Entangled Chain Structure Trapped in a Styrene-Butadiene Random Copolymer by Cross-Linking in Simple Extension

Steve Granick, John D. Ferry

Research output: Contribution to journalArticlepeer-review


Rubber networks were prepared by cross-linking linear styrene-butadiene random copolymer (67% styrene content) with γ-radiation. Before cross-linking, the polymer was stretched in simple extension, allowed to relax at constant strain and temperature for a controlled time, and then quenched 20°C below Tg and maintained at this temperature during cross-linking. Upon warming above Tg, the equilibrium length was intermediate between the stretched and unstretched lengths and was describable as the result of additive contributions from the cross-link and trapped entanglement networks. The fractions of trapped unrelaxed entanglements Te and trapped relaxed entanglements Te,r were estimated and compared with the Langley theory. For minimal terminal zone relaxation before quench, Te agreed rather well with the Langley theory and Te,r was zero. With increasingly long terminal zone relaxation before quench, Te increased and Te,r became finite and increased. This behavior is consistent with the terminal mechanism of relaxation in the tube theory of Doi and Edwards. These experiments confirm the presence of permanently trapped entangled chain structure (or equivalent trapped topological restraints), in agreement with earlier extensive work on 1,2-polybutadiene.

Original languageEnglish (US)
Pages (from-to)39-45
Number of pages7
Issue number1
StatePublished - Jan 1983
Externally publishedYes

ASJC Scopus subject areas

  • Organic Chemistry
  • Polymers and Plastics
  • Inorganic Chemistry
  • Materials Chemistry


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