Pultrusion is a common semi-automated manufacturing method for the production of fibre- reinforced polymer matrix composite materials having a uniform cross-section. The properties of the pultrudate are strongly influenced by the chosen fibre reinforcement and resin matrix, and the resulting micro- and/or macrostructure that evolves as a function of the processing conditions.

The polymer resin used in pultrusion may be formulated using a range of additives including the fillers, mould release agents and catalysts. The quantity of the additives relative the resin fraction is known to also affect the curing behaviour of the resin and the end-properties of the pultrudate. The degree of cure of the resin matrix is critical for optimising the properties of the final composite materials. Ensuring completion of the crosslinking reaction results in the highest possible mechanical properties and long term stability of the pultrudate.

In the present work, the objective is to investigate the influence of the catalyst combination (type and content) on the curing behaviour of a polyurethane resin used during the pultrusion process. The catalysts are responsible for ensuring complete curing of the resin, and their selection is critical to the realisation of the pultrusion process. Therefore, it is of interest to determine the optimal quantity of catalyst that will achieve a sufficient degree of cure. The effect of the catalyst combination is also correlated to the mechanical properties of pultruded glass fibre-reinforced polymer composites (GFRPs). A variety of commercially- available catalysts were added to a polyurethane resin. The effect of the catalyst combination on the curing behaviour was studied by thermal analysis. Resin formulations that exhibited optimal curing characteristics were then used in experiments using a commercial pultrusion set up. The results from the pultrusion experiments were compared to that from laboratory-scale experiments that utilised thermal analysis. The effect of the resin formulation on the shear and flexural strength of the pultruded GFRPs was investigated. Results demonstrated improvements in mechanical properties with increasing degree of cure and crosslinking achieved by catalyst combinations. The addition of a second catalyst to the resin formulation significantly improved the degree of cure and crosslinking achieved during the pultrusion of GFRPs. The optimal shear and flexural properties were achieved by the combination of catalysts Perkadox 16 and TBPB at a ratio of 100 parts of resin to 1 part of Perkadox 16 and 1 part of TBPB.