Effect of Mold Temperature on High-resilience Cold-cure Flexible Polyurethane Foam Surface Texture

Abstract

Flexible polyurethane foam is often molded directly into preheated tools for foaming reaction which expands to fill the mold cavity. The foam that is directly in contact with the mold surface cures as the foam skin. Parts frequently have surface defects ranging from shrink marks, to voids, to mottling, and knit lines. There are many possible causes such as applying too much or too little release agent, or mold surface not cleaned and conditioned as required before the foaming process. Uneven mold temperatures are also suspected to be a cause of surface defects, especially in high-resilience (HR) cold-cure polyurethane foam systems. A specially designed mold capable of maintaining tight temperature tolerance is built to produce foam samples at varying temperatures. The effects of mold surface temperature on the foam surface texture are studied and analyzed. The effect of processing temperature on the macro and micro surface texture is examined. It is shown that the processing temperature has a significant effect on the foam surface texture. Three-dimensional topographical analysis of foam surface texture has discovered a trend from samples produced at varying temperatures from 30 to 80 C. This research is funded by EPSRC and assisted by Collins and Aikman UK, and Rojac Tooling Technologies Ltd.

Keywords

polyurethane foam surface texture mold temperature surface roughness

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