Oxazolidone formation: myth or fact? The case of biobased polyurethane foams from different epoxidized triglycerides

Abstract

Polyurethane foams (PUF) are generally obtained by polyaddition between polyisocyanate and polyols. In this context, biobased polyols can be obtained by oleochemistry, modifying triglycerides by epoxidation and epoxide ring-opening with a nucleophile. In the frame of green chemistry principles, which claims, e.g., the reduction of the derivatives and the synthesis steps, we explore the direct use of epoxidized oil for PUF fabrication to avoid the specific intermediate step of polyols synthesis. The reaction between epoxides and isocyanates is known to yield the thermally stable oxazolidone groups. In the PUF system, the incomplete reaction between epoxidized oil and isocyanate was proved by the presence of unreacted epoxidized oil identified by ¹H NMR and FTIR in compounds unbonded to the polymer network. To understand this incomplete reaction, oxazolidone formation was largely investigated through different reactional models using various catalysts and epoxides. The steric hindrance of the epoxide group was found to limit the formation of oxazolidone.