The forming method of large diameter plastic pipe and its research

With the development of pipeline transportation industry, the requirements for pipeline transportation capacity are becoming higher and higher, and the application of large-diameter plastic pipe is becoming more and more extensive. The research and development of large-diameter plastic pipe with high production intensity, light quality, impact resistance and corrosion resistance is one of the main development directions of pipeline transportation in the future.

In this paper, the forming method of large diameter plastic pipe, its research status, existing problems and development trend are summarized. In view of the traditional method of large diameter plastic pipe forming problem, this paper proposes a combined with increase of material manufacturing technology of traditional molding and extrusion molding technology of large diameter plastic pipe forming new technology, the polymer melt injection pile forming, namely the role of plastic melt extrusion machine pressure, jet filled by rolling pipe and keep-off device, block formed by the constraints of the space, then the rolling device and continuous screw pile under the action of tractor molding line.

Then, according to the principle of polymer melt injection and stacking technology, a large diameter plastic pipe melt injection and stacking equipment was developed. The equipment consists of extruder, pipe forming device, tractor, control system and so on. Compared with the traditional pipe molding equipment, the equipment not only don't need extrusion die head, winding mandrel, mould, also can flexible pipe molding, can Ø molding diameter 749 ~ Ø 948 mm, 30 ~ 50 mm plastic pipe wall thickness.

The main process parameters of the molding process are analyzed, including molding temperature, screw speed, traction speed, rotation speed and pitch, etc. According to the mathematical relationship between the process parameters, the process parameters set and calculated for subsequent numerical simulation analysis and experiment are required.

According to the principle of the molding process of establishing mathematical model and geometric model, using POLYFLOW software to carry on the numerical simulation, analyzes the melt velocity distribution, temperature distribution, local flow, such as law, combined with traction speed, rotating speed, cooling to finalize the design temperature, injection molding process parameters such as temperature, numerical simulation analysis, the results of experiments with theoretical guidance significance.

Finally, according to the calculated parameters and numerical simulation analysis of the conclusion, large diameter plastic pipe melt injection pile forming experiments, including on the pipe forming ring stiffness, tensile properties and impact properties and mechanical properties test, differential scanning calorimetry analysis results, analysis of the pulling speed, rotating speed, finalize the design temperature, cooling spray forming temperature and other process parameters on the molding pipe mechanical properties, the influence of the validation of numerical simulation analysis.

In addition, the mechanical properties and molding pipe by mechanical properties compared with extrusion molding pipe sizes, the results show that through the process forming of large diameter, the mechanical properties of plastic pipe is better than that of the extrusion molding, especially the impact performance, among them, the axial impact strength is 1.6 times that of extrusion molding pipe and circumferential impact strength is 2.2 times that of the extrusion molding pipe.