Microcellular Elastomers by Single-Stage Technology

Abstract

A series of single-stage, ambient cured microcellular polyurethane elastomers, based on liquid methylenebis(phenyl isocyanate), was prepared employing a variety of polyols and extenders at varying isocyanate indices and polymer densities. Significant differences in polymer properties may be obtained by employing various high molecular weight base polyols. However, for any given system, polymer properties can be varied through increasing isocyanate index and polymer density. In general, hardness and strength properties are increased with increasing isocyanate indices and polymer density, while elongation and cold flexing are decreased. Optimum tear strengths are obtained by using a slight excess of isocyanate required to react with all active hydrogen. These polymers which can be processed on conventional foam metering and dispensing equipment are suitable for energy absorbing, abrasion resistant and high flexing applications.

Molding Castable Urethane Polymers

“…Solvent expansion using methylene chloride has been evaluated for producing microcellular elastomers with a densified skin (20), and ambient cured microcellular polyurethane elastomers based on liquid MDI have been made (21). Microcellular foams, of the type used in automotive bumpers, vibration isolators, and shock absorbing pads are made by reacting polyether polyols and reactive diamines with TDI in the presence of carefully controlled amounts of water as the blowing agent.…”