The influence of different melt temperatures on the mechanical properties of injection moulded PA-12 and the post process detection by thermal analysis

Polyamide 12 (PA-12) test plates were injection moulded using different melt temperatures and the influence on mechanical properties was investigated using quasi-static tensile and instrumented impact behaviour in two conditioned states: dried, and following accelerated moisture intake. Energy absorption in tension is strongly dependent on process temperature (variations up to 99 %) and additional variation (around 18%) was evident when testing at different conditioning states. Under high-velocity loading, the total impact energy varied by up to 8.70% and 9.05%, when systematic changes were made to process melt temperature and at moisture content, respectively, with all samples failing ductile. Differential Scanning Calorimetry (DSC) was used to characterise the unique endothermic melting behaviour of moulded PA-12 samples, by linking different process histories to the respective mechanical properties. With focus on the first heating curve progression, significant changes within the endothermic melting region were pointed out and quantified by using MatLab (software), proving DSC as a reliable testing tool for post-production analysis with increased practical implications regarding quality control as well as failure analysis. Findings for the initial heating curve progression were explained by studying the re-crystallisation peak values during cooling phase and obtained data for the second heating.