Low polymerized PVC Resin SG-5 type shall be selected for UPVC pipe manufacturing. The higher degree of polymerization, the better physical mechanical property and heat resistance. But PVC Resin SG-5 has relatively low fluidity, thus causing difficulty in processing. Anyway PVC Resin SG-5 with viscosity of（1.7~1.8）×10-3Pa•s is a good choice.
Lead based Stabilizer is usually used in UPVC pipe making thanks to its good stability. Generally used lead salt is tribasic lead sulfate, but it is always used with Lead soap and Barium soap due to its poor lubrication.
Selection and use of PVC lubricants are also very important. There are two basic factors shall take into consideration: internal lubrication for reducing intermolecular force and viscosity of melts for good moulding; external lubrication to protect melts from adhesion with metal parts of machinery and enhance product surface brightness.
Metallic soap is usually used as internal lubricant, while low melting-point wax as external lubricant.
Calcium Carbonate and Barium Sulfate (barite powder) are two major materials used as filler. Calcium Carbonate will make UPVC pipe have good surface properties. Barium Sulfate will enhance the moulding and make pipe sizing easier. Both of them will can be used to reduce costs. But overuse of filler will bring bad effect on properties of UPVC pipe. Absence of filler or small quantity of filler added for UPVC pipe making is a good choice.
Formula of UPVC Pipe for Reference
PVC Resin SG-5
Lead Compound Stabilizer