The influence of long-term hydrothermal and physical ageing on the characteristics of additively manufactured bio-based photopolymer resin

Exposure to unpleasant environmental conditions can lead to the degradation of polymer material. This study presents an experimental investigation of the long-term hydrothermal and physical ageing behaviour of bio-based photopolymer resin. Bio-based resin specimens were prepared using vat photopolymerization-based 3D printing and submersed in water at 28.5 °C (SW-28.5 °C), 50 °C (SW-50 °C) and 75 °C (SW-75 °C) for 90 days to evaluate the influence of moisture, temperature and ageing time on the characteristics of bio-based resin specimens. Several tests were performed, including moisture absorption, fourier transform infrared spectroscopy (FTIR), tensile, hardness and microstructural tests to determine the mechanical, chemical and microstructural characteristics of bio-based resin specimens. The result showed that moisture absorption of SW-75 °C specimens were far higher up to 3 times extra moisture content than dry-fresh (DA) specimens. A direct relationship between moisture absorption and reduction in tensile and hardness properties was observed, with the tensile strength and hardness of specimens decreased up to 55.6% and 7.8%, respectively, after submersion in water at 28.5 °C for 90 days. As expected, the bio-based resin specimens showed notable physical degradation after being submersed in water at 75 °C, indicated by a decrease in tensile strength up to 58.9% only after one day of submersion. Formation of cracks on the specimens was observed after submersion in water at 50 °C and 75 °C, which also contributes to a decrease in the mechanical properties of bio-based resin specimens. The FTIR analysis showed several absorption peaks were getting less visible after submersion in water at 75 °C, indicating the notable degradation of bio-based resin specimens. Accordingly, understanding the polymer degradation is very important in the context of design considerations and predicting the service life of polymeric components.