Heat transfer and cure in pultrusion: Model and experimental verification

Though pultrusion has existed for nearly 40 years, factors affecting temperature and resin reactivity are not completely understood. A model is tested to help explain the effects of die temperature, line speed and initiator concentration on curing inside a pultrusion die. The model includes radio frequency preheating, heat conduction, heat of cure, changing thermal properties with temperature and degree of cure, and hindered heat transfer due to shrinkage of the profile away from the die. The analysis is compared to experimental temperature measurements for a 1‐in. (25‐mm) round die, where die temperature, line speed, and initiator concentration were varied. Temperature predictions by the model are in good agreement with the data for many of the conditions tested. Considerable disagreement still persists, however, under processing conditions with faster line speeds and lower die temperatures.