Fast & energy-efficient composite processing by self-catalysed frontal polymerisation
Topic(s) : Manufacturing
Co-authors :
Jeroen STAAL (SWITZERLAND), Baris CAGLAR (NETHERLANDS), Véronique MICHAUD (SWITZERLAND)Abstract :
Frontal polymerisation is emerging as a promising out-of-autoclave (OoA) processing strategy, allowing for the production of fibre reinforced polymer (FRP) composites in a fraction of curing times encountered with conventional composite processing techniques, while also reducing environmental and economic impacts[1]. Employing a Radical Induced Cationic Frontal Polymerisation (RICFP) mechanism[2], several recent reports demonstrated the possibility to produce epoxide-based FRPs in seconds to minutes[3–5] that typically scales with the part size. RICFP is driven by an autocatalytic mechanism that, after an initial external trigger, allows for the formation of a distinct front between hot (> 200°C) formed epoxide polymer and cold monomer resin, that subsequently progresses through an impregnated resin-textile system as long as a threshold activation energy is exceeded. The temperature of the front is a direct result of the local heat balance, which is governed by the exothermic heat of polymerisation that is counterbalanced by thermal diffusion, heat transfer to the environment and to reinforcement materials.
The use of RICFP for the production of FRPs is hindered by the extensive heat uptake of fibrous reinforcements, which limit the maximum fibre volume fraction (Vf) that could be successfully be polymerised to ~40%[3,5] above which fronts are typically quenched. We have previously demonstrated[6,7] that this limit could be extended to 45.8% by precise engineering of the local heat balance. The system limits remain however well-below the Vfs of >55% that are typically sought for in industry. Alternative strategies such as pre-heating of the system[1,8] or relying on the application[9] or integration[10] of resistive heaters have shown to be effective but these add to the energy input to the process and reduce the advantage of a versatile, low-energy FRP processing method. During the talk, we will introduce our novel self-catalysed processing method that can produce FRPs with Vfs up to 60%, i.e. 15% higher than reported by our previous study, without the need for a continuous external energy input. After a brief description of the process, we will demonstrate the thermal validation and potential for enhanced process control. Finally, we will show that the new process is beneficial for the resulting FRP properties such as the glass transition temperature and mechanical properties compared to conventional oven-curing at an energy demand reduced by >99.5 %.
The use of RICFP for the production of FRPs is hindered by the extensive heat uptake of fibrous reinforcements, which limit the maximum fibre volume fraction (Vf) that could be successfully be polymerised to ~40%[3,5] above which fronts are typically quenched. We have previously demonstrated[6,7] that this limit could be extended to 45.8% by precise engineering of the local heat balance. The system limits remain however well-below the Vfs of >55% that are typically sought for in industry. Alternative strategies such as pre-heating of the system[1,8] or relying on the application[9] or integration[10] of resistive heaters have shown to be effective but these add to the energy input to the process and reduce the advantage of a versatile, low-energy FRP processing method. During the talk, we will introduce our novel self-catalysed processing method that can produce FRPs with Vfs up to 60%, i.e. 15% higher than reported by our previous study, without the need for a continuous external energy input. After a brief description of the process, we will demonstrate the thermal validation and potential for enhanced process control. Finally, we will show that the new process is beneficial for the resulting FRP properties such as the glass transition temperature and mechanical properties compared to conventional oven-curing at an energy demand reduced by >99.5 %.