sliding on a hot metal surface was investigated. An analytical model was developed for predicting the melting rate and the shear stress of an incompletely compacted solid bed of pellets in terms of the rheological and thermodynamic properties of the polymer, the pellet size, the degree of compaction, and the operating conditions. This investigation extends the results of the previous investigators obtained for a fully compacted solid bed of polymers to an incompletely compacted solid bed of polymers, closely representing the initial stage of the plasticating mechanism inside a screw extruder. Experimental verification of the analytical model developed here was made by testing six different commercial polymers.
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  • 112
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 456-462 
    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: Vitrification occurs during the reaction injection molding (RIM) of epoxy resin, and the curing reaction rate is reduced as the Tg of the reacting mixture exceeds or approaches the local reaction temperature inside the mold cavity. The effect will be manifested in the distribution of the glass transition temperature across the thickness direction of the molded product. The reaction kinetic equation which includes the vitrification term in the form of the WLF equation is used in the computer simulation of the epoxy RIM process and the effect of the vitrification is shown by comparing with models with no vitrification considerations.
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  • 113
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 479-487 
    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 performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature.The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi-channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.
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  • 114
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 505-512 
    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 impact fracture energy (Gc) for a polypropylene homopolymer and a copolymer with and without calcium carbonate fillers was measured over a range of temperatures between -40°C and 40°C using fracture mechanics principles. The fillers studied were Omyacarb (∼2.7 μm) and Winnofil (∼75 nm) and 10% by weight was added to the matrix material. These fillers did not have any appreciable effect on Gc of the copolymer-based composites. However, the Omyacarb fillers improved Gc of the homopolymer at low temperatures (≤20°C) due to enhanced microplastic flow as observed on the fracture surfaces. The fillers increased the stiffness of both the homopolymer and copolymer. It would appear that up to 10% of cheap calcium carbonate fillers could be added to the more expensive polypropylene to reduce the production cost without any significant loss of impact fracture energy.
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  • 115
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 499-504 
    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 novel sliding plate rheometer has been developed that is suitable for use with molten plastics, concentrated polymer solutions, raw elastomers, and other viscoelastic or thixotropic materials. It can generate steady shear rates from 0.05 to 500 s-1 and can also be used to measure linear viscoelastic properties. In addition, it can be used to measure a broad spectrum of nonlinear viscoelastic properties such as the nonlinear relaxation modulus and the shear stress growth coefficient. In order to measure these nonlinear properties it is necessary to generate large, uniform, transient deformations Involving high strain rates. Rotational and capillary melt rheometers are not capable of generating this type of deformation, and until now it was not convenient to use sliding plate rheometers for this type of application. However, the recent development of a reliable and robust shear stress transducer makes it very convenient to use the sliding plate geometry to carry out all of these tests. The new rheometer is described, and examples of the types of data it can generate are shown.
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  • 116
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 308-314 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: During the sheet molding compound (SMC) compression molding process, a premeasured polymer charge is placed between the heated halves of a mold which are then brought together to squeeze the polymer and fill the mold, after which pressure is maintained while the part cures. The cure stage constitutes the larger part of the molding cycle and thus affords the largest potential for cycle time reduction. In general, cure times in SMC processing are set longer than necessary, since the inherent material and process variation make it difficult to predict cure times with more than 10 to 20% accuracy. Accurate methods to detect the end of cure would be very beneficial and would permit opening the mold as soon as the material has cured, avoiding unnecessary waste of time. In this paper, several techniques that show promise for monitoring the state of cure are reviewed and experimental results given. Their relative advantages and accuracies are compared. In particular, the use of linear variable displacement transducers, pressure transducers, and thermocouples is discussed. We also show how the measurements compare to theoretical predictions of the state of cure.
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  • 117
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 339-346 
    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 parallel-plate test fixture on a Rheometrics viscometer was electrically isolated so that the rheological and dielectric properties of a thermoset polymer system could be simultaneously measured. This enabled the relationship between the dielectric properties and the rheological properties to be directly examined. A close relationship was established between the dielectric properties (dipole relaxation time and specific conductivity) and the pre-gelation bulk viscosity. This relationship suggested that models similar in form to those used to describe the change in viscosity might be used to describe the changing dielectric properties. The limitations and advantages of two such models, which attempt to describe the time-temperature behavior of the dielectric properties, were then tested for use with a typical aerospace epoxy resin system.
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  • 118
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989) 
    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
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  • 119
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 586-592 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We investigated the miscibility of polybutadienes with butadiene-styrene copolymers of varying styrene content. The methods of optical microscopy, differential scanning calorimetry, and small angle light scattering (SALS) were used. All polymers/copolymers used in this study have equivalent butadiene microstructures. Copolymers with high styrene levels are immiscible with polybutadiene. The tendency to miscibility increases with decreasing styrene content. An upper critical solution temperature is observed with the 23 percent styrene copolymer.
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  • 120
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 405-414 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Poly(ether-ether-ketone) (PEEK) is a newly developed engineering thermoplastic with potentially vast application in advanced composites due to its exceptional performance. It is thus desired to understand the relationship between physical processing, microstructure and fracture in this semicrystalline polymer. Both oriented and unoriented PEEK were mechanically characterized using static test of three-point bend specimens. The molecular chain orientation was imposed using a rolltrusion technique. The effects of thickness, strain rate, Initial crack length ratio, and orientation on fracture toughness (Kc) are investigated. The crystallinity is also examined by density measurement. The degree of orientation is determined qualitatively by wide-angle X-ray scattering diffraction patterns and quantitatively by further measurement using an image analysis system. Fractographic analysis, using scanning electron microscopy, provides precise information about the mode of fracture, Results indicate that both the modulus and the fracture toughness are remarkedly increased in the direction of drawing (T-type) as opposed to the transverse direction (L-type).
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  • 121
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 420-425 
    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: Herein is more detail to microscopic aspects of electron transport through a conductor-filled polymer than has yet been considered in the literature (irrespective of quantum mechanical tunneling and thermal expansion). Some of these details only clarify earlier theories, but others lead to new discoveries such as the cubic conduction path coordination number z = 18 (contrasted with the classical geometric coordination number of z = 6). New also are simplified derivations of the high and low fill asymptotes of the master equation for conductance as a function of fill fraction in the effective medium theory of conductor-filled polymers.
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  • 122
    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: Several recent calculations of the stress field around crazes in glassy polymers have been based on experimentally obtained craze opening displacements. Although various techniques for performing these calculations have been presented (i.e., Fourier transform, boundary integral, and finite element methods), all are based on the solution of the same ill-conditioned boundary value problem. Specific boundary conditions required to calculate the stresses around a craze lead to a large change in the stress field with small changes in the craze profile which are within the reported experimental tolerance.
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  • 123
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    Polymer Engineering and Science 29 (1989), S. 433-440 
    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 of Newtonian and non-Newtonian fluids which obeys a power law relationship between shear stress and shear rate has been modeled in the melt conveying section of a self-wiping co-rotating twin-screw extruder using a finite element analysis of an unwound channel section. Predictions of throughput against pressure gradient are compared with experimentally obtained results for maize grits which is represented as a power law material. Rheological data applicable to extrusion simulation were obtained from capillary rheometry. Comparisons are reasonable with predicted characteristic showing similar behavior.
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  • 124
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    Polymer Engineering and Science 28 (1988), S. 1042-1045 
    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: Over the last four decades, numerous reports have appeared on the physico-chemical kinetics, especially crystallization kinetics, based on the Avrami equation, φ = exp [-Ktn] where φ is the fraction of material unchanged at time t, K is an overall rate constant and “n” is the Avrami exponent indicative of process mechanism. The usage of the Avrami equation has been limited to the determination of “n” and its temperature dependence. It is shown that the evaluation of K and the activation energy (E) using this equation is erroneous since K and E are both influenced by “n” although such would be unexpected from the Avrami equation. On the other hand, if one uses a modified expression, φ = exp[-Kt]n, then in addition to the value of “n”, correct values of K and E are obtained. This retains the original correspondence of the Avrami equation to nuclea-tion and crystal growth processes but extends its applicability to (i) correctly evaluate K and E parameters, and (ii) correctly compare transformation rates when the systems differ in their n values. Experimental data are presented to support these conclusions.
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  • 125
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    Polymer Engineering and Science 28 (1988), S. 1071-1075 
    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: Thermosetting resin/glass cloth composites find extensive use in the packaging of electrical circuits into multi-layered circuit boards. To determine optimum processing conditions, it is necessary to understand the rheology of the resin as it cures. In this study, a squeezing flow geometry was used to determine the shear viscosity of a high performance epoxy resin during cure; Viscosity profiles were obtained during rising temperature cure. The results were compared with the complex viscosities obtained using the dynamic oscillatory parallel plate geometry. A numerical optimization algorithm was used to obtain the dual Arrhenius viscosity model parameters from the experimental viscosity data. The sensitivities of the model parameters and their effects on the predicted viscosity profiles were also determined.
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  • 126
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    Polymer Engineering and Science 28 (1988) 
    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
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  • 127
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    Polymer Engineering and Science 28 (1988), S. 1107-1114 
    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: Rheological and spiral mold flow measurements were made on blends of a chlorinated poly (vinyl chloride) (CPVC) compound and a thermotropic liquid crystalline copolyester of p-hydroxybenzoic acid/poly (ethylene terephthalate) (60/40), hereafter referred to as LCC, at 210°C. Several interesting flow phenomena have been observed. While the shape of the flow curve (i.e., G′ vs. ω; G″ vs. ω) of LCC is solidlike, those of the blends are pseudoplastic. The dynamic viscosity of the blends increases as the concentration of LCC increases. However, the shear viscosity of the blends is reduced with LCC and may be described using the relationship of additivity of fluidity. Although the melt elasticity of the blends is increased with the concentration of LCC, the extrudate swell of the blends after extrusion from a capillary is decreased. This phenomenon, however, is complicated. A Theological analysis based on an idealized runner system is used to describe the spiral flow length as a function of the Theological properties of the molten polymers and also the operating conditions. The relative improvement of the spiral flow length of the CPVC compound due to blending with LCC could be correlated with the power-law fluid model at high shear rates.
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  • 128
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The emulsifying activity of a poly(hydrogenated butadiene-b-methyl methacrylate) (HPB-b-PMMA) copolymer is investigated in incompatible blends of a low density polyethylene and poly(styrene-co-acrylonitrile) resins (mainly ABS) prepared in the melt state on a two-roll mill. Optical and scanning electron microscopy observations clearly demonstrate that a moderate amount of copolymer (5 wt %) very significantly decreases the particle size and enhances interfacial adhesion. The block copolymer is also responsible for a strong improvement in both the ductility and Charpy impact resistance of PE/ABS blends.
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  • 129
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    Polymer Engineering and Science 29 (1989), S. 564-572 
    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: To improve the powder processing behavior of ultrahigh-molecular-weight polyethylene, a conductive iron filler was distributed within the polymer in a segregated network. The filler level was kept at a minimum of 10 volume percent, which was sufficient to coat completely all the polymer particle surfaces. This filler level was low enough to avoid modifying the resin properties to a significant extent. Compaction of these filled samples showed a slower densification, under pressure, similar level of final densification at 80% densification parameter, and a doubling of plateau pressure value to 200 MPa in comparison with the unfilled polymer. The filler was found to reduce drastically the postcompaction relaxation time from 24 h to 6 h. The magnitude of the axial (compaction direction) relaxation was unchanged, but the radial relaxation was one quarter of that for the unfilled polymer. Sintering behavior showed improved densification because of lower dimensional changes during sintering resulting in 80% relative sintered density, higher than the 75% percent value for the unfilled polymer, but yielded a 20% lower sintered strength, An alternative process of rapid sintering by induction heating was explored, its feasibility demonstrated, and a recommendation is made to make powder processing of this polymer commercially attractive.
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  • 130
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    Polymer Engineering and Science 29 (1989), S. 874-877 
    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 application of X-Ray lithography in mass production of devices is only economically viable if resist materials of highest sensitivity can be provided. Chemical amplification is the key concept to achieve such performance. It is outlined for a highly sensitive three component positive tone X-Ray resist, consisting of a Novolak binder matrix, a starter compound, which - on X-Ray exposure - yields an acid, which catalytically decomposes a dissolution inhibitor. Resist performance is discussed in terms of reaction kinetics and their implications on resist response, simulation, and handling procedures.
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    Polymer Engineering and Science 29 (1989) 
    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
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  • 132
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    Polymer Engineering and Science 29 (1989), S. 898-901 
    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: Many styrylpyridinium compounds (SPC), which are very stable in the dark, were prepared and evaluated as photobleachable dyes for contrast enhanced lithography (CEL). The photobleaching characteristics of water-soluble contrast enhancing materials composed of SPC and water-soluble polymer depend on the structure of the SPC and the kind of polymers used. The technique using SPC-based CEL proved to be very effective for the resist pattern profiles.
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  • 133
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    Polymer Engineering and Science 29 (1989), S. 916-919 
    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: Dissolution inhibition mechanisms of naphthoquinone diazides in novolak based positive photoresists were investigated from three different aspects: • Dipolar interaction.• Interfacial chemical reactions.• Chemical structures of naphthoquinone diazides.The results suggest that there exists a hydrogen bonding interaction between the compounds with the matrix novolak resin and that naphthoquinone diazides would crosslink the resin in contact with an alkaline developer, both of which contribute to dissolution inhibition mechanisms. However, there seems to exist another dissolution inhibition mechanism; namely, 1,2-naphthoquinone diazide does not inhibit dissolution of the matrix novolak resin at all while a clear dissolution inhibition effect Is observed for its derivatives containing sulfonyl groups. In the present paper, three dissolution inhibition mechanisms of naphthoquinone diazides will be proposed.
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  • 134
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    Polymer Engineering and Science 29 (1989), S. 625-631 
    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 commercial liquid crystalline polymer (LCP) sample was characterized both in shear and in nonisothermal elongational flow over a wide range of temperatures (240-350°C). The LCP sample employed was a copolyesteramide of 2,6 hydroxynaphthoic acid, terephthalic acid, and aminophenol manufactured by Celanese and commercially known as Vectra B950. The viscosity decreases dramatically at temperatures above the crystal-nematic transition of the polymer. At lower temperatures, the extrusion of the sample is mainly due to plastic flow. Die-swell values are very small and contraction of the extrudate is also revealed, but the sample shows high elasticity. The polymer is not spinnable at very low temperatures, and the melt strength rapidly decreases with increasing temperature.
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  • 135
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    Polymer Engineering and Science 29 (1989), S. 639-644 
    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: Calculation of gas permeation in food packaging structures can be done using a steady-state analysis employing the permeability coefficient. While this approach is adequate for some applications, for many others a time-dependent transport analysis must be considered to make quantitative predictions of shelf life. The limitation of the simple permeability analysis for multilayer structures is illustrated for Saran-coated polycarbonate and poly(ethylene terephthalate) soda cans. These more detailed calculations on package structures can be done using standard computer library routines to include both the effect of gas sorption and diffusion.
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  • 136
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    Polymer Engineering and Science 28 (1988), S. 1355-1361 
    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: Several authors have suggested a monotonic variation of the glass transition temperature (Tg) of miscible polymer blends as a function of composition. They usually express the results in terms of equations proposed by Couchman-Karasz, Gordon-Taylor, Fox, and several others. However, we have noticed that numerous systems exhibit a cusp when Tg is plotted as a function of composition (after correction for the presence of crystallinity when semi-crystalline polymers are involved). This cusp cannot appear when the Tg's of the two homopolymers involved are separated by less than about 52 degrees., It will be shown that this observation is quite general since it has been observed with several polyester/chlorinated polymer blends, polycaprolactone/nitrocellulose blends, and polystyrene/poly(vinylmethylether) blends; It will also be shown that this behavior is predicted in the framework of the free volume theory, with equations derived by Kovacs. According to this theory, above a critical concentration φc (relative to the plasticizer) and below a critical temperature Tc, the high-Tc, polymer no longer contributes to the free volume of the mixture whereas it does above Tc. This difference leads to a Tg-composition variation which has to be expressed by two different equations, one below Tc and the other above Tc, the cusp defining the limit of applicability of each equation.
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    Polymer Engineering and Science 28 (1988), S. 1401-1404 
    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: There is a reciprocal relation between flow and structure in multiphase systems such as polymer blends or composites. For this reason characterization of these materials must be carried out under conditions which guarantee minimum modification of structure. Capillary rheometry is particularly ill suited as a test tool, but the small strain dynamic oscillatory method may provide the true material responses, Most frequently these are expressed as frequency, ω, dependent storage and loss shear moduli, G′ and G″, or real and imaginary viscosities, η′ = G″/ω and η″ = G′/ω. However, two other methods of data presentation seem to be more sensitive to melt structure. They are the Cole-Cole plot of η″ vs. η′ and the relaxation spectrum. Frequently, both of them indicate a binomial response. Various mechanisms leading to such behavior will be discussed.
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    Polymer Engineering and Science 28 (1988), S. 1416-1426 
    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 morphology of compatibilized polyolef in/polyamide blends was found to be significantly dependent on the concentration of an ionomer compatibilizer (polyethylene-methacrylic acid-isobutyl acrylate terpolymer) in the blend. For a dispersed phase content of 10% by weight, a maximum reduction in phase size was observed when only 0.5% by weight of ionomer was added to the blend, A more significant reduction of the dispersed phase size was observed when the minor phase was nylon, due to interactions which exist between the ionomer and the polyamide. These interactions have been confirmed by Fourier transform infrared spectroscopy. At high concentrations of the ionomer, flocculation of the nylon dispersed phase was observed. In comparison to one-step mixing, blends prepared by two-step or batch mixing were characterized by a smaller dispersed phase when nylon was the matrix, and a larger particle size when nylon was the minor phase. The results observed are explained in terms of a speculative model of the interactions occurring across the nylon-polvolefin interface.
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    Polymer Engineering and Science 28 (1988), S. 1445-1449 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: It is shown that polyethylene and crossllnked polyethylene resins used for cable applications contain an antioxidant synergist in addition to an antioxidant. Their nature and content have been determined by a combination of ultraviolet and Fourier transform infrared spectroscopy and neutron activation analysis measurements. The results thus obtained suggest that part of the antioxidant compound is grafted to polymer chains during crosslinking.
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  • 140
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    Polymer Engineering and Science 28 (1988), S. 1455-1461 
    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 Cryogenically Ground Rubber (CGR) from old tires on some mechanical properties of an unsaturated polyester resin is presented. A delay in the free radical cure reaction of the unsaturated polyester resin was observed upon the addition of ground rubber. This delay in the cure reaction could be overcome with the further addition of the free radical initiator. The particle size, surface chemistry, and the chemical composition of the rubber had an effect on the cure and on the final properties of the rubber-filled composites. It was also found that the rubber particles decreased the tensile, flexural, and storage shear modulus of the unsaturated polyester. Composites made from silane-treated ground rubber showed better mechanical properties than composites made from untreated CGR. Finally, the particle size of the ground rubber was apparently too large to produce a toughening effect on the filled materials.
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    Polymer Engineering and Science 29 (1989), S. 1097-1102 
    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: Nonisothermal differential scanning calorimetry (DSC) measurements were used to estimate the kinetic parameters for the curing reaction of a commercial unsaturated polyester resin. The reaction rate expression was derived from a mechanistic kinetic model based on the concept of free radical polymerization, accounting also for the diffusion controlled reaction. The total heat of reaction was evaluated in experiments run at very low scan speeds and using high amount of initiator. The kinetic parameters were found to show no dependency on the heating rate nor on the initiator concentration. Dynamic DSC measurements provide reliable kinetic data over a broad range of temperatures that is mostly significant for process simulations.
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    Polymer Engineering and Science 29 (1989), S. 1103-1106 
    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 solid state hydrolysis of a copolyester based on a mixture of 1,4-cyclohexanedimethanol and ethylene glycol condensed with terephthalic acid was studied at 100°C and 57 to 96 kPa water vapor partial pressure (55% to 95% relative humidity). The equilibrium water sorption in weight percent (C∞) was found to be \documentclass{article}\pagestyle{empty}\begin{document}$$ C_\infty = 1.45 \times \,10^{ - 5} (P_{H_2 O} )^{1.2} $$\end{document} where PH2O is the water vapor partial pressure in kPa. For specimens 0.32-cm thick, it took about 24 h to reach 0.9C∞. The intrinsic viscosity (IV) was measured and used to calculate the relative change in molecular weight (M̄w) from the relationship IV ∝ (M̄w)0.7. The decrease in molecular weight was linear with time, and the rate of decrease was found to be proportional to C∞; the empirical correlation is \documentclass{article}\pagestyle{empty}\begin{document}$$ k = 0.026 \times C_\infty $$\end{document} where the rate constant, k, is in day-1. A decrease of 50% in M̄w was observed after 22 days at 95% relative humidity.
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    Polymer Engineering and Science 29 (1989) 
    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
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    Polymer Engineering and Science 28 (1988), S. 1517-1526 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We describe the computer-aided engineering analysis of a linearly tapered coat-hanger die in this paper. The general governing equation for flow distribution inside the die was derived first. On the basis of this equation, we have developed the design formula for a die to deliver uniform flow. In addition, we have also examined the variations of lateral flow uniformities and residence time distributions of polymeric liquids under several different design and operating conditions: (1) using manifolds with non-circular cross-sections, (2) adjusting production widths, (3) delivering fluids with different viscosities, and (4) enlarging manifolds for practical production considerations.
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    Polymer Engineering and Science 28 (1988), S. 1559-1564 
    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 pressure drop/flow rate equation for non-Newtonian fluid flow in channels of irregular cross-section is determined theoretically by two numerical methods. Two representative non-Newtonian fluid models, the Ellis and the Herschel-Bulkley models, have been studied for several commonly encountered non-circular channels. The empirical methods proposed by Kozicki, et al, and Miller have been analyzed. The validity of their methods is discussed.
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    Polymer Engineering and Science 29 (1989), S. 887-890 
    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 positive-working photosensitive system of silicon polymer, containing silylether groups in the main chain and a photo-induced acid precursor was investigated. The silicon polymer is hydrolized by a photogenerated acid and degraded to low molecular weight compounds. Thus the effect of solubility inhibition of the polymer is diminished. The higher photosensitivity of this system as compared with 1,2-quinone diazide compounds is due to the catalytic reaction of the acid on the hydrolysis of the silicon polymer. The chemical structure around silylether groups in the polymer, in particular more hydrophilic and less steric structures, affects the rate of hydrolysis and thus the photosensitivity. Among various types of photo-induced acid precursors examined, e.g., s-triazine and 1,3,4-oxadiazole compounds substituted by trihalomethyl groups were effective.
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    Polymer Engineering and Science 28 (1988), S. 1600-1606 
    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 observation of a novel phenomenon is reported whereby the processing history of a nylon 6 leads to a memory effect which in turn affects its crystallization rate from the molten state. Differential scanning calorimetry (DSC) and optical microscopy are the primary techniques used to demonstrate that the melt-crystallization behavior of nylon 6 can be controlled by processing variables. Characterization data is presented to show that obvious parameters such as molecular weight, impurities, monomer and oligomers, etc. are not responsible for the observed changes in crystallization behavior upon processing. It is shown that the mechanical properties and/or morphology of a nylon 6 article can depend upon the processing technique (e.g., compression or injection molding) as well as the processing history of the nylon 6 resin itself.
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  • 148
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    Polymer Engineering and Science 28 (1988), S. 1616-1627 
    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: Bubble nucleation in a mixture of volatile liquid and polymer melt under shear flow conditions was investigated, using a light scattering technique. In the study, a mixture of polystyrene and trichlorofluoromethane was extruded through a slit die having glass windows and bubble nucleation in the flow channel was observed optically. A He-Ne laser was used to illuminate the nucleating and growing bubbles. The light flux scattered by the growing bubbles at a fixed angle was detected by a photomultiplier with the aid of a high-voltage power supply. The bubble nucleating site in the flow channel was located using a computer controlled tracking system, which was designed to move the entire optical system automatically in the three dimensional space, and also had the ability to follow the software control command and cooperate with the data acquisition system. When the site of bubble nucleation was located, the coordinates of this site in the flow channel and the experimental conditions were automatically recorded on a floppy diskette by entering a software command. The pressure profile along the flow channel was measured by pressure transducers, with the aid of a microprocessor-based pressure reading system. It has been found that the site of bubble nucleation varies with the position in the direction perpendicular to the flow direction, which is attributed to the nonuniform velocity and stress distributions in the slit flow channel. The present investigation suggests that bubble nucleation can be induced either by flow and/or shear stress; specifically, flow-induced bubble nucleation is the dominant mechanism at positions near the center of the die opening, and shear-induced bubble nucleation is the dominant mechanism at positions near the die wall. It should be mentioned that the bubble near the die wall may also be generated by cavitation brought about by the surface roughness of the wall and also by thermal fluctuations due to the heat transfer between the metal (die wall) and the mixture of polymer and volatile component. The present study indicates that bubble nucleation in a shear flow field can occur at an unsaturated condition. This is in contrast to bubble nucleation under static conditions, where supersaturation is necessary.
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  • 149
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    Notes: A finite element technique has been developed for coupled reaction and heat transfer analysis in which mass diffusion is negligible. The temperature unknowns are located at nodal points, while the reaction variables (species concentrations, reaction rates) are at the Gauss points in each element. With a mechanistic kinetic model, the SMC (sheet molding compound) cure in 2-D and 3-D geometries was analyzed. The results for plate-and-rib configurations show the progression of cure and heat transfer and the influence of geometry on the progression. The analysis for a flat sheet of SMC in a mold with localized heating using bubblers indicates the thermal interaction between the mold and the curing SMC. Temperature and reaction profiles are given for each case.
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    Polymer Engineering and Science 29 (1989), S. 1309-1309 
    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
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    Polymer Engineering and Science 29 (1989), S. 1340-1367 
    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 of strength development at polymer-polymer interfaces are examined and applications to welding of similar and dissimilar polymers are considered. The fracture properties of the weld, namely, fracture stress, σ, fracture energy, GIc, fatigue crack propagation rate da/dN, and microscopic aspects of the deformation process are determined using compact tension, wedge cleavage, and double cantilever beam healing experiments. The mechanical properties are related to the structure of the interface via microscopic deformation mechanisms involving disentanglement and bond rupture. The time dependent structure of the welding interface is determined in terms of the molecular dynamics of the polymer chains, the chemical compatibility, and the fractal nature of diffuse interfaces. Several experimental methods are used to probe the weld structure and compare with theoretical scaling laws, Results are given for symmetric amorphous welds, incompatible and compatible asymmetric amorphous welds, incompatible semicrystalline and polymer-metal welds. The relevance of interface healing studies to thermal, friction, solvent and ultrasonic welds is discussed.
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    Polymer Engineering and Science 29 (1989), S. 1387-1395 
    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 integrity of a pipeline system is determined by its weakest links. Joints may be such places. Heat fusion is the most common joining method for distribution gas piping. There are procedural, thermal, and mechanical aspects of making fusion joints. Procedural aspects, such as heater calibration and cleanliness, can be assured only by rigorous training and certification of the operators. Thermal and mechanical aspects consist of specifying joining conditions such as the heater temperature, heating time, and joining pressure. In the absence of procedural errors, the strength of a fusion joint should depend on the pipe material, pipe dimensions, and the thermal and mechanical joining conditions.The measured parameters that are measures of strength are impact energy and location of failure in the tensile impact test. A parameter, termed the joining parameter, was found to characterize the joining conditions. This parameter is a function of bead volume, melt volume at the end of the heating phase, and pipe wall thickness. Of the mechanical test parameters, the impact energy was found to correlate best with the joining parameter.
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    Polymer Engineering and Science 29 (1989), S. 1413-1418 
    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 variety of thermoplastic fully imidized poly(imide siloxane) segmented copolymers with useful thermal and mechanical properties have been prepared. Other interesting properties described are the materials' hydrophobic character, surface domination, UV stability, and atomic oxygen plasma resistance.
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  • 154
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    Polymer Engineering and Science 29 (1989), S. 1446-1455 
    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 study deals with the cold compaction of polyether-etherketone (PEEK) and nickel powder blends. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were utilized for this investigation. These PEEK powders included fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P). Each of the four different PEEK powders were blended with about 10 vol-% nickel powder (Novamet) using a dry mixing technique. These PEEK/nickel powder blends were then successfully compacted at room temperature. Green strengths as high as 39.5 MPa and 26.3 MPa were measured on nickel filled 150 grade and 450 grade compacts, respectively. The higher strength values of the nickel filled compacts compared to their respective unfilled ones were attributed to a higher degree of mechanical interlocking and plastic deformation, which was induced in the polymer particles during compaction by the hard nickel filler. These composites also exhibited lower viscoelastic recoveries than their respective unfilled compacts. Electrical resistivities as low as 0.06 ohm-cm were achieved by compacting 150P/nickel powder blends. This resistivity value agreed well with the calculated value predicted from the literature.
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  • 155
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    Polymer Engineering and Science 29 (1989), S. 1456-1465 
    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 study deals with the characterization and cold compaction of polyetheretherketone (PEEK) powders. Four different types of PEEK powders which are commercially available from Imperial Chemical Industries (ICI) were characterized for density, crystallinity, particle size, particle size distribution, and particle morphology. Fine and coarse size powders of a low viscosity grade (150PF and 150P) and similar powders of a high viscosity grade (450PF and 450P) were processed. Compaction was successful at room temperature using the 150 grade powders but not with the 450 grade powders. Compressibility curves were obtained at room temperature for the 150 grade powders and their post-compaction viscoelastic recoveries were measured. The coarse and fine size 150 grade powders reached relative plateau densities of 95.8% and 95.1%, respectively, when compacted at pressures exceeding 300 MPa. These high densification values at room temperature were associated with minimal post-compaction viscoelastic recoveries and as-compacted strengths as high as 8.9 MPa. A modified densification parameter (DP*) was developed based on the plastic deformation of the crystalline regions alone. This new dimensionless parameter, DP*, demonstrated a better fit of all the compaction data. The transverse rupture strength and the green density data are presented and explained in terms of this DP*.
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  • 156
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    Polymer Engineering and Science 29 (1989) 
    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
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  • 157
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    Polymer Engineering and Science 29 (1989), S. 1528-1533 
    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 conducted of blends of poly(vinyl chloride) (PVC) with a poly(methyl methacrylate co imide). The latter polymer was found to be miscible in PVC and to raise the glass transition temperature of the blend. Blends of all compositions could be oriented, but the processing temperature increased in proportion with Tg. For a given blend composition, orientation increased with increasing stretch ratio and strain rate and with decreasing stretch temperature. Increasing copolyimide content and increasing orientation generally lead to improved mechanical properties, though the blends containing high levels of copolyimide exhibited low ductilities.
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  • 158
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    Polymer Engineering and Science 29 (1989), S. 1574-1578 
    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 optical properties of polyetherimide resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40 μm ≥ λ ≥105 nm. Potential uses of this polymer as a printed circuit board material and as a packaging medium for microelectronic circuitry and the relevance of optical data in laser-assisted processing schemes used in these and other applications are briefly discussed.
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  • 159
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    Polymer Engineering and Science 29 (1989), S. 214-226 
    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: Shear modification treatment represents a special shearing history affecting mainly the elastic behavior of polymer melts. This process has been attributed to reversible physical changes in the entanglement structure of the polymer chain network. Shear modification studies were performed for two well-characterized low-density polyethylene (LDPE) grades differing in molecular weight distribution and degree of long chain branching. The shear working of the material was carried out using a specially designed shearing unit producing definable amounts of pure shear in a continuous process. Measurements of the dynamic storage modulus, G′, steady-state shear compliance; Je, extrudate swell, melt flow index, and the extensional behavior (Rheotens test) indicate that primarily properties associated with the elasticity of the melt are reduced in value. The observed reduction is found to correlate with the mean specific energy dissipated during sample preparation. Comparing the two LDPE grades showed that higher degrees of modification can be obtained at lower energy input levels for the more highly branched grade. Reversibility tests were performed and complete recovery of the initial material behavior was observed. Comparison of measurement results for samples prepared using the shearing unit presented here and a Brabender Plasticorder indicates that the degree of modification depends not only on the molecular structure of the polymer but also on the manner in which the shearing history is imposed upon the material.
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  • 160
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    Polymer Engineering and Science 29 (1989) 
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    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
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  • 161
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    Polymer Engineering and Science 29 (1989), S. 1637-1637 
    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
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  • 162
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    Polymer Engineering and Science 29 (1989), S. 1628-1635 
    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 compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.
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  • 163
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    Polymer Engineering and Science 29 (1989), S. 1667-1676 
    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: Under the right conditions, high strengths are shown to be achievable in vibration welded polycarbonate to polyetherimide Joints. While welding of thermoplastic interfaces of the same material can be understood in terms of interchain diffusion at elevated temperatures, this mechanism is severely limited in the case of dissimilar materials. Scanning electron microscopy is used to show that part of the bond strength in such dissimilar materials results from mechanical interlocking of the two polymers, which is caused by viscous mixing. The effects of the weld parameters on the weld morphology are considered in detail.
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  • 164
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    Polymer Engineering and Science 29 (1989), S. 1689-1698 
    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: Ultrasonic welding is one of the most popular techniques for joining thermoplastics because it is fast, economical, and easily automated. In near-field ultrasonic welding, the distance between the horn and the joint interface is 6 mm or less. This study investigated the near-field ultrasonic welding of amorphous (acrylonitrile-butadiene-styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. High frequency ultrasonic wave propagation and attenuation measurements were made in order to estimate the dynamic mechanical moduli of the polymers. The estimated moduli were entered into a lumped parameter model in order to predict heating rates and energy dissipation. Experimental results showed that variations in the welding pressure had little effect on energy dissipation or joint strength; Increasing the amplitude of vibration increased the energy dissipation and the weld strength. For the semicrystalline polymers, increasing the weld time improved strength up to weld times greater than 1.5 s, where strength leveled off. For the amorphous polymers, the weld strength increased with Increasing weld time up to times of 0.8 s; for longer weld times, the power required was too high, causing overloading of the welder. Monitoring of the energy dissipation and static displacement or collapse provided valuable information on weld quality.
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  • 165
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    Polymer Engineering and Science 29 (1989), S. 1733-1737 
    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 hydrolytic stability of a new commercial polycarbonate (Calibre 300, Dow Chemical USA) was investigated and compared with that of other commercial polycarbonates. The tests were conducted between 56% and 95% relative humidity (R. H.) at 100°C. Also performed were water immersion tests at 80 and 100°C. The water diffusivity was found to be 8.7 × 10-7 cm2/s at 100°C with an activation energy of 7.9 kcal/mole. These values are similar to other glassy polymers. The equilibrium water sorption, C∞, was found to increase with temperature and R.H. The isotherm at 100°C was determined to be: C∞ = 0.005945 [R.H.]. When samples immersed in a water bath at 100°C were transferred into room-temperature water, visible aqueous microcavities were formed due to the condition of super-saturation, and under stress may become crack initiation sites. For the polycarbonate investigated here, it was found that the decrease in weight-average molecular weight (M̄)w was a first-order process under a constant R.H. and temperature, and that hydrolytic embrittlement, i. e., (M̄)w 〈34,000, was reached after ca. 188, 143, 99, and 66 days under 56%, 73%, 87%, and 95% R.H., respectively, at 100°C. A comparison with reported hydrolytic stability data for other polycarbonates showed large differences in their stability which are believed to be due to the extent of end-group capping (over 95% in Calibre 300) and resin purity: both phenolic end-groups and some additives (i.e., fire retardants, thermal stabilizers) are known to accelerate hydrolytic degradation.
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  • 166
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    Polymer Engineering and Science 29 (1989), S. 1766-1773 
    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: Moldability and mechanical properties of polyethylene terephthalate (PET) under normal molding conditions were found to improve significantly when it was blended with bisphenol-A-polycarbonate (PC) and polypropylene (PP) to form ternary polymer blend systems. DSC results of these blends revealed that the PET and PC components formed a miscible blend while PP being incompatible with them, formed a separate phase. PP was also found to form a sleeve around the PET-PC miscible phase and, thereby, showed a skin-core type of morphology. Variations of mechanical properties with varying amounts of PP was measured keeping the ratio of PET and PC constant. Tensile and flexural properties of the blends decrease with the amount of PP. Notched impact strength increases up to a certain level of PP and then decreases, while the unnotched values decrease gradually. The effect of annealing on the mechanical properties of these blends have been discussed on the basis of the increased crystallinity of some of the components.
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  • 167
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    Polymer Engineering and Science 29 (1989), S. 1786-1795 
    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 possible multimodal sorption mechanisms in glassy amorphous poly-ether-ether-ketone (PEEK) are presented. By varying the penetrant-polymer affinity, experimental temperature, and external solvent activity, a broad range of sorption behaviors from ideal Fickian diffusion to limiting relaxation controlled kinetics is observed. In particular, water, methylene chloride, and n-heptane sorption kinetics are analyzed and interpreted on the basis of the multiple transport mechanisms. Low uptake liquid n-heptane sorption follows ordinary Fickian diffusion. Analogously, water vapor at low activity, is sorbed in small amounts in the same limiting mode while, at higher activities, the moderately higher penetrant uptakes induce slow relaxation coupled with ideal Fickian diffusion. The highly interacting methylene chloride leads to ideal Fickian diffusion only at very low activities, while anomalous non-ideal Fickian diffusion and limiting Case II and diffusion controlled swelling are observed at moderate and at high solvent activities, respectively. Limiting Case II sorption of methylene chloride in PEEK has been observed only at a very low temperature (-32°C). The optical microscopy observations of cryogenically fractured samples contacted with liquid methylene chloride at 5, 20 and 36°C revealed the presence of a sharp front moving linearly with the square root of time. Solvent induced crystallization in methylene chloride swollen samples was detected by means of differential scanning calorimetry (DSC) and wide angle X-ray scattering (WAXS). Finally, sorption from liquid methylene chloride/n-heptane solutions with varying compositions are presented. The progressive increase of the more high sorbing methylene chloride concentration in the solutions, leads to the same wide variety of sorption behavior observed in the methylene chloride vapor sorptions. The gas chromatographic (GC) analysis indicated that the presence of methylene chloride enhanced the n-heptane sorption in the polymer.
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  • 168
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    Polymer Engineering and Science 29 (1989), S. 1649-1654 
    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: Welding represents one of the key stages in the manufacture of injection molded or blow molded plastics products. One process frequently employed is heated-tool butt welding. However, the high seam quality associated with this process can only be attained through reliable process control and optimized welding parameters. This paper presents a simple new method for determining these parameters. Mathematical and physical descriptions of the individual process stages and a computer-controlled heated-tool butt welding machine serve as the basis for determining the parameters.
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  • 169
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    Polymer Engineering and Science 29 (1989), S. 1661-1666 
    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 measuring method is presented for process monitoring and process analysis of linear vibration welding of thermoplastics. The method works by recording and evaluating time-dependent signals that describe the process - such as the frequency-dependent signals of the displacement of the two parts being joined, the tangential force in the welding plane - and the nonperiodic signals of the welding process, i.e. the normal force in the welding plane and the melting or joining displacement of the parts being joined. It is possible to determine the energy input into the welding zone as a function of the selected machine parameters and the process sequence over time.
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  • 170
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    Polymer Engineering and Science 29 (1989), S. 1699-1704 
    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 far-field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far-field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far-field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far-field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.
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    Polymer Engineering and Science 29 (1989) 
    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
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    Polymer Engineering and Science 29 (1989), S. 1746-1758 
    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 methodological survey of preparation of microspheres and microcapsules by suspension cross-linking is presented. Thus, basic features of suspension cross-linking, i.e., the formation of small droplets of a polymer solution (or melt) in an immiscible liquid followed by hardening of these droplets by covalent cross-linking, are discussed. Typical microspherical and microcapsular products manufactured by suspension cross-linking of naturally occurring and preformed synthetic polymers, including agarose and cellulose beads, albumin microspheres and microcapsules, polystyrene beads and epoxy resin microcapsules, are described. Manufacturing parameters controlling microsphere/microcapsule characteristics are also briefly outlined.
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    Polymer Engineering and Science 29 (1989) 
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    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
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  • 174
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    Polymer Engineering and Science 29 (1989), S. 1325-1331 
    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 structures composed of polymer matrix composite materials, components must be joined such that the overall structure retains its structural integrity while it is performing its, intended function which can include both mechanical loads (static and dynamic) and environmental loads (temperature and humidity). The use of composite materials in complex structures almost always reduces the number of components in the structures compared to the use of metallic alloys for the same structure. Thus, using composite materials not only results in great savings in weight, but also through a reduced number of joining operations, results in significant savings in assembly, inspection, parts storage, and movement, resulting in increased reliability and lower cost. Yet joining is still required. Joining metallic structures is a mature technology involving riveting, bolting, welding, glueing, brazing, soldering, and other methods. However, for most polymer matrix composites only adhesive bonding and mechanical fastening can be utilized. Attention has been given recently, however, to localized welding of thermoplastic polymer matrix composites, and this will be discussed briefly later. Inherently, adhesive bonding is preferable to mechanical fastening because of the continuous connection, whereas in drilling holes for bolts or rivets, fibers or other reinforcements are cut, and large stress concentrations occar at each discrete fastener hole. The following is a review of much of the literature dealing with adhesive bonding of polymer matrix composite structures. It is Intended not only to be a review, but also a background for detailed study of the referenced and other documents, and a catalyst for future research.
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    Polymer Engineering and Science 29 (1989), S. 1488-1491 
    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: Gelation phenomenon in thermoset polymers is an area of extreme importance from the processing point of view. Gel point (GP) has traditionally been detected using rheological and mechanical techniques. We wish to report the use of dielectric and especially calorimetric techniques for detecting GP. Using a particular thermoset system, we have compared the calorimetric, dielectric, and mechanical techniques and shown how to define GP in terms of time and temperature. As a matter of convenience, we have briefly defined the gelation phenomenon in thermosets, its significance and measurement, and a critical evaluation of the techniques for detecting GP.
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    Polymer Engineering and Science 29 (1989), S. 1516-1523 
    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 of orientation development in polystyrene film by biaxial stretching is described. Stretch ratios up to 7.2 × 7.2 were used. Mechanical properties of polystyrene films were correlated with the level of molecular orientation developed by uniaxial or biaxial stretching. Sensitivity of the mechanical properties to change due to development of orientation varied as follows: Yield strength 〈 Young's modulus 〈 Tensile strength 〈 Elongation to break. Brittle to ductile transition phenomena were observed at certain orientation values in the orientation triangle diagram. The transition occurs when f1B × f2B ∼ 0.0025 for biaxially oriented and f1B ∼ 0.015 in the machine direction for uniaxially oriented films. SEM photomicrographs show that the fracture surfaces of ductile failures exhibit many fibrils while brittle failures exhibit no fibrils.
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    Polymer Engineering and Science 29 (1989) 
    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
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  • 178
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    Polymer Engineering and Science 29 (1989), S. 1579-1587 
    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 general kinetic model was developed to simulate the grafting of monomers such as unsaturated carboxylic acids and silanes to ethylene polymers. The polymers considered were ethylene-co-vinyl acetate (EVA), ethylene-co-butyl acrylate (EBA), and low-density polyethylene (LDPE). Grafting was assumed to proceed by a free-radical mechanism involving chain transfer. Organic peroxides having a strong tendency for hydrogen abstraction were selected as the source of primary radicals. The model simulated the grafting reaction as taking place in a single screw extruder. The residence time distribution in the extruder was experimentally determined by tracer analysis, according to which the extruder was a plug-flow reactor connected to two mixed reactors in parallel. The model is able to predict the extent of grafting in terms of predefined parameters. Comparison of model predictions with available experimental data showed slight deviations, the possible causes of which are discussed. However, the kinetic behavior expected on the basis of the input parameters was observed, and, as such, the model allowed study of the effect of process variables on grafting kinetics and provided insight into the reaction mechanism.
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    Polymer Engineering and Science 29 (1989), S. 1598-1603 
    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 describes characterizations performed on two types of polyethylene T-Joints as well as the starting resin from which they were manufactured. It was found that the melt flow rate of material taken from the two types of joints differed from that of the starting resin and differed from each other by as much as a factor of two. Investigation of the environmental stress-crack resistance (ESCR) and uniaxial creep behavior of material from the two joints revealed further significant differences in behavior between the two joints. These observations lead to the conclusion that subtle differences in the processing conditions can result in significant differences in the long-term mechanical behavior.
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  • 180
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    Polymer Engineering and Science 29 (1989), S. 1614-1617 
    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 strength of solid-filled rubbers is predicted by the statistical model proposed in this paper, by which the maximum area fraction of the solid filler in a representative cube is calculated. The minimum net cross-section area of the rubber matrix is thus obtained, and this is used to calculate the reduction in strength of the compound in comparison to that of the unfilled rubber. The prediction is then tested by experiments using hydroxyl-terminated polybutadiene (HTPB) filled with glass spheres. After curing, tensile specimens were cut from sheets and exposed to humidity-controlled environments so as to debond the filler particles from the rubber matrix, and were tested in tension. The experimental results were found consistent with the predictions.
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  • 181
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    Polymer Engineering and Science 29 (1989), S. 1683-1688 
    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 vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. Past work on welding characterized the effects of weld parameters such as the weld frequency, the weld pressure, and the weld time, on the welding process and weld strength, and showed that the most important parameter affecting weld strength Is the weld penetration - the decrease in the distance between the parts being welded that is caused by lateral outflow of material in the molten film. However, those weld studies were based on specimens of constant nominal thickness (6.35 mm, 0.25 in). This paper is concerned with the effects of specimen thickness on the weld process and weld strength.
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  • 182
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    Polymer Engineering and Science 29 (1989), S. 1722-1729 
    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 transient two-dimensional thermal model for resistance welding of thermoplastic composites is presented. A parametric study is conducted that yields insight into the welding process enabling some critical process and material parameters to be identified. Time to melt is predicted by the model and is successfully compared to experimental observations. Local heating and meltthrough can also be explained by the transient thermal model in agreement with experimental observations. Mode I fracture toughness of unidirectional graphite reinforced poly(etheretherketone) resistance welded double cantilever beam specimens are conducted under various process conditions. Experimental results indicate that under optimum process conditions, the interlaminar fracture toughness of the bulk compression-molded thermoplastic composite material can be achieved using resistance heating as a joining technique.
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  • 183
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    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: Although fibers are subject to complex deformations during processing and end use, most research has concentrated on tensile properties. We have extended our studies to include the ultimate torsional properties, i.e., the breaking twist angle (BTA), and the flexural fatigue life of single fibers. We now have sufficient data on diverse fiber types that we may compare their mechanical properties. Thus, in this paper we report the mechanical properties of the different starting, untreated, fibers, tested under fiducial conditions. We then develop and consider some interrelationships between these selected single fiber physical properties.
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  • 184
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    Polymer Engineering and Science 29 (1989), S. 1774-1785 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We have analyzed step growth polymerization in a flat film with finite mass transfer resistance. We have shown rigorously that the molecular weight distribution (MWD) at equilibrium is given by the Flory distribution, and under reaction the form of the MWD does not change if the feed is either pure monomer or in equilibrium initially. Extensive computations have shown that it is possible to split the film into growing interfacial and shrinking bulk regions. It is possible to obtain similarity transformations of concentrations of condensation product, and polymer as time invariant profiles. Based on this finding, we have determined a solution for step growth polymerization with finite mass transfer in films. The results lie within 5% of the “exact” numerical computations, for all possible variations of parameters.
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  • 185
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    Polymer Engineering and Science 28 (1988), S. 578-582 
    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 describes the utility of Torsion Impregnated Cloth Analysis, a very versatile technique to characterize resin behavior during cure or after repeated thermal and environmental treatment. Multi-frequency scan data have been shown to help tremendously in interpreting the behavior during experimentation. The technique is also very useful in defining the cure conditions for new resin chemistry/systems.
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  • 186
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    Polymer Engineering and Science 28 (1988), S. 568-577 
    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: Oxidized carbon fibers were coated using an on-line filament winding process with an elastomeric adduct crosslinkable and compatible with an epoxy matrix. The coating and modifications of the epoxy network were studied by dynamic mechanical measurements. Assuming that apparent activation energies of the secondary relaxation βe of the epoxy network and main relaxation αa of adduct are very different, it is possible at low frequencies to separate the two peaks. The composite material can be described as a three phase system: an epoxy network as matrix, carbon fibers, and a soft interlayer. The mechanical behavior of unidirectional composite materials studied by impact and bending tests is strongly dependent on the presence and the thickness of the coating at the carbon fiber surface.
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  • 187
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    Polymer Engineering and Science 28 (1988), S. 610-625 
    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 influence of the hard or soft inclusions and the mesophase layers in either a soft-hard-soft or hard-soft-hard combination of biphase plates submitted to dynamic tensile loads on the fracture mode and bifurcation process in both phases was investigated in this paper. It was assumed that the soft or hard matrix is infolding the hard or soft inclusion of the plate, so that the plate constitutes a meridional section of the representative volume element of a unidirectional fiber composite, or a principal section of a particulate. The influence of the mechanical properties of either phase on the crack propagation velocity and the initiation of crack bifurcation was studied by using high-speed photography and dynamic caustics. The results showed that the propagating crack tended to bifurcate either in the brittle or in the mesophase layer under certain conditions of propagation velocity. It was shown that bifurcation of a propagating crack depends on the elastic moduli and Poisson's ratios of the phases, as well as on the extent of the mesophase layer, which depended on the adhesion quality of phases.
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  • 188
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    Polymer Engineering and Science 28 (1988) 
    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
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  • 189
    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: Thermal analysis of oriented polymers involves several transitional processes which may be coupled in a complex way. The disorientation process that occurs during heating is often accompanied by dimensional shrinkage which may occur in both amorphous and crystalline oriented polymers. From differential scanning calorimetry (DSC) measurements it has been determined that shrinkage is an exothermic process. In amorphous atactic polystyrene (PS), hot drawn uniaxially, the shrinkage occurs just above Tg. In triaxially oriented polyethylene (PE) and isotactic polypropylene (iPP), shrinkage and melting take place concomitantly, producing multiple melting peaks. In rolltruded (and also in biaxially oriented) poly(ethyleneterephthalate) (PET) films, shrinkage and crystallization are found to be coupled and to occur between Tg and Tm upon heating. If the enthalpy contribution due to shrinkage is ignored, it follows that crystallinities determined by DSC are incorrect. In this study, the influence of shrinkage upon transitional changes in oriented polymers is investigated in a systematic manner.
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  • 190
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    Polymer Engineering and Science 29 (1989), S. 1534-1543 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We offer a detailed study on the anisotropic optical properties in uni and simultaneous biaxially stretched Poly(ethylene terephthalate) (PET) films. Cast amorphous sheets of PET were stretched to a series of extension ratios in two mutually perpendicular directions at 80, 90, and 100°C. Additionally, 0selected films were subsequently “heat-set” by annealing with their width and lengths constrained. The principal refractive indices at sodium D wavelength of these, asstretched and heat-set films were obtained using a modified Abbe refractometer. The changes in the principal refractive indices with the processing history were correlated with the orientation of PET chains and phenyl plane normals, which were determined independently by wide angle X-ray (WAXS) pole figure technique.
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  • 191
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    Polymer Engineering and Science 29 (1989), S. 1642-1648 
    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 order to achieve high fatigue strengths in heated-tool butt welds in plastic pipes used in gas and water supply lines, it is essential that optimum welding parameters be selected. In this paper, the different process phases are described by means of dimensionless characteristic parameters that have been obtained by applying similarity principles to heated-tool butt welding. On the basis of strength studies conducted on welded Joints, it is shown that the best weld quality is attained when the welding parameters are selected such that identical sheaf deformations result in the joint zones of small and large pipes. Laws for scaling data from small-pipe to large-pipe welds are then based on the values of these nondimensional numbers.
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  • 192
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    Polymer Engineering and Science 29 (1989), S. 1569-1573 
    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 gel melting temperature and crystallization kinetics of ultra-high molecular weight polyethylene (UHMW-PE)/decalin systems were investigated. Two methods were used to determine gel melting temperature; thermomechanical analysis (TMA) with a penetration probe and differential scanning calorimetry (DSC). The melting points determined from TMA and DSC were in good agreement, indicating that the crystallization of UHME-PE is an essential step for gelation. The gel melting temperature increases with UHMW-PE concentration. The change in gel melting temperature with composition results from interaction of the components in the amorphous phase. The gelation and crystallization rates increase with decreasing UHMW-PE concentration.
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  • 193
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    Polymer Engineering and Science 29 (1989), S. 1553-1559 
    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 cure of an epoxy-anhydride resin system used in pultrusion was characterized to develop an understanding of the cure behavior and to determine potential process controls parameters. Isothermal cures of neat resin formulations were monitored by differential scanning calorimetry (DSC), torsional braid analysis (TBA), and microdielectrometry (MDE). The processing conditions define a time/ temperature region in which monitoring would be applicable. Both DSC and MDE were found to yield useful information in this region, however, the events typically monitored by TBA either did not occur or occurred too quickly to be monitored. Significant ionic conductivity was observed in the fully cured resins at temperatures above the glass transition temperature and could possibly be used as a control parameter. This study revealed an apparent change in reaction mechanism with increasing cure temperature. DSC showed a change in activation energy with extent of reaction and a decrease in heat of reaction at the higher isothermal cure temperatures. The formation of a different network structure was indicated by a decreasing glass transition temperature of the cured resin with increasing cure temperature by both DSC and TBA.
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  • 194
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    Polymer Engineering and Science 29 (1989), S. 1604-1610 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An investigation of the effect of physical aging on excess enthalpy of compatible polymer blends was carried out. Poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN) were chosen for this study. Blends of different ratios of PMMA and SAN were physically aged at different times and temperatures below their glass transition (Tg) and then subjected to enthalpy relaxation measurement in a differential scanning calorimeter (DSC). An improved procedure was developed and, employed to analyze the data. The error associated with the calculation of the normalized deviation in enthalpy, known as the “Φ” function, was below 4%. The relaxation was observed to proceed faster at higher aging temperature. It was also found that at higher aging temperatures of Tg - 20 and Tg- 35°C, enthalpy relaxation in SAN-rich blends proceeds faster than in PMMA rich blends, while at the low aging temperature of Tg- 50°C the rate of relaxation becomes independent of the composition.
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  • 195
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    Polymer Engineering and Science 29 (1989), S. 1638-1641 
    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 techniques recently developed at Leeds University make it possible to produce oriented polymer tubes with both axial draw and hoopwise expansion. These products have increased axial stiffness, improved barrier properties, and excellent resistance to chemical reagents. Normally mechanical methods are used to join such tubes in order to preserve their orientation: however we show that electrofusion techniques produce joints of strengths such that in tensile tests, failure always occurs in the fittings, not at the joint interfaces. Optical and electron microscopy reveal different zones in the welds and indicate that only 20 percent of the wall thickness is affected by the electrofusion process. The pipe studied was biaxially drawn medium density polyethylene of outside diameter 63 mm with draw ratios of 4 in the axial direction and 2, inner hoop. Optimum welding conditions were determined using socket and saddle electrofusion fittings. The joints did not fail in a standard crush test. Careful control of welding parameters is essential in butt fusion welding when the maximum weld strength exceeds that of the undrawn polymer.
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  • 196
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    Polymer Engineering and Science 29 (1989), S. 1677-1682 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study has been made of vibration butt welds between plaques of polypropylene. The quality of the welds, as determined by impact tests, has been examined as a function of the welding variables: pressure and vibration amplitude. In addition, the microstructure of the welds has also been examined, classified, and correlated with the welding variables and weld quality. Penetration as a function of time shows three distinct regimes and It is shown that the impact strength of the welds is independent of time once the third regime is reached. The time required to reach the third regime decreases as pressure or amplitude increases and is more sensitive to amplitude of vibration than to pressure. The highest quality welds were produced at low pressure and low amplitude with corresponding long times to reach regime three and exhibited a unique, readily identifiable microstructure.
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  • 197
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    Polymer Engineering and Science 29 (1989), S. 1705-1721 
    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 ultrasonic welding process is modeled using a five part model that includes mechanics and vibration of the parts, viscoelastic heating, heat transfer, flow and wetting, and intermolecular diffusion. The model predicts that melting and flow occur in steps, which has been confirmed by experiments. The model also indicates the possibility of monitoring joint quality by measuring the dynamic mechanical impedance of the parts during welding, which has also been verified experimentally by indirectly monitoring the magnitude of the impedance. via measurements of both the power and the acceleration of the base. When the melt fronts of the energy directors meet, at the end of welding, the dynamic impedance of the composites' interface is shown to rise rapidly. This raises the possibility of developing closed loop control procedures for the ultrasonic welding of thermoplastic composites. Ultrasonic welding of polyetheretherketone (PEEK) graphite APC-2 composites produced joints with excellent strengths.
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  • 198
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    Polymer Engineering and Science 29 (1989), S. 1759-1765 
    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: Fluorescence spectroscopy has been employed to monitor the mixing of polymer melts with filler material. The polymer melts were low molecular weight polybutadiene and PBAN, a terpolymer consisting of 85% butadiene, 11% acrylonitrile, 4% acrylic acid, and the filler material was aluminum oxide. To carry out the fluorescence observations, a dopant chromophore was mixed into the polymer melt at very low concentrations, 10-4 to 10-6 molar or 11 to 0.11 ppm by weight. The mixing experiments were carried out using a small laboratory mixer which had glass walls for viewing the fluorescence spectra from the dopant chromophore. Fluctuations in fluorescence intensity were observed to decrease as a function of mixing time indicating that the spatial distribution of the fluorescent chromophores was becoming more uniform. Concerning the mixing of polymer melt and filler, we hypothesize that uniform mixing of ingredients is achieved when fluorescence intensity as a function of time is constant. In order to obtain quantitative support for this hypothesis, we used a fluorescence microscope to measure fluorescence intensity and optical transmittance from microscopic regions of well-mixed and poorly mixed specimens.
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  • 199
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    Journal of Applied Polymer Science 30 (1985), S. 19-33 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: Chemical etching of poly(ethylene terephthalate) filaments with aqueous methylamine has revealed a complex stress - cracking behavior, which varied with orientation and thermal crystallization conditions. The appearance of both longitudinal and transverse cracks, can be explained on the basis of the existence of two types of domains, where the stresses are preferentially concentrated. They are explained on the basis of Prevorsek's structural model. In heat-set fibers, there exists a skin to core differentiation in the internal stress distribution. The crack pattern also varied depending on whether the fibers were heat-set in the taut or slack conditions. This chemical etching technique can prove to be a very useful tool, for the study of the internal stress distribution induced in fibers by various fabrication processes or post mechanical deformations.
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    Journal of Applied Polymer Science 30 (1985), S. 445-460 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 polymerization of ARB type reversible step growth polymerization in semibatch reactors has been simulated. It is assumed that the condensation byproduct W and the monomer P1 both can vaporize, but P1 is refluxed back to the reactor. Raoults law as well as Flory-Huggins theory have been used to account for vapor-liquid equilibrium. The degree of polymerization, μn, and the polydispersity index DN have been computed for various situations. The results are found to be most sensitive to the total pressure and the equilibrium constant. A limiting total pressure history PT(T) has been obtained, going below which does not help to increase μn. The final set of equations incorporate both equalities as well as inequalities, and a simple and efficient computational scheme has been suggested to solve them.
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