Effect of hydrostatic pressure on mechanical properties of crystalline polymers under shear

1. Superimposing hydrostatic pressure increases shear strain resistance and leads to a reduction in structural defects. 2. A sharp reduction in shear modulus and yield point at 50–60 °C caused by superimposing hydrostatic pressure is explained by the presence of a relaxation transition at this temperature and is the result of freezing the amorphous phase of the partially recrystallized polymer by the action of pressure. 3. A uniform change in elasticity modulus and yield point with increasing pressure was established in the temperature ranges not containing relaxation transitions. 4. Limits were established for external parameters at which shear diagram similarity is observed.