Effects of preparation conditions on properties of rigid polyurethane foam composites based on liquefied bagasse and jute fibre

Rigid polyurethane foams based on liquefied bagasse and reinforced with jute fibre were prepared. The effects of preparation conditions were investigated using a paper cup with a small horizontal section area as a mould. They were reflected in the foam height, which acted as a sensitive indicator. Density gradient existed in the foam rise direction and decreased from the bottom to top. Although the amount of blowing agent water was fixed, the foam height increased with stirring time after the addition of diphenyl methane diisocyanate, the isocyanate index and the catalyst content. This was partly due to the released heat that also contributed to the foam expansion. The relative intensity of the C─N stretching band at 1510 cm−1 and the N─H out-of-plane bending band at 1527 cm−1 in the FTIR spectrum reflected isocyanate reactions, which had a close relationship with the crosslink density. The normalized compressive strength was essentially attributed to the combined effects of the crosslink density and the thickness of cell walls and struts. Jute fibre enhanced the compressive strength only slightly due to poor interfacial adhesion between some fibres and the matrix.