Effects of biaxial orientation on the properties of films prepared from poly (vinyl chloride) and poly (methyl methacrylate co imide) blends

A study was carried out of the poly(vinyl chloride) (PVC) and poly (methyl methacrylate co imide) (PI) blends to investigate their potential for packaging applications at increased use temperatures. PVC-PI blends were prepared by extrusion blending and the blends were characterized for miscibility. Based on the dynamic mechanical analysis it was concluded that the PVC-PI system was miscible over the entire range of compositions. Biaxially oriented films were prepared on the T. M. Long extensional tester. The processing conditions required for successful stretch orienting the blends were determined. The preferred processing temperature range increased from 100°-105°C for PVC to 165°-170°C for the neat PI, although the latter range depends on the molecular weight and degree of imidization of the polyimide. For a blend of given composition the degree of orientation increased with the stretch ratio for a fixed strain rate and stretching temperature. The degree of orientation was found to be very sensitive to the stretching temperature for a blend of given composition and decreased sharply with increasing stretch temperatures. The mechanical properties of the biaxially oriented films were found to be dependent on the degree of molecular orientation and blend composition.