Multi-stage, in-situ polymerisation for low-exotherm, liquid resin infusion of thick thermoplastic laminates at room temperature

This study exploits the unique attributes of a reactive thermoplastic acrylic resin system (room-temperature liquid-resin infusibility, in-situ polymerisability, and room-temperature weldability) to achieve additive-free mitigation of exothermic heat generation during thick laminate production. Additives are typically required when thicknesses exceed 12 mm, but their use often compromises the degree of polymerisation and mechanical performance. An innovative multi-stage manufacturing scheme has been used to achieve a 55°C reduction in exothermic peak temperature during the production of a 16-mm-thick laminate compared to the use of a standard resin infusion (89°C) for the same thickness. Laminates produced using the multi-stage scheme were also found to exhibit 24% higher short-beam shear strengths than those obtained via standard resin infusion, suggesting improved part quality as an additional benefit. Further demonstrating the applicability of the proposed method, a 40-mm-thick laminate was successfully produced with a peak temperature of only 60°C. This work highlights the potential of room-temperature welding for practical and low-cost production of ultra-thick laminates at room temperature.