PVC Compounding Process
The rigid PVC dry blend powder (called the Resin), which also contains other materials like stabilizers, additives, fillers, reinforcements, and flame retardants, must be intensively mixed in the compounding machinery. The dispersive and distributive mixing is critical, and all in compliance with well defined temperature limits.
According to the formulation, the PVC resin, plasticizer, Filler, stabilizer and other auxiliaries are put into hot mixer mixing. After 6-10 mins discharge into the cold mixer (6-10 mins) for premixing. PVC compound must use the cold mixer to prevent material stick together after the hot mixer.
The mixture material after plasticizing, mixing and dispersing evenly at around 155°C-165°C, then fed to the cold mixer. The melting cooling PVC mixture feed into twin screw extruder for compounding, then into single screw extruder for cooling and extrusion. After pelletizing, the granules temperature can be dropped to 35°C-40°C. Then after the air cooling vibrating sieve, the particle temperature drops below room temperature to be sent to the final product silo for packaging.
PVC cable compounds including sheathing compound and insulation compound.The sheathing compound requires good heat resistance, and the insulation compound requires good insulation.
Basic formulation for the production of PVC insulation and jacket compounds for wire and cable is generally composed of the following:
|2||Plasticizer||To soft material, enhance Flexibility and make compounding material easy to processing||Phthalates series: DPHP，DINP，DOP，DIDP|
Others: TOTM，DOTP,DOA，Soybean oil,Chlorinated Paraffin
|3||Stabilizer||To defer and stop the degradation of PVC resin||Calcium and zinc, lead salts, fatty acid soaps, organotin, phosphatides and epoxides etc|
|4||Filler||To lower cost and fabricate specific property||Calcium carbonate, kaolin, talc, silica, graphite, carbon black, etc|
|5||Flame retardant||Fire resistance||Organic: some flame retardants represented by bromine, phosphorus and nitrogen, nitrogen and red phosphorus and their compounds|
Inorganic: antimony trioxide, magnesium hydroxide, aluminum hydroxide, zinc borate, silicon series of flame retardant system.
|6||Lubricant||Improve the fluidity and improve the processing and surface performance, can also be used to promote melting, anti – adhesion and anti – static agent, smooth agent.||Fatty acids and their esters (HSt), fatty acid amide (EBS), metal soap (CaSt), hydrocarbons (low molecular polymer), organosilicone compounds, etc.|
|7||Others||Antioxidant: prevents plastics from aging during production|
Light stabilizer:resistant to UV, strong light exposure
Colorant: Coloring plastic
|PVC Sheathing Cable Compound formula (105℃) for reference only|
|Dibasic Lead Phthalate||8||Stabilizer|
|PVC Insulation Cable Compound formula for reference only|
|Phenyl Alkyl Sulfonate||15||Antioxidant|