Optimization of bio based glass polyfurfuryl alcohol prepreg for composite applications

Global sustainability and emissions concerns in the manufacture and application of fibre composites have recently fueled research and development of bio-based alternatives to mitigate these challenges. One such material that has been developed and recently explored for composites applications is bio-based polyfurfuryl alcohol resin. It has demonstrated impressive mechanical and thermal properties in fibre applications. However, this comes with a major disadvantage of the long processing time, which for its manufacture is synonymous with manufacturing processes such as oven or autoclave curing, which limits its application for high volume production. To this end, this project aims to optimize the curing cycle of the glass / PFA prepreg for rapid manufacturing. Model-free and model-based kinetic studies were performed to understand the curing mechanism that occurs during the curing reaction. The Friedman and Ozawa-Flynn wall models were used to investigate the conversion-dependent activation energy. Both methods found that the average activation energy for the curing process was 88.9 ± 4.9 kJ/mol and further revealed a curing mechanism with a multi-step curing reaction consisting of parallel and competing reactions taking place simultaneously during the reaction. This was found to be relatively consistent with that obtained by the Kamal-Sourour fitted model. The excellent correlation between the Friedman model and the experimental data made it suitable for predicting the evolution of the reaction time under isothermal conditions, leading to an optimization of the total process cycle time from the manufacturer's recommended cycle of 113 minutes to 30 minutes when held isothermally at 160℃. Thus, suggestively making it suitable for rapid manufacturing processes such as the compression moulding process. Mechanical and thermal characterization was performed on Glass/PFA laminate manufactured by a hot press using the optimized cycle from the kinetic study at two different pressure (5 and 10bars) and this was benchmarked against laminates manufactured by the vacuum bagging - oven curing method using the manufacturer’s recommended cycle. The experimental results reveal that the cured glass/PFA laminate manufactured using the optimized cycle at 5 bar pressure was found to exhibit the best result showing an increase in the glass transition temperature (Tg) from 175℃ to 201℃. The impact of the optimized cure parameters on the mechanical properties of the glass/PFA composite was significant. It resulted in a notable 10.25% improvement in tensile strength, a substantial 13.04% increase in flexural strength, and a commendable 10.34% enhancement in apparent shear strength compared to the reference oven-cured glass/PFA sample. This successful study has effectively established the ideal cure parameters for the glass/PFA prepreg, enabling rapid and efficient composite fabrication.