Effect of Wood Flour Fillers on Density and Mechanical Properties of Polyurethane Foams

A comparison analysis has been undertaken to study the effect of different wood fillers on density and mechanical properties of two different types of commercial polyurethane (PUR) foams: low-density flexible foams and high-density rigid foams. The micro-fillers used were based on wood flour particles of size 70-250 microns (wood waste of furniture industry). The relationships between the filler size and content, density and various mechanical properties - compression test, compression force deflection test and modulus of elasticity have been studied. It was found that micro-fillers provide various effects depending on flexibility and density of PUR foams. For low-density flexible PUR foams, the density and mechanical properties increased for both types of fillers. However, for high-density rigid PUR foams these effects were just the opposite: the density and compression strengths decreased for both types of fillers. Explanation of the observed effects should take into consideration the chemical nature and physical structure of flexible and rigid PUR binders based on various types of polyol-isocyanate systems, as well as chemical and physical affiliation of cellulose based fillers with the matrices.