Thermal stability and compression strength of rigid polyurethane/kenaf fibre biocomposite foam

Abstract

Rigid palm oil-based polyurethane/kenaf fibre biocomposite foams were prepared at various amounts of kenaf fibre (i.e. 2.5, 5.0, 7.5, 10.0 and 12.5 pphp). Effects of kenaf fibre (KF) loadings on thermal stabilities and compressive strength were investigated. The peaks detected by Fourier transform infrared (FTIR) at 3,310 cm-1 (OH stretching), 1,533 cm-1 (NH bending) and 1,510 cm-1 (CN stretching) had proved the formation of urethane linkages in the system. Results from thermogravimetric analysis (TGA) showed that the thermal stabilities of biocomposite foams were higher than that of control PU foam. Higher KF contents resulted in agglomeration of which reduced the rate of heat transfer throughout the system. The presence of intrahydrogen bonds in agglomerated KF caused more heat needs to break the bonds, thus increasing the thermal stabilities. Consequently, the agglomeration of KF created stress concentration, which reduced the compression strength of the foams with respect to the control PU foam. The presence of intra-hydrogen bonding in PU chains had surpassed the agglomeration effect, thus causing just a small reduction percentage. The foams have potentials to be used in non-load bearing applications such as insulators and wall panels.