PVC Resin: Production, Classification & Applications
Polyvinyl chloride (PVC) is a thermoplastic synthetic resin formed by the polymerization reaction of vinyl chloride monomer (VCM). It is one of the world's largest plastic varieties, with the characteristics of chemical corrosion resistance, good insulation, and low cost. It is widely used in construction, packaging, electronics and other fields. From the perspective of material form, PVC can be either a solid polymer or a general term for various products after processing.
PVC resin is the initial form of polyvinyl chloride, referring to pure polyvinyl chloride polymer without processing modification. It usually exists in the form of white powder, and its molecular structure is linear or slightly branched long chain. Due to the strong intermolecular force, it has poor fluidity, high hardness and high brittleness when used directly, and cannot be used directly to manufacture products. It needs to be processed and modified by adding plasticizers, stabilizers and other additives.
Production process and classification of PVC resin
1. Production process
PVC resin is prepared with vinyl chloride monomer (VCM) as raw material, and is mainly polymerized by the following methods:
Suspension polymerization: The most commonly used process, VCM is dispersed in water, and polymerization is initiated by an initiator to obtain a powder resin with uniform particle size, which is suitable for hard products such as pipes and plates.
Emulsion polymerization: Polymerization in an emulsion system, the product is a paste resin, which is often used to make soft products such as artificial leather and coatings.
Bulk polymerization: No solvent is used, direct polymerization, the product is high in purity, suitable for transparent products.
2. Classification and characteristics
General PVC resin: It is divided into different models (such as SG-3, SG-5) according to the degree of polymerization (molecular weight). The higher the degree of polymerization, the higher the mechanical strength, which is suitable for hard products (such as pipes); the lower the degree of polymerization, the better the plasticity, which is suitable for soft products (such as films).
Special PVC resin: including high-polymerization PVC (strong high temperature resistance), chlorinated PVC (CPVC, better corrosion resistance), cross-linked PVC (improved heat deformation resistance), etc., used in high-end fields such as chemical pipelines and automotive accessories.
PVC processing system and application scenarios
1. Core modification methods of the processing system
PVC resin must improve its performance by adding additives:
Plasticizer: such as dioctyl phthalate (DOP), which reduces the intermolecular force and makes PVC from hard to soft, used for film, cable materials, etc.
Stabilizer: such as calcium zinc composite stabilizer and organic tin, to prevent high temperature decomposition during processing and extend the life of the product.
Filler: calcium carbonate, talcum powder, etc., to reduce costs and improve product rigidity.
Modifier: impact modifier (ACR), processing aid, to improve toughness and formability.
2. Diversified expansion of application scenarios
Construction field: rigid PVC pipes (drainage pipes, water supply pipes), door and window profiles (good weather resistance), floor leather (soft, wear-resistant).
Packaging field: PVC film (food cling film, shrink film), sheet (drug packaging blister), but due to environmental disputes, some scenes are replaced by PE and PLA.
Electronic field: wire and cable sheath (excellent insulation), socket shell (flame retardant PVC).
Medical field: soft PVC is used for infusion bags and blood bags (environmentally friendly plasticizers are required), but due to chlorine problems, it is gradually being replaced by materials such as TPU.
The relationship between PVC resin and polyvinyl chloride PVC is essentially a progressive relationship between "raw materials" and "processing system/finished products". As a basic polymer, PVC resin has derived a variety of PVC products through innovations in formula design and processing technology, supporting many fields of modern industry.
In the face of environmental challenges, the development of the two is merging towards greening and functionalization, driving the PVC industry to transform from a "white pollution controversy" to a "pillar of the circular economy."
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