Solvent-free flexible epoxy intumescent fire-retardant coatings

Solvent-free epoxy-based intumescent fire-retardant coatings are of significant importance in harsh environments, such as petrochemical facilities, due to their excellent overall protection performance. However, the challenge of low-temperature brittleness and limited intumescence resulting from a highly crosslinked structure still persists. In this study, epoxy-terminated polyester oligomers with an asymmetric structure and low viscosity were synthesized using azelaic acid (AA) and dodecanedioic acid (DA) as dibasic acids with odd and even carbon numbers to address this challenge. The chemical structures of these polyester were thoroughly characterized. Among them, the polyester prepared with a molar ratio of 1:3 for AA and DA (ADE) was optimized as a suitable toughener for solvent-free intumescent fire-retardant coatings based on E-51 epoxy resin. The influence of ADE dosage on thermal stability, fire resistance performance, flexibility, and freeze cracking resistance was investigated in detail. The findings demonstrated that incorporating 50% ADE in ADE/E-51 blends resulted in coating film with an appropriate glass transition temperature and thermal deformation property to match the intumescence behavior of intumescent flame-retardant system. The coating formulated in this way exhibited the best fire protective performance, toughness and freeze cracking resistance.