Thermo‐mechanical property enhancement of rigid polyurethane foam using silica and alumina as hybrid fillers over single filler

Abstract

AbstractSilica and alumina particles were loaded in the rigid polyurethane foam composite as hybrid fillers. After the successful addition of silica and alumina as fillers, various properties of the foam composite were enhanced up to a particular weight percentage (7.5 wt% of silica and alumina each) with respect to alumina loaded foams. Hard urea domains are well distributed in the urethane matrix which indicates the absence of the peak representing H‐bonded urea in the Fourier‐transform infrared spectroscopy results. The addition of hybrid fillers into the rigid polyurethane foam matrix improved the compressive strength of the foam composite by 14% in comparison to alumina loaded foams due to the synergistic effect of the hybrid fillers. The foam composite at 7.5 wt% loading of hybrid fillers was successful in decreasing the thermal conductivity by 9% with respect to the thermal conductivity of the unloaded foam. There was a reduction in the gross calorific value up to 7% in the hybrid filler loaded foam composite when compared with that of the alumina loaded composite. Hence, hybrid fillers should be added to enhance the composite's properties by a greater extent.Highlights From the compressive test results, an increase in the compressive strength up to 14% was observed in the samples loaded with hybrid fillers with respect to the samples loaded with alumina due to the synergistic effects of the two fillers. For the foam composite loaded with alumina, the gross calorific value decreased up to 6% when compared to the unloaded foam. The gross calorific value decreased by a further 7% when hybrid fillers were added to the polyurethane foam composite with respect to the alumina loaded foam composite. The foam composite loaded with 7.5 weight % of hybrid fillers had lower values of thermal conductivity when compared with that of the unloaded polyurethane foam. We propose the addition of both alumina and silica as hybrid filler particles as they enhanced the various properties of the polyurethane foam composite to a greater extent than the addition of alumina particles as a single filler and have potential to replace unloaded polyurethane foams in different applications.