Waste plastic is a popular term that does not refer to waste, old and useless plastic products. The properties of most plastic products, especially those that are disposable in large quantities, do not change significantly after use. Therefore, they can be recycled and reprocessed into plastic products using appropriate methods for reuse.
Basic introduction
The more formal term for waste plastic is post-consumer plastic waste, which refers to discarded plastic products after consumption or use. Plastics also produce waste products and waste materials during the synthesis, molding, processing, circulation and other processes. These plastic wastes are also called pre-consumer plastic wastes. Although this also belongs to the scope of waste plastics, because the amount produced is relatively small, it is easy to recover and recycle The value is high, and generally manufacturers will recycle it themselves and use the recycled products directly in production. Therefore, what we usually call waste plastic mainly refers to post-consumer plastic waste. If there is no special instructions, the scrap recycling dealer network mentioned [1]Also refers generally to post-consumer plastic waste.
Produce
Plastic products are everywhere in our daily lives and in various fields of agricultural production. When these products have reached their useful life or purpose, they will be discarded and become waste plastics. Of course, the sources of waste plastics are not limited to this. As mentioned before on the Waste Recycler Network, waste materials or discarded products will be generated in every link of plastic synthesis, molding processing, circulation and consumption. Its specific sources mainly include the following aspects.
Produced in resin production
Waste generated in resin production is reported in the following three aspects:
- The auxiliary materials scraped from the inner wall of the reactor during the polymerization process (commonly known as “Cooker”) and unqualified reaction materials.
- Extruder cleaning waste and unqualified compound materials during the compounding process.
- Material falling to the ground (throwing material) and slag material during transportation and storage.
The amount of waste depends on the complexity of the polymerization reaction, the number of manufacturing processes, the production equipment and the proficiency of the operation. Among all types of resin production, polyethylene produces the least waste and PVC produces the most.
Produced during the molding process
In various molding processes of thermoplastic plastics, varying amounts of waste products, substandard products and scraps will be produced. For example, six-channel cold materials, gate cold solid materials, cleaning waste, waste edges, etc. in injection molding; cleaning waste, trimming materials, and cut-off materials on the final product in extrusion molding; The blank mouth on the blow molding machine, the cold solid material and cleaning waste in the equipment, and the flash of the hollow container (the waste rate of the blank mouth when producing bottles with handles can reach %40); in the calendering process, the waste from the mixing machine, scrap materials, trimming materials and waste products dropped from the calender; flash material on the mold parting county during rotational molding processing, removed edge seam materials and waste products, etc.
The amount of waste generated during molding depends on the processing technology, molds and equipment. Generally speaking, the recycling rate of this kind of waste is relatively high. They have clear varieties, clear filling amounts, less pollution, performance close to the original materials, and small pretreatment workload. They are usually only crushed and can be used as recycled materials to be mixed into new materials, and have a positive impact on the performance and quality of the products. The impact is small.
Thermosetting plastics will also produce waste products and waste materials during molding and processing. If the waste products have undergone cross-linking reactions, it will be very difficult to recycle these waste products.
Produced during the mixing and recycling process
The waste generated during the compounding and recycling process only accounts for a small part of all waste plastics. They are waste materials removed when compounding equipment is cleaned and defective products produced under abnormal operation. Most of them are recyclable waste plastics.
Produced during secondary processing
Secondary processing usually involves transferring the semi-finished plastic products purchased from the molding processing plant (to the effect: the process of transferring the toner image formed on the drum surface to paper is called transfer), sealing, thermoforming, and mechanical processing. When processed into finished products, the waste produced here is often more difficult to process than the waste produced in the molding processing plant. For example, after printing, electroplating, etc., it is difficult and costly to remove the printed and electroplated layers., while the value of recycled materials obtained by directly crushing or granulating them is much lower. It is easier to recycle the waste edges and waste particles produced by thermoforming and mechanical cutting, and the value of the recycled waste materials is also relatively high.
Produced after consumption
This type of waste plastic comes from a wide range of sources and has complex usage conditions. It must be processed before it can be recycled and reused. This type of waste includes:
- Bags, barrels, etc. used in the chemical industry.
- Containers, artificial fibers, etc. in the textile industry.
- Packaging materials, foam anti-shock pads, etc. in the home appliance industry.
- Building materials, pipes, etc. in the construction industry.
- Shrink film, stretch film, etc. in the canning industry.
- Turnover boxes, egg trays, etc. in food processing.
- Mulch film, greenhouse film, fertilizer bag, etc. in agriculture.
- Fishing nets, floating balls, etc. in fishery.
- Bumpers, fuel tanks, battery boxes, etc. removed from scrapped vehicles.
Produced in municipal solid waste
This type of waste plastic is also post-consumer plastic. Due to its large quantity and difficulty in recycling, it has posed a serious threat to the environment and is the focus of future recycling work, so it is classified separately. Waste plastics account for more than 2% to 4% of my country’s urban domestic waste, most of which are disposable packaging materials. They are basically polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene, etc. Vinyl chloride (PVC), polyethylene terephthalate (PET), etc. Among these waste plastics, polyolefin (PO) accounts for 70%.
There are many types of waste plastic products in domestic waste, including various packaging products, such as bottles, films, and cans; daily products, such as buckets, basins, cups, plates, etc.; toys, accessories, entertainment supplies, clothing and footwear, strapping ropes, packing tapes, woven bags, health care products, etc.
Distinguish
The difference with recycled plastic.
Waste plastic is directly crushed into powder or granular form, and the material can still be distinguished, such as injection molding, wire drawing, film, etc. Recycled materials have been recycled countless times and cannot be accurately distinguished. They can only be classified into grades according to the number of cycles. Starting with the smallest ones, they are divided into special grade, first grade, and second grade.
