STUDIES ON THE EFFECT OF VARIOUS FILLERS ON THE PROPERTIES OF RIGID POLYURETHANE FOAM

Abstract

Polyurethane serves the mankind in its various roles such as flexible foam, rigid foam, elastomers, surface coatings and adhesives. PU foam is versatile material and can be produced with open cell structure to be more flexible or a close cell structure to be more rigid. Rigid polyurethane foams (RPUFs) are very popular and highly energy-efficient materials of polyurethane product and are good at both through its physical strength and mechanical properties. RPUFs have closed cell structure with low thermal conductivity, high compression strength, low density, high strength to weight ratio and low moisture permeability. Consequently, polyurethane rigid foams find such applications as insulations of refrigerators, freezers, piping, tanks, ship building and in the construction field as polymeric concrete and sealants. As there is a growing worldwide interest in the development of vegetable oil based polyurethane because of being relatively inexpensive and a renewable resource, the present studies had been carried out on castor oil based rigid polyurethane foams. In the present project rigid polyurethane foams have been prepared from modified castor oil and 4, 4-diphenylmethane diisocyanate. The studies had been conducted for the effect of addition of various fillers on the castor oil based rigid polyurethane foam. The fillers used for this purpose the fillers were flyash, glass fibre, mica, talc and calcium carbonate. The formation of RPUF was confirmed by FTIR studies .The resulted RPUFs had been characterized for their mechanical properties suchtensile, flexural and compressive strength. It had been found that by the addition of the filler such as mica, calcium carbonate and glass fibre the mechanical properties of the rigid polyurethane got improved. The addition of glass fibre resulted in many folds increase in the strength to the foam as compared to

D E L H I T e c h n o l o g i c a l U N I V E R S I T Y Page 5 neat RPUs. The addition of the fly-ash as well as talc did not contributed much toward the strength. The SEM analysis of the resulted castor oil based rigid polyurethane foam showed the decrease in pore size with addition of fillers. Thus overall density of the rigid PU material was found to be increased. As per the various test performed, the resulted filled RPUFS are found to be comparable to that of commercial material specially in the cases where mica and calcium carbonate are used as fillers. The retardence in the properties of flyash and talc filled RPUFs is due to hollowness of fly-ash particles and weak interfacial contact between resin & fly-ash. The glass fibre filled RPUF even showed better properties as compared to neat RPUF, thus acted more or less acted as a reinforcing agent.