Glass Transition and Crystal Growth of Rubbers

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In the research on glass transition, the memory effect. upon glassification is studied in the glass to rubber transition of vulcanized rubber with the strain as a controlling parameter. A phenomenological model is proposed taking the history of the temperature and the strain into account, by which the experimental results are interpreted. The data and the model demonstrate that the glassy state, memorizes the time-course of strain upon glassification, not as a single parameter but as the history itself.The crystallization and the melting of vulcanized isoprene rubber under uniaxial deformation have been studied by the measurements of the stress-strain-temperature relation. The melting temperature increases approximately linearly with nominal stress for the rubbers crystallized at a fixed temperature and stress condition. It: has been shown that the main origin, of the rise in melting temperature with stress is the work of contraction upon melting rather than the entropy reduction on deformation in the molten state. The crystallization rate monotonically increases with nominal stress above the melting stress at a given temperature, while it shows a maximum against temperature at a given stress.. The relation between the temperature and the nominal stress at the onset of crystallization is satisfactorily reproduced by the simplified kinetic model.