Performance characteristics of chlorinated polyvinyl chloride
Date：2022/7/22 9:29:28 / Read： / Source：本站
Performance characteristics of chlorinated polyvinyl chloride
Chlorinated polyvinyl chloride is a white powder resin with a relative density of 1.48 ~ 1.58, and the chlorine content is generally 61% - 68%; It has good adhesion, fire resistance, chemical corrosion resistance and electrical insulation; The product does not deform in boiling water, and the maximum service temperature can reach 105 ℃, the melting temperature 110 ℃, and the shrinkage (3 ~ 7) × 10-*cm/cm； Rockwell hardness r117 ~ 122; With the increase of chlorine content, the tensile strength and bending strength of the products increase, but the brittleness increases; Generally, the tensile breaking strength of chlorinated PVC products is 52 ~ 62mpa, the elongation at break is 4 ~ 65%, the compressive strength is 62 ~ 152mpa, the bending strength is 100 ~ 117mpa, the tensile modulus is 2482 ~ 3280mpa, the impact strength of cantilever beam is 53 ~ 298j/m, and the linear expansion coefficient is (6876) × 10 bow chlorinated polyvinyl chloride is easily soluble in esters, ketones, aromatic hydrocarbons and other organic solvents.2.3.9.3 key points of forming process
Raw materials are easy to absorb moisture. Before processing, the resin should be dried in an oven at 80 ℃. 2 ~ chlorinated polyvinyl chloride is easier to plasticize than polyvinyl chloride, but the thermal stability time of molten material is shorter than that of PVC material; The higher the chlorine content in domestic CPVC resin, the easier it is to produce melt fracture during processing. The resin is easy to decompose during the molding process, which is highly corrosive to the equipment and molding mold. It is required that the equipment should have an anti-corrosion coating in contact with the culture material. The lattice material has high viscosity, which is easy to stick during the flow process, and the molten material flows through the equipment to work.It should have high machining accuracy, clear surface and low resistance. When the screw is working, the oil medium shall be used to cool and control the temperature to ensure the screw working disc kissstable. Oil or water should be used as the heat conducting medium to control the temperature of the machine, and the fluctuation of 8 degrees should not be greater than 5 ℃. Suspension chlorinated polyvinyl chloride resin is used for molding plastic products, and lotion fakai polyvinyl chloride resin is used to make coatings, varnishes and adhesives.When forming pipes, heating rods and warm cooling devices should be installed in the mandrel in the forming mold. CPVC, like PVC resin, is not dangerous goods. At present, the domestic production units of chlorinated polyvinyl chloride resin include Beijing No.2 Chemical Co., Ltd., shangshoudian chemical Yibin Tianyuan Chemical Plant and Huludao Chemical Group Co., Ltd.
2.3.10 polyvinylidene chloride
Polyvinylidene chloride is a homopolymer of vinylidene chloride, abbreviated as PVDC. Due to its high softening point temperature, close to its decomposition temperature, and poor compatibility with general plasticizers, polyvinylidene chloride Zi (VDC) homocyst is still large compared with heated PVC. It is possible to heat and melt oxyethylene resin to form products, but its molding processing is difficult to judge, while the original high crystallinity of PVDC resin has not changed much. As a result of copolymerization, polymer I acts, appropriately reducing its softening point temperature, and improving its compatibility with plasticizers (an), methacrylate, etc.]. After copolymerization of vinylidene chloride and monomer, Vinylidene chloride or copolymers with other monomers [such as vinylidene chloride (PVDC) used in products made of vinylidene acetate (VAC) and propylene marriage 1 are plastic products molded by the method of vinylidene chloride (accounting for more than 85%), so this resin has little practical value. At present, PVDC resin is widely used. This product has dried powdered 9-vinyl chloride (VC) - vinylidene chloride (VDC) Copolymers are polyvinylidene ethyl% in other countries and in the original state of water latex.
2.3.11.2. Key points of vinyl chloride vinylidene chloride copolymer molding process
When vc-vdc copolymer is used to form film or fiber, the resin with vinylidene chloride content of 80% - 95% and produced by suspension method shall be selected; Copolymers used as coatings and adhesives should be produced by lotion method, and the resin with vinylidene chloride content of no more than 70%. ② Due to the large crystallization tendency of vc-vdc copolymer, water cooling (10 ℃) should be carried out quickly after extruding the film blank or tapping, and then enter the preheating bath. In the extrusion molding technician's Manual of this kind of industrial plastics, the film after treatment is suitable for blow molding film. In the process of extruding resin, the raw materials are easy to decompose and release chlorine chloride (HCI) gas. The amount of heat stabilizer in the formula should be appropriately increased. For films used for shaped food packaging, non-toxic and odorless additives (plasticizers, heat stabilizers, etc.) such as plasticizers such as epoxy soybean oil should be added to the raw materials. In order to avoid the decomposition of alkali or less resin in extrusion high temperature, a better heat stabilizer should be selected. The thread depth of the feeding section is 8 ~ 13mm, and the compression ratio is about 4:1, which is also the screw structure requirements in the extruder: the ratio of pitch to screw diameter should be less than 10:1 (this is to shorten the residence time of molten material in the barrel). The process temperature control of extruded products should be stable, and the allowable value of temperature (barrel, mold water bath) fluctuation control should be ± 1 ℃.
2.3.12 vinyl chloride vinyl acetate copolymer
Vinyl chloride vinyl acetate copolymer is an important variety of modified polyvinyl chloride, which can be called vinyl chloride resin or vinyl chloride vinyl acetate copolymer, abbreviated as VC-VAc. Vinyl chloride vinyl acetate copolymer is internally plasticized polyvinyl chloride. The content of vinyl acetate (VAC) in industrial products is generally 2% - 20%, and the molecular weight is expressed as logarithm of specific concentration as 0.45 ~ 0.80. There are also products with vinyl acetate content greater than 20%. With the increase of VAC content, the softening point of this polymer decreases, the molding of the product is easier, and the service life of the product is prolonged. It is more suitable for the production of hard products and high filler products. The copolymer with vinyl acetate content of 5% is a paste forming resin, and the solubility in the solvent is small. Ethylene copolymer lysomethyl ketone, tetrachlorofuran, methyl isobutyl ketone, Rockwell hardness R50, cantilever notch impact strength 10j/m at 57 ℃ of aromatic hydrocarbon cold. Take 15% vinyl chloride vinegar as an example: tensile strength 60MPa, thermal deformation temperature (0.46mpa). The performance of vinyl acetate copolymer is related to the content of vinyl acetate. With VAC content, it has excellent solubility, which is suitable for preparing coatings and can improve the adhesion to metals.
2.3.12.2 forming method and Application
Vinyl chloride vinyl acetate copolymer can be processed into plastic products by extrusion, injection molding, calendering and blow molding, just like general thermoplastics. It is more suitable for hard products with a large proportion of fillers in raw materials such as asbestos board, floor, hard compact disc, etc. The process characteristics of vinyl chloride vinyl acetate copolymer molding products are: molding soft products with this resin can produce products by adding less plasticizing dose to the raw materials or using chlorinated paraffin auxiliary plasticizers with low plasticizing efficiency. In the production process, as long as the raw materials are measured separately according to the formula requirements, and then mixed evenly, the raw materials can be mixed into pieces on the open mill. Compared with processing vinyl chloride homopolymer with the same molecular weight, molding products with vinyl chloride vinyl acetate copolymer has lower processing temperature, faster plasticization and shorter production cycle. The production units of vinyl chloride vinyl acetate copolymer include Shanghai Tianyuan Group Tianyuan Chemical Co., Ltd., Beijing No. 2 Chemical Co., Ltd., Tianjin chemical plant, Hangzhou Electrochemical Group Co., Ltd., Jiangsu North chlor alkali Group Co., Ltd. and Nantong Jiangshan Pesticide Chemical Co., Ltd.
2.3.13 vinyl chloride ethylene vinyl acetate copolymer
Vinyl chloride ethylene vinyl acetate copolymer is a new type of internally plasticized polyvinyl chloride. It has several names: vinyl chloride ethylene vinyl acetate copolymer, vinyl chloride grafted ethylene vinyl acetate, ethylene vinyl acetate vinyl chloride graft copolymer. Abbreviations: vc-eva, vc-e-eva, eva-g-pvc. Vinyl chloride, containing 6% - LM of ethylene vinyl acetate copolymer (EVA) resin. According to different uses, vc-eva can be divided into two categories: one is hard impact resistant (mass fraction); The other is soft plasticized polyvinyl chloride, which contains 30% - 60% of ethylene acetic acid z/ zone copolymer (EVA). Because of the excellent properties and processability, in addition, the temperature range of plasticizing and melting is wide. The products formed by resin medium grade vinyl chloride ethylene vinyl acetate copolymer have high impact strength, and the content of ethylene vinyl acetate copolymer is different. The functional hard, semi-hard or soft products can be processed without plasticizer in the raw materials; EVA in raw materials can be blended with PV in any proportion; The content and properties of EVA in the copolymer, the degree of polymerization of PVC components and money.
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