Perspectives for Reactive Molding of PPA as Matrix for High-performance Composite Materials

Abstract

While liquid composite molding (LCM) technologies for thermoset composites are increasingly used for manufacturing high quality structural components, LCM technologies based on thermoplastic matrices are still in development. Reactive thermoplastic LCM processes are at present applicable only to a few engineering polymers. This work presents perspectives for reactive molding of a high-temperature resistant polyphthalamide (PPA). Thermoanalytical, rheological, and optical tests were performed to assess the behavior of low-melting PA 6T/6I oligomers with increasing temperature and to monitor the polymerization and crystallization reactions. The raw oligomeric material first undergoes a solid-liquid phase transition at around 135 C. At this stage, it shows a shear-thinning behavior and its viscosity is around 102 Pa s. At higher temperatures, the viscosity of the oligomeric melt decreases further until a high temperature crystallization process occurs at about 180 C. Polymerization starts at about 220 C and ends at 290 C. During the reaction the polymer crystallizes as soon as it is formed with an achievable degree of crystallinity considerably higher than that of melt-crystallized samples. In accordance with the results, a viable processing technology based on powder impregnated intermediate materials is proposed.