Effect of the silanization process on the fire resistance and thermal properties of closed-cell foams with sunflower husk ash

Abstract

The topics covered in this paper are relevant to the further development of polyurethane materials and propose a new method for producing sustainable and innovative foams. In this study, the effect of filler silanization on the flammability and thermal stability of rigid polyurethane foam (RPUF) was investigated. The RPUF composites study was preceded by an analysis of sunflower husk ash (SHA). Thermal decomposition behaviour and particle size distribution were carried out for the SHA samples. More, the elemental composition and structure of the fillers were investigated. The use of silanization of the filler results in homogenization of its structure. Sunflower husk ash has higher characteristic melting points than most biomass ashes and good thermal stability. The foam flammability results were preceded by an analysis of density and cell morphology. The use of silanized filler in RPUFs results in a homogenized structure and a 14 % reduction in apparent density. A wide range of tests were carried out as part of the flammability tests, which included: limiting oxygen index (LOI), gross calorific value, cone calorimeter, and optical density test. Additionally, thermal analysis methods were used to investigate the thermal stability of the foams. Flammability tests carried out confirm the positive effect of filler salinization on flammability. Heat release during combustion is reduced by 10 % and the release of toxic gases is also reduced. On the other hand, the thermal stability results are similar for foam with unmodified filler and those with silanized ash. Based on the comprehensive flammability and smoke results, a trend towards improved flame-retardant properties of RPUFs was observed.