Handbook of Thermosetting Foams, Aerogels, and Hydrogels: From Fundamentals to Advanced Applications

Abstract

Polyurethanes (PU) are an inevitable class of versatile polymeric material comprising carbamate (urethane) organic units links. Polyurethane polymers are formed by reacting polyol with a di- or tri-isocyanate. They comprise of two kinds of monomers, which polymerize one after the other, are categorized under the alternating copolymers. Both the types of monomers contain, at least two functional group per molecule. While most of the polyurethanes do not melt when temperature is applied (thermosetting polymers), recently thermoplastic polyurethanes are also prepared and are available. The versatility accounts due to the innumerable applications based on structure-property relationships. Its vast potential is reflected in the expected statistics of global PU market share for the year 2021, which forecasts an estimate of 26.47 million tons by volume production of PU products based on its utility. The research conducted in recent past about PU composites (thermoset, thermoplastic, and biobased PU with natural and synthetic fibers) used as reinforcement of polymers has amplified due to its durability, low cost, lightness, biodegradability, favored mechanical properties, etc. The unique chemical, mechanical, and thermal properties of PU can be designed based on the basic reaction between polyisocyanates and polyols, and hence the polyurethane industry is attracting the global market. Raw material modification and its production processes through appropriate methods has paved the way for the production of PU composites with desired properties. This chapter mainly focuses on the early PU synthesis, structural property relations of polyurethanes, prominent advanced methodologies, and newest green technologies concerning the production of ecological PU. This chapter also addresses the recent progress in overcoming and handling the major challenges that researchers face today in the development, management, and implementation of suitable recycling and recovering strategies that enhance the environmental friendliness and work-life of PU products. In a nutshell, this chapter aims to shed light on the various types, synthetic pathways, characteristic properties, applications, major green alternatives as raw materials, and the future of the polyurethane industry. © 2024 Elsevier Inc. All rights reserved.