Analysing the effect of Mold Temperature on Foam Density and Foam Surface Texture

Abstract

Polyurethane (PU) foam is molded into preheated tools and expands to fill the mold cavity. Foam parts frequently have defects such as varying density and flaws in surface texture. Although there are many possible causes uneven mold temperatures are suspected to be a leading cause of defects^(1,2). Much of the work previously undertaken to reduce flexible foam molding scrap and improved quality has focused on chemical compositions, chemical reactions and materials development. This research is to investigate the effects of mold temperature on high-resilience cold-cure polyurethane foam molded parts. A specially designed airtight mold capable of holding tight temperature tolerance was used to produce standard size foam specimens at varying temperatures ranging from 30 °C to 80 °C. The specimens were kept in a controlled temperature and humidity environment for a stipulated time before analysis. The effect of mold temperature on the average foam density, density gradients and surface texture were measured.

The foam specimens were weighed and measured for the overall density while Computerized Tomography was used to examine the density gradients throughout each foam specimen. 3D topographical analysis of the foam surface structure was conducted using a non-contact laser triangulation gauge. The results show that the mold temperature has an effect on the foam density and foam surface texture with specimens produced at 50 °C having the ideal texture.