When I first came into contact with this industry, I heard predecessors often say: our product is "industrial monosodium glutamate", which is used in a small amount but cannot be underestimated. the performance and quality of PVC products are directly related to it. later, I found that many people in the industry actually have more or less vague understanding of the classification and function of ACR. I specially combed the understanding of PVC processing additives over the years, hope to help friends to improve understanding!
From the large categories of PVC processing aids ACR can be divided into three categories:
1, to promote the plasticization of processing additives: this kind of rigid PVC products are widely used, the main role is to promote plasticization, improve the melt rheological properties and improve the dispersion of other additives, improve the apparent quality of products.
Suitable for most PVC products such as profiles, pipes, plates (coils), etc., with reference to the dosage of 1-2phr
2, foaming regulator: PVC foaming regulator because of its high molecular weight, can greatly improve the melt strength of PVC materials, so as to effectively wrap the foaming gas, form a uniform honeycomb structure, prevent gas escape, while PVC foaming regulator is also conducive to the dispersion of other additives including foaming agent, improve the surface quality of products, improve gloss
Suitable for foaming plates, foaming rods, foaming pipes, foaming profiles, foaming wood plastic, etc., with a reference dosage of 4-8phr
3. External lubricating processing aid: it has the same good metal peeling property as oxidized polyethylene wax, except that it has good compatibility with PVC, can increase the processing plasticizing performance and improve the melt rheological performance to a certain extent, and does not change the export expansion during extrusion processing, does not change the thermoforming performance, and prevents the haze effect caused by the precipitation of slip agent in transparent products.
It is suitable for adding formula or equipment with high process requirements, especially transparent sheet, foam profile, foam board and foam wood plastic, etc. Reference dosage 0.5-2phr
Specifically, in the process and products, the melt elasticity can be improved during calendering, so that the residual material between the two rollers can roll smoothly. Pipe extrusion can improve the apparent quality, eliminate the phenomenon of "sharkskin" and increase the extrusion rate. Transparent extrusion can greatly reduce the number of "fisheyes" in the product. Melt elasticity is increased in injection molding, thus reducing injection volume, reducing "white stria" phenomenon and improving surface gloss, to improve the welding strength, if the addition of lubricating processing aids can improve the stripping efficiency, speed up the injection cycle and increase the output, to prevent the "spray" phenomenon caused by the external slip precipitation; blow molding can improve the plasticization, reduce the fisheye phenomenon, improve the melt elasticity, so that the molding thickness is more uniform.