The Effect of Rotational Extrusion on the Structure and Properties of HDPE Pipes

Guo, Yue; Wang, Qi; Bai, Shibing

doi:10.1080/03602551003773098

Cited by 21 publications

(11 citation statements)

References 26 publications

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“…To further reveal the crystalline morphologies in PB-1 pipes, SEM observation was carried out. As shown in Figure 7, the inner wall of PB-1 pipes produced via both rotational extrusion and conventional extrusion were covered with spherulites, and even when the rotation speed reached a level as high as 8 rpm, there existed no anisotropic shish-kebab structure as reported in PE pipes prepared by rotational extrusion earlier [15,19]. The reasons for the absence of this oriented crystals could be two: first, longer and larger ethyl side chains increased the relatively steric barrier for the formation of the extended molecule shish, which was a precursor for shish-kebab; however, the crystallization rate of PB-1 was relatively slow, so it was very difficult to fix the extended molecule shish also through epitaxial crystallization.…”

Section: Effect Of Mandrel Rotation On the Orientation And Crystallinmentioning

confidence: 81%

“…The schematic mechanical drawing of this equipment is shown in Figure 1. More detailed information about this equipment has been described in previous work [15,18,19]. This equipment can achieve rotation of the mandrel so as to adjust the stress direction during the polymer pipe extrusion.…”

Section: Sample Preparationmentioning

confidence: 99%

“…Numerous techniques have been developed to improve the pipe's mechanical properties of a given polymer through manipulating the molecular orientation in extruded pipes, by optimizing pipe processing conditions or inducing external fields such as vibration plasticating extrusion [7], spiral flowing extrusion [10], flow-forming process [11], die drawing process [12], and rotational extrusion [13][14][15]. Among these approaches, rotational extrusion is a relatively efficient processing route for polymer pipe mass manufacturing.…”

Section: Introductionmentioning

confidence: 99%

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Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

Liu¹,

Wang²,

Nie³

2013

Journal of Polymer Engineering

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Abstract:In this article, a new rotational extrusion processing system was adopted for manufacturing of polybutene-1 (PB-1) pipes, and the effects of mandrel rotation speed on their structures and mechanical performances were studied. The experimental results showed that besides the conventional axial extrusion flow field, a hoop shear stress field imposed to the melt, which was generated by the introduction of mandrel rotation, could lead the combined stress apart from the axial direction of the pipes to induce the molecular orientation deviated from the axial direction. Thus, the axial orientation of PB-1 was restrained, which was revealed by thermal shrinkage measurements and polarized infrared spectra. Moreover, it was also found and confirmed by scanning electron microscopy and two-dimensional wide-angle X-ray diffraction that orientation mainly existed in the amorphous region rather than the crystal region. Differential scanning calorimetry tests showed that the mandrel rotation could facilitate the formation of more perfect crystals and higher crystallinity. As a result, compared with the PB-1 pipe produced by conventional extrusion, the hoop strength of the PB-1 pipes manufactured at a mandrel rotation speed of 8 rpm increased from 20.2 to 24.9 MPa, achieving a mechanical balance in both axial and hoop directions.

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Section: Effect Of Mandrel Rotation On the Orientation And Crystallinmentioning

confidence: 81%

Section: Sample Preparationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

Liu¹,

Wang²,

Nie³

2013

Journal of Polymer Engineering

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“…As mandrel speed increased, the circumferential stress imposed on melt strengthened, thereby promoting the circumferential orientation of the molecular chains and resulting in a tilt angle between the general orientation direction and MD. Accordingly, this tilt was positively related to mandrel speed . Supporting Information Figs.…”

Section: Resultsmentioning

confidence: 99%

A novel method for industrial manufacturing of thermoplastic multilayer films: Processing, microstructure, and properties

Luo

2018

Polymer Engineering & Sci

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This article reports a facile approach for industrial‐scale manufacturing of multilayer coextrusion‐blown films by developing a novel rotation homogenization distribution (RHD) method. Materials in this unique process are subjected to a flow field combining both shear circulation and pressure flow. In RHD, circumferential shear causes a laminar flow, where the stable interface between layers can be obtained, and assigns melt evenly to the entire circumferential direction. This equipment has been used to prepare multilayer low‐density polyethylene (LDPE) films under various shear rates by altering the mandrel rotation speed. The effects of mandrel rotation speed on the microstructure, morphology, and properties of bilayer LDPE films were investigated. Multilayer LDPE films with superior interfacial stability and uniform layer distribution, which differ from the multiple melt channels in conventional multilayer coextrusion blown facilities, were successfully fabricated using the proposed equipment. Evident enhancements were observed in thermal shrinkage and mechanical properties of the multilayer films, especially in the transverse direction. © 2018 Society of Plastics Engineers POLYM. ENG. SCI., 59:E339–E349, 2019. © 2018 Society of Plastics Engineers

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“…Among the above approaches, rotation extrusion has attracted much attention. [17][18][19] This article further focused on the effects of the mandrel-die-same direction-rotation extrusion on the obtained PE pipe's microstructure and resistance to SCG and studied the relationship among the stress, cooling rate, and final structure, so as to prepare the PE pipe with better resistance to SCG. 10,12 However, the previous studies focused on mandrel rotation extrusion where the inner layer of the pipe rotated together with the mandrel while the outer layer remained stationary, so the hoop stress imposed by the mandrel rotation was gradually decreased from the inner to the outer layer.…”

Section: Introductionmentioning

confidence: 99%

Control of rotation extrusion over shish‐kebab crystal alignment in polyethylene pipe and its effect on the pipe's crack resistance

Nie

Wang

2012

J of Applied Polymer Sci

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A self-designed rotation extrusion system was adopted to extrude polyethylene (PE) pipe. The experimental results showed that when the mandrel and die rotated in the same directions during the PE pipe extrusion, apart from the axial stress, all polymer melts in PE pipes were also subjected to the hoop stress so that the formed shish-kebab crystal in the whole pipe deviated from the axial direction greatly, which was further fixed by the double cooling on both inner and outer walls. As a result, the PE pipe with better resistance to slow crack growth was prepared. As compared to the PE pipe produced by the convention extrusion, the crack initiation time of the PE pipe manufactured by the novel method increased from 27 to 174 h, by 544%.

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The Effect of Rotational Extrusion on the Structure and Properties of HDPE Pipes

Cited by 21 publications

References 26 publications

Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

A novel method for industrial manufacturing of thermoplastic multilayer films: Processing, microstructure, and properties

Control of rotation extrusion over shish‐kebab crystal alignment in polyethylene pipe and its effect on the pipe's crack resistance

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