Load Bearing Response of HR Molded Foam as a Function of Processing and Testing Parameters

Abstract

There are critical processing and testing parameters which have major impacts upon the apparent firmness of HR molded polyurethane foam. Inadequate control of these parameters hinders the ability of the molder to meet narrow IFD specifications. This paper addresses five of these parameters and defines model equations which are useful in predicting load response to specific control parameters. In addition, the data are presented in a format that should be useful to the molder in better understanding the criticality of each parameter, singularly and in unison. The study was made possible by utilizing specialized equipment which allows accurate determination of IFD measurements under controlled and variable environments. It is well known that the load bearing responses of HR polyurethane foam are influenced by ambient temperature and humidity. These load bearing responses are generally reversible, and are not the permanent effects often seen as a function of environmental conditions at time of pour and post mold cure of the polyurethane. The idealized cushioning material would be unaffected by either temperature or humidity. Subsequent experimental designs exploring variables in polyol structures were conducted which have resulted in the definition of new high performance polyol systems that demonstrate less sensitivity to the reversible effects of temperature and humidity.