摘要:

AbstractThe microstructure of polypropylene, annealed after cold drawing to an oriented state, was examined using density measurements and small‐ and wide‐angle x‐ray scattering (SAXS and WAXS) techniques. SAXS patterns were obtained after annealing (in an oil bath), and during annealing (of samples annealed in a furnace placed directly in the x‐ray beam). Data, for isothermal annealing, showed an increase in SAXS intensity, in crystal perfection, and in density over the observed time range, but no change in long spacing during the same period. Long spacing, SAXS intensity, and density were all strongly dependent upon annealing temperature, increasing at higher temperatures. Upon annealing the elastic modulus and yield strength dropped below the as‐drawn values in an immeasurably short time, and did not appear to change thereafter during the time range examined. The decrease was more marked for higher‐temperature annealing. The kinetics of the micro‐structural changes are compared qualitatively to the predictions of nucleation and growth theory and of spinodal decomposition. The defects in the microstructure are considered as the “solute molecules” of the spinodal model. The experimental results do not agree neatly with either model. However, a nonequilibrium thermodynamic approach appears to be the more promising. It is suggested that the kinetics of mechanical property change may be due to different rates of migration for differe

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200311

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe protonation of a heterocyclic rigid‐rod polymer poly(p‐phenylene benzbisthiazole) and its model compound has been studied by UV‐visible and Raman spectroscopy. Because of the two nitrogens on the heterocyclic ring, spectroscopic features of unprotonated, half‐protonated, and fully protonated structures have been identified. For the fully protonated molecule, there is also an increase in conjugation between the phenyl ring and the heterocycl

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200312

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractPolypropylene films were produced by solidification during high‐rate (>104s−1) melt drawing. Small‐angle x‐ray scattering (SAXS) data were collected during interruptions of the annealing of these films. Fibrillar crystallization took place during the melt‐drawing process. The fibrils exhibit an axial density modulation as determined by SAXS and transmission electron microscopy. Annealing increases the amplitude of the density modulation. Detailed examination of the SAXS curves shows that the modulation is approximately sinusoidal and that the amplification of the density modulation occurs with no change in periodicity. Comparison of SAXS curves taken at different times during annealing suggests a process similar to spinodal decomposition. It is proposed that the microstructural change within a fibril takes place by the axial motion and clustering of chai

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200313

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

摘要:

AbstractThe crystal structure of the alternating copolymer of hexafluoroisobutylene and vinylidene fluoride, P(HFIB/VF2), was determined usingx‐ray diffraction techniques. Oriented specimens of the copolymer were produced by drawing melt‐pressed film at 300°C. The unit cell of P(HFIB/VF2) is orthorhombic with dimensions ata= 1.064,b= 1.837, and c = 0.783 nm. The chain conformation is a 21helix with an approximatetrans‐trans‐gauche‐gauchebackbone dihedral‐angle sequence. Severe intrachain steric crowding exists; as a consequence, the chain is quite rigid and some of the backbone bond angles are highly extended. The unit cell contains four such chains packed according to the symmetry of space group Iba2. Neighboring chains in a crystal are mechanically interlocked; in combination with the rigidity of the chains, this is the basis for the superior mechanical properties of the copolymer compared to PTFE. A structure containing up to 20‐30% of head‐to‐head residues was found to be statistically indistinguishable from a completely head

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200314

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200315

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY

ISSN:0098-1273    

DOI:10.1002/pol.1982.180200316

出版商:John Wiley&Sons, Inc.    

年代:1982

数据来源: WILEY