Development and Production Trials of First Polyurethane Structural Foam Internal Mold Release System

Abstract

IM elastomers have been commercial since the late 1960's. Their R initial markets have been in the automotive industry for front and rear high impact fascia and later as external body parts such as doors and fenders. RIM Structural foams have been commercial equally as long attempting to penetrate markets traditionally held by thermoplastic structural foams.The initial attempts to penetrate these markets were made trying to utilize RIM's ability to mold parts at lower foam densities. However, these low density materials (.4 to .6 sp. gr.) also had lower strength properties thus requiring a change in design criteria which meant thicker cross-sections and additional ribbing. Even though this concept gave definite weight savings, it only received token acceptance of the different design requirements, so a different approach was taken. The improvements came rapidly, first increased impact, followed closely by higher strength properties and then a significant reduction in cure time (1.5 to 2.0 min.). With superior physical properties and inmold times less than thermoplastic structural foam, the next target would be in the area of process improvement.The area of primary concern was RIM's requirement to apply mold release after each molding. This requirement resulted in adding one-This paper was presented at The