Waste plastic is a popular term, not referring to waste, old and useless plastic products. For most plastic products, especially those that are used once in large quantities, the properties of the plastic materials themselves have not changed much after use, so it is entirely possible to recycle them and reprocess them into plastic products using appropriate methods and then reuse them.

Basic Introduction

The more formal term for waste plastic is post-consumer plastic waste, which refers to discarded plastic products after consumption or use. Plastic will also produce waste and waste materials in the synthesis, molding, processing, and circulation of plastic. These plastic wastes are also called pre-consumer plastic waste. Although this also belongs to the scope of waste plastic, due to the relatively small amount of production, easy recycling and high recycling value, manufacturers generally recycle them themselves and use the recycled products directly in production. Therefore, the waste plastic we usually refer to mainly refer to post-consumer plastic waste. If not otherwise specified, the waste recycling website also refers to post-consumer plastic waste.

Generation

Plastic products are everywhere in our daily life and agricultural production. When the lifespan or purpose of use of these products is reached, they will be discarded and become waste plastic. Of course, the source of waste plastic is not limited to this. As mentioned earlier on the waste recycling website, waste or discarded products will be generated in every link of plastic synthesis, molding, circulation and consumption. Its specific sources are mainly the following aspects.

Generated in resin production

The waste generated in resin production is reported in the following three aspects:

¢Ù. The auxiliary materials (commonly known as "rice crust") scraped off the inner wall of the reactor during the polymerization process and unqualified reaction materials.

¢Ú. The cleaning waste of the extruder during the mixing process and unqualified mixing materials.

¢Û. The falling materials (throwing materials) and slag materials 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 kinds of resin production, polyethylene produces the least waste, while polyvinyl chloride produces the most waste.

Generated during the molding process

In various molding processes of thermoplastic, varying amounts of waste, substandard products and scraps will be generated. Such as six 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 during the blow molding process, the cold solid materials and cleaning waste in the equipment, and the flash of the hollow container (the waste rate of the fart mouth can reach 40% when producing bottles with handles); waste, trimming materials and waste products dropped from the mixer and calender during the calendering process; overflow materials, removed edge seam materials and waste products on the mold parting county during rotational molding.

The amount of waste generated during the molding process depends on the processing technology, mold and equipment. Generally speaking, the recycling rate of this kind of waste is relatively high. They have clear varieties, clear filler amounts, low pollution, and performance close to the original material. The pretreatment workload is small. Usually only crushing is done. They can be mixed into new materials as recycled materials, and have little impact on the performance and quality of the products.

Thermosetting plastic will also produce waste and waste materials during the molding process. If the waste has undergone cross-linking reactions, it will be very difficult to recycle these waste materials.

Produced during the compounding and regeneration process

The waste generated during the compounding and regeneration process only accounts for a small part of all waste plastic. They are waste materials removed during the cleaning of the compounding equipment and defective products produced under abnormal operation. Most of them are recyclable waste plastic.

Produced in secondary processing

Secondary processing usually involves transferring (roughly speaking: the process of transferring the toner image formed on the drum surface to paper is called transfer), sealing, thermoforming, machining, etc., the semi-finished plastic products purchased from the molding factory are processed into finished products. The waste generated here is often more difficult to handle than the waste generated by the molding factory. For example, it is very difficult and costly to remove the printed layer and electroplated layer of the waste after printing and electroplating. The value of the recycled materials obtained by direct crushing or granulation is much lower. The waste edges and waste pellets generated by thermoforming and mechanical cutting are easier to recycle and the value of the recycled waste is also higher.

Produced after consumption

This type of waste plastic has a wide source and complex usage, and must be processed before it can be recycled. This type of waste includes:

(1) Bags and barrels used in the chemical industry.

(2) Containers and artificial fiber yarns in the textile industry.

(3) Packaging materials, foam shock pads, etc. in the home appliance industry.

(4) Building materials, pipes, etc. in the construction industry.

(5) Shrink film, stretch film, etc. in the canning industry.

(6) Turnover boxes, egg trays, etc. in food processing.

(7) Ground film, greenhouse film, fertilizer bags, etc. in agriculture.

(8) Fishing nets, floats, etc. in fisheries.

(9) Bumpers, fuel tanks, battery boxes, etc. removed from scrapped vehicles.

Generated from urban domestic waste

This type of waste plastic also belongs to 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. Among the domestic garbage in Chinese cities, waste plastic account for 2% to 4%, most of which are disposable packaging materials, which are basically polyethylene (PE), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), etc. Among these waste plastic, polyolefins (PO) account for 70%.

There are many types of waste plastic products in domestic garbage, including various packaging products, such as bottles, films, cans; daily products, such as barrels, basins, cups, plates, etc.; toys and accessories, entertainment products, clothing and shoes, strapping ropes, packing tapes, woven bags, health care products, etc.

Identification

The difference with recycled plastic

Waste plastic are plastic products that are directly crushed into powder or granules, and it is still possible to distinguish what material they are, such as injection molding, wire drawing, or film, etc. Recycled materials are recycled countless times and cannot be accurately identified. They can only be classified according to the number of times they are recycled, starting with the least, and then divided into special grade, first grade, and second grade.

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