In order to control reaction temperatures, auxiliary blowing agents such as freon were once used. The polyurethane foam industry in the United States has been successful in finding chemical and mechanical process substitutes for freon resulting in the virtual elimination of CFCs in flexible foam processing. The Clean Air Act Amendments of 1990 have further pushed the industry to reduce all airborne chemical emissions. Colorants do not affect physical performance. For application where FPF is to be used in moist, warm environments conducive to growth of mold and mildew.
Density is a measurement of the mass per unit volume.
Remember that flexible polyurethane foam is made up of struts and voids. Since voids are empty spaces, when you weigh a sample of foam, you are actually weighing the struts, not the voids. The diameter and length of the struts represent the mass. High density foams can be produced very soft and low density foams can be made very firm. High density foam products generally offer a great deal of support, but they may actually be fairly soft foams.