THERMAL-STRESS IN POLYMER SPHERULITES

The aim of this letter is to show that the curvilinear anisotropy of the spherulite causes a peculiar thermal stress distribution. To make the problem tractable it is assumed that in cases where the spherulites are equiaxed, the actual deformation due to thermal strain can be deduced by analyzing the deformation within a prototype spherical 'test' spherulite. The 'test' spherulite is embedded in an isotropic matrix to which is assigned the bulk polymer properties. Within an unconstrained spherically anisotropic solid, thermal stresses will arise. These thermal stresses may be partially responsible for fatigue cracking which has been observed in pipelines made of semi-crystalline polymers. These materials are susceptible to corrosion cracking which may be accelerated by hydrostatic tensile stresses.