PVC plastics have injection molding properties in terms of drying treatment, melting temperature, injection pressure, runners and gates; in terms of chemical modification, there are copolymerization modification, grafting reaction, chlorination and other methods. The following is a specific introduction to "pvc plastics" Injection molding performance and chemical modification methods".
1. Injection performance of pvc plastic
1. Drying treatment: usually no drying treatment is required.
2. Melting temperature: 185~205℃ Mold temperature: 20~50℃.
3. Injection pressure: up to 1500bar. Holding pressure: up to 1000bar. Injection speed: In order to avoid material degradation, it is generally necessary to use a relatively fast injection speed. ?????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
4. Runner and gate: all conventional gates can be used. If processing smaller parts, it is best to use needle-point gates or submerged gates; for thicker parts, it is best to use fan gates. The minimum diameter of needle-point gates or submerged gates should be 1mm; the thickness of sector gates should not be less than 1mm.
Second, what are the chemical modification methods of pvc plastics
1. Copolymerization modification: that is, let vinyl chloride monomer and other monomers undergo copolymerization reaction. For example, it can be copolymerized with monomers such as vinyl acetate, vinylidene chloride, acrylonitrile, acrylate, maleic anhydride, etc., to improve the molding processability, or reduce the molding temperature, or open up new uses, or appear as a new material.
2. Grafting reaction: Introduce another monomer group or another polymer on the side chain of PVC to carry out the grafting reaction. For example: ethylene-vinyl acetate is grafted with vinyl chloride to control the number of vinyl chloride grafted parts and the degree of polymerization, so as to improve the impact performance, low temperature brittleness, and aging resistance of this modified material.
3. Chlorination: The PVC is chlorinated by the aqueous phase suspension method (or gas phase method) to increase the chlorine content from 57% to about 65%. The purpose of this modification is to improve the heat resistance and use temperature of PVC. It is 35-40°C higher than the original PVC and is called chlorinated polyvinyl chloride (CPVC). The density of CPVC is higher than that of PVC, 1.7 g/cm3. Its flame retardancy is better than PVC, and its tensile strength is also better than PVC. The disadvantage is low impact strength. CPVC can be used to produce products by extrusion, injection, and calendering methods. CPVC can be used for pipes, plates, profiles, foaming materials, adhesives, coatings, modifiers, etc.
