Compressive behavior after simulated service conditions of some foamed materials intended as orthotic shoe insoles.

The compressive characteristics of a group of foamed plastics and rubbers, suitable for use as orthotic shoe insoles, were assessed for any changes incurred as a result of exposure to a series of simulated service conditions. The service conditions considered in this study were heat (accelerated aging), sustained deflection (compression set), and cyclic loading. Since the stress/strain characteristics computed from the load/deformation curves were non-linear, it was necessary to develop a new procedure for comparing the relative compressive characteristics. The results from this study identified a group of preferred materials whose virgin compressive characteristics have been judged to be the most suitable, and which exhibited the least change following exposure to the three simulated service conditions.