Enhanced flame retardant performance of rigid polyurethane foam by using the modified OMMT layers with large surface area and ammonium polyphosphate

Abstract

A phosphorus-containing organosilicon compound (PCOC) was synthesized and used to modify organic-montmorillonite named M-OMMT. The results showed that the interlayer spacing of the intercalated M-OMMT layers became larger and the exfoliated M-OMMT layers were connected by PCOC after the modification. Then, M-OMMT was combined with ammonium polyphosphate (APP) to improve the flame retardancy of rigid polyurethane foam (RPUF) composites. The thermal stability and flame retardancy of RPUF with M-OMMT and APP was lucubrated using thermogravimetric analysis (TGA), limited oxygen index (LOI) and cone calorimeter test. After the addition of modified OMMT layers, the Td,5%, Tmax1 and Tmax2 of RPFU/APP/M-OMMT (234 °C,304 °C and 462 °C) were all higher in contrast to RPUF/APP/OMMT (223 °C, 298 °C and 454 °C). Compared with RPUF/APP/OMMT, the peak heat release rate and total smoke release of RPUF/APP/M-OMMT were apparently reduced from 292 kW/m2 and 552 m2/ m2 to 156 kW/m2 and 350 m2/ m2, and the residual char yield increased by 37%. The SEM results showed that the addition of M-OMMT promoted the formation of a more compact and intumescent char layer. After the modification of PCOC, the layers of M-OMMT overlapped each other to form a larger surface area, which can exert a better physical barrier and protective effect together with APP on RPUF, fabricating the RPUF/APP/M-OMMT composite with the good flame-retardant property.