When I first came into this industry, I heard that our product is "industrial monosodium glutamate", which is used in small amounts but has a significant impact. The performance and quality of PVC products are directly related to it. Later, in my work, I found that many people, including those in the industry, have a more or less vague understanding of the classification and role of ACR. I specially sorted out my understanding of PVC processing additives over the years, I hope to help all friends improve their understanding!
From a general perspective, PVC processing aids ACR can be divided into three categories:
1. Promoting plasticization type processing aids: These types of additives are widely used in hard PVC products, mainly to promote plasticization, improve melt rheological properties, improve the dispersibility of other additives, and improve the apparent quality of products.
Suitable for most PVC products such as profiles, pipes, plates (rolls), etc., with a reference dosage of 1-2phr
2. Foam regulator: PVC foam regulator, due to its high molecular weight, can significantly improve the melt strength of PVC materials, effectively encapsulate the foaming gas, form a uniform honeycomb structure, and prevent gas escape. At the same time, PVC foam regulator is also conducive to the dispersion of other additives, including foaming agents, improving the surface quality of products and increasing glossiness
Suitable for foam board, foam rod, foam pipe, foam profile, foam wood plastic, etc., reference dosage 4-8phr
3. External lubrication type processing aid: It has the same good metal peeling ability as oxidized polyethylene wax, but it has good compatibility with PVC. To a certain extent, it can also increase processing plasticization performance, improve melt rheological properties, and maintain outlet expansion during extrusion processing without changing hot forming performance. It prevents the haze effect caused by lubricant precipitation in transparent products.
Suitable for formulas or equipment with high processing requirements, especially transparent sheets, foam profiles, foam boards, and foam wood plastics. Reference dosage 0.5-2phr
Specifically, in terms of technology and products, during rolling processing, the elasticity of the melt can be improved to ensure smooth rolling of the remaining material between the two rollers; In pipe extrusion, the apparent quality can be improved, the "shark skin" phenomenon can be eliminated, and the extrusion rate can be increased; Transparent extrusion can significantly reduce the number of "fish eyes" in the product; By increasing the elasticity of the melt in injection molding, the injection volume is reduced, the phenomenon of "white lines" is reduced, the surface glossiness is improved, and the welding strength is improved. If lubricating processing aids are added, the film removal efficiency can be improved, the injection cycle can be accelerated, and the yield can be increased to prevent the "frost" phenomenon caused by external sliding and precipitation; Blow molding can improve plasticization, reduce fisheye phenomenon, improve melt elasticity, and make the molding thickness more uniform.