1. A certain amount of internal lubricant and external lubricant are added into PVC pipe making as a ingredient to keep the balance between external and internal lubrication.
2. Most kinds of PVC Stabilizer have certain lubricity. In the early time, Tri-basic Lead Sulfate, Di-basic Lead Phosphite, Lead Stearate and Barium Stearate were usually used as PVC Heat Stabilizer. But in recent years, PVC Heat Stabilizer tends to be compound and multi-functional. Now compound heat stabilizer is generally used.
Metallic Soap type PVC Heat Stabilizer has good internal lubricity, like Calcium Stearate and Barium Stearate.
Lubricant’s Effect on PVC Pipe & Fitting
PVC pipe manufacturers have to consider the changes in ingredients, because sometimes it’s a little bit hard to get expected plasticization due to difference in raw materials even though process index like temperature and screw speed is adjusted. Now general formula of PVC pipe contains PVC Resin, Calcium Carbonate, Compound Heat Stabilizer and PVC lubricants.
The test result shows:-
(1) Lubrication system matching of different PVC Heat stabilizers has big difference. Better plasticization will be acquired if proper amount of lubricant is added.
(2) PVC Resin with high polymerization degree requires more internal lubricant to reduce melting viscosity. PVC Resin with low heat stability requires higher dosage of PVC Heat Stabilizer. If PVC Heat Stabilizer with higher lubricity is added, it’s better to decrease the dosage of PVC lubricant.
(3) If filler with low activation grade is used, PVC lubricant shall be reduced accordingly.