ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The styrene-butadiene block copolymers of SB, SBS, and SBSBS types were investigated by means of the stress-birefringence technique to elucidate the effects of the block multiplicity on the mechanical properties of copolymers. The SBS-type and the SBSBS-type block copolymers exhibit nonlinear stress-birefringence relations, which were classified into three regions. They are a low stress-optical coefficient region (optical creep), an increasing coefficient region, and a region of retarded increase in coefficient, as pointed out by Henderson et al.8 It was found that optical creep is associated with the polystyrene continuum. The third region, however, originates not only from the phenyl groups of the polystyrene block but also from a form-birefringence due to the orientation of the polystyrene domain. The multiblock copolymer of SBSBS type was found to be rheo-optically similar to the SBS type, both being affected solely by the details of the terminal styrene block.Pure gum vulcanizates of the SB-type and SBS-type block copolymers also exhibit optical creep. In a vulcanized block copolymer having both chemical and physical crosslinks, the latter seemed to disappear at elevated temperatures. At decreasing temperatures, the vulcanizates of block copolymers showed higher modulus of elasticity and lower stress-optical coefficients.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1970.070140323
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