Researchers at Aarhus University have discovered an improved technique for recycling polyurethane foam from products like mattresses. This is encouraging news for the emerging sector focused on chemically reclaiming the material’s original components, ultimately leading to lower costs and enhanced product quality.
Scientists from Aarhus University have developed a new method for recycling polyurethane foam found in items such as mattresses. This advancement is promising for the growing industry that targets the chemical recovery of the material’s fundamental components, resulting in more affordable and superior products.
Polyurethane (PUR) is a crucial plastic commonly used in various applications, including mattresses, insulative materials in fridges and buildings, footwear, vehicles, aircraft, wind turbine blades, wiring, and more. It might be considered a remarkable material if it weren’t for the negative impact it has on the environment and climate. Globally, most discarded PUR items are either burned or sent to landfills.
This poses a significant issue as the primary components of PUR are mainly derived from fossil fuels, and the quantities are substantial. In 2022, the worldwide PUR market approached nearly 26 million tons, and projections for 2030 estimate it will reach about 31.3 million tons, with roughly 60% comprising foams in various formats.
Diligently, a small yet expanding industry is focusing on chemically breaking down PUR (depolymerization) to reclaim its core components, polyol and isocyanate, aiming to reuse them as raw materials for new PUR products.
Nonetheless, there’s still a significant gap to close before their products can compete with “virgin” materials since the processes involved in purifying the necessary components are costly.
Simultaneous Breakdown and Separation
This is where the research team from Aarhus University presents an innovative solution. Their approach builds on the existing method employed by companies, which involves breaking down PUR foam using acid (acidolysis).
However, these companies typically don’t separate the resultant mixture into polyol and isocyanate, leading to a compound that cannot be readily recycled and instead requires new formulation methods from clients.
The researchers from AU have successfully managed to not only decompose PUR but also isolate the two primary components in a single step. They achieve this by subjecting flexible PUR foam to heat at 220°C in a reactor containing a small amount of succinic acid. Following this process, a filter is utilized to separate one component while allowing the other to pass through.
The polyols are the components that pass through the filter, and they do so with a quality comparable to virgin polyol, enabling their use in the production of new polyurethane. Meanwhile, the solid residue is transformed into a compound called diamine through a straightforward hydrolysis process, which then can be used to produce isocyanates, and subsequently, PUR.
Through this method, the researchers can recover as much as 82% of the original weight from flexible PUR foam used in mattresses, successfully obtaining two distinct fractions of diamines and polyols. Their findings have recently been published in the scientific journal Green Chemistry.
Significant Potential in the Industry
“This method can be easily scaled up,” states one of the authors, Steffan Kvist Kristensen, who is an assistant professor at the Interdisciplinary Nanoscience Center (iNANO) at Aarhus University.
He envisions substantial opportunities for recycling PUR foam waste at manufacturing facilities that utilize it as raw material (slabstock) in production lines.
“However, the capability to manage PUR waste from consumers will require additional advancements,” he notes with considerable work remaining for a circular economy
Manufacturers within the PUR sector implement unique formulations to achieve specific characteristics in their products.
Consequently, several challenges must be addressed before a true economy of polyurethane recycling can become reality:
– Waste sorting
– Logistics
– Classifying PUR into different types
Thus, depolymerization is merely a part of the overall solution.
More Than Just Soft Foam
The AU researchers have also applied the acidolysis and hydrolysis method to regenerated PUR foam and rigid PUR foam, yielding positive results.
However, the journey toward a circular economy remains lengthy for these foam types.
Rigid PUR foam, primarily utilized as insulation materials, is still at the beginning stages of being converted into valuable raw materials.
Currently, researchers are testing this innovative technology on other forms of polyurethane to explore recycling possibilities. They are also examining approaches to reuse the dicarboxylic acid involved in the process. Additionally, they plan to experiment with recycled materials to create new products to demonstrate the technology’s capability to foster a circular economy.
FACTS:
Polyurethane is commonly formed through a chemical reaction involving the key components polyol and isocyanate, which largely come from fossil fuels. As polyurethane is a polymer (a long chain of molecules), the process of chemically breaking it down is referred to as depolymerization.
Succinic acid is a naturally occurring acid that serves as an antioxidant essential for energy production in the body. It is utilized as both a food additive and a precursor for various plastics. In this case, succinic acid can break down polyurethane (PUR) without relying on additional chemicals.
