Investigations to the Effect of Preheating the Resin on the Pultrusion Process

Pultrusion is the only continuous process for production of composite structural components with constant cross-sectional area. So far, thermosets have been used nearly exclusively. Now resins will be tested, which cure to thermoplastic polymers having all advantages of thermoplastic materials like recyclability, the possibility of subsequent shaping, etc. The curing time of these resins limits the pultrusion speed, which significantly influences the cost of the product. Against this background we have investigated effects of pre-heating the resin on the pultrusion parameters. For pre-heating we use microwaves in special die and conventional heat just before resin injection in the impregnation chamber. These effects of resin pre-heating depend strongly on the thickness of the pultrudate and can be estimated with the thermal relaxation time. If the pultrudate is thick enough, an improvement of up to 50% pulling speed was proven by drastically reduced pulling forces. For thin parts resin pre-heating effects are negligible. On the other hand, the temperature of the fibres has a positive effect on the pultrusion process regardless of the thickness of the part