Polyvinyl chloride (PVC) is a polymer polymerized by vinyl chloride monomer (VCM) in peroxide, azo compound and other initiators or according to the free radical polymerization mechanism under the action of light and heat. Vinyl chloride homopolymer and vinyl chloride copolymer are collectively referred to as vinyl chloride resin.
PVC is a white powder with amorphous structure, with small branching degree, glass transition temperature of 77 ~ 90 ℃, and it begins to decompose at about 170 ℃ [1]. It has poor stability to light and heat. When it is above 100 ℃ or exposed to sunlight for a long time, it will decompose to produce hydrogen chloride, and further Autocatalytic Decomposition will cause discoloration, and its physical and mechanical properties will also decline rapidly, In practical application, stabilizer must be added to improve the stability to heat and light.
The molecular weight of industrial PVC is generally in the range of 50000 ~ 110000, with great polydispersity. The molecular weight increases with the decrease of polymerization temperature. There is no fixed melting point. It begins to soften at 80 ~ 85 ℃, changes to viscoelastic state at 130 ℃, and changes to viscous flow state at 160 ~ 180 ℃; It has good mechanical properties, with tensile strength of about 60MPa and impact strength of 5 ~ 10kj / m2; It has excellent dielectric properties.
PVC was once the world's largest general-purpose plastic, which was widely used. It is widely used in building materials, industrial products, daily necessities, floor leather, floor tiles, artificial leather, pipes, wires and cables, packaging film, bottles, foaming materials, sealing materials, fibers and so on.
According to the different application scope, PVC can be divided into: General PVC Resin, high degree of polymerization PVC resin and cross-linked PVC resin. Universal PVC resin is formed by polymerization of vinyl chloride monomer under the action of initiator; High degree of polymerization PVC resin refers to the resin polymerized by adding chain growth agent in vinyl chloride monomer polymerization system; Crosslinked PVC resin is a resin polymerized by adding crosslinking agent containing diene and polyene into vinyl chloride monomer polymerization system.
According to the method of obtaining vinyl chloride monomer, it can be divided into calcium carbide method, ethylene method and imported (EDC, VCM) monomer method (traditionally, ethylene method and imported monomer method are collectively referred to as ethylene method).
Main purpose:
1. PVC profile
Profile and profile are the areas with the largest consumption of PVC in China, accounting for about 25% of the total consumption of PVC. They are mainly used to make doors and windows and energy-saving materials. Their application is still growing by a large margin throughout the country. In developed countries, the market share of plastic doors and windows is also the highest, such as 50% in Germany, 56% in France and 45% in the United States.
2. PVC pipe
Among many PVC products, PVC pipe is the second largest consumption field, accounting for about 20% of its consumption. In China, PVC pipe is developed earlier than PE pipe and PP pipe, with many varieties, excellent performance and wide application range, which occupies an important position in the market.
3. PVC membrane
The consumption of PVC in the field of PVC membrane ranks third, accounting for about 10%. After PVC is mixed and plasticized with additives, a transparent or colored film with a specified thickness is made by a three roll or four roll calender. The film is processed by this method to become a calendered film. You can also cut and heat seal packaging bags, raincoats, tablecloths, curtains, inflatable toys, etc. The wide transparent film can be used for greenhouse, plastic greenhouse and plastic film. The biaxially stretched film has the characteristics of thermal shrinkage and can be used for shrinkage packaging.
4. PVC hard materials and plates
PVC is added with stabilizer, lubricant and filler. After mixing, hard pipes, special-shaped pipes and corrugated pipes of various diameters can be extruded by extruder for downcomer, drinking water pipe, wire sleeve or stair handrail. The calendered sheets can be overlapped and hot pressed to make hard plates of various thicknesses. The plate can be cut into the required shape, and then welded into various chemical corrosion-resistant storage tanks, air ducts and containers with PVC electrode and hot air.
5. PVC general soft products
It can be extruded into hoses, cables, wires, etc. by extruder; Plastic sandals, soles, slippers, toys, auto parts, etc. can be made by injection molding machine with various molds.
6. PVC packaging materials
PVC products are mainly used for packaging various containers, films and hard pieces. PVC containers mainly produce mineral water, beverage and cosmetic bottles, and are also used for the packaging of refined oil. PVC film can be used for CO extrusion with other polymers to produce low-cost laminated products and transparent products with good barrier. PVC film can also be used for stretch or heat shrinkable packaging, and for packaging mattresses, cloth, toys and industrial commodities.
7. Pvc wall panels and floors
Pvc wall panels are mainly used to replace aluminum wall panels. In addition to a part of PVC resin, the other components of PVC floor tiles are recycled materials, adhesives, fillers and other components, which are mainly used in the ground of airport terminal building and hard ground in other places.
8. PVC consumer goods
Luggage bag is a traditional product made of PVC. PVC is used to make all kinds of imitation leather, luggage bag and sports products, such as basketball, football and football. It can also be used to make uniforms and belts for special protective equipment. PVC fabrics for clothing are generally absorbent fabrics (without coating), such as ponchos, baby pants, imitation leather jackets and various rain boots. Polyvinyl chloride is used in many sports and entertainment products, such as toys, records and sporting goods. Polyvinyl chloride toys and sporting goods have a large growth. It has an advantage because of its low production cost and easy molding.
9. PVC coated products
Artificial leather with substrate is made by applying PVC onto cloth or paper and plasticizing it above 100 ℃. PVC and additives can also be calendered into a film, and then pressed with the substrate. The artificial leather without substrate is directly calendered into soft sheets of a certain thickness by calender, and then pressed with patterns. Artificial leather can be used to make suitcases, bags, book covers, sofas and car cushions, as well as floor leather, which can be used as paving materials for buildings.
10.PVC foam products
When the soft PVC is mixed, a suitable amount of foaming agent is added into the sheet to form foam plastic, which can be used as foam slippers, sandals, insoles, and shockproof cushioning packaging materials. It can also be formed into low foaming rigid PVC plates and profiles based on extruder, which can replace wood. It is a new building material.
11. PVC transparent sheet
PVC is mixed, plasticized and calendered into transparent sheet by adding impact modifier and organotin stabilizer. Thermoforming can be used to make thin-walled transparent containers or vacuum blister packaging. It is an excellent packaging material and decorative material.
12. Others
Doors and windows are assembled with hard special-shaped materials. In some countries, it has occupied the market of doors and windows together with wooden doors, windows and aluminum windows; Imitation wood materials and steel building materials (North and seaside); Hollow container.
