Currently, polyurethane (PU) manufacturers seek green alternatives for sustainable production. In this work, sunflower oil is studied as a replacement and converted to a reactive form through epoxidation and oxirane opening to produce rigid PU foams. Confirmatory tests such as Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and hydroxyl value among others were performed to characterize the synthesized polyol. Despite the versatility of rigid PU foams, they are highly flammable, which makes eco-friendly flame retardants (FRs) desired. Herein, expandable graphite (EG) and dimethyl methyl phosphonate (DMMP), both non-halogenated FR, were incorporated under different concentrations to prepare rigid PU foams. Their effects on the physio-mechanical and fire-quenching properties of the sunflower oil-based PU foams were elucidated. Thermogravimetric and compression analysis showed that these foams presented appreciable compressive strength along with good thermal stability. The closed-cell contents (CCC) were around 90% for the EG-containing foams and suffered a decrease at higher concentrations of DMMP to 72%. The burning test showed a decrease in the foam’s flammability as the neat foam had a burning time of 80 s whereas after the addition of 13.6 wt.% of EG and DMMP, separately, there was a decrease to 6 and 2 s, respectively. Hence, our research suggested that EG and DMMP could be a more viable alternative to halogen-based FR for PU foams. Additionally, the adoption of sunflower polyol yielded foams with results comparable to commercial ones.

No abstract

Polyurethanes can be used in many applications by modifying their properties via facile methods. Most of the polyurethanes currently used for industrial applications originated from petrochemical-based chemicals. There is a growing demand in industries to use renewable resources for polyurethanes. Vegetable oil-based polyurethanes have shown properties comparable to that of petroleum-based polyurethanes. In this research, sunflower oil was used as a renewable resource for polyurethanes. Rigid polyurethane foams were prepared using sunflower-based polyols. The polyols were synthesized via epoxidation followed by a ring-opening reaction. Epoxy number, hydroxyl number, viscosity, and spectroscopy characterizations confirm the synthesis of bio-polyol. One of the major issues in polyurethanes is their high flammability which was reduced by using flame-retardants. Two flame-retardants using melamine and diphenylphosphinic acid (DPPMA) and a phosphorous‐nitrogen intumescent flame‐retardant (2,2‐diethyl‐1,3‐propanediol phosphoryl melamine, DPPM) were synthesized and used in bio-based polyurethanes. as used as an additive flame retardant. The foams with DPPMA and DPPM showed high closed cell content ( >90%) with a high compression strength of 217 kPa and 208 kPa, respectively. The microstructure analysis of the foams using scanning electron microscopy revealed an even distribution of the pore size. The addition of DPPMA and DPPM in polyurethane foams results in the formation of a protective char layer during the flammability test and reduces the weight loss from 43% to 2.5% and 1.4% and burning time from 70 seconds to 6 seconds and 4.5 seconds, respectively. Our research suggests that sunflower oil could be a potential candidate for the polyurethane industries and DPPMA and DPPM can be used as an effective flame-retardant in these bio-based polyurethane foams.