Polyurethane is a polymer formed by the reaction of isocyanate and polyol. These polymers cover an extremely wide range of stiffness, hardness and density, and are commonly used in the manufacture of high-resilience foam seats, rigid foam insulation panels, foam seats and gaskets, elastic wheels and tires, high-performance adhesives and surfaces Coating, together with sealant.
In terms of quantity, polyurethane foam is the most important as a soft or rigid foam, and the furniture market is its most important area. The global annual demand for furniture cushions, carpet cushions, mattresses, etc. exceeds 5 million tons.
In addition, due to the increasing use of lightweight and insulating materials in other fields such as construction, electronics, automotive and packaging materials, the global demand for polyurethane materials has continued to grow in recent years.
Polyurethane waste is problematic because many hazardous chemicals such as isocyanates, hydrocyanic acid and dioxins are released when these materials are incinerated. Polyurethane products deposited in landfills can also decompose into harmful and environmentally damaging substances. In addition, recycling polyurethane is currently very difficult and energy intensive, because most polyurethanes are thermoset polymers and will not melt when heated.
As the responsibility for shifting to more sustainable practices grows, research has been invested in strategies to recycle polyurethane, for example, through mechanical recycling of polymers (that is, turning old mattress foam into insulating material), or through Chemical recovery.
With this in mind, the University of Illinois team led by Professor Steven Zimmerman developed a method to decompose polyurethane waste and convert it into other useful products.
Graduate student Ephraim Morado wants to solve the polyurethane waste problem by reusing polymers chemically. Unfortunately, polyurethane is very stable, which contributes to its wide range of commercial uses, and consists of two components that are difficult to decompose: isocyanate and polyol.
Polyols are problematic because they are petroleum-based and are not easily degraded. To circumvent this difficulty, the team added a chemical unit that is more easily degradable and water-soluble, namely acetal.
The degradation products formed by dissolving the polymer in a mixture of trichloroacetic acid and dichloromethane at room temperature can be reused in new materials. As a proof of concept, Morado is able to convert elastomers widely used in packaging and auto parts into viscous glues.
The researchers will report their findings at the American Chemical Society National Conference and Exposition.
Professor Zimmerman commented that the biggest disadvantage of this new recycling method is the cost and toxicity of the raw materials used for the reaction. Therefore, researchers are currently trying to find a better, lower-cost way to use milder solvents (such as vinegar) to achieve the same process for degradation.
Although there is still a long way to go, this is an important first step in tackling the growing environmental problems.