Reactive Flame Retardation Strategy Inspired High‐Performance Rigid Polyurethane Foam With Superior Charring Ability and Low Fire Toxicity

ABSTRACT With the merits of low thermal conductivity, low density, and high mechanical properties, rigid polyurethane foam (RPUF) has been widely utilized in building energy conservation. However, the further application was severely inhibited by its high inherent fire hazard. This article introduces the preparation of flame retardant rigid polyurethane foam (FR‐RPUF) using a reactive flame retardant, halogen‐free oligomeric diol of ethyl phosphate (OP550). The degradation of FR‐RPUF was promoted after introducing OP550. Of note, the release intensity of gaseous products of FR‐RPUF was lower than that of pure RPUF. As revealed, the limited oxygen index (LOI) value of FR‐RPUF enhanced with the increase of OP550 loading. In specific, FR‐RPUF‐5 exhibited an LOI value of 24.2%, while RPUF showed a low value of 19.7%. Both the peak heat release rate (PHRR) and total heat release (THR) of FR‐RPUF were decreased with the increase of OP550 loading. Concretely, PHRR of FR‐RPUF‐5 was decreased by 36.8%. The mechanism investigation verifies that the use of OP550 promoted the carbonization process of the polyurethane molecular chain, to form more graphited char residues, significantly enhancing the fire resistance of FR‐RPUF. This work can provide inspiration for the designing of FR‐RPUF with high safety, via facilely developing reactive flame retardants.