Rigid polyurethane-palm oil based polyol/kenaf fibre biocomposite foam

Abstract

Economic and environmental issues have driven the use of palm oil based polyol (PO-p) to replace petrochemical-based polyol as one of the components in polyurethane (PU) foam’s production. PO-p was reacted with polymeric 4, 4 – diphenylmethane diisocyanate (p-MDI) in the presence of silicone surfactant as a foam stabiliser and distilled water as a blowing agent to produce rigid PU foam. The PU/POp- based foam has good compression strength but moderate thermal stability. The benefits offered by the polymer-natural fiber blend had triggered the idea to incorporate kenaf fiber as filler in PU foam. Few reaction parameter were varied such as the amounts of surfactant (1.5, 1.75, 2.0, 2.25 and 2.5 pphp), fiber sizes (150-300 μm and 300-500 μm) and fiber contents (2.5, 5.0, 7.5, 10.0 and 12.5 wt. %). Their effects towards the foam properties and morphology were studied. The wavebands detected at 3300 cm-1, 1710 cm-1 and 1500 cm-1 by Fourier transform infrared confirmed the formation of urethane linkages in all samples. The addition of silicone surfactant as foam stabiliser at 2.0 pphp, imparted good thermal stability, regular cell shape and size with fewer voids, higher compressive strength, and moderate biodegradability when compared to the control sample. Meanwhile, by varying the fiber size, it was found that sample with bigger fiber size (300 – 500 μm) showed two apparent peaks i.e. hydrogen bonded –OH/–NH2 at 3300 cm-1 and free –OH/–NH at 3600 cm-1. The presence of many hydrogen bonded molecules contributed to the increase of thermal stability, smaller cell size, higher compression strength, and density, as well as the slowest fungi growth rate. Apart from that, the effects of various fiber loadings on the samples had revealed that 7.5 pphp was the best amount that gave the highest compression strength (0.89 MPa) and density (0.117 g/cm3) with the smallest cell size. The sample also exhibited the fastest fungi growth rate, as well as higher percentage of biodegradability.