Extrusion molding process method of PPH pipe. Selection of raw materials: resin for extruded polypropylene pipes, and its melt flow rate is in the range of 0.2 to 0.3 g/10min. Generally, resins with a melt flow rate in the range of 0.2 to 0.4 g/10min are used more. Production process sequence of polypropylene pipe: the same as the production process sequence of general-purpose polyethylene pipe, the process sequence is as follows. Open the bag to check the quality of raw materials → extruder plasticizes and melts raw materials → mold forming tube blank → vacuum sizing sleeve cooling and sizing → vacuum spray cooling → pipe cooling and cooling → traction → cutting → quality inspection → storage. Selection of equipment: Polypropylene pipes are mostly produced by general-purpose single-screw extruders. The screw structure is of equal pitch and unequal depth gradient type, the aspect ratio is (25～30):1, and the compression ratio is 2.5～4. The structure of the forming die is mostly straight-through type, and the length of the straight part of the mandrel is L=(2～5)D (D is the diameter of the pipe, the larger value is taken when the diameter is small, and the small value is taken when the diameter of the pipe is large). The inner diameter of the sizing sleeve is d=D/(1-δ) (D is the diameter of the pipe, δ is the shrinkage rate of the pipe, generally δ=2.7%～4.7%).
