Microcellular Polyurethane Research Articles

Low-Density Microcellular Polymer Foams: Applications in Biomaterials

AbstractMicrocellular polymer foams are of interest as biomaterials for uses such as artificial skin, synthetic vascular replacements, artificial organs, and for use in permeable drug delivery systems. We wish to report the use of thermally - induced phase separation as a technology by which a variety of polymer foams can be prepared. This process permits control of foam morphology, cell size, and density. Importantly, the phase separation process results in fully open-celled foam structures. Additives such as small molecules and functionalized polymers have been incorporated into these microcellular foams resulting in polymer surfaces with controlled porosity and chemical modification. Microcellular polyurethane foams, with chemically modified surfaces, have potential application as small-diameter vascular replacements.

Boots for oily surfaces

A field trial of footwear was commenced 5 years ago to try and find the most suitable boots to prevent slipping accidents on floors contaminated with mineral oil. After preliminary trials nitrile rubber (NR) and microcellular polyurethane (PU) were selected for comparison. Boots soled and heeled with these materials were worn by 12 volunteers for periods of up to 2 years. Friction was measured at intervals throughout the trial by determining the angle of slip on an oily steel plate. Smooth, wet or oily floors caused polishing of the soles, whereas loose metal chippings on the floor roughened the surface and improved friction. Microcellular PU resisted polishing better than NR and had a longer life. In the final phase of the trial, volunteers who had tested NR boots wore PU and vice versa. A direct comparison of the two materials tested by seven volunteers revealed that PU always produced higher angles of slip than NR. Mean coefficient of friction (COF) for PU was 0·26 and for NR was 0·18. The COF of PU bo...

Microcellular Elastomers by Single-Stage Technology

A series of single-stage, ambient cured microcellular polyure thane elastomers, based on liquid methylenebis(phenyl isocyanate), was prepared employing a variety of polyols and extenders at varying isocyanate indices and polymer densities. Significant dif ferences 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 in dices 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 ab sorbing, abrasion resistant and high flexing applications.