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Behavior of cis ‐polybutadiene during mastication
Author(s) -
Kraus Gerard,
Rollmann K. W.
Publication year - 1964
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.1964.070080608
Subject(s) - polybutadiene , bond cleavage , radical , shear rate , materials science , polymer , oxygen , natural rubber , shear (geology) , reaction mechanism , chemistry , degradation (telecommunications) , polymer chemistry , composite material , catalysis , rheology , organic chemistry , copolymer , telecommunications , computer science
Cold mastication of natural rubber in presence of oxygen leads to scission by a shear mechanism with subsequent stabilization of the free radicals by oxygen, while at high temperatures oxidative scission becomes the dominant mechanism. Studies of the behavior of cis ‐polybutadiene reveal that similar reactions are effective, but occur at much reduced rates. Shear degradation is particularly difficult to achieve in typical cis ‐polybutadienes. This is related to the molecular weight distribution of these polymers which usually lack the very high molecular species most subject to shear‐induced degradation, in agreement with the theory of F. Bueche. It is shown that when such a high molecular weight fraction is supplied, shear breakdown may be realized. All cis ‐polybutadienes undergo oxidative breakdown at high temperatures, the scission rate becoming appreciable above 140°C. A number of oxidation catalysts have been found which markedly increase the scission rate without leading to a correspondingly large increase in crosslinking. Significant improvements in processing may be realized in this manner.