Layer-by-layer assembled diatomite based on chitosan and ammonium polyphosphate to increase the fire safety of unsaturated polyester resins.

In order to develop an environmentally benign flame retardant for unsaturated polyester resins (UPR), an effective intumescent flame retardant architecture based on chitosan (CH) and ammonium polyphosphate (APP) was successfully deposited on the surface of diatomite particles by Layer-by-layer (LbL) assembly. With nine bilayers of CH/APP coating, UPR/ 9 BL@Dia composites exhibiting LOI value of 25.7% and V -0 rating. Cone calorimetry test reveals that 9 BL@Dia reduces the peak heat release rate and total heat release of UPR by 40.8% and 18.1%, respectively. Due to the unique morphology of 9 BL@Dia particles, UPR/ 9 BL@Dia composites achieves greater thermal stability and higher char yields than pure UPR. Based on the investigation of the gas and condensed phase, flame retardant mechanism of n BL@Dia was proposed as that APP/CH was heated to form phosphate esters, and then combined with diatomite to form a more stable and firm carbon structure, which can improve the fire safety of UPR composites. Unlabelled Image • A bilayer polyelectrolytes coated Dia (n BL@Dia) was fabricated by LbL assembly. • Water contact angle(WCA) of Dia and n BL@Dia increased from 9.7 to 32.3 o. • After incorporation of 9 BL@Dia, the pHRR of UPR/ 9 BL@Dia was reduces by 40.8%. • The incorporation of n BL@Dia increases the fire safety of UPR composites. • Flame retardance of n BL@Dia exceed the addition effect of Dia, CH and APP. [ABSTRACT FROM AUTHOR]