Along with density and thermal conductivity, the amount of post-demold expansion exhibited by a foam is one of the most critical properties to processors of rigid polyurethane foams. The reason for this is the myriad of problems which can be caused by foam systems which show high post-demold expansion. Excessive post-demold expansion of a polyurethane foam can hurt the performance of the foam, detract from the appearance of the foamed article, and reduce productivity of the manufacturer. To illustrate these problems, this paper will focus on the use of polyurethane foam in household refrigerators. This paper describes how we assess the post-demold swelling behavior during development of new foam systems in our laboratory and discusses some of the causes of post-demold expansion. We will then discuss some of the factors which influence the amount of post-demold swelling exhibited by foam. And finally, we will give information on some of the foam systems we have developed to reduce the amount of post-demold expansion that occurs.
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