Basic understanding and application of PVC polyvinyl chloride

Polyvinyl chloride, referred to as PVC in English, is a polymer polymerized by vinyl chloride monomer (VCM) with initiators such as peroxides and azo compounds or under the action of light and heat according to the free radical polymerization reaction mechanism. . Polyvinyl chloride was discovered by V. Renault of the United States as early as 1835. When vinyl chloride (VCM) is irradiated with sunlight, a white solid, namely polyvinyl chloride, is generated. Polyvinyl chloride (PVC) is a polymer material that uses a chlorine atom to replace a hydrogen atom in polyethylene. Vinyl chloride homopolymer and vinyl chloride copolymer are collectively called vinyl chloride resin.

01 Structure of PVC

The PVC molecular chain contains highly polar chlorine atoms, and the intermolecular force is large, which improves the rigidity, hardness, and mechanical properties of PVC products, and has excellent flame retardancy (flame retardancy refers to the properties of a substance or after the material has been processed It has the property of obviously delaying the spread of flame); but its dielectric constant and dielectric loss tangent are larger than PE.

PVC resin contains a small amount of double bonds, branch chains and initiator residues remaining in the polymerization reaction. In addition, there are chlorine atoms and hydrogen atoms between two adjacent carbon atoms, which are easy to dehydrochloride, causing PVC to be easily dehydrated under the action of light and heat. Degradation reactions occur.

The spatial arrangement of chlorine and hydrogen atoms on the PVC molecular chain is basically disordered, so the crystallinity of its products is low, generally only 5 to 15%.

02 Main purpose

Polyvinyl chloride plastics come in many different forms, and their processing methods are also diverse, including pressing, extrusion, injection, coating, etc. PVC plastic is often used to make films, artificial leather, insulation layers of wires and cables, hard products, floors, furniture, sports equipment, etc.

PVC polyvinyl chloride products can generally be divided into two categories: hard and soft. No plasticizer is added during the processing of hard products, while a large amount of plasticizer is added during processing of soft products. PVC is originally a rigid plastic with a glass transition temperature of 80 to 85°C. After adding plasticizer, the glass transition temperature can be lowered, which facilitates processing at lower temperatures, increases the flexibility and plasticity of the molecular chain, and can be made into soft products that are elastic at room temperature. Generally, the amount of plasticizer added to soft PVC plastic is 30% to 70% of PVC. ​

PVC polyvinyl chloride can be processed into various profiles and products after adding plasticizers, stabilizers, lubricants, colorants, and fillers during processing.

Company: Henan Hesu Industrial Co., Ltd., a professional plastic supplier