In situ pultrusion of urea-formaldehyde matrix composites.: I.: Processability, kinetic analysis, and dynamic mechanical properties

We conducted a feasibility study on the pultrusion of a glass-fiber-reinforced urea-formaldehyde (UF) composite using a proprietary method. The UF prepolymer synthesized in this study was prepared from blends of UF monomer and a curing agent (NH4Cl). The process feasibility, kinetic analysis, and dynamic mechanical properties of the glass-fiber-reinforced UF composites by pultrusion were investigated. From investigations of the long pot life of the UF prepolymer, the high reactivity of the UF prepolymer, and excellent fiber wet-out, we found that the UF resin showed excellent process feasibility for pultrusion. A kinetic model, d alpha /dt = A exp(-E/RT)alpha (m)(1-alpha)(n), is proposed to describe the curing behavior of a UF resin. Kinetic parameters for the model were obtained from dynamic differential scanning calorimetry scans with a multiple-regression technique. The dynamic storage modulus of the pultruded-glass-fiber-reinforced UF composites increased with increasing die temperature, filler content and glass-fiber content and with decreasing pulling rate. (C) 2002 John Wiley & Sons, Inc. J Appl Polym Sci 83: 1242-1251, 2002.