Rigid polyvinyl chloride, UPVC, also known as hard PVC, is an amorphous thermoplastic resin made by the polymerization of vinyl chloride monomer plus certain additives (such as stabilizers, lubricants, fillers, etc.). But strictly speaking , UPVC is hard PVC, while hard PVC is not UPVC. A rigorous and scientific discussion of UPVC should be that UPVC cannot contain or use plasticizers, while hard PVC contains plasticizers. In addition to using additives, the method of blending with other resins is also used to make it have obvious practical value. These resins are CPVC, PE, ABS, EVA, MBS and so on. UPVC has high melt viscosity and poor fluidity. Even if the injection pressure and melt temperature are increased, the fluidity will not change much. In addition, the molding temperature of the resin is very close to the thermal decomposition temperature, and the temperature range that can be molded is very narrow, making it a difficult-to-mold material.