Material characterisationInvestigations on cure kinetics and thermal degradation of stereolithography Renshape™ 5260 photosensitive resin

The stereolithography resin Renshape™ 5260 was characterized by infrared and nuclear magnetic resonance spectroscopy, indicating the presence of epoxy and acrylic reactive groups as well as aromatic and aliphatic ether groups. Infrared spectroscopy was also used to evaluate the curing process and identify the components of the thermal degradation of liquid and cured resins. Kinetics studies indicated that this solvent-free polymerization was diffusion-controlled during the chemical crosslinking, due to the reaction order of the curing process. The cured resin had only one degradation stage with activation energy of 90-250 kJ mol−1 in the weight loss fraction of 0.10-0.92, whereas a second degradation stage was observed for the liquid resin above the 0.6 weight loss fraction. This second degradation stage gives Ea values in the range of 70-140 kJ mol−1. The higher weight loss temperature of the cured resin compared with the liquid resin and the single decomposition stage observed for the former suggest a different decomposition mechanism and stability of the cured resin at higher temperatures compared to the liquid resin.