When unpigmented, it is milky white, translucent and waxy; the product feels smooth when touched by hand, flexible and flexible; it can stretch slightly. Generally, low-density polyethylene is softer and has better transparency; high-density polyethylene is harder.
Common products: handbags, water pipes, oil drums, beverage bottles (calcium milk bottles), daily necessities, etc.
Polypropylene PP
White translucent, waxy when unpigmented; lighter than polyethylene. The transparency is also better than that of polyethylene, and it is harder than polyethylene.
Common products: basins, barrels, furniture, films, woven bags, bottle caps, car bumpers, etc.
polystyrene PS
Transparent when unpigmented. When the product is dropped or tapped, it has a metal-like crisp sound, good luster and transparency, similar to glass, brittle and easy to break, and the surface of the product can be scratched with fingernails. Modified polystyrene is opaque.
Common products: stationery, cups, food containers, home appliance shells, electrical accessories, etc.
Polyvinyl chloride PVC
The natural color is light yellow, translucent and shiny. The transparency is better than that of polyethylene and polystyrene, but worse than that of polystyrene. Depending on the dosage of additives, it can be divided into soft and hard polyvinyl chloride. Soft products are flexible and flexible, and feel sticky. The hardness of hard products is higher than that of low-density polyethylene. , while lower than polypropylene, whitening occurs at the inflection point.
Common products: plates, pipes, soles, toys, doors and windows, wire sheaths, stationery, etc.
polyethylene terephthalate PET
The transparency is very good, the strength and toughness are better than that of polystyrene and polyvinyl chloride, and it is not easy to break.
Common products: often bottle products such as cola, mineral water bottles, etc.
polyethylene waste
Polyethylene is a thermoplastic with the largest output and a wide range of uses among plastics. It is polymerized from ethylene and is a partially crystalline material that can be processed by ordinary thermoplastic molding methods. Polyethylene can be divided into three categories: high density polyethylene, low density polyethylene and linear low density polyethylene.
The density of high-density polyethylene is generally higher than 0.94g/cm, while the density of low-density polyethylene and linear low-density polyethylene is between 0.91 and 0.94g/cm. There are two main sources of waste polyethylene film:
1. Leftovers, defective products, etc. produced in film production. These wastes are clean and of clear varieties, and can be crushed and compressed directly into the extruder for granulation, and the recycling process is relatively simple.
2. Waste films from the chemical industry, electrical industry, food and consumer goods industries, etc. These waste films are all contaminated, some are colored and branded, and some contain impurities such as sand, sawdust or shredded paper.
Because polyethylene is cheap and easy to obtain and easy to form, its products have a wide range of applications, but the most used are packaging products, which are estimated to be more than 60%. High-density polyethylene is mainly used in packaging films, bottles, and hollow containers; low-density polyethylene is mainly used in packaging films and agricultural films; linear low-density polyethylene is mainly used in films, film plastic parts, and pipes. and wire and cable.
PVC waste
Polyvinyl chloride used to be the most used plastic in history, and now it has been replaced by polyethylene and PET in some fields, but it is still used in large quantities, and its consumption is second only to polyethylene and polypropylene. There are many forms of PVC products, which can be divided into three categories: rigid PVC, soft PVC and PVC paste. Rigid PVC is mainly used for extrusion products such as pipes, door and window profiles, sheets, as well as injection parts such as pipe joints, electrical parts, and extrusion-blown bottle products, which account for more than 65% of the consumption of PVC. Soft PVC is mainly used in calendered sheets, automotive interior accessories, handbags, films, labels, wires and cables, medical products, etc. PVC paste accounts for about 10% of PVC products, and the main products are slush plastic products.
Polymethyl methacrylate waste
Polymethyl methacrylate (PMMA) is commonly known as plexiglass. PMMA has unique properties that other plastics do not have: excellent transparency (close to glass); good toughness, chemical resistance, and weather resistance. Therefore, it has been widely used in automobiles, medical equipment, indoor swimming pools and other places. With the development of related industries such as automobiles, the amount of PMMA is also increasing. There are three main types of PMMA products: sheets made by casting or extrusion; specific products already containing modifiers, pigments and other auxiliaries; paints and coatings.
Polystyrene waste Polystyrene is a homopolymer of styrene, a thermoplastic general-purpose plastic, second only to polyethylene, polypropylene, and polyvinyl chloride in output. Polystyrene has a wide range of applications. It can be roughly divided into the following four aspects:
General-purpose polystyrene: a large number of daily necessities and transparent products such as home appliances, computers, and medical care.
High impact polystyrene: greatly improved its impact strength and elongation at break, the products are widely used in electrical accessories, home appliance shells, food containers, etc.
Extruded expanded polystyrene sheet and its thermoformed products: Thick sheets are mainly used for thermal insulation, sound insulation and shockproof materials. Thermoformed products are widely used in food packaging and snack food containers.
Expandable polystyrene foam products: products are used for shock-proof packaging of electrical appliances, thermal insulation materials in construction, refrigeration and other industries.
The first two types of polystyrene products have a long service life, and the waste can be recycled by conventional recycling methods, so the pressure on the environment is also small. The second type of polystyrene products are mostly disposable packaging, which is large in size and consumes a lot of money. If they are directly discarded without treatment, it will cause great pressure on the environment. A large part of what is often referred to as "white pollution" is Styrofoam.
polyethylene terephthalate waste
Polyethylene terephthalate (PET) is a polycondensate of terephthalic acid or dimethyl terephthalate and ethylene glycol ester, and is a linear thermoplastic. PET is usually a crystalline plastic, but in bottles and film products, special process conditions can be used to make it an amorphous plastic for its high transparency.
PET has a wide range of uses due to its excellent performance and low cost. According to its product form, it can be divided into four categories: polyester fiber, film, engineering injection parts, and bottles. PET bottles have replaced some traditional packaging materials due to the advantages of light weight, unbreakable and low energy consumption, and are widely used in food, beverage, cosmetics and other fields, especially beverage bottles, PET has an absolute advantage. Beverage bottles are single-use, so the amount of waste is huge.
The recycling technology of PET bottles has reached a very high level abroad, and the recycling rate in the United States, Germany and other countries has reached more than 80%. Not only that, in order to facilitate recycling, these countries have also formulated some local regulations, which impose mandatory regulations on the waste, collection, use, design and manufacture of PET bottles.
Simple classification of waste plastic sources[/B]
Plastics, especially thermoplastics, will produce waste or waste products in every link of synthesis, molding, processing, circulation and consumption, collectively referred to as "plastic waste", most of which are produced in the process of consumption and use, and especially packaging. Materials, agricultural films and disposable medicines are the largest wastes.
Generation of waste plastics:
1. Waste generated in resin production;
2. Waste generated during the molding process;
3. Waste generated in the process of compounding and recycling;
4. Waste generated in secondary processing;
5. Industrial post-consumer plastic waste;
Such wastes come from a wide range of sources and are complicated to use, and must be processed before they can be recycled. Such wastes include:
1) Bags, barrels, etc. used in the chemical industry;
2) Containers, waste rayon, etc. in the textile industry;
3) Packaging materials, foam shockproof pads, etc. in the home appliance industry;
4) Building materials, pipes, etc. in the construction industry;
5) Shrink film, stretch film, etc. in the filling industry;
6) Turnover boxes, egg trays, etc. in the food processing industry;
7) Plastic film, greenhouse film, fertilizer bags, etc. in agriculture;
8) Fishing nets, floating balls, etc. in fishery;
9) Bumpers, fuel tanks, battery boxes, etc. removed from scrapped vehicles.
6. Post-consumer waste plastics
