Preparation of aliphatic bio-based polyester polyols for water-blown and halogen-free flame retardant rigid polyurethane foam

A bio-based polyester polyol (BP41) was synthesized through a one-pot esterification and condensation reaction involving bio-based 1,2-propanediol, trimethylolpropane, and adipic acid. The mechanical properties, thermal stability, and thermal degradation behavior of the resulting BP41-based RPUF (PRPUF) were investigated. The prepared RPUF exhibited a density of 47.69 kg/m³, and a compressive strength of approximately 217 kPa. Additionally, it displayed excellent thermal insulation properties, demonstrated by a low thermal conductivity of 0.0261 W/(m·K) and a high initial thermal degradation temperature surpassing 281°C. Furthermore, the incorporation of 10% dimethyl methyl phosphonate (DMMP) terminated by erythritol (FRD) into PRPUF led to a limited oxygen index (LOI) of 32.0% and a UL 94 rating of V-0 in vertical burning tests. The peak heat release rate was reduced by 48.9%, while the residual char was increased significantly from 6.53% to 15.82%. These findings emphasize the considerable potential of the demonstrated bio-based RPUF for various commercial applications.