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Extended‐chain and folded‐chain crystallite formation during the crystallization of stretched crosslinked rubbers
Author(s) -
Wu W.
Publication year - 1979
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760190604
Subject(s) - crystallite , materials science , crystallization , chain (unit) , polymer , crystallinity , crystallization of polymers , work (physics) , crystallography , thermodynamics , composite material , physics , chemistry , astronomy , metallurgy
The strain‐induced crystallization phenomenon of a crosslinked polymer network was studied using statistical, thermodynamics. The basic approach was essentially that used by Flory (1), but in this work Flory's assumption of only a single crystalline phase (the extended‐chain crystalline structure with chain parallel to stretch direction) was abandoned. The dimension of the crystalline vector‐which is assumed to be parallel to the stretch direction and the percent crystallinity is taken as two independent variables instead of being treated as one single variable. A single variable treatment is inherent in the assumption of a single extended‐chain crystallite. By use of the present approach, either the folded‐chain crystallite or the extended‐chain one is found to be thermodynamically stable depending on temperature, stretch ratio and molecular weight. The retractive force of a crystallized polymer network has been calculated. It is shown theoretically that the formation of an extended‐chain crystallite will cause the retractive force to decrease, and that the formation of a folded‐chain crystallite will cause the retractive force to increase in a reversible crystallization process.