The formula of PVC plastic profile is mainly composed of PVC resin and additives. The additives are divided into heat stabilizers, lubricating agents, processing modifiers, impact modifiers, fillers, anti-aging agents, and coloring agents according to their functions. Wait. Before designing PVC formula, we should first understand the performance of PVC resin and various additives.
Raw materials and additives
The resin for the production of PVC plastic profiles is polyvinyl chloride resin (PVC), which is a polymer formed by the polymerization of vinyl chloride monomers. Its output is second only to PE.
PVC resin can be divided into loose type (XS) and compact type (XI) due to the different dispersants in polymerization. The loose particle size is 0.1-0.2mm, the surface is irregular and porous, it is cotton ball shape, easy to absorb the plasticizer, the compact particle size is less than 0.1mm, the surface is regular, solid, it is ping pong-shaped, not easy to absorb Plasticizers are currently used more loosely.
PVC can be divided into ordinary grade (toxic PVC) and sanitary grade' (non-toxic PVC). The sanitary grade requires that the content of vinyl chloride (VC) is lower than 10x10-6, which can be used in food and medicine. The synthesis process is different, PVC can be divided into suspension PVC and emulsion PVC. According to the national standard GB/T5761-93 "General Purpose Polyvinyl Chloride Resin Inspection Standard for Suspension Method", the suspension method PVC is divided into PVC-SGl to PVC-SG8Jk resins. The smaller the number, the greater the degree of polymerization and the greater the molecular weight. Larger, higher strength, but the more difficult the melt flow, the more difficult the processing. When making specific choices, when making soft products, PVC-SGl, PVC-SG2, and PVC-SG3 are generally used, and a large amount of plasticizer needs to be added. For example, polyvinyl chloride film uses SG-2 resin and adds 50 to 80 parts of plasticizer. When processing hard products, generally no or very little plasticizer is added, so PVC-SG4, VC-SG5, PVC-SG6, PVC-SG7, PVC-SG8 are used. For example, SG-4 resin is used for PVC hard pipes, SG-5 resin is used for plastic door and window profiles, SG-6 resin is used for rigid transparent sheets, and SG-7 and SG-8 resins are used for rigid foaming profiles. The emulsion PVC paste is mainly used for artificial leather, wallpaper, floor leather and plastic products. The PVC resins manufactured by some PVC resin manufacturers are classified according to the degree of polymerization (the degree of polymerization is the number of unit chain links, and the degree of polymerization multiplied by the molecular weight of the chain link is equal to the molecular weight of the polymer). For SK-700; SK-800; SK-1000; SK-1100; SK-1200 and so on. The corresponding degree of polymerization of the SG-5 resin is 1000-1100. For the physical and chemical properties of PVC resin, see Chapter 4.
PVC powder is a white powder with a density between 1.35 and 1.45 g/cm3 and an apparent density between 0.4 and 0.5 g/cm3. Depending on the plasticizer content, it can be soft or hard products. Generally, 0-5 parts of plasticizers are hard products, 5-25 parts are semi-hard products, and more than 25 parts are soft products.
PVC is a kind of non-crystalline and polar high molecular polymer. Its softening temperature and melting temperature are relatively high. Generally, pure PVC can be plasticized and processed at 160-210~C. The polar bond between macromolecules makes PVC Shows hard and brittle performance. Moreover, the PVC molecule contains chlorine groups. When the temperature reaches 120~C, pure PVC begins to undergo HCl removal reaction, which will cause thermal degradation of PVC. Therefore, various additives must be added during processing to modify and impact the PVC so that it can be processed into useful products.
PVC resin is mainly used to produce all kinds of films (such as daily printing film, industrial packaging film, agricultural greenhouse film and heat shrinkable film, etc.), various boards, sheets (the sheets can be used for blister products), various pipes (Such as non-toxic water supply pipes, construction threading pipes, transparent hoses, etc.), various shaped materials (such as doors, windows, decorative panels), hollow blown bottles (for cosmetics and beverages), cables, various injection molded products and artificial leather , Floor leather, slush plastic toys, etc.
Pure PVC resin is extremely sensitive to heat. When the heating temperature reaches 90Y: above, a slight thermal decomposition reaction will occur. When the temperature rises to 120C, the decomposition reaction intensifies. At 150C, 10 minutes, the PVC resin will turn from its original white color. It gradually becomes yellow-red-brown-black. The decomposition process of PVC resin is a series of chain reactions caused by the HCL removal reaction, which finally leads to the break of the macromolecular chain. The thermal stability mechanism to prevent thermal decomposition of PVC is achieved through the following aspects.
Yangzhou Sanxing Plastic Co., Ltd. mainly involves PET sheet, PET transparent sheet, PET coil, PET anti-fog sheet, PET antistatic sheet, PET sheet, PET plastic sheet, PET clothing template, PVC sheet, PVC transparent sheet, PVC roll Materials, PVC sheets, PVC profiles, PVC membranes, GAG sheets, RPET sheets, PET plastic folding box sheets, PVC plastic folding box sheets, APETG sheets, APETG plastic folding boxes and other products.
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