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In the process of processing and shaping CPVC resin int […]
In the process of processing and shaping CPVC resin into finished or semi-finished products plasticization Foot Valve is a key. Whether it is extrusion molding or injection molding, the quality of plasticization is directly related to the internal quality and surface quality of the product. Therefore, how to obtain good plasticization quality from the process, equipment and technology is the key to CPVC processing. Increase the thermal deformation temperature, increase the rigidity, improve the chemical stability, and at the same time improve the weather resistance and flame resistance, and reduce the smoke density. This kind of product is usually used to make products to improve the solubility of materials in occasions with special requirements. This product is commonly known as perchlorovinyl, and is mainly used for the production of adhesives, coatings and chlorine fiber.
Because the melt viscosity of CPVC is at least twice that of PVC, and the processing temperature is high, the release of hcl due to thermal decomposition during processing causes difficulties in processing and molding and corrosion of equipment. In the extrusion process, how to make CPVC, a high-viscosity material, achieve the ideal plasticization plasticization in place is the key to CPVC processing technology. Due to the high processing temperature of CPVC, the amount of heat stabilizer in the formulation is much higher than that of PVC. Obviously, it is not suitable to use traditional three-salt and two-salt heat stabilizers. At present, the more mature heat stabilizer is the composite lead series stabilizer with lubricating system. Due to the high melt viscosity of CPVC, especially melt fracture during injection molding, it is not appropriate to use traditional paraffin, stearic acid and metal soap lubricating systems.
In the extrusion process of CPVC, because CPVC has a tendency to adhere to the metal surface of the thermal post-processing equipment (especially the head and die), in order to eliminate this adhesion, an external lubricant must be added to the formulation. The external lubricant and CPVC resin should be incompatible. In CPVC molding processing (especially injection processing), under pressure, the friction between CPVC resins generates frictional heat. The generation of frictional heat is detrimental to molding processing and must be controlled. The internal lubricant can reduce the friction between the resins of CPVC during processing. The internal lubricant and CPVC resin should be compatible. In the extrusion and injection molding of CPVC, processing aids must be used, the purpose of which is to improve the quality of plasticization and increase the low-temperature impact resistance of CPVC materials and the toughness of products.
Using different heat stabilizers and applying different processing methods, the ratio of internal and external lubricants in the formulation is different. Generally speaking, the use of lead stabilizers requires more internal lubricants and appropriate external lubricants; the use of organotin stabilizers requires more external lubricants and appropriate internal lubricants; extruded pipes More internal lubrication brakes are required than injection pipe fittings, and injection pipe fittings require more external lubricant than extrusion pipe fittings. The amount of lubricant added must be appropriate, not too much. Too much lubricant will not only affect the plasticization of the melt, but also, because the melting point of the lubricant is generally very low, it will also reduce the Vib softening temperature of the product. It is worth noting that in the formula, in addition to organotin stabilizers, do not add any liquid lubricants, because this will significantly reduce the Vib softening temperature and other physical and mechanical properties of the pipes and fittings.