Non-Isocyanate Hybrid Polyurethanes

Polyurethanes are products formed through multiple addition reactions of di (or poly) isocyanates with di (or poly) ols. The use of polyurethanes is very high, accounting for approximately 5% of global polymer consumption. Particularly due to the properties they provide—high gloss, abrasion resistance, hardness and sufficient elasticity—they are used as final coatings in the coatings sector. Despite the positive properties they display, alternative polyurethane systems have been developed due to the toxic effects of unreacted isocyanates on health and the environment, application difficulties arising from their moisture sensitivity, and the short decomposition times of isocyanates during storage. Among these, isocyanate-free polyurethanes have been studied since 1954, and although numerous patents have been obtained by many companies, these products have not gained sufficient market share in the sector due to negative effects such as weak mechanical properties compared to conventional polyurethanes, long drying times, and low reaction rates. The reaction rates of isocyanate-free polymers are comparable to those of epoxy-amine systems. Additionally, due to hydroxyl groups formed in the polymer chain after the reaction, their water resistance is extremely low. Nevertheless, the hydroxyl groups increase adhesion to surfaces.

Figure 1. Isocyanate-free polyurethanes

While epoxy resins react with primary and secondary amines, cyclic carbonate structures in isocyanate-free polyurethanes react only with primary amines. This causes a decrease in cross-link density in isocyanate-free polyurethanes, leading to negative effects on the mechanical properties of the polymeric structure. As elasticity increases, hardness decreases, and network structures with worse mechanical and chemical resistance properties compared to conventional isocyanates are obtained. Modifying isocyanate-free polyurethanes with multifunctional chemicals to obtain properties similar to conventional isocyanates is an extremely popular topic. Hybrid isocyanate-free polyurethanes are obtained through the reaction of star cyclo oligomers with amines or the reaction of amine-functional hydroxyurethanes with multiple epoxides. In recent years, due to the decline in petroleum products and the harm caused by petroleum derivatives to the environment, research efforts have increased toward the synthesis and use of bio-compatible, environmentally friendly, solvent-free and plant-based products. Epoxidized oils are used in many fields because they are inexpensive, abundantly available and easily accessible. Our research continues on obtaining hybrid isocyanate-free polyurethanes through the modification of epoxidized oils with cyclic carbonates and their reaction with primary amines.   Dr. Cemil Dızman R&D Director İzel Kimya         Elif Ozman R&D Manager İzel Kimya      

References 1)https://www.chemarc.com/feed/article/recent-advances-in- isocyanate-free-coating-technologies/5965bf3a2fd19338 b037efe9, Recent advances in isocyanate free coating technologies 2) Asemani, H., Zareanshahraki, F., Mannari, V. (2018), Design of hybrid nonisocyanate polyurethane coatings for advanced ambient temperature curing applications. J. Appl. Polym. Sci., 136, 47266. doi: 10.1002/app47266 3) Kamila Błażek & Janusz Datta (2019) Renewable natural resources as green alternative substrates to obtain bio-based non-isocyanate polyurethanes-review, Critical Reviews in Environmental Science and Technology, 49:3, 173-211, DOI: 10.1080/10643389.2018.1537741 4) Ke, J., Li, X., Jiang, S., Liang, C., Wang, J., Kang, M., Li, Q. and Zhao, Y. (2019), Promising approaches to improve the performances of hybrid non- isocyanate polyurethane. Polym. Int., 68: 651-660. doi:10.1002/pi.5746