Mainly composed of PVC resin and additives, which additives by function is divided into: heat stabilizers, lubricants, processing modifiers, impact modifiers, fillers, aging agents, colouring agents, etc.. In the design of PVC formulations, should first understand the performance of PVC resin and various additives.
Raw materials and additives
PVC resin
Production of PVC plastic profiles resin is polyvinyl chloride resin (PVC), polyvinyl chloride is made of vinyl chloride monomer polymerisation of polymer, the output is second only to PVC.
Polyvinyl chloride is a polymerisation of vinyl chloride monomer and ranks second only to PE in terms of production.
PVC resin can be divided into loose type (XS) and compact type (Ⅺ) due to the different dispersants in the polymerisation. Loose-type particle size of 0.1-0.2mm, the surface is irregular, porous, cotton balls, easy to absorb plasticiser, compact particle size of 0.1mm or less, the surface is regular, solid, ping-pong-like, not easy to absorb plasticisers, the current use of loose-type more.
PVC can be divided into general grade (toxic PVC) and health grade ‘ (non-toxic PVC). Sanitary grade requires vinyl chloride (VC) content of less than lOXl0-6, can be used for food and medicine. Synthesis process, PVC can be divided into suspension method PVC and emulsion method PVC, according to the national standard GB / T5761-93 “suspension method of general-purpose polyvinyl chloride resin test standards”, suspension method PVC is divided into PVC-SGl to PVC-SG8Jk kinds of resins, in which the smaller the number, the greater the degree of polymerisation, the greater the molecular weight, the greater the strength, but the more difficult to melt flow, the more difficult to process. However, the more difficult the melt flow is, the more difficult the processing is. Specific selection, to make soft products, generally use PVC-SGl, PVC-SG2, PVC-SG3 type, need to add a large number of plasticisers. For example, PVC film uses SG-2 resin, adding 50~80 parts of plasticiser. And when processing hard products, generally do not add or a very small amount of plasticiser, so use PVC-SG4, VC-SG5,
PVC-SG6, PVC-SG7, PVC-SG8. Such as PVC hard pipe using SG-4 resin, plastic door and window profiles using SG-5 resin, rigid transparent sheet using SG-6 resin, rigid foam profiles using SG-7, SG-8 resin. And emulsion method PVC paste is mainly used for artificial leather, wallpaper and floor leather and dipped plastic products. Some PVC resin manufacturers factory PVC resin according to the degree of polymerisation (degree of polymerisation is the number of unit links, degree of polymerisation multiplied by the molecular weight of the links is equal to the molecular weight of the polymer) classification, such as Shandong Qilu Petrochemical General Factory production of PVC resins, factory products for the SK-700; SK-800; SK-1000; SK-1200; SK-1200; SK-1100; SK-1200 1100; SK-1200 and so on. Its SG-5 resin corresponds to the degree of polymerisation of 1000-1100.The physical and chemical properties of PVC resin are shown in Part IV.
PVC powder is a white powder, density in 1.35-1.45g/cm3, apparent density in 0.4-0.5g/cm3, depending on the size of the plasticiser content can be soft, hard products, the general plasticiser content of 0-5 parts of the hard products, 5-25 parts of the semi-hard products, more than 25 parts of the soft products.
PVC is a non-crystalline, polar polymer, softening temperature and melting temperature is high, pure PVC generally must be 160-210 ~ C when the plasticisation process, due to the polar bond between the molecules so that PVC shows hard and brittle properties. Moreover, PVC molecules contain chlorine groups, when the temperature reaches 120 ~ C, pure PVC that is the beginning of the dehydrogenation reaction, which will lead to thermal degradation of PVC. Therefore, it is necessary to add a variety of additives to PVC processing modification and impact modification, so that it can be processed into useful products.
PVC resin is mainly used in the production of various types of film (such as daily printing film, industrial packaging film, agricultural greenhouse film and heat-shrinkable film, etc.), all kinds of boards, sheets (the sheet can be used for blister products), all kinds of pipe (such as non-toxic water pipe, construction of threaded pipe, transparent hoses, etc.), all kinds of profiles (such as doors, windows, decorative panels), hollow blow molding bottles (used for cosmetics and beverages), cables, all kinds of injection moulding products and artificial leather, floor leather, plastic-lined toys. PVC stabilisers can be used in a variety of PVC products, such as artificial leather, floor leather, plastic-lined toys, and so on. The physical and chemical properties of various PVC stabilisers are shown in Table 1 (to the next page).
Stabiliser
Pure PVC resin is extremely sensitive to heat, when the heating temperature reaches 90Y: above, there will be a slight thermal decomposition reaction, when the temperature rises to 120C after the decomposition reaction intensified, at 150C, 10 minutes, PVC resin from the original white gradually become yellow – red – brown The decomposition process of PVC resin is due to a series of chain reaction caused by de-HCL reaction, which finally leads to the breakage of macromolecule chain. Preventing
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