The effect of PAEK crystallization and stress in the forming process on pull-off properties of over-molded T-joint

In the over-molding process, injection molding most directly affects the sample properties, and the relationship between the resin crystallization behavior that occurs during this period and the sample properties has not been systematically studied. In this paper, poly(aryl ether ketone) (PAEK) and poly(ether ether ketone) (PEEK) with similar properties were used as injection materials to compare the different T-joints' mechanical properties under the same process, variable injection temperatures (T_inj) and variable annealing temperatures (T_anneal). The non-isothermal crystallization behavior of different resins and the stress after annealing were studied, and the influence of process conditions was summarized. Under the same conditions, resin-composite T-joints with low crystallization starting temperature (T_on) and slow crystallization rate have better pull-off properties. Increasing T_inj can increase the interface temperature, which prolongs the mutual diffusion of resin and improves the pull-off properties of the T-joint. Increasing T_anneal promotes resin crystallization but increases the stress during resin cooling, thus the T-joints' pull-off properties decrease.