摘要:

AbstractFor film blowing of polyethylene it has been shown previously that melt elongation is very powerful for polymer characterization. With two types of rheometers, simple (also called “uniaxial”) elongational tests as well as creep tests can be performed homogeneously. In simple elongation, the melts of branched polyethylene show a remarkable strain hardening. With respect to their advantages and disadvantages, these rheometers complement each other. For multiaxial elongations the various modes of deformation can be performed by means of the rotary clamp technique. With the strain rate components ordered such that\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}11⩾\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}22≥\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}33, the ratiom=\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}22/\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}11characterizes the test mode. The Stephenson definition of the elongational viscosities makes use of the linear viscoelastic material equation and proves to be very efficient because the linear shear viscosity η0(t) (“stressing” viscosity) can act as the reference for the nonlinear behavior in elongation. Results are given for polyisobutylene measured not only in simple, equibiaxial, and planar elongations, but also in new test modes with a change ofmduring the deformation. This allows one to investigate the consequences of a deformation‐induced anisotropy of the rheo

ISSN:0032-3888    

DOI:10.1002/pen.760270802

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe crystalline structure and morphology have been investigated for powder processed poly(phenylene sulfide) blended with high‐density polyethylene and poly(tetrafluoroethylene). The crystallinity in the former case showed large deviations from those estimated from rule of mixtures, while in the latter blends it closely followed the values predicted from the linear relation for homogeneous mixtures. Pronounced changes in some reflections were found in the X‐ray pattern on thermal curing of the samples. These results have been explained on the basis of compaction behavior of the powder blends together with the orientations induced during the processing st

ISSN:0032-3888    

DOI:10.1002/pen.760270803

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIn this study the apparent rate constant model was used to determine the mechanism of termination and other rate constants for free radical copolymerizations that are chemically controlled with no penultimate effect. The data required were the number average molecular weight and the conversion obtained at various initial initiator concentrations and monomer compositions, and two rate constants of propagation of the homopolymerizations of its two monomers. The bulk free radical copolymerization of methyl methacrylate (MMA) and styrene(St) at 60°C was studied. Three published literature values of the propagation rate constantsk11andk22. 750, 150; 515, 145; 705, 145, were used for the determination. The unit of the rate constants used was liter/mole/s. The modes of the termination reaction obtained, depending onk11,k22used, are given as follows:textmole percent Combination in the Termination(k11, k22)MMA‐MMA radicalsSt‐St radicalsSt‐MMA radicals(750, 150)179996(515, 145)549991(705, 145)409887The modes of termination obtained by the case ofk11= 750 andk22= 150 are in good agreement with those shown by Bevington, Melville, and Tayl

ISSN:0032-3888    

DOI:10.1002/pen.760270804

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractBiaxially oriented Nylon 66 film has been developed by a new tubular process. The relationship between the structure resulting from the manufacturing conditions and properties have been examined. A key technology of manufacturing is quenching of the melt, because of the high rate of polymer crystallization. The properties of biaxially oriented Nylon 66 film are found to be determined mainly by the degree of polymerization, the molecular and hydrogen bond plane structure, orientation within the film, and the degree of crystallinity. Toughness and high thermal resistance are also properties of this film. Therefore, applications for packaging have been examined, and a “retortable pouch” seems especially promis

ISSN:0032-3888    

DOI:10.1002/pen.760270805

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractFourier transform infrared (FT‐IR) studies of poly(ethylene terephthalate) (PET)/poly/(amide‐6,6) (PA) blends are presented. The blends were prepared in the molten state and in solution with trifluoroacetic acid (TFA) as the solvent. The PET/PA blend is a complex system containing, two crystallizable polymers with the ability to interact chemically. Some of the blends were prepared in the molten state in the presence of a catalytic amount of p‐toluenesulfonic acid (TsOH) to undergo the ester‐amide interchange reaction. Nuclear magnetic resonance (NMR) and FT‐IR have proven to be excellent techniques with which to study these blends.1HNMR was used to follow the ester‐amide interchange reaction and FT‐IR to detect the presence of hydrogen bonding. FT‐IR studies showed the lack of hydrogen bonding in all the blends prepared in the molten state and its presence in the blends prepa

ISSN:0032-3888    

DOI:10.1002/pen.760270806

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractThe dispersion processes in multilayer laminate composites of styrene acrylonitrile (SAN) and polycarbonate (PC) were studied utilizing the torsion pendulum. A third damping peak with a log decrement intensity of approximately one was observed at a temperature intermediate to the damping peaks corresponding to theTg's of the two constituent phases. Variations of numerous material and experimental parameters such as composition ratio, orientation, thermal history, thermal cycling, number of layers, and layer thickness, as well as overall changes in the composition of the phases had no effect on the observance of a third peak. Only the disruption of the continuous layer structure effectively eliminated this novel transition. The origin of this transition was explained by assuming appropriate temperature dependencies for the controlling viscoelastic parameters in such a continuous layer composite.

ISSN:0032-3888    

DOI:10.1002/pen.760270807

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractFor batchwise radical chain solution copolymerization, the minimum end time problem with constant copolymer composition control is studied by considering the initiator concentration (or feed rate) and temperature as two control variables. During copolymerization, the more rapidly depleting monomer is continuously fed to the reactor to maintain the comonomer ratio constant. The volume variation due to contraction during copolymerization, in addition to monomer and solvent feeding, is also considered. It is found that the optimal initiator addition policy is to make the rate of initiation (2fkdIV) constant. The volume factorVis for taking account of volume variation. For the isothermal case, the number of moles of initiator in the reactor should remain constant. Experimental verification for acrylonitrile and styrene isothermal copolymerization with the proposed stepwise feeding of the more rapidly depleting monomer to simulate the optimal continuous monomer feeding policy shows that the present method is applicable.

ISSN:0032-3888    

DOI:10.1002/pen.760270808

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractCreep experiments on two thermoplastics at constant values of tensile stress, temperature, and relative humidity previously reported for 132,000 h were continued to about 230,000 h. An equation of the form ϵ = ϵo+ ϵ+tnwas used to predict the creep, wheretis time and ϵo, ϵ+, andnare constants for a given stress. ϵo, ϵ+, andnwere determined from the first 1900 h of data and were used to predict the creep to 230,000 h. The subsequent recovery on unloading was predicted using the same equation together with the superposition principle. Also reported are creep and recovery of companion specimens aged for about 98

ISSN:0032-3888    

DOI:10.1002/pen.760270809

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractA parallel‐plate constant‐stress rheometer is used to measure the yield stress τy, and the post‐yield flow curveT(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}), where τ is shear stress and\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}is shear rate, for microphase‐separated triblock copolymer melts. Five polymer samples, all styrene‐butadiene‐styrene but with differing composition ratios and molecular weights, are tested at 125°C. Specimens are prepared by casting sheets from solutions made with different solvents. The τ(\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}) is found usually to be sigmoidal, for the range 10−5<\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document}<10−3s−1, representing different stages of microstructural degradation in flow. Measurements indicate that a true τyexists, with values in the range 100<τy<500 Pa for these melts. A general trend is detected for τyto decrease as the casting solvent solubility parameter increases. A scheme for correlating the dependence of τy, on composition and molecular weight is proposed for the various polymers. For selected samples, the effect of mechanical history (sequence of stress application) and a temperature variation that crossesTs(110 to

ISSN:0032-3888    

DOI:10.1002/pen.760270810

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY

摘要:

AbstractIt is frequently necessary to measure the viscosity of polymer solutions at high shear rates to obtain data under the conditions encountered in industrial processes. Such measurements are most often made on a capillary viscometer. This paper presents a method of determining solution viscosities at shear rates up to 50,000 s−1in a rotational rheometer using a parallel plate geometry. The two keys to performing these measurements are very small gaps between the parallel plates (on the order of 50 microns) to eliminate inertial secondary flows, and the ability to increase and decrease the shear rate quickly to minimize viscous heating. A technique for setting and measuring small gaps is presented. Possible sources of error including inertia, axial compliance, and viscous heating are analyzed. A comparison Is made between the viscosity of a 0.7 percent hydroxypropyl guar (HPG) solution measured on the parallel plate rheometer and the viscosity measured in a capillary viscometer. Viscosities of HPG solutions having concentrations of 0.25, 0.50, 1.00, and 1.45 percent are presented over the shear rate range 100 to 50,000 s

ISSN:0032-3888    

DOI:10.1002/pen.760270811

出版商:Society of Plastics Engineers    

年代:1987

数据来源: WILEY