The recycling and reuse of PE accordion bags requires a systematic process to achieve a closed-loop resource system. Its core components include sorting, washing, crushing, melt granulation, and reprocessing applications. Each step needs to be optimized for the folded structure of the PE accordion bag and the characteristics of the PE material.
Sorting is the first step in the recycling process, separating discarded PE accordion bags from other materials (such as PVC and PET) or items containing impurities. Because the folded structure of PE accordion bags easily traps debris, labels, or adhesives, sorting requires a combination of manual screening and automated equipment. Near-infrared spectroscopy or X-ray fluorescence technology is used to identify material composition, while air separation or vibrating screens remove light impurities. For example, some recycling companies use multi-stage sorting lines, first manually removing obviously contaminated bags, and then using optical sorting machines to further separate them by color and material to ensure raw material purity.
The washing stage needs to address the cleaning challenges caused by the folded structure of PE accordion bags. The multi-layered pleats of PE accordion bags easily trap oil, food residue, or printing ink, requiring a multi-stage cleaning process: first, a high-speed friction cleaner removes large surface particles; then, an ultrasonic cleaner decomposes minute contaminants; finally, it is rinsed with pure water and centrifuged for dehydration. For printing ink, some companies use alkaline soaking or organic solvent wiping, but a more environmentally friendly method is to use a water-based deinking agent, which chemically removes the ink from the bag's surface. The cleaned PE must meet a standard of impurity content below 0.5% before proceeding to the next process.
The crushing process must be adapted to the thin-walled characteristics of PE accordion bags. Their thickness is typically between 0.04-0.2 mm; direct crushing easily produces long, strip-shaped fragments, affecting subsequent melting efficiency. Therefore, a low-temperature shear crusher is required, using rotating blades to cut the bag into 3-5 cm fragments while controlling the equipment temperature below the PE melting point to prevent material adhesion. Some companies also pre-compress the PE accordion bags before crushing to reduce their volume and increase the processing capacity of the crushing line.
Melt granulation is the core of the recycling process, requiring solutions to the thermal stability of PE materials and the residual structure of PE accordion bags. Crushed PE fragments are fed into a single-screw or twin-screw extruder, where they melt at 160-220℃. The rotating screw forces the melt through a filter to remove incompletely crushed impurities or gel points. A mesh size of 40-60 is typically chosen to ensure melt purity while avoiding frequent filter replacements and increased costs. After being extruded into strips through a die, the melt is rapidly shaped using water or air cooling, and finally cut into uniform granules by a pelletizer. Strict temperature control is crucial in this stage to prevent PE degradation leading to a decrease in molecular weight and affecting the performance of the recycled material.
The application of recycled PE granules requires performance-based grading. Granules with high transparency and few impurities can be used in blown film processes to remake food packaging bags or shopping bags; granules with darker colors or fewer impurities are used in injection molding to produce products with lower aesthetic requirements, such as trash cans and flower pots. To address the folding structure of PE accordion bags, some companies blend them with virgin materials in certain proportions, adding toughening agents or anti-aging agents to improve the flexibility and weather resistance of the recycled materials, making them suitable for manufacturing packaging materials that require repeated folding.
Chemical recycling provides a new path for the high-value utilization of PE accordion bags. Through pyrolysis technology, PE can be decomposed into fuel oil or basic chemical raw materials in an oxygen-free environment, achieving a closed loop from "waste plastic to new plastic." For example, one company uses a catalytic cracking process to convert PE accordion bags into polymer-grade propylene at 400-600℃, producing butane and other gases as byproducts. The hydrocarbon conversion efficiency is 15%-20% higher than traditional processes. Although this technology requires a larger equipment investment, it can handle heavily polluted waste bags and reduce dependence on virgin plastics.
The recycling and reuse of PE accordion bags has formed a complete technological system from physical recycling to chemical conversion. Physical recycling transforms waste bags into recycled pellets through processes such as sorting, washing, crushing, and granulation, which can then be used in packaging, daily necessities, and other fields. Chemical recycling, on the other hand, uses pyrolysis technology to upgrade materials and produce high-value-added chemical products. With technological advancements, the recycling rate and performance of recycled materials for PE accordion bags will be further improved in the future, driving the plastic packaging industry towards a circular economy model.
