Effect of tris(1-chloro-2-propyl)phosphate and modified aramid fiber on cellular structure, thermal stability and flammability of rigid polyurethane foams

Abstract

Effect of tris(1-chloro-2-propyl)phosphate (TCPP) and modified aramid fiber (MAF) on cellular structure, thermal stability and flammability of rigid polyurethane foams (RPUF) has been investigated. RPUF with liquid TCPP and MAF alone, as well as the mix of TCPP and MAF, were prepared via a one-step process in this work. Phosphoric acid was used to modify AF, the P-OH in the MAF and the improvement of interfacial strength between MAF and PU was characterized using infrared spectrum analysis and scanning electron microscopy (SEM). Limited oxygen index (LOI) results indicated that TCPP exhibited more pronounced flame retardant efficiency than MAF for the RPUF. Gas chromatography/mass spectroscopy (GC/MS) illustrated that its flame retardancy took place in both condensed and gaseous phases. Meanwhile, the use of TCPP decreased the thermal stability of RPUF unlike MAF. The decrease by 9.4, 35.7% in the max smoke density (MSD) and peak smoke product rate (PSPR) respectively compared with RPUF showed that MAF was an environmentally friendly flame retardant. However, when TCPP and MAF were used in combination, they effectively enhanced the fire resistance and ensure macro- and micro-cellular structure of RPUF, unlike standalone use of TCPP and MAF. When 20%TCPP was simultaneously used with 5%MAF, the macro- and micro-cellular structures of the residue after cone calorimeter test (CCT) were clearly improved compared with foams prepared using MAF only. Their main advantage is related to the enhancement of compactness of the char layer and higher density. Compared with foams without flame retardants, the fire resistance of RPUF prepared with 20% RPUF and 5%MAF was enhanced; specially, the LOI was enhanced by 39.2%, MSD and peak heat release rate (PHRR) decreased by 25%, 59.6% respectively. Thus, the use of liquid and solid flame retardants in combination may effectively manufacture RPUF with high quality cellular structures and excellent fire resistance.