摘要:

AbstractA series of polyetherpolyol−4,4/‐diphenylmethane diisocyanate based polyurethanes were prepared by reaction injection molding (RIM). The degree of phase separation and morphology, which govern the mechanical properties, was investigated by X‐ray scattering, dynamic mechanical spectroscopy, and electron microscopy. The phase reversion occurred at just a 70 weight percent concentration of the based reagent. The degree of phase separation increased with the molecular weight of polypropyleneglycol and decreased with the ethyleneoxide capping content. Morphology was influenced by injection

ISSN:0032-3888    

DOI:10.1002/pen.760260902

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA simple and useful experimental method has been developed for obtaining shear compliance properties for film samples using sonic velocity measurements at room temperature. In this method, the transmit and receive transducers were aligned in such a way that a shear wave was generated and transmitted through the sample. The method was used to determine the in‐plane shear compliance properties of three well characterized uniaxially oriented isotactic polypropylene films with draw ratios of 1.2, 4, and 6 respectively. It was observed that shear velocities at angles 0 through 45° were symmetrical to those from 90 through 45°. Further, as the draw ratio of these film samples increases, the determined sonic shear compliance in the draw direction decreased linearly. In addition to he shear data, the in‐plane tensile compliance data were also determined for these three films for comparison. Collectively, these sonic tensile and shear data were analyzed to evaluate the four in‐plane material compliance constants, S33, S22, S44, and S23, required to characterize a film in plane stress. Finally, a previously developed two parameter model was used to predict both the shear and tensile sonic modulus properties based on orientation parameters and intrinsic properties of isotactic polypropylene. The predicted properties agreed reasonably well to the experimental data generated for these film samples in spite of the fact that the two parameter model assumes the in‐plane shear compliance to be a constant independent of the t

ISSN:0032-3888    

DOI:10.1002/pen.760260903

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractRecovery experiments aboveTghave been performed on polymeric liquid crystal (PLC) ‐ polystyrene (PS) blend sheets obtained from extrusion and subsequent hot drawing. The data reported show that a significant improvement of the dimensional stability of a drawn thermoplastic material can be obtained by adding a low percentage of non‐compatible polymeric liquid crystals that are oriented during the hot drawing process. The fibrils formed act as a constraint for a certain amount of polymer surrounding them and consequently these highly oriented sheets, once exposed to high temperature, will mainly stress relax and do not creep. This effect disappears when the melting temperature of the oriented crystalline phase is reached. Compatible PLC‐PS blends do not show any improvement on the dimensional stability compared to the unfilled m

ISSN:0032-3888    

DOI:10.1002/pen.760260904

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe packaging industry is undergoing a period of rapid expansion in the use of multilayer and coextruded containers. This presents a challenge to the analytical chemist, who must characterize these extremely complex structures. The state of the art for the production of the new generation of containers, including methods, materials and structures, will be briefly reviewed. The applications of such containers and the motivations for the analysis of the structures involved will also be reviewed. The methods for the analysis of these multilayer and coextruded structures will then be considered in detail. The characterization of the surfaces involved will be emphasized. Techniques to identify, quantify, and determine the orientation of the structures will be discussed. The use of infrared spectroscopy (with emphasis on internal reflection spectroscopy) for the identification of the materials in these structures will be discussed. Also, the use of infrared spectroscopy in quantitatively determining the composition and orientation of the structures will be presented. The use of optical microscopy and combined microscopy/infrared spectroscopy for the quantification of the layer structures will be discussed. The use of auxiliary techniques for the completion of the analysis of the complex layer structures will be presented.

ISSN:0032-3888    

DOI:10.1002/pen.760260905

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe Maxwell‐Voigt type mechanical model proposed by Haward and Thackray was further modified to describe the strain rate dependent stress‐strain behavior of polycarbonate under the uniaxial loading condition. Major modifications included effects associated with different hardening components of inelastic resistance and the related temperature dependent material behavior. The modified analytical model was shown to describe some of the important features of the stress‐strain behavior of polycarbonate specimens tested over the range of strain rates and temperatures. Using the stress‐strain relationship as input data; several finite element analyses were made to predict the behavior of polycarbonate sheets under a simple solid phase cup forming process. The computed strain distributions agreed reasonably with the measured values obtained from the gridded polycarbonate sheet that was formed at an elevated temperature. Some of the key assumptions that were used in the analysis are di

ISSN:0032-3888    

DOI:10.1002/pen.760260906

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractPoly(ethylene terephthalate) (PET) is known to be a hygroscopic thermoplastic, which absorbs moisture from its environment at a rapid rate. The water absorption characteristics of PET as a function of relative humidity, exposure time, temperature, thickness, and molecular weight are reported here. Results indicate that absorbed moisture has significant influences on the physical properties of PET, leading to large decreases in the glass transition temperature, crystallization temperature, and degree of molecular orientation.

ISSN:0032-3888    

DOI:10.1002/pen.760260907

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe nature of the yield zone at the crack tip of poly(vinyl chloride) (PVC) pipe materials has been investigated. Microscopy studies employing a plasma etching technique reveal the presence of multiple crazes ahead of the crack tip in the interior of specimens of pure PVC, CaCO3filled PVC, and PVC pipe compound. The craze zone and the fracture toughness of blade‐notched specimens are compared with those of fatigue pre‐cracked specimens. Both types of specimens have similar fracture toughness values and form multiple crazes upon loading, suggesting that multiple crazing Is an intrinsic property of the material. The kinetics of craze initiation and the development of the multiple craze zones have also been explo

ISSN:0032-3888    

DOI:10.1002/pen.760260908

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe tendency of carbon fiber to nucleate the zation of poly(etherettterlcetone) (PEEK) has been evaluated by DSC and other techniques. As the carbon fiber content was increased, the supercooling necessary for PEEK crystallization decreased. The repeated melting (at 396°C) of the same PEEK sample results in a decrease of the number of nuclei for crystallization. At equivalent thermal histories, PEEK with carbon fiber was found to have a higher nucleation density than PEEK itself. The surface of carbon fibers and nuclei in the PEEK matrix compete for crystallization growth. As the holding time in melt was increased, the number of matrix spherulites formed on cooling decreased, hence a more pronounced transcrystalline region was developed. Correspondingly, the composites preheated in the melt for 100 min showed about two times the transverse tensile strength and strain‐to‐failure of those preheated for only 30 min. Corresponding fracture surface produced in tension showed that the former samples had a greater matrix adhesion to the carbon fiber than the latter.A strong interfacial bond is thus developed by crystallization on carbon fiber surface. Destroying nuclei in the PEEK matrix by long preheating enhances crystallization on the carbon f

ISSN:0032-3888    

DOI:10.1002/pen.760260909

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe residence time distribution of poly(vinyl chloride) (PVC) polymers in a counterrotating twin screw commercial extruder was determined and analyzed. The experimental technique involved the use of manganese dioxide as a tracer after being neutron activated and was injected into the extruder during normal operation without interrupting the poly(vinyl chloride) compound production. The experimental results enabled us to better understand the flow and mixing conditions in the extruder.

ISSN:0032-3888    

DOI:10.1002/pen.760260910

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA mass transfer model was developed to represent the desorption of a volatile species from a molten polymer in an extruder consisting of co‐rotating twin screws in a figure‐eight bore. The melt undergoes a series of alternating exposure and mixing processes while being transported axially through the device. The model relates the ratio of entrance to exit concentrations of the volatile species to the dimensions of the screws, the rate of their rotation, the rate of polymer flow, and the diffusion coefficient of the volatile species in the polymer. Experimental data, obtained with a halocarbon‐polybutene system in a twin‐screw extruder, were compared with predictions of the model. For the observed performance, the model predicts a process screw length about 14 percent below the actual screw length in the experimental e

ISSN:0032-3888    

DOI:10.1002/pen.760260911

出版商:Society of Plastics Engineers    

年代:1986

数据来源: WILEY