Effect of annular expansion pipe extruder head on mechanical properties of pipes

Abstract

With polymer pipes being used more commonly, performance requirements are increasing. Studies on the enhancement of mechanical properties of polymer pipes are particularly important. In this study, a self-designed annular expansion pipe extruder head was used to enhance the mechanical properties of HDPE pipes. Different morphologies of the HDPE pipes were produced under different processing conditions. When the extrusion angle was 30 (P30), the best mechanical properties were obtained. The hoop tensile strength and axial tensile strength were 14.5% and 41.0% higher, respectively, compared with the specimen without expansion (P0). This improvement of mechanical properties can be attributed to several reasons. First, the processing parameters of P30 reached the threshold shear rate and strain for shish-kebab formation, as shown by scanning electron microscopy. Second, P30 has the highest orientation parameter and crystallinity of 0.679 and 67.27%, respectively, from 2D wide-angle diffraction (WAXD). Polarized FTIR shows the same trend as 2D-WAXD. Third, the outer bamboo-like self-reinforced structure is formed inside the pipe at 30 expansion angle while the core layer has a well-formed crystal structure; the special structure improves the overall performance of HDPE pipe. This method can be utilized in large-scale industrial production.

Annular expansion for enhanced orientation and mechanical properties of extruded amorphous PPESK/PES pipes

“…Notably, upon the achievement of orientation, its retention is crucial to ensure that the Rouse relaxation time of the polymer is lower than the action time for improving the mechanical properties. 36 Although the KS‐45 and KS‐60 samples have larger tensile forces, the application time is insufficient to stretch the molecular chains inside the samples and arrange them preferentially to form an orientation‐enhancing structure.…”

“…Under the action of the annular expansion head, the PPESK/PES melt undergoes accelerated flow along the direction of the runner in the expansion section, generating an extensional flow field and a shear force field. This process can align the molecular chain in a preferred direction 36 . These polymer chains then form an oriented reinforcement structure, enhancing the axial strength of the pipe.…”

“…Prior studies have suggested that the orientation results obtained from high-temperature rapid stretch tests, depending on the force applied to the polymer melt through the extruder head and application time are reliable indicators of the orientation in actual polymer-pipe extruded products. 36 Thus, Figure 8 shows the results of samples with different annular expansion angles subjected to high-temperature rapid stretch testing. All samples exhibit increased tensile strengths after hightemperature rapid stretch compared with unexpanded samples.…”

“…This process can align the molecular chain in a preferred direction. 36 These polymer chains then form an oriented reinforcement structure, enhancing the axial strength of pipe. This improvement in the axial strength is attributed to the oriented structures formed along the preferred direction during the preparation of the PPESK/PES-30 pipe.…”

Effects of Different Die Metals on the Performance and Friction and Wear of Composite Materials during the Extrusion Process

“…The extruder head of the extrusion machine is a critical component of extrusion technology, with its structure, materials, and manufacturing processes significantly influencing the efficiency and product quality of the extrusion process [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ]. The damage evolution of powder metallurgy copper/titanium dioxide composites, with a focus on the reduction of Young’s modulus, was investigated by Majzoobi GH [ 31 ].…”