Deformation of Cross-Linked Polymers Below Tg
Tensile tests were carried out on oriented elastomers in the glassy condition, and the deformation process was monitored by ESR. Both the nature and quantity of radicals formed are discussed. It is found that the radical concentration varies with the rate of deformation, the crosslink density of the sample used, the degree of deformation and the purity of the sample. Tests to explore the effect of crystalline morphology on radical formation are also briefly discussed.
Different modes of deformation occur, depending on the preorientation the sample receives prior to testing at temperatures below Tg. The three possible modes are found to be brittle failure, ductile failure associated with crazing, and ductile deformation with no observable crazing. When visible crazing occurs, it is always associated with the absorption of environmental gases, and where oxygen is present, this leads to the formation of peroxy radicals.
KeywordsTensile Test Natural Rubber Crosslink Density Network Chain Peroxy Radical
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