A feasibility study on the pultrusion of a fibre reinforced polyurethane (PU) composite has been conducted by using a proprietary method. The blocked NCO-terminated PU prepolymer synthesized in this study was prepared from epsilon-caprolactam blocked prepolymer blended with toluene di-isocyanate (TDI-80) and branched polyester. From the investigations of gel permeation chromatography, IR and H-1 nuclear magnetic resonance spectra and viscosity, the molecular weight, degree of blocked reaction and viscosity of the blocked PU prepolymer were obtained. From the mono-n-butylamine back-titration (wet) method, the equivalent weight and NCO content of unblocked NCO-terminated PU prepolymer were determined. A long pot life of blocked NCO-terminated PU prepolymer with various chain extenders, such as cycloaliphatic diamine, aromatic diamine and 1,4-butane diol, was observed in the impregnation temperature range (55-70-degrees-C). A high reactivity of prepolymer was found from Brookfield viscometer measurements at elevated temperature. From a morphological study of scanning electron micrographs, it was confirmed that the wetting of fibres by blocked PU resin was complete, and the fibre bundles were evenly distributed in the PU matrices.
