Introduction to each model of PVC resin powder
For each type of PPVC resin powder, the viscosity or K value commonly used in the industry indicates the average molecular weight (or average degree of polymerization) of PVC, that is, the length of the PVC molecular chain, which determines the grade of the resin and the corresponding processing parameters. The molecular weight of the resin is related to the physical and mechanical properties of the article. PVC resin is a non-crystalline linear polymer compound. The higher the relative molecular mass, the higher the viscosity number. The higher the molecular weight, the higher the tensile strength, impact strength and elastic modulus of the product, but the flow of the resin melt. Sex and plasticity decline. The viscosity number is usually used to indicate the molecular weight of the polymer, and the polymer type is classified.
The most common one in China is SG-5, followed by SG-3, SG-7, SG-8 and so on. Compared with Type 5, the production of Type 3 PVC requires a long reaction time, a high polymerization temperature, high requirements for the addition of excipients, and a production cost of 50-100 yuan/ton higher than that of Type 5. Type 3 PVC has high purity, less fisheye, easy to absorb plastic, and has the characteristics of high temperature resistance, insulation and soft texture of products. It is mainly used for the production of soft products such as wire and cable, agricultural film, conveyor belt and daily plastic products.
The production process of SG-7/SG-8 and SG-5 resin is basically the same, and the production equipment is exactly the same. The main differences are in the formulation of the additive, the polymerization temperature, and the reaction pressure. The reaction temperature and reaction pressure of SG-8 resin have basically reached the working pressure limit of the polymerization reactor. The reaction requirements are more demanding, and the requirements on operation, safety, technology and personnel quality are more strict, and the resin quality is more difficult to control. In terms of product quality, the main difference between SG-8 and SG-7 resin is the viscosity number, and the other indexes are not much different. The production risk is greater than that of the SG-7 resin. The production cost of SG-8 resin SG-7 resin is basically the same, it will be slightly higher than SG-7 type, and should not exceed 15 yuan/ton per ton. Most companies say that the cost of SG-8 is slightly higher than that of SG-5, but the cost difference between different companies is slightly different. Companies that need to switch to other models say that the cost of the SG-8 is slightly higher than the SG-5 type of 100-150 yuan / ton, but companies with dedicated production said that the cost of SG-8 and SG-5 is not much different.
In principle, the higher the model, the greater the hardness of the product.
SG5 (K-65, S1000): pipe, profile, sheet, etc.
SG3 (K-70, S1300): Mostly soft products, hoses, wire and cable, film, shoe materials, toys, auto parts.
SG7, SG8 (K-60, S800, S700): pipe fittings, sheets, containers, etc.
