Non-Isocyanate Polyurethanes (NIPUs)- Polyhydroxyurethanes (PHUs)
Polyurethane products are polymers obtained by urethane bonds formed as a result of the addition reaction of a compound with isocyanate functional groups and another compound with hydroxyl functional groups. The raw materials used in the production of polyurethane are based on petroleum resources. Due to the limited resource and price fluctuations of petroleum, studies on bio-based polyurethanes have gained momentum in recent years. For more detailed information on this subject, you can read our article http://www.evocopolymers.com/blog-detail/synthesis-of-bio-polyol-from-vegetable-oils/
In addition to bio-based polyurethane synthesis studies, to find alternative sources and new methods to replace limited petroleum sources and because of the toxicity of isocyanate groups, there have been many studies covering the synthesis and use of non-isocyanate polyurethanes (NIPUs) in other words polyhydroxyurethanes (PHUs), which developed with a more environmentally friendly approach than traditional isocyanate-based polyurethanes [1-5]. There are different synthesis methods of NIPUs in studies in the literature and one of the synthesis methods is addition polymerization. In this method, NIPUs are obtained by the formation of hydroxypolyurethane groups as a result of the ring-opening reaction between cyclic carbonate groups and amine groups [2]. The desired product properties can be achieved by considering the molecular chain structure and functionality of the cyclic carbonate functional compound and amine compound used in the synthesis of NIPUs. Since there are many studies on the synthesis of NIPUs by addition polymerization and this method has advantages over other methods, its application to the industry draws attention as the most appropriate method [1,2].
NIPUs are environmentally friendly products, but it is not possible to use them in all conventional polyurethane application areas. There are limitations especially in obtaining polyurethane foam products by NIPU synthesis method. For this reason, studies are mostly on the use of NIPUs as thermoset polyurethane systems and examining the properties of the obtained synthesis products. NIPUs are used in the development of thermoset polyurethanes for applications such as coatings, adhesives, paints, and sealants [1,2]. It has been determined in the literature that NIPUs exhibit better mechanical and physical properties compared to conventional polyurethanes, with effects such as lack of side reaction structures and reduced moisture sensitivity [1,2].
The use of NIPUs as thermoset polymers is also limited compared to conventional polyurethanes. The reason for this is the low reactivity of cyclic carbonate functional groups, high temperatures (higher temperatures than room conditions) are required for synthesis, and the molecular weights of the polymers formed are low or limited [3-5]. In the literature, scientific research on the kinetics of the reaction between cyclic carbonate and amine functional groups has been carried out for the synthesis of NIPUs. The main factors affecting the reaction efficiency in the synthesis of NIPUs are the molecular structures and initial concentrations of the reactants used. Also, the effects of solvent, catalyst, and temperature on reaction kinetics have been investigated with studies in the literature [2-4].
NIPUs are environmentally friendly products that are obtained by innovative synthesis methods and have the potential to be used. It is possible that the use of NIPUs will become widespread in the future with the development of alternative raw materials, functional compounds, synthesis methods, and more active catalysts in order to overcome the limitations mentioned above.
References
[1] Rokicki, G., Parzuchowski, PG, & Mazurek, M. (2015). Non‐isocyanate polyurethanes: synthesis, properties, and applications. Polymers for Advanced Technologies, 26(7), 707-761.
[2] Kathalewar, MS, Joshi, PB, Sabnis, AS, & Malshe, VC (2013). Non-isocyanate polyurethanes: from chemistry to applications. Rsc Advances , 3 (13), 4110-4129.
[3] Maisonneuve, L., Lamarzelle, O., Rix, E., Grau, E., & Cramail, H. (2015). Isocyanate-free routes to polyurethanes and poly (hydroxy urethane) p. Chemical reviews, 115(22), 12407-12439.
[4] Lambeth, RH, & Henderson, TJ (2013). Organocatalytic synthesis of (poly) hydroxyurethanes from cyclic carbonates and amines. Polymer, 54(21), 5568-5573.
[5] Blain, M., Cornille, A., Boutevin, B., Auvergne, R., Benazet, D., Andrioletti, B., & Caillol, S. (2017). Hydrogen bonds prevent obtaining high molar mass PHU s. Journal of Applied Polymer Science, 134(45), 44958.
Authors: Eser Bingöl Date: October 2022
