IISc breakthrough promises greener recycling of high-performance polymer

Bengaluru: In a breakthrough that could facilitate wider adoption of carbon fibre-reinforced polymer (CFRP) composites across industries, a research group at the Indian Institute of Science (IISc) has developed and patented a technique that addresses the material’s biggest downside – its poor recyclability.

The lightweight composites are noted for their durability, high strength, and low density and are widely used in aerospace and construction sectors, wind turbines, and sporting goods. They have found new thrust as the world increasingly adopts manufacturing techniques that involve reduced CO2 emissions.

A team from the Department of Materials Engineering, led by Prof Suryasarathi Bose and Prof Subodh Kumar, has developed a bio-based aqueous solution that enables CFRP laminate recycling.

CFRP consists of carbon fibres embedded in a polymer matrix, usually an epoxy resin. CFRP waste is primarily composed of thermoset (permanently hardened when heated or cured) matrices which makes recycling difficult. The solution, SaLSo, is developed with everyday ingredients and helps easy recovery of the epoxy and the carbon fibres, simplifying the recycling process.

Samir Mandal, a PhD student working with Prof Bose and Prof Kumar, explained that the solution “selectively cleaves” the Carbon-Nitrogen and Carbon-Oxygen bonds in the thermoset polymer matrix (like epoxy and vinyl ester) and breaks down its network structure.

Cost-effective waste management

The recycled epoxy and carbon fibres were found to maintain structural integrity and can be reused in new composites or blended with other polymers to create new products.

Prof Bose said the technique addressed both the costs and carbon footprint associated with carbon fibre production. “This is a concoction that can break the resin down and reclaim the fabric. The epoxy broken down into fragments can also be put to use as a hardener to design other materials, helping the industry achieve a circular economy,” he told DH.

Traditional CFRP recycling methods involve the use of industrial crushers and the regrinding processes involve CO2 emissions. The resultant products also have limited utility because they cannot blend in with all materials.

India produces, annually, an estimated 2,000 to 4,000 metric tons of CFRP composites. As demand rises and the industry adopts advanced manufacturing technologies, CFRP production in India is expected to grow at a compound annual growth rate (CAGR) of 10-15% over the next decade. The production is estimated to be in the 6,000-10,000 metric tons range by 2030, making the country a key player in the global market.

Studies project that by 2025, the annual global carbon fibre-reinforced epoxy waste will reach 20,000 tons. The researchers said viable recycling solutions were critical because large portions of this waste could end up in landfills or be incinerated, contributing significantly to environmental degradation.

“Aircraft components after their limited useful life, for instance, are shredded and sent to the landfills. We are in talks with agencies like NAL (National Aerospace Laboratories) and windmill manufacturers to see how efficiently we can put this high-performance material to better, wider use,” Prof Bose said.