Recycling and Regeneration of Plastic Waste: Direct & Modified Reuse Methods
Recycling and reuse of waste plastics is the primary method adopted worldwide for plastic waste recovery, due to its relatively low technical investment and cost. This approach has mature industrial processes in place. Compared with modified regeneration, direct reuse is simpler and more cost-effective, making it the most common method. However, modified regeneration is considered the future development trend as it significantly improves product performance.
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1. Direct Recycling (Direct Reuse)
Direct recycling involves sorting, cleaning, crushing, and pelletizing waste plastics before directly molding them into new products. In some cases, additives such as stabilizers, anti-aging agents, and colorants are added to improve processing, appearance, or resistance to aging. However, these additives do not fundamentally improve the mechanical properties of the recycled plastic.
For example, a Japanese construction company processes waste foam plastics by crushing and heating them with infrared radiation, reducing their volume by more than 80%. The material is then mixed with special cement to produce a “rice cracker”–like sound insulation board, offering low-cost, high-efficiency noise reduction for various building applications.
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2. Modified Recycling (Performance-Enhanced Reuse)
Modified recycling improves the properties of recycled plastics via mechanical blending or chemical grafting, such as toughening, reinforcing, compounding, particle activation, crosslinking, chlorination, and other chemical modifications. This process enhances performance — especially mechanical strength — enabling the production of higher-grade recycled products. However, it requires more complex processes and specialized equipment.
Almost all thermoplastic waste plastics can be collected, sorted, cleaned, crushed, dried, melted, and then reprocessed into recycled plastic sheets, pipes, rods, components, containers, and more. For instance, banned EPS foam food containers can be cleaned, dried, crushed, defoamed via a single-screw extruder, pelletized, and then blended with LDPE to create LDPE/PS composites with higher tensile strength, improved elongation, and impact resistance — suitable for products like cable cover boards and household items.
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3. Chemical Degradation Technologies
Chemical degradation breaks down the polymer chains of waste plastics into monomers or other basic organic raw materials. This process depends heavily on degradation temperature, catalysts, and specialized equipment.
3.1 Depolymerization
Depolymerization returns plastics to monomers or chemical feedstocks via hydrolysis or alcoholysis. This method requires clean waste plastics, removal of additives, and purification of monomers.
3.2 Pyrolysis
Pyrolysis is the thermal decomposition of plastics at high temperatures (above 500°C) in the absence of oxygen.
For example, a German company operates a 10t/day pilot plant that heats mixed waste plastics at 699–800°C for 30 minutes, yielding 35–58% diesel and 23–40% gas. Research from China University of Petroleum shows that pyrolyzing waste polyethylene can produce 50–90% wax, which offers higher economic returns than producing oil.
3.3 Hydrogenation
Hydrogenation involves breaking down plastics under high hydrogen pressure (around 30MPa) at temperatures below 500°C. This produces liquid fuels of lower purity than pyrolysis but can be directly refined in oil refineries. However, it requires strict pre-treatment, separation, and costly equipment.
3.4 Gasification
Gasification degrades waste plastics at extremely high temperatures (up to 1500°C) into CO and H₂ gas, which can then be used to synthesize methanol and other chemical products.
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Conclusion
From low-cost direct reuse to high-tech chemical recycling, plastic waste regeneration offers a sustainable pathway for reducing environmental pollution and creating valuable products. As global environmental regulations tighten, modified recycling and chemical recovery technologies will play an increasingly important role in the circular economy of plastics
