Mechanical properties of radiation cross linked polyamide 12 after vacuum thermoforming

Abstract

Generally semi-crystalline thermoplastics have an inferior thermoformability compared to amorphous thermoplastics. This is because of their sharp drop in stiffness and viscosity with crystalline melting. Radiation cross-linking of semi-crystalline thermoplastics offers a solution for this limitation. The thermoformability is essential for processing, but the parts properties like the mechanical ones are important for the application of thermoformed parts. In this article the effects of mold geometry and temperature, forming temperature and film thickness on the mechanical properties of thermoformed cross-linked polyamide 12 (PA12) are investigated. The results show the improvement of the thermoformability of semi-crystalline thermoplastics by cross-linking. Concerning the mechanical properties of the parts, a significant enhancement in stiffness and tensile strength can be obtained, while the ultimate strain at break decreases compared to the smooth film's properties. Thermal processing conditions, deformations during forming and the degree of cross-linking of the film material have an influence on these effects.