Macro- and microfillers as reinforcing agents for polyurethane elastomers

The main goals of the research were to develop the new types of inexpensive reinforced polyurethane (PUR) elastomers and to study the effect of different commercial fillers on the density and mechanical properties of the developed materials. Two types of inexpensive commercial fillers based on synthetic and natural polymers have been studied: expandable polystyrene beads (macrofillers) of size 0.254-2.54 mm, and wood flour and starch (microfillers) of size 0.212-0.425 mm. The quantitative relationships between the filler nature, size, content, density, and various mechanical properties have been developed. For both fillers it was found that PUR elastomers produced with less filler content (up to 5-10%) showed improved mechanical properties over the composites made with higher filler content (up to 10-30%). Regardless of the filler content, all filled elastomers demonstrated improvement of tensile properties over unfilled elastomers. The maximal improvement of tensile properties has been found as 10% for macrofillers, and 5% for microfillers. All developed materials are based on commercial formulations and mixing, metering, and pouring equipment. Thus, these materials are easy to commercialize. The developed reinforced cold-curing PUR composites have been recommended as inexpensive materials for structural, thermal insulation, and packaging applications, especially for in situ production.