Environmentally-benign rigid polyurethane foam produced from a reactive and phosphorus-functionalized biopolyol: Assessment of physicomechanical and flame-retardant properties

In the present study, after the epoxidation reaction of sunflower oil (SF) was optimized using a response surface methodology (RSM) of central composite design (CCD), the oxirane ring-opening reaction of epoxidized SF was carried out with 1,4-butanediol, and consequently, the SF-based biopolyol (14BD-pol) was obtained. A novel and reactive phosphorylated biopolyol (DPP-14BD-pol) was synthesized using the Atherton-Todd reaction of diphenyl phosphite (DPP) with the 14BD-pol. The DPP-14BD-pol was characterized in detail and a series of environmentally-benign RPUFs were fabricated using one-shot and free-rising methods with the partial substitution of DPP-14BD-pol (10, 25, 50 php). The obtained bio-RPUFs were assessed through the effect of the increasing amount of DPP-14BD-pol on the morphology, physicomechanical, thermal, and flame retardant properties. With the increase in DPP-14BD-pol addition, the apparent density and compressive strength values of bio-based RPUFs increased from 43.1 to 46.7 kg/m3 and from 239 to 260 kPa, respectively. The thermal conductivity values of bio-based RPUFs varied between 27.49 and 28.14 mW/m.K. The cellular structures were in polyhedral form, and the cell size distributions were quite homogeneous. The LOI values slightly improved from 19.3% to 20.5% up to the amount of 50 php DPP-14BD-pol. These results show that DPP-14BD-pol can partly replace the petroleum-based polyol to synthesize water-blown bio-based RPUFs with the properties that meet the demands of the polyurethane industry.