ABSTRACT
Elimination of postcure in the manufacture of RRIM automotive body panels would result in significant savings. Bayflexl90 polyurea, which attains virtually all properties at demold, is a candidate for manufacturing without postcure. Several very sensitive analytical methods have been employed to characterize the degree of cure at demold. Differential scanning calorimetry (DSC) shows no exothermic chemical reaction up to 200°C. Thermal gravimetric analysis (TGA) shows no CO2 loss from unreacted isocyanates. And Fourier transform infrared spectroscopy (FTIR) scans indicate only trace free isocyanate in freshly molded samples.
The ability of an organic composite to anisotropically match thermal expansion behavior of metallic materials is highly desirable for automotive body panels such as door skins. Bayflexl80 high performance polyurethane has been reformulated to accept higher loading of reinforcing filler. Using 25% by weight loading of fiber fillers a coefficient of linear thermal expansion (CLTE) of 26 × 10−6 cm/cm/°C has been attained parallel to flow into the mold. This value is equal to that of aluminum.
