Tar is byproduct in production of Toluene Di isocyanate. How to use this tar product in different ways to produce valuable chemicals.
22 and📷Sarla Yadav
1
Department of Polymer Science and Chemical Technology, Delhi Technological University (Formerly Delhi College of Engineering), Delhi 110042, India
2
Department of Applied Chemistry and Polymer Technology, Delhi Technological University (Formerly Delhi College of Engineering), Delhi 110042, India
*
Author to whom correspondence should be addressed.
Macromol 2022, 2(3), 284-314; https://doi.org/10.3390/macromol2030019
Received: 26 May 2022/ Revised: 25 June 2022/ Accepted: 29 June 2022/ Published: 4 July 2022
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Abstract Among numerous synthetic macromolecules, polyurethane in its different forms has proven its sheer dominance and established a reputation as a reliable and trusted material due to its proficiency in terms of superior properties, which include: high mechanical strength and abrasion resistance, good durability, good adhesion, good thermal stability, excellent chemical and weathering resistance. Synthetic polyurethane materials are non-biodegradable, poisonous, and use petrochemical-based raw materials, which are now depleting, leading to a surge in polyurethane production costs. Bio-based polyurethanes (PU) have been synthesized by researchers in recent decades and have mostly overtaken petrochemical-based PU in terms of challenges such as solid pollution, economic effectiveness, and availability of raw materials. Enormous kinds of available bio-renewable sources as predecessors for the production of polyols and isocyanates have been explored for the development of “greener” PU materials; these bio-based polyurethanes have significant potential to be used as future PU products, with a partial or total replacement of petroleum-based polyurethanes, due to increasing concern about the environment, their relatively low cost and biodegradability. This critical review concentrates on the possibilities of renewable sources to be used for polyurethane production and gives a clear perspective on the journey, utilization, and recent advancements in the field of different bio-based polyurethane polymers that have arisen over the last decade.polyurethanes; non-isocyanate polyurethanes; adhesives; coatings; recycling; biodegradationKeywords: 📷Graphical Abstract
1. Introduction Polyurethanes (PU) represent nearly 8% of the total plastics production and stand tall as the 6th most widely used polymer in the world, with total production reaching 18 MTon in 2016 [1] and still progressing. The superior properties of PU, such as flexibility, corrosion, resistance to chemicals, high automatic strength, low-temperature comfortability, adhesiveness, and chemical structure adaptability, etc. account for their considerable popularity among researchers. PU have urethane groups as major repeating units along their main backbone chains, which are derived by reacting hydroxyl (-OH) terminated chemical entities, with isocyanate (-NCO) terminated compounds, as represented by a generalized scheme shown in Figure 1. In addition, some other functional groups may also be present in the end constitutions of the PU chains, including ethers, esters, urea, biuret, and aromatic moieties [2].
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