In modern society, the multifarious polymeric material polyurethane (PU) is used in household appliances and commercial sectors. Statistics shows the usage of PU as rigid and flexible foams is the highest among different PU-based materials. Industrially viable synthesis, tailor-made porosity and pore morphology, robustness to micro-organisms, weathering, hydrolytic degradation, and resistance to a wide range of chemicals are the excellent attributes of PU foams. Despite achieving significant attention in academia and industries, the prominent tendency to fire-catching or flammability and rapid-fire spread on ignition are the serious concerns of PU foams at their end-use. The figures on home fire accidents and associated fire injuries, loss of civilians, and properties primarily due to fire-catching of furniture are highly devastating. Therefore, a large volume of efforts has been dedicated to decorating flame retardancy in PU foams using a wide range of flame retardants (FRs) (in-situ or post-synthesis). Hence, the focus of this review is to summarize various FRs for rigid and flexible PU foams. The mechanism of flame retardancy, advantages and limitations of various FRs, and the past decade’s advancements achieved concerning the flame retardancy of PU foams have been explored.

No abstract

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.

No abstract