Transformation of 'Non-Recyclable' Heating Pipes... Development of Upcycling Technology

[Asia Economy Reporter Kim Bong-su] A technology has been developed that can recycle heating pipes, which used to harden and be discarded when heated, into products for preventing noise between floors. It is analyzed that this could contribute to solving the increasingly serious microplastic problem by reducing plastic waste.

The Korea Institute of Science and Technology (KIST) announced on the 11th that Dr. Hong Soon-man's research team at the Center for Material Structure Control succeeded in developing a technology to recycle about 10% defective products, scraps (by-products), and post-use waste generated during the manufacturing of heating pipes (cross-linked polyethylene pipes). Although the annual usage of heating pipes is increasing, they are thermosetting resins that harden when heated, making reprocessing difficult, so most have been landfilled or incinerated.

The research team combined an eco-friendly super(sub)critical technology with a continuous twin-screw extrusion process. Through selective de-crosslinking reactions, they succeeded in producing recycled polyethylene. Super(sub)critical fluids have both the diffusivity of gases and the solubility of liquids, allowing them to penetrate the bonds between cross-linked polyethylene materials in heating pipes, inducing rapid de-crosslinking reactions. By applying high heat and pressure simultaneously, the molecular chains of cross-linked polyethylene are selectively cut while preserving the inherent physical and chemical properties of polyethylene.

The recycled polyethylene produced in this way has a molecular weight and properties similar to virgin polyethylene (molecular weight Mw over 180,000), enabling upcycling into lightweight building materials, slab balls for preventing noise between floors, and Combine Duct (CD) pipes for wire protection. Collecting and utilizing waste heating pipes can reduce costs.

This research outcome is expected to reduce carbon dioxide emissions by recycling waste heating pipes that were previously incinerated, contributing to achieving carbon neutrality by 2050. Additionally, the process using super(sub)critical fluids is environmentally friendly because it uses low-toxicity solvents such as water or alcohol instead of organic solvents that cause harmful VOCs to humans and the atmosphere, and solvents can be recovered without additional separation processes after use.

Dr. Hong said, "As a fundamental technology, it can be expanded to recycle thermosetting plastics that are entirely discarded and to regenerate raw materials (monomers) that overcome the rapid deterioration of recycled plastics' properties," adding, "We hope this will provide a solution to the global challenges of plastic waste treatment and microplastic pollution."

This content was produced with the assistance of AI translation services.