What is the problem that the secondary granulation calcium powder of PVC is not plasticized?

Brief introduction of PVC

The molecular weight and distribution of PVC were determined by general calibration method, using polystyrene standard, THF as mobile phase (note that your column should be used for THF) and differential refractive index detector.

Most literatures give the K values and α values of various polymers at 25℃, but the K values and α values of polystyrene and PVC at 28℃ have not been found in reliable literatures at present.

If it is not necessary to determine the molecular weight of PVC at 28℃, it can be determined at 25℃. At this time, k and a of PS and PVC are as follows: PS: K = 0.0 16, A = 0.706 PCV: K = 0.0 163, A = 0.766.

Definition and characteristics

PVC roofing tile (UPVC lightweight roofing tile) is a new type of roofing waterproof material. PVC tile is made of rigid polyvinyl chloride (UPVC) as the main material, with heat stabilizer, lubricant, filler, sunscreen, ultraviolet absorber, foaming agent and so on. Three layers of mixed plasticizing extrusion form three layers of extruded core foam.

What's the difference between polyethylene, PVC, polystyrene and polypropylene?

When uncolored, it is milky white and translucent wax-like; Touching the product by hand feels greasy, soft and tough; Slightly scalable. Generally, low density polyethylene is soft and transparent; High density polyethylene is very hard.

Common products: handbags, water pipes, oil drums, beverage bottles (calcium milk bottles), daily necessities, etc.

Polypropylene PP

When uncolored, it is white, translucent and waxy; Lighter than polyethylene. Transparency is also better than polyethylene, and rigidity is also greater than polyethylene.

Common products: pots, barrels, furniture, films, woven bags, bottle caps, car bumpers, etc.

Polystyrene PS

Transparent when colorless. When the product falls to the ground or knocks, it has a metallic crisp sound, good luster and transparency, similar to glass, fragile and easy to break, and can be used to mark the surface of the product with nails. Modified polystyrene is opaque.

Common products: stationery, cups, food containers, household appliance shells, electrical accessories, etc.

polyvinyl chloride

Natural color is yellowish, translucent and shiny. Transparency is better than polyethylene and polystyrene, but worse than polystyrene. With the different dosage of additives, it can be divided into soft PVC and hard PVC. Soft-packed products are soft and tough and sticky to the touch. The hardness of hard products is higher than that of low density polyethylene, but lower than that of polypropylene, and whitening will occur at the bending point.

Common products: plates, pipes, soles, toys, doors and windows, wire sheaths, stationery, etc.

Polyethylene terephthalate PET

Good transparency, better strength and toughness than polystyrene and PVC, and not easy to break.

Common products: often bottle products such as cola, mineral water bottles, etc.

Polyethylene waste

Polyethylene is the most abundant and widely used thermoplastic in plastics. It is a partially crystalline material polymerized from ethylene and can be processed by general 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/, while the density of low density polyethylene and linear low density polyethylene is between 0.9 1 ~ 0.94 g/cm. Waste polyethylene film has two main sources:

1. Waste and defective products produced in film production. These wastes are clean and clear in variety, and can be directly sent to the extruder for granulation after crushing and compression, and the recovery process is simple.

2. Waste films from chemical industry, electrical industry, food and consumer goods industry. These waste films have been polluted, some have been colored and printed with trademarks, and some still contain impurities such as sand, sawdust or shredded paper.

Polyethylene is widely used because of its low price, easy availability and wide application, but the most used is packaging products, which is estimated to be above 60%. High density polyethylene is mainly used for packaging films, bottles and hollow containers; The main uses of low density polyethylene are packaging film and agricultural film; Linear low density polyethylene is mainly used in films, film plastic parts, pipelines and wires and cables.

PVC waste

Polyvinyl chloride used to be the most used plastic in history, but now it is replaced by polyethylene and PET in some fields, but it is still widely used, and its consumption is second only to polyethylene and polypropylene. There are many forms of PVC products, which can be divided into three categories: hard PVC, soft PVC and PVC paste. Rigid PVC is mainly used for extruded products such as pipes, door and window profiles and sheets, as well as injection-molded parts and bottle products such as pipe joints and electrical parts by extrusion blow molding, accounting for more than 65% of PVC consumption. Soft PVC is mainly used in calendered sheets, automobile interior accessories, handbags, films, labels, wires and cables, medical supplies and so on. PVC paste accounts for about 10% of PVC products, and the main products are plastic-lined 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); Toughness, chemical resistance and weather resistance are all good. Therefore, it is widely used in automobiles, medical equipment, indoor swimming pools and other places. With the development of automobile and other related industries, the amount of PMMA is increasing. There are three main types of PMMA products: sheets made by casting or extrusion; Specific products that already contain additives (such as modifiers and pigments); Paints and coatings.

Polystyrene waste polystyrene is a homopolymer of styrene, which is a kind of thermoplastic general plastic, and its output is second only to polyethylene, polypropylene and polyvinyl chloride. Polystyrene has a wide range of uses. It can be roughly divided into the following four aspects:

General purpose polystyrene: products are widely used in household appliances, computers, medical care and other daily necessities and transparent products.

High impact polystyrene: the impact strength and elongation at break are greatly improved, and the products are widely used in electrical accessories, household appliance shells, food containers and so on.

Extruded polystyrene foam board and its thermoformed products: thick board is mainly used as heat insulation, sound insulation and shock-proof material. Thermoforming products are widely used in food packaging and fast food containers.

Expandable polystyrene foam products: products are used for shock-proof packaging of electrical appliances and thermal insulation materials in construction, refrigeration and other industries.

The first two kinds of polystyrene products have long service life, and the thickness of waste can be recovered by conventional recycling methods, so the pressure on the environment is also small. The latter two kinds of polystyrene products are mostly disposable packages, which are bulky and consume a lot. If it is directly discarded without treatment, it will cause great pressure on the environment. People often say "white pollution", a large part of which is styrofoam.

Polyethylene terephthalate waste

Polyethylene terephthalate (PET) is a linear thermoplastic, which is a condensation polymer of terephthalic acid or dimethyl terephthalate and ethylene glycol ester. PET is usually a crystalline plastic, but in bottles and film products, because of its high transparency, special technical conditions can be used to make it amorphous.

PET is widely used because of its excellent performance and low cost. According to the product form, it can be divided into four categories: polyester fiber, film, engineering injection molded parts and bottles. Because of its light weight and low energy consumption, PET bottles have replaced some traditional packaging materials and are widely used in food, beverage, cosmetics and other fields, especially beverage bottles, and PET has occupied an absolute advantage. Beverage bottles are disposable, so the waste is huge.

The recycling technology of PET bottles has reached a very high level abroad, and the recovery rate in the United States, Germany and other countries has now reached more than 80%. Moreover, in order to facilitate recycling, these countries have also formulated some local laws and regulations, which have mandatory provisions on the abandonment, collection, use, design and manufacture of PET bottles.

Simple classification of waste plastics sources

Plastics, especially thermoplastics, will produce wastes or discarded products in all aspects such as synthesis, molding, circulation and consumption, which are collectively called "plastic wastes", and most of them are produced in the process of consumption and use, especially packaging materials, agricultural films and disposable drugs.

Generation of waste plastics:

1. Waste generated in resin production;

2. Waste generated in the molding process;

3. Waste generated in the process of mixing and recycling;

4. Waste generated by secondary processing;

5. Plastic waste after industrial consumption;

This kind of waste has a wide range of sources and complex uses, and it must be treated before it can be recycled. Such wastes include:

1) bags and barrels for chemical industry;

2) containers and waste man-made fiber filaments in textile industry;

3) packaging materials, foam shock pads, etc. In the home appliance industry;

4) Building materials and pipes in the construction industry;

5) Shrinking film and stretching film in the filling industry;