Additives are indispensable raw materials in the production of PVC plastics, which are determined by the inherent characteristics of PVC resins. PVC additives are divided into two categories:

　　(1) Process additives are necessary for the plastic molding process to proceed. Such as stabilizers and lubricants in the production of hard pvc plastics, without them, processing cannot be carried out.

　　(2) Functional additives give plastics certain functionality or improve certain properties of PVC plastics. For example, the use of impact modifiers can double the impact toughness.

The requirements for additives are:

　　(1) Compatibility with PVC resin Additives should be able to be dispersed in the product stably and uniformly for a long time and exert their effects. Therefore, the additives should have good compatibility with PVC. For fillers, inorganic pigments and other additives that are insoluble in PVC, small fineness and good dispersibility are required. In addition, the additives should not interact with the PVC resin, that is, the additives will not promote the degradation of PVC, nor will it be affected by the HCl generated by the degradation of PVC.

　　(2) Durability It should meet the requirements of low volatility, resistance to water, oil or solvent extraction, and good resistance to migration.

　　(3) Processing adaptability Additives should have good heat resistance, and they should not decompose, volatilize and sublime at the processing temperature, and do not corrode processing equipment and molds.

　　(4) Restrictions on product performance Refers to the requirements for product appearance, odor, pollution, durability, electrical insulation, thermal performance, weather resistance, toxicity, etc.

　　(5) Interaction between additives refers to the synergistic effect or opposing effect between additives. The compounding of different varieties in the same type of additives is very necessary.

　　(6) Economy The cost of additives should be as low as possible.