Mechanical behavior of polycarbonate rods by hot extrusion

摘要

The dependence of the mechanical behavior of an amorphous polymer on processing conditions was experimentally investigated. Hot rods of polycarbonate were extruded and cooled rapidly under constraint of strain recovery. Rods were extruded at elevated temperature close to the glass transition temperature. Uniaxial tensile tests and shear tests were made at room temperature. The stress-strain curves were affected by extrusion processing conditions, such as extrusion ratio, extrusion temperature and constraint of strain recovery. The Young's modulus, tensile strength and shear strength of extrudates below the glass transition temperature increased with increasing extrusion ratio. The mechanical properties of extrudates under free strain recovery were smaller than that under constraint of strain recovery at the same extrusion ratio. Since marked strain recovery appeared in products under free strain recovery, products with high extrusion ratio could not be obtained with increasing extrusion temperature and extrusion rate. The mechanical properties of extrudates above the glass transition temperature hardly depended upon the extrusion ratio and the degree of strain recovery. A high degree of molecular orientation was exhibited by polycarbonate extruded at high extrusion ratio below the glass transition temperature under constraint of strain recovery. The mechanical properties of extrudates followed a linear trend with increasing birefringence. The stress-strain curve of a cold drawn sample was almost coincident with that of an extrudate at the same drawing ratio.