摘要:

AbstractA study has been made of the gas transport properties of polyethylene films of two different grades, Hizex 7000F and Rigidex 002‐55, one‐way drawn at 115°C to draw ratios in the range 1–20. Measurements of the permeability and diffusion coefficients of helium, oxygen, carbon dioxide and nitrogen have been made with a dynamic flow rate technique, utilizing a mass spectrometer detection system, and of oxygen using a commercial OXTRAN system. The samples were characterized by the measurement of density, birefringence and modulus and by wide‐angle x‐ray diffraction and differential scanning calorimetry. There is a large decrease in both the permeability and diffusion coefficients for all gases with increasing polymer draw ratio, with up to an 80‐fold decrease in permeability for the larger permeants compared with the 10‐fold decrease observed for helium. The solubilities of all the gases decrease only by a factor of ∼ 2. The diffusion results are discussed in terms of geometric impedance and chain immobilization factors. The solubilities, on the other hand, appear to relate primarily to the amorphous volume fraction of the polymer. © 1993 Joh

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310701

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractTensile yield stress measurements have been performed on a serie of four ethylene/1‐butene copolymers covering the crystallinity range 0.33–0.74. Samples have been prepared from melt‐crystallization and from solution‐crystallization at various concentrations in decalin in order to span a wide range of crystal thickness. It is shown that tensile yield stress depends on crystal thickness rather than on crystallinity. This result is perfectly consistent with a plasticity model based on the nucleation of dislocations. Besides, it in‐dicates that the main role of the amorphous phase is only to transmit the load upon the crystals, irrespective of its proportion. The yield stress dependence on crystallinity reported previously relies on the direct correlation of crystal thickness and crystallinity, in the case of melt‐crystallized samples only. Discrepancies with the model are amply discussed. © 1993 John Wil

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310702

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe slow crack growth behavior of a linear polyethylene with different morphologies was studied by using three point bending with a single edge notched specimen at testing tem‐peratures from 30 to 80°C. The morphology was varied by annealing the quenched material at temperatures from 86°C to 135°C. It was found that at test temperatures of 60°C or less, the changes in failure time with annealing temperature are very similar to the change in density with a maximum at 130°C. At testing temperatures above 60°C, the relationship of between failure time and annealing temperature is altered when the test is in the range of the α transition temperature. These results indicate that with respect to slow crack growth in the case of a homopolymer the strength of the crystals is relatively more important than the number of tie molecules. © 1993 John Wiley&

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310703

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn this work we have used synchrotron x‐radiation diffraction to follow in real‐time the isotropic‐smoetic phase transition of a side‐chain liquid crystalline polymer. The analysis of the x‐ray data indicated that the transition occurs within a very narrow biphasic region. As the transition takes place, the size of the smectic regions, as indicated by the width of the diffraction peaks, changed only very slightly before impingement, suggesting a two‐dimensional growth pattern. A thermal investigation of the polymer paralleling the x‐ray experiments was undertaken and a kinetic analysis applied to the resulting data. Qualitative agreement with a disk‐like growth of the smectic regions was found. We have shown that the overall kinetics of the isotropic‐smectic transition of a side‐chain polymer can be studied by x‐ray diffraction permitting the evaluation of several structural parameters. © 199

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310704

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have performed and analyzed extensive pressure‐volume‐temperature (PVT) measurements on uncrosslinked polybutadiene and polyisoprene elastomers from ambient temperature to about 200°C and 200 MPa. In the polybutadiene series, 1,2 content varied from 8 to 87%, the remainder being similar amounts of cis‐1,4 and trans‐1,4. In the polyisoprene series the 3,4 content varied from 8 to 64%, the trans‐1,4 content was 12–16%, and the remainder was cis‐1,4, with<4% 1,2 content. We report parameters describing the experimental data in terms of the empirical Tait equation, the cell model, the Simha‐Som‐cynsky equation, the Sanchez‐Lacombe, and the Flory‐Orwoll‐Vrij models. In general the parameters show systematic changes with the microstructure content. The agreement between theory and experiment is excellent for the Tait equation, and also for the Simha‐Somcynsky model and the cell model. The maximum deviation between theory and experiment was less than 0.004 cm3/g for the Simha‐Somcynsky theory, and less than 0.005 cm3/g for the cell model. Average absolute deviations are three to four times less. For the Sanchez‐Lacombe and the Flory‐Orwoll‐Vrij models, the maximum deviations are 5–8 times as large, and very systematic. Parameter derived from the Simha‐Somcynsky theory are discussed with respect to the microstructure, and with respect to the glass transition of these two series of

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310705

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe structure of a polymer prepared by the polymerization ofN‐benzoyl‐8‐octanelactam initiated with benzoic acid was studied by1H and13C NMR, using S‐INEPT, COSY, COLOC, and ROSEY methods, with the aid of model oligomers. Beside the expectedN‐benzoylated segments, the polymer also contained deacylated segments and about 50% of branching units. The polymer can be characterized as a statistical, highly branched copolymer ofN‐benzoyl‐8‐octanelactam and 8‐octanelactam. © 1993 Jo

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310706

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe orientational–deformational nature of flow birefringence (FB) in solutions of rigid‐chain polymers is confirmed experimentally. The possibility of a direct determination of the internal viscosity parameter by the dependence of the FB relaxation time on the solvent viscosity is demonstrated. Indirect manifestation of internal viscosity in the FB relaxation time is confirmed by the dependence of the form factor on the degree of coiling. © 1993 John Wiley&Sons,

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310707

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe repeated heating and cooling cycles under sinusoidal deformation have been investigated on nylon 6 fibers. The fibers zone‐drawn twice at high temperatures were used, which have a crystallinity of 52.2% and a birefringence of 59.4×10−3. The heating and cooling cycle was performed twice at a frequency of 110 Hz over a temperature range from 0°C to 180°C and 190°C. The crystallinity and birefringence of the treated fiber were 51.7% and 60.7×10−3, respectively, indicating almost no changes in molecular orientation and crystallinity. However, the dynamic modulus, E′, increased steadily over whole temperature range measured. Finally, the E′ value reached 21 GPa at room temperature and 10 GPa ever at 180°C. The elongation of fiber after two cycles was only about 5%. © 1993 John

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310708

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractElectron‐spin resonance (ESR) and altraviolet (UV) visible spectroscopic evidence has been found for the formation of diene, triene and tetraene, following the irradiation of polyethylene in the presence of acetylene. The polyenes are formed by a mechanism which is different from that observed under vacuum or with inert gas saturation. The sum of the G (polyene) values obtained by UV spectroscopy is almost half that of initial radical formation. It is concluded that polyene bridges, predominantly diene, form crosslinks between radical pairs. G (X) values determined from gel fraction data, using Saito‐Kang‐Dole theory, are found to be greatly in error and misrepresentative of crosslink changes. © 1993 John Wiley&Son

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310709

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and then‐phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley&Sons, I

ISSN:0887-6266    

DOI:10.1002/polb.1993.090310710

出版商:John Wiley&Sons, Inc.    

年代:1993

数据来源: WILEY