Meaning
Recycling post-consumer plastic waste into high-quality chemical feedstocks requires thermal processes to break the polymer chains back into basic hydrocarbons. This transformation is known as thermochemical conversion and it involves pyrolysis or gasification at elevated temperatures in the absence of oxygen. The process yields liquid and gaseous fractions that can be refined into new resins.
It does not include mechanical recycling methods where the plastic is simply melted and re-pelletized.
Reaction Mechanism
High heat provides the energy needed to cleave the strong carbon-carbon bonds of the plastic waste. Under thermochemical conversion, the long-term polymer chains are cracked into a mixture of shorter hydrocarbons. This reaction must occur in an oxygen-free environment to prevent combustion and maximize the yield of liquid pyrolysis oil.
Process Input
The efficiency of this process depends on the type and purity of the incoming plastic stream. While mixed polyolefins like polyethylene and polypropylene convert readily into high-yield liquid feedstocks, contaminants like polyvinyl chloride release hydrochloric acid which corrodes the processing equipment.
Sourcing Strategy
Moulding companies use resins derived from these thermal recycling processes to meet recycled content targets without sacrificing the mechanical properties of their parts. Because the process breaks the polymer down to the monomer level, the resulting virgin-quality resin behaves identically to fossil-based plastic during injection moulding. This sourcing approach allows manufacturers to use recycled materials in high-performance applications, such as medical devices or food packaging, where mechanically recycled plastics are banned due to contamination risks.
