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复合应力场下挤出HDPE增强管材性能的研究 总被引:1,自引:0,他引:1
用自行研制的能产生先剪切后拉伸的复合应力场挤出成型装置,挤出高密度聚乙烯(HDPE)管材,对管材周向、轴向力学性能进行了初步的研究。与一般牌号为DGDA6098的HDPE比,在HDPE中添加高相对分子质量高密度聚乙烯(HMWHDPE)后,发现HMWHDPE能够诱导HDPE沿应力场方向产生大分子取向和结晶。利用差示扫描量热仪(DSC)和扫描电镜(SEM)检测手段对试样的凝聚态结构进行分析,证实了复合应力场下制备的自增强管材双向力学性能都提高了。 相似文献
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Summary The effect of vibration frequency and vibration amplitude on the microstructure and mechanical properties of high-density
polyethylene (HDPE) sheets, obtained through electromagnetic dynamic plasticating extruder, were studied systematically. The
mechanical properties, characterized by tensile and impact strengths, have been tested along the flowing and transverse directions
(MD&TD). The mechanical tests show that the tensile strength and impact toughness, especially in TD, were much improved under
the reciprocating axial vibration. Differential scanning calorimetry (DSC), scanning electron microcopy (SEM) and wide angle
X-ray diffraction (WAXD) were executed to analyze the microstructure of the samples. The results indicate that the vibration
extrudate has higher crystallinity, perfect crystallite, and strong inter-spherulite ties, which account for enhancement of
the mechanical properties of sheets, compared to conventional static extrusion. 相似文献
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Yu Xi Pan Nan Li Jin Yan Wang Dan Hui Wang Xiao Tong Pan Cheng Liu Xi Gao Jian 《Polymer Engineering and Science》2021,61(11):2918-2930
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. 相似文献
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利用塑料电磁塑化挤出机挤出聚烯烃片材,系统研究了挤出机螺杆轴向振动对聚乙烯挤出制品结构与性能的影响。采用DSC对挤出试样的结晶结构及形态进行分析。结果表明,振动塑化挤出使聚合物挤出试样结晶度提高,结晶完善,晶片之间的连接分子数量增加,因而制品的力学性能有所提高,特别在横向上表现明显。在适当的振动条件下,高密度聚乙烯(HDPE)试样的横向拉伸强度和冲击强度分别从22.68MPa和12.7kJ/m^2提高到了25.55MPa和23.5kJ/m^2;而聚丙烯(PP)试样横向拉伸强度和冲击强度则分别提高了20%和64%。 相似文献
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High density polyethylene (HDPE) pipes were prepared using a novel rotational extrusion processing system. The experimental results showed that the hoop stress exerted by either mandrel rotation or die rotation could have the macromolecular chains oriented in hoop direction and alter the crystallization behavior of HDPE during rotational extrusion, resulting in forming transcrystals with larger crystalline size, thicker lamellae, higher Tm. Therefore, the mechanical properties of HDPE pipes were greatly improved in hoop direction, which was attributed to the changes of the crystalline morphology and the molecular orientation under the action of the hoop stress field. 相似文献
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Shan-Ming Yan Xue-Qin Gao Cong Deng Qiang Yu Li Wang Jie Zhang 《Polymer-Plastics Technology and Engineering》2013,52(11):1091-1095
A vibration technique was applied in extrusion molding of HDPE 6100M/OMMT nanocomposites. The results from the study suggest that samples obtained by vibration extrusion were strengthened effectively. The maximum increase percentage of tensile strength at 180°C and 200°C reached 25.14% and 21.43% respectively. It was found from microscopic structures measured by DSC, WAXD and SEM that the crystalline grains of polyethylene matrix became fine, that the orientation degree of crystalline increased and that crystallinity became perfect under the vibration field. Moreover, vibration can make nano-OMMT disperse more homogeneously in the HDPE matrix. 相似文献
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Xiaotong Pan Yuxi Pan Haiyang Zhao Cheng Liu Wenguang Zeng Yujie Guo Ce Song Xigao Jian 《应用聚合物科学杂志》2024,141(18):e55326
With the discovery of deeper oil fields, conventional metal pumping pipes have been proven to be ineffective in meeting the requirements for deep well oil production due to their high weights and limited corrosion resistance. Therefore, in this study, a composite of Poly(phthalazinone ether sulfone ketone) (PPESK) and polyethersulfone (PES) was used to fabricate nonmetal pipes. To enhance the mechanical properties of the PPESK/PES pipes, a self-designed annular expansion pipe extruder head was used. The circumferential burst stress and axial tensile strength of the PPESK/PES pipes subjected to 30° expansion were 73.0% and 48.9% higher than those of the unexpanded sample, respectively. When annular expansion was integrated into the extrusion of PPESK/PES/carbon fiber pipes, the axial tensile strength and circumferential burst stress were 45.9% and 88.8% higher than those of the unexpanded sample, respectively. Results of polarized infrared testing and metallographic microscopic examinations demonstrated that molecular chains present a regular orientation at a certain angle to the extrusion direction, under the effect of annular expansion extrusion. These findings highlight the efficiency of annular expansion in promoting the large-scale production of pipes. 相似文献
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Xue-qin Gao Cong Deng Jing Xu Zhong-ming Li Jie Zhang Kai-zhi Shen 《Polymer Bulletin》2010,65(1):59-68
Melt vibration technology was used to prepare injection sample of HDPE/nano-CaCO3 blend, whose mechanical properties were improved significantly. Compared with conventional injection molding, the enhancements
of the tensile strength and impact strength of the sample molded by vibration injection molding were 41.2 and 43.2%, respectively.
According to the SEM, WAXD, and DSC measurement, it was found that a much better dispersion of nano-CaCO3 in sample was achieved by vibration injection molding. Moreover, crystal orientation degree of matrix HDPE increased under
the effect of melt vibration. The crystallinity degree of HDPE in vibration sample increased by 5.5% compared with conventional
one. The improvement of mechanical properties of HDPE/nano-CaCO3 blend prepared by low-frequency vibration injection molding attributes to the even distribution of nano-CaCO3 particles and the orientation of HDPE crystals and increase of crystallinity degree under the influence of melt vibration. 相似文献
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The row‐nucleated lamellar crystalline structure of high‐density polyethylene (HDPE) films was prepared by applying elongation stress to HDPE melt during T‐die cast film extrusion and subsequently annealing the extruded films. This unusual crystalline structure was analyzed in terms of lamellar crystalline orientation, long‐period lamellar spacing, crystallite size, and degree of crystallinity. The contribution of melt‐extension represented by draw‐down‐ratio (DDR) to the overall orientation was found to be most noticeable than other processing variables. Meanwhile, the long‐period lamellar spacing, the crystallite size, and the degree of crystallinity were influenced predominantly by the annealing temperature. Finally, the processing (melt extension and annealing temperature) – structure (lamellar crystalline structure) – property (hard elasticity) relationship of HDPE films was investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3326–3333, 2007 相似文献
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通过在挤出成型过程中引入振动场,研究了加工过程中HDPE/碳纤维(CF)复合材料在振动场中的流变行为,并借助拉伸性能检测以及差示扫描量热分析(DSC)、扫描电镜(SEM)等测试方法,分析了HDPE/CF复合材料的结构与性能。结果表明:振动挤出可以显著降低熔体的表观黏度,最大降幅为56.95%,同时还可改善制品的力学性能,拉伸强度最大增幅为15.1%;材料力学性能的提高可归因于其微观形态结构的变化,振动使HDPE/CF复合材料基体晶粒细化、晶体排列更加规整、结晶度略有提高,并增强了CF与基体间的界面黏合作用。 相似文献
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A novel rotation extrusion processing system was self‐designed to prepare high‐performance polyethylene (PE) pipes. In this study, during the extrusion of the PE pipes at a high mandrel rotation speed, compressed air, as a cooling medium, was introduced through their interior to achieve the quick cooling of the inner wall and the effects of the inner wall cooling rate on the microstructure and mechanical properties of the obtained PE pipes were investigated. The experimental results showed that in contrast to conventional extrusion, the molecular orientation deviated from the axial direction under a high mandrel rotation speed and was fixed by the inner wall cooling; with increasing cooling rate, the orientation degree also increased. On the other hand, cooling promoted the augmentation of spherulites. So when the cooling rate reached a certain high point, the effect of cooling on the formation of spherulites was stronger than that on the fixation of the orientation. A much higher cooling rate decreased the orientation degree, which was closely related to the performance of the PE pipe. As a result, there was an optimal cooling rate of the inner wall during the rotation extrusion for better performance of the PE pipe. When the cooling rate was 1.5°C/s, the hoop strength of the PE pipe produced by the novel extrusion method increased from the original 24.1 MPa up to 37.1 MPa without a decrease in the axial strength, and the pipe's crack initiation time increased from 27 to 70 h. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
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振动力场对m-PE-LLD薄膜拉伸强度的影响 总被引:1,自引:0,他引:1
使用电磁动态吹膜机组加工m-PE-LLD薄膜,将振动力场引入到塑化挤出的全过程,考察了振动力场对m-PE-LLD薄膜拉伸强度的影响。研究发现,振动力场的加入使m-PE-LLD吹塑薄膜的横向强度增大、纵向强度减小,纵、横向拉伸强度趋于均匀。振动力场对PE-LD和PE-HD的拉伸强度的影响具有相似的规律,初步的分析机理认为:振动力场引入后,聚合物熔体同时受到轴向和周向的作用力,分子链会沿两个作用力的方向进行排列,形成网格化排列的结构,从而使薄膜纵、横向强度趋于均一。 相似文献
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Slow crack growth (SCG) is one failure principal mode in polyethylene (PE) pressure pipe applications. In the conventional
extrusion process, the molecular chains in the plastic pipes are oriented along the axial direction, which are disadvantageous
to their resistance to SCG. In order to change the orientation direction of molecules in the plastic pipe, a new rotation
extrusion processing system was designed to extrude high-density polyethylene (HDPE) pipes, and a thorough research was done
on the effect of the rotation speed on its microstructure and resistance to SCG during the rotation extrusion. The experimental
results showed that when the die rotated during the extrusion process of PE pipes, the hoop stress exerted on the polymer
melt could make the molecular orientation deviate from the axial direction, and therefore the consequent multi-axial orientation
of molecular chains could be obtained. As a result, the PE pipe with better resistance to SCG was prepared. Compared to the
PE pipe produced by the conventional extrusion, the crack initiation time of the PE pipe manufactured by the novel method
increased from 27 to 57 h. 相似文献
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Changes in the molecular orientation, melting behavior, and percent crystallinity of the individual components in a fibrous blend of isotactic polypropylene (iPP) and high-density polyethylene (HDPE) that occur during the melt extrusion process were examined using wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystalline orientation of each component was found using Wilchinsky's treatment of uniaxial orientation and described by the Hermans–Stein orientation parameter. The amorphous orientation was found by resolving the X-ray diffraction pattern in steps of the azimuthal angle into its iPP and HDPE crystalline and amorphous reflections. The utility of DSC and WAXD analyses to capture the effects of small differences in processing, and the use of these results as fingerprints of a particular manufacturing process were demonstrated. Major increases in the melting temperatures, percent crystallinities, and molecular orientations of the iPP and HDPE components occurred during the main stretching stage of the melt extrusion process. The annealing stage was found to have little to no effect on the melting behavior and molecular orientation of these components. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
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A vibration force field was applied to the whole process of polymer plasticating extrusion by periodical vibration of the screw. It observably affected both the extruder screw extrusion characteristics and the round-section die extrusion characteristics. It also affected the polymer plasticating extrusion process and the quality of the extrudates. An analytical model of typical dynamic extrusion of round-section dies was created. The results showed that a vibration force field can improve extrusion output. 相似文献
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A series of high‐density polyethylene (HDPE)/CaCO3 blends were prepared with different kinds of coupling agents, with CaCO3 particles of different sizes, and with matrixes of different molecular weights during the melt‐mixing of HDPE and CaCO3 particles. The mechanical properties of these blends and their dependence on the interfacial adhesion and matrix crystalline structure were studied. The results showed that the Charpy notched impact strength of these blends could be significantly improved with an increase in the interfacial adhesion or matrix molecular weight or a decrease in the CaCO3 particle size. When a CaCO3 surface was treated with a compounded coupling agent, the impact strength of the HDPE/CaCO3(60/40) blend was 62.0 kJ/m2, 2.3 times higher than that of unimproved HDPE; its Young's modulus was 2070 MPa, 1.07 times higher than that of unimproved HDPE. The heat distortion temperature of this blend was also obviously improved. The improvement of the mechanical properties and the occurrence of the brittle–tough transition of these blends were the results of a crystallization effect induced by the interfacial stress. When the interfacial adhesion was higher and the CaCO3 content was greater than 30%, the interfacial stress produced from matrix shrinkage in the blend molding process could strain‐induce crystallization of the matrix, leading to an increase in the matrix crystallinity and the formation of an extended‐chain (or microfibrillar) crystal network. The increase in the critical ligament thickness with an increasing matrix molecular weight was attributed to the strain‐induced areas becoming wider, the extended‐chain crystal layers becoming thicker, and the interparticle distance that formed the extended‐chain crystal network structure becoming larger with a higher matrix molecular weight. The formation of the extended‐chain crystal network and the increase in the matrix crystallinity were also the main reasons that Young's modulus and the heat distortion temperature of this blend were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2120–2129, 2003 相似文献