A hypothesis is put forward to explain the plastic-elastic behavior of ebonite and its dependence on temperature. This is based on the previously described mechanical conception of ebonite as a system comprising a heat-stable elastic phase and a viscous temperature-sensitive phase, but the difficulty of reconciling this two-phase concept with the probable structure of ebonite is avoided by replacing the elastic and viscous phases respectively by primary and secondary (cohesional) bonds, the relaxation of the latter, due to their relatively low temperature-stability, being responsible for all time effects in the deformation of ebonite. The hypothesis explains the main facts relating to so-called plastic yield and to the residual strain after recovery from deformation, and thus appears to form a useful basis for further research on ebonite.

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