Effects of resin types on the durability of single yarn polymer composites exposed to hygrothermal environment

This study evaluated the durability of glass fibre composites prepared using bio-epoxy, vinyl ester and epoxy resin when exposed to a simulated hygrothermal environment. Initially, glass fibre yarns, resins and single yarn composites were exposed to 60oC at 98% relative humidity for up to 3000 hours. This was followed by the thermal (DSC), chemical (FTIR), tensile and interfacial shear strength characterization, and the morphological observations under the scanning electron microscope. Results revealed that the resin types significantly influenced the durability of glass fibre yarn composites. Bio-epoxy and vinyl ester resin exhibited thermal stability after exposure to a hygrothermal environment for 3000 hours, with an increment of 19oC in the glass transition temperature of epoxy because of the additional cross-linking of the polymeric chain. FTIR spectra reveal that bio-epoxy was chemically stable, while epoxy and vinyl ester resin have undergone chemical degradation because of hydrolysis. The tensile strength of fibre yarn was decreased by 37% because of blistering at the fibre surface, while a reduction of 22%, 10%, and 20% was observed for epoxy, bio-epoxy, and vinyl ester, respectively. Furthermore, the interfacial shear strength was reduced by 15%, 6%, and 25% for epoxy, bio-epoxy, and vinyl ester composites, respectively. Despite the Tg increase, hydrolytic chain scission and damage at the interface reduced the mechanical strength of epoxy. Analytical Hierarchy Process revealed that bio-epoxy resin performed best under hygrothermal conditions when mechanical properties were a priority, whereas vinyl ester resin performed best if physical or thermal properties were most important.