摘要:

AbstractThe Raman spectrum of ultrahigh‐molecular‐weight polyethylene (UHMWPE) has been obtained in the temperature interval 135–208°C, a region where optical anisotropy was observed to exist. On the basis of our spectroscopic evidence, we believe that ordered regions persist in the melt above the calorimetrically determined melting point, and that part of the polyethylene chain is in an enviroment which is similar to that of the orthorhombic crystal. These ordered domains disappear with increasing temperature, but no calorimetric phase transition is associated with this change. We postulate that the very long relaxation times associated with the highly viscous melt keep the polyethylene chains in ordered environments which persist until decreased viscosity at increased temperature allows long‐range segmental motion. Our evidence supports the view that the melt anisotropy of UHMWPE arises from oriented slowly melting superheated crystals and not from a smectic liquid‐crystal

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240111

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe influence of a small rotational mobility on the measured orientation factorsf2andf4(connected with the second and fourth moments of the orientation distribution function), of uniaxial probe molecules in uniaxial polymer systems is calculated with special regard to the fluorescence polarization method. A mean angle of rotation of about 10° within the time scale of the experiment, i.e., the fluorescence lifetime, affectsf4considerably, while it has practically no influence onf2. On the other hand, the knowledge of the truef4of the sample and some assumptions on the mobility—orientation correlation make it possible to evaluate the mean rotational angle θ from the measuredf4. Moreover, the measuredf2value can be precisely corrected. The effect of the assumptions on the reliability off2and θ is analyzed. Experimental results on two partially mobile probe molecules in drawn polyethylene are discu

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240112

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe precise pressure dependence of apparent diffusion and permeation coefficients was measured by using a microcomputer system for collecting and treating permeation data for CO2in glassy poly(ethylene terephthalate) below 1 atm between 15 and 40°C. The partial immobilization model was used to determine the dual‐mode sorption and mobility parameters. The curves calculated with these parameters were in excellent agreement with experimental data. These parameters were also compared with sorption parameters obtained from measurements at 30°C. There was a small difference between the values of the parameters obtained from these permeation data and those from sorption data which we had previously obtained. Relations between this difference and the method of determination of the parameters are discus

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240113

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractA study of iodine‐complexed nylon 6 films by polarized resonance Raman spectra shows the presence of bothI3−andI5−species, the latter most likely in the form of anI2/I3−complex. Polarization characteristics of the Raman spectra show that theI2/I3units are orinted along the polymer chain and theI3−ions are perpendicular to the chain axis. TheI2/I3−units are in a more stable moiety than theI3−species. These Raman results are consistent with the x‐ray d

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240114

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe interfacial structure and diffusion kinetics of two compatible polymers, poly(methyl methacrylate) and poly(vinylidene fluoride) are studied in the melt. The interdiffusion rates of the two components are found to be unequal, giving unequal diffusion coefficients, a net mass flow across the interface, and an asymmetric interfacial composition profile. The structure and kinetics confirm the predictions of the reptation theory. The interfacial thicknessdgrows witht1/2, and the interdiffusion coefficient is proportional toM−2, wheretis the time andMis the molecular weight. The scaling law for the interfacial thickness is therefored∝M−1t1/2. The number of chains per unit area crossing the original interface reaches a constant value independent of diffusion time after a short induction time on the order of the tube disengagement time (about 0.1–10 s in the present cases depending on the molecular weights). The adhesive bond strength σ is scaled by σ ∝t1/4M−1/2and σ/σ∞ ∝t1/4M−1/2[1‐ (Mc/M)]−1, where σ∞is the σ at infinite molecular weight andMcis the

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240115

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractBiaxial stress relaxation data acquired for a carbon‐black‐filled elastomer are analyzed. Consistent with previously published simple‐tension and pure‐shear results for this elastomer, the biaxial relaxation behavior is also found to be a separable function of time and strain effects. A departure from separability is observed at the larger strain; this might be a manifestation of strain‐induced crystallization. An analysis of the biaxial results together with the earlier reported simple‐tension and pure‐shear data reveals that the deformational dependence of this elastomer obeys the Valanis—Landel hypothesis up to moderate deformations. The Ogden strain energy function is found to be an excellent analytical representation of all of the multiaxial data. Large relative errors found at small tensile strains between the data and the Ogden fit are attributed to carbon black str

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240116

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractSorption of carbon dioxide, ethylene, and nitrous oxide in poly(methyl methacrylate) (PMMA) at 35°C has been characterized for each gas as a pure component and for mixtures of carbon dioxide/ethylene and carbon dioxide/nitrous oxide. Pressures up to 20 atm were examined. Pure‐component sorption isotherms are concave to the pressure axis for each of the gases. This behavior is accurately described by the dual‐mode sorption model. Using only the purecomponent dual‐mode parameters and the generalization of the model for gas mixtures, one can predict the total concentration of gas sorbed in the polymer to within an average deviation of ±2.01% for the CO2/C2H4/PMMA system and ±0.98% for the CO2/N2O/PMMA system. In both systems, for each component of the mixture, sorption levels were lower than corresponding pure‐component sorption levels at pressures equal to the partial pressure of the respective components in the mixture. Depression of the sorbed concentration in mixture situations appears to be a general feature of the above systems and can be substantial in some situations. For the CO2/C2H4/PMMA system, use of pure‐component sorption data to estimate the total sorbed concentration in the mixture would be in error by as much as 40% if one failed to account for competition phenomena responsible for depression in mixed‐gas situations. Mixture pressures as high as 20 atm were studied for both systems and in the CO2/N2O/PMMA system sorbed concentrations reach 33.90 [cm3(STP)/cm3polymer] without any significant deviation from mod

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240117

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

摘要:

AbstractThe rheology of hydroxypropylcellulose (HPC)—acetic acid solutions was investigated by using a cone‐and‐plate rheometer and a capillary rheometer, for polymer concentrations ranging from 10 to 80%. Isotropic solutions exhibit a Newtonian plateau followed at higher shear rates by a pseudoplastic zone. The apparent viscosity varies asC5.2if concentrationCis less than 27% and asC13for 27%

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240118

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY

ISSN:0887-6266    

DOI:10.1002/polb.1986.180240119

出版商:John Wiley&Sons, Inc.    

年代:1986

数据来源: WILEY