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The stress birefringence of vulcanizates of polyisoprene–polyethylene blends
Author(s) -
Nishioka A.,
Furukawa J.,
Yamashita S.,
Kotani T.
Publication year - 1970
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1970.070140506
Subject(s) - materials science , polyethylene , birefringence , copolymer , vulcanization , creep , composite material , stress (linguistics) , dispersion (optics) , polymer chemistry , elongation , natural rubber , polymer , ultimate tensile strength , optics , linguistics , philosophy , physics
As a model for the vulcanizates of block copolymers, mixtures of polyisoprene and polyethylene vulcanized both with a peroxide and with sulfur were investigated by stress birefringence. It was found that the polyethylene dispersion showed a reinforcing effect only in the peroxide vulcanizates. On the other hand, the stress birefringence was decreased with increased polyethylene content except at high polyethylene content. In the latter case, the slope of the line in the birefringence–stress plot was almost equal to that for the pure polyisoprene vulcanizate at high stress levels. However, at lower stresses significant optical creep was observed, i.e., the stress increased without bire‐fringence. Such an optical creep as this exists also in styrene–butadiene block copolymer. These facts are interpreted by the assumption that polyethylene dispersion, when it is linked chemically with polyisoprene matrix, acts as a reinforcing agent by forming physical crosslinks similar to the hard domains in block copolymers. Such physical crosslinks can slip during elongation, resulting in the observed optical creep. These phenomena disappear at the elevated temperature.