Title: A HALOGEN-FREE APPROACH TO FLAME RETARDANCY IN UNSATURATED POLYESTER-BASED GFRP COMPOSITES

Authors: Roshan Patil, Dipak Tadse, Ankush Sharma, Nand kishore Singh

DOI: https://doi.org/10.33599/GL.2026.INCOMAT.TP26-0012

Abstract: Although unsaturated polyester resins (UPR) are extensively used in sectors like electrical, automotive, and construction, their application in extremely fire-prone environments is severely limited because of their high heat release and flammability. This research work provides a thorough analysis of the fire resistance properties, curing abilities, and combustion characteristics of thermoset materials made by mixing non-halogen flame-retardant additives such as piperazine pyrophosphate (PPAP), aluminum hypophosphite (AHP), and zinc borate (ZB) into the UPR matrix. In comparison with neat UPR, the LOI and UL-94 tests showed that adding PPAP, AHP, and ZB to the UPR composites greatly increased their ability to resist fire. Phosphorus and nitrogen-derived flame retardants worked together in this composite, leading to an increase in the LOI value from 19.1 % for neat UPR to 30 %, which enabled the material to achieve the UL-94 V-0 classification. According to cone calorimetry results, the fire severity significantly declined. The total heat release (THR) decreased from 128.4 MJ m-² to 27.3 MJ m-², and the peak heat release rate (PHRR) dropped from 750.8 kW m-² for neat UPR to 72.6 kW m-² for the UPR/P12-A6-Z2 mixture. The primary reason for the advancement in fire protection performance was the initial development of a compact and thermally durable puffy char layer, which was promoted by PPAP and AHP and bolstered by zinc borate. The resultant layer partly restricted gas-phase flames and effectively stopped the transfer of mass and heat in the condensed phase. Therefore, the PPAP-AHP-ZB flame-retardant solution provides a practical and environmentally responsible way to improve the fire protection of UPR-based composites intended for structural purposes.

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Conference: INCOMAT 2026

Publication Date: 2026/03/13

SKU: INCOMAT.TP26-0012

Pages: 11

Price: $22.00