PREDICTING ENERGY-REQUIREMENTS FOR MOLDING FLEXIBLE POLYURETHANE FOAMSHEETS

Moulding is a method of inducing a permanent three-dimensional shape i n thermoplastic materials by heat setting. Using polyurethane foam mou lding for brassiere pads as an example, the most essential problem is to predict the optimum conditions that result in the best cup shape co nformity with the most efficient use of heat energy. To study the best moulding quality, a response surface method is used to examine the re lationship between a measured response (shape conformity) and a number of input variables (moulding temperature and time). The optimum mould ing conditions for individual foam types can be found by examining the contour plots of response surfaces. A relationship between the mouldi ng temperature and time is then derived. The heat energy required for optimum moulding can be expressed in terms of these two moulding varia bles and three other foam attributes (mass, specific heat, and thermal conductivity).