Preparation and mechanism study of intrinsic hard segment flame‐retardant polyurethane foam

Abstract The hard segment of polyurethane foam (PUF) plays a special role in degradation and carbonization. In this work, flame‐retardant hard segment (HSFR) used to promote fire resistance was synthesized successfully. The limiting oxygen index (LOI), vertical combustion, and micro‐combustion calorimetry tests indicated the flame retardancy of the foam was elevated by introducing HSFR. When HSFR with an addition of 60 phr, the LOI value was increased from 17.0 to 25.5%, UL‐94 reached V‐0 rating, the peak heat release rate (p‐HRR) and total heat release (THR) decreased by 63.9% and 10.0%, respectively. In addition, the compressive strength of HSFR‐60 increased by five times. Further, the flame‐retardant mechanism of HSFR was proposed. In vapor phase, HSFR could generate PO and PO 2 , which combine with flammable free radical and hinder segment decomposition. In condensed phase, HSFR could promote the dehydration and carbonization of chain and the formation of dense and graphitized char. This article provides a practical method for the preparation of green, highly effective, and durable flame‐retardant PUF.