Raw material combination formula
DATE：2022/8/10 9:28:12 / READ： / SOURCE：This station
Raw material combination formula
It is also a plastic product formed with a certain plastic resin as the main raw material. It can produce products with different properties, such as plastic films with good transparency, cables with excellent insulation performance, plastic products such as hard metal components and soft hoses such as rubber. The main reason is that additives with different functions are added to the raw materials. This kind of raw material combination with new performance is mainly composed of a certain kind of plastic tree energy and other auxiliary materials (additives) in different proportions, which is the formula of plastic product molding materials.
4.6.1 precautions for raw material combination
Taking the formula of PVC products as an example, PVC products can be divided into hard and soft products. For two products with different hardness, the formula combination of forming materials has its own characteristics.4.6.1.1 precautions for material formula combination of rigid PVC products
Rigid PVC products include plates, sheets, pipes, pipe fittings and profiled materials. The following points should be paid attention to when selecting the composition of materials for forming such PVC products. ① Polyvinyl chloride shall be made of suspension loose polyvinyl chloride sg4-sg6 resin ② generally, plasticizer is not added in the formula for extruded or pressed rigid PVC products to avoid reducing the heat resistance and corrosion resistance of the products; A small amount of plasticizer can be added to the material formula of injection molding products to improve the fluidity of the melt and facilitate the molding of the products. ③ In order to prevent degradation and discoloration of PVC resin caused by heat and light during plasticization and use, a stabilizer must be added in the formula: basic lead salt additives with good heat resistance should be added as the main stabilizer in the formula of transparent products; The dibasic lead phosphite stabilizer with excellent light resistance and stability should be added to the material formula for outdoor PVC products; Lead dibasic phthalate should be added to the material formula for producing high temperature resistant or foam PVC products; Organotin stabilizers should be added to the formula of materials used in contact with food. ④ In order to prevent the PVC resin melt from adhering to the working surface of the equipment, facilitate the melt processing and improve the processing speed, stearic acid or paraffin lubricant must be added to the formula. When extruding PVC, the amount of stabilizer added in the formula should be less than 1% (amount); The mass fraction of resin and stabilizer in injection molding materials shall be within the range of 0.5% ~ 1%. ⑤ Adding filler to PVC products can not only reduce the production cost of products, but also improve some properties and processability. If the filler is added to the extruded product, the hardness can be improved, the process control is convenient, and the molten material can be easily formed. Barium sulfate and calcium carbonate are generally added to the formulation of hard pipe forming materials; Titanium dioxide is mostly used in white products or products requiring good toughness. The shrinkage of injection molding products can be reduced by adding filler into the formula of injection molding products; Titanium dioxide filler is usually used in the formulation of injection molding materials that require good fluidity and high impact toughness. ⑥ For some hard products with special requirements, some special modifiers should be added to the material formula: for example, in order to improve the impact toughness of the products, impact modifiers should be added; In order to improve the heat resistance of the products, chlorinated polyvinyl chloride (PVC-C) and glass fiber can be used for reinforcement; In order to improve the rigidity of products, xylene formaldehyde resin with relative molecular weight of 400 ~ 500 can be added as reactive plasticizer. 4.6.1.2 notes on the composition of materials for soft PVC products soft PVC products include films, hoses, cable materials, sealing strips, etc. the following points shall be paid attention to when selecting the composition of materials for forming such PVC products. ① The difference between the formula of soft PVC products and that of hard PVC products is that a large proportion of plasticizer (the mass fraction of plasticizer in PVC resin is more than 30%) needs to be added in the formula, and the amount of other auxiliary materials should be adjusted appropriately according to the amount of plasticizer added. ② The main material of PVC shall be suspension loose PVC SG2 ~ SG4 resin. ③ Due to the large amount of plasticizer added in the formula, attention should be paid to the influence of plasticizer on the process conditions and product properties of PVC molded products. ④ The addition of plasticizer makes the temperature of PVC melt drop slightly, and the molding processing performance is improved. Therefore, the amount of stabilizer used in the formula can be less than that in the formula of hard PVC products, and the requirements are not so strict. ⑤ In order to prevent the resin and plasticizer from aging and deterioration due to oxidation and ultraviolet radiation during processing and use, some antioxidants and ultraviolet absorbers shall be added to the formulation when necessary. ⑥ In order to reduce the production cost of products, a certain proportion of filler should also be added to the formula of soft PVC products. However, attention should be paid to the absorption of plasticizer by the filler, and materials with low price and good dispersion, thermal stability and weather resistance should be selected. ⑦ When the flame retardancy of the product is required to be high, a certain proportion of flame retardant shall be added to the raw material formula. ⑧ The material meets the requirements of VC tree and non-toxic additives (refer to gb4803-94 and gb9685-94).
4.6.2 design
Polyvinyl chloride plastic products are multi-component plastics. The design of product formula is a relatively complicated technical work, which involves the application performance of main raw materials and auxiliary materials, product specifications and quality, the use performance of production equipment, molds and various production auxiliary equipment, and the control of production process and process parameters of polyvinyl chloride. Therefore, it is required that the formulation designers of PVC products should have a comprehensive and systematic understanding of raw materials, equipment and production process, and have comprehensive theoretical knowledge and practical production experience. Selecting such technicians to design the product material formula can design a more reasonable material formula from the consideration of raw materials, equipment, technology and other factors. The following points should be noted in the formulation design of PVC products. ① Before formulation design, it is necessary to understand the application conditions of the products and distinguish the primary and secondary items in the product quality requirements. Under the condition of meeting the product quality requirements, try to select the raw material composition formula with convenient raw material source, sufficient raw material source, low price and relatively stable performance. ② Attention shall be paid to the mutual influence of various raw materials and the feasibility of process operation for the proposed raw materials. For example, in order to ensure better mechanical strength of products, PVC resin with high molecular weight is prepared to be selected. However, such raw materials require high process temperature during production, which brings certain difficulties to production operation and increases product manufacturing cost; Moreover, it is difficult to guarantee the quality of the products. Therefore, such raw materials are not desirable. When designing the formula, attention should be paid to: the selection of materials in the formula must be comprehensively measured. Do not emphasize one point unilaterally and ignore the consequences of the interaction between raw materials. ③ Pay attention to whether the raw materials in the formula have strict requirements on the process operating conditions. The raw materials that are sensitive to the process temperature change, are not easy to mix with other raw materials, and are easy to decompose and precipitate should be used or not used as much as possible.
Author：admin