Effect of Diisocyanate Structure on Polyurethanes Prepared From Brown Grease‐Derived Polyols

Waste‐derived feedstocks are a sustainable alternative for petroleum‐based materials. Brown grease (BG), a low‐value waste fat produced from rendering and food service, comprises mono/di/triglycerides and free fatty acids (>5%). Though BG cannot be used for consumption, it is an affordable and abundant source of long alkyl chain‐bearing molecules. In this work, BG and pure oleic acid (OLA) were each converted into polyols through allyl esterification followed by thiol‐ene addition of 2‐mercaptoethanol to give BG‐diol and OLA‐diol , respectively. Each diol served as a comonomer for polymerization with each of three diisocyanates: 4,4′‐methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), and hexamethylene diisocyanate (HDI) to afford six polyurethanes. Polyurethanes were characterized by 1 H NMR and IR spectroscopy, gel permeation chromatography (GPC) ( M n = 14.4–27.4 kDa), thermogravimetric analysis (TGA) ( T d > 260°C), and differential scanning calorimetry (DSC) (showing glass transition temperatures of −20°C for HDI‐based polyurethanes to 24°C for MDI‐based polyurethanes). Mechanical testing revealed that IPDI‐based polyurethanes had higher tensile strength compared to the other polymers. These results establish BG as a practical precursor for polyurethanes with tunable properties based on diisocyanate structure.