Effect of high pulling speeds on the morphologies of pultrudates in a thermoplastic pultrusion process

Abstract

During thermoplastic pultrusion, increasing the pulling speed generally leads to a melted polymer pressure rise in the pultrusion dies. Yet, it was not clear if the polymer pressure’s increase would result in a faster impregnation flow that would compensate for the lower residency time inside the heating dies. Thus, the aim of this study was to verify if the speed-induced pressure can counterbalance the decrease in residency time that is required for impregnation quality and to analyze possible pultrudate morphology’s reconfiguration. Three distant pulling speeds were selected: namely 50, 500 and 1000 mm/min. Using a model, the polymer pressure in the pultrusion dies was computed to reach up to 1.0, 10.42, and 20.6 MPa for the respective pultrusion pulling speed. The morphology’s characterization showed a reconfiguration of the pultrudate at a higher pulling speed leading to larger unimpregnated agglomerations and polymer rich areas. The highest tensile strength achieved was 233.4 ± 1.5 MPa at 50 mm/min and dropped by around 20% when the pulling speed was raised to 1000 mm/min. The pultrudate reconfiguration at higher speed, attributed to delayed melting of PP fibers in underfilled dies, is deemed responsible for the loss in impregnation and mechanical properties.

Fatigue and Impact Properties of Kenaf/Glass-Reinforced Hybrid Pultruded Composites for Structural Applications

“…Calcium carbonate, CaCO3, and aluminium hydroxide, Al(OH)3, were used as fillers at 40% of the total resin weight [34]. Calcium carbonate serves as The pultrusion process parameters such as pull speed (30 cm/min), pull force (6 Bar), and die temperature (159 • C) has been set optimally according to the kenaf fibre mats' ability to withstand the force and temperature without being damaged [30,31]. The overall fibre/matrix ratio was fixed at 55/45 to achieve a high strength-to-weight ratio in the profiles [32].…”