Manufacturing and testing of single polymer polyamide 66 composites

In the last decades, a new class of polymer composites has attracted the attention of research activities and has driven the development of new materials with interesting potential in many industrial fields. The idea of these new materials, better known as single polymer composites (SPCs) or self-reinforced polymeric composites (SRPCs), arises from the observation that the same polymer shows different melting points depending on the form in which it is available (eg powder, fibre or film). In other words, it is possible to obtain innovative composites by combining matrices and reinforcements made of the same polymer ensuring, among other things, products with perfect interfacial adhesion and recyclability. In this work, self reinforced laminated samples based on a technical polyamide 66 (PA66) fabric were manufactured by hot-compaction technique and compared with compression molded plaques based on commercial polyamide 66, neat and filled with 30 wt% of glass fibres, taken as the reference materials. Preliminary calorimetric analyses made possible to establish the most appropriate process conditions. With the awareness of a narrow window of processability of the raw materials, plates from the PA66 fabric were produced by considering two cooling protocols. The calorimetric analysis and the mechanical tests carried out in quasi-static, dynamic and impulsive modalities have highlighted distinctions between the 2 types of self-reinforced composites essentially due to the different structural features promoted by the applied process conditions. The results were systematically validated with morphological investigations of the fractured surfaces coming from the impact tests. Analysis of micrographs, among other things, made it possible to identify the main damage mechanisms characterizing the failure of the new self reinforced materials.