Opportunities in Closed-Loop Molecular Recycling of End-of-Life Polyurethane

Abstract

Polyurethane (PU) is the sixth most used plastic. Total production reached 24 million metric tons in 2018 and continues to grow at an annual rate of 4%. As production increases, so does the accumulation of PU waste and the need to find a viable recycling method. However, due to the highly cross-linked structure and complex composition of postconsumer PU, mechanical recycling methods produce lower-value products with limited reusability. Chemical treatments that extract reusable components can offer alternative approaches to PU waste valorization. Chemical recycling of PU waste is underdeveloped given the significant potential economic and environmental impacts. Mechanistic studies on chemical recycling pathways, such as hydrolysis, acidolysis, glycolysis, and aminolysis, are incomplete, and few of these methods have been used commercially. This perspective provides an overview of several closed-loop chemical recycling methods that can be used to produce recycled polyol (repolyol) from waste PU, which can be used in place of virgin polyol. We delineate what is known regarding the chemistry and mechanisms, identify knowledge gaps, and compare the utility of the products from each recycling method. We also suggest ways that density functional theory can be used to fill knowledge gaps.

Foam-to-Elastomer Recycling of Polyurethane Materials through Incorporation of Dynamic Covalent TAD–Indole Linkages

“…Although the industrially employed techniques for mechanical recycling typically result in downcycling, rather than recycling or upcycling, the thermo-mechanical reprocessing is seen to be a circular solution when dynamic covalent bonds are considered. Thus, thermo-mechanical recycling and reprocessing are accepted as to be potential for the direct reuse of PU foam waste products. – …”

Selective chemical disassembly of elastane fibres and polyurethane coatings in textiles

“…Potential recycling methods for elastane could be inspired by the current strive towards a circular PU economy. 18–23 Existing recycling strategies for PU, such as mechanical reuse, have very limited applications for textile waste streams containing elastane, as considerable forces are needed to shred and unravel such elastic materials. 11,24 On the other hand, chemical recycling by means of disassembly of the textile polymer to monomers could represent a potential solution.…”

Highly transparent polyurethane thermosets with tunable properties and enzymatic degradability derived from polyols originating from hemicellulosic sugars

“…The production of polyurethanes (PUs) reached 24 million metric tons in 2018 and continues to grow annually by 4%, making PUs the sixth most produced plastic-type worldwide. 1 PUs are renowned for their versatility with applications ranging from appliances to adhesives, furniture, insulation, coatings, elastomers, flexible and rigid foams, and automotive applications. 1 The global market size of PU materials accounted for 69 billion USD in 2020, and is forecast to reach a market cap of 89 billion USD by 2030.…”

“…1 PUs are renowned for their versatility with applications ranging from appliances to adhesives, furniture, insulation, coatings, elastomers, flexible and rigid foams, and automotive applications. 1 The global market size of PU materials accounted for 69 billion USD in 2020, and is forecast to reach a market cap of 89 billion USD by 2030. 2 However, most of the PUs are still produced from petrochemical resources.…”