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聚乙烯在复合应力场中临界状态挤出成型的研究 总被引:1,自引:0,他引:1
采用具有复合应力场的双向拉伸挤出口模,在临界状态下成功制备了聚乙烯双向自增强片材。研究表明,制备的增强片材的纵横向力学性能均有明显提高,维卡软化点提高了21℃。微观测试表明,其晶态结构为串晶,正是由于片材内部生成了大量的串晶结构,才赋予了增强片材比较好的力学性能。 相似文献
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《塑料》2001,30(6)
发泡片材挤出装置的发展方向
(日)《プラスチツクスエ—ジ》第47卷第8期第105~110页 2001年
近年来,为了满足成型制品回收再生利用、节能、安全、薄壁轻量化等要求,PP发泡片材逐渐取代了PP填充改性片材、PS发泡片材等发泡材料,受到人们的关注。发泡片材挤出装置的发展动向是:①化学发泡片材装置:一般发泡倍率为1.5~3倍。成型设备主要以T型机头,单螺杆挤出机为主流。同时配置了高精度温度控制装置,强制加料装置,进行低温、高挤出量的生产。②物理发泡片材装置:A.使用同向旋转双螺杆挤出机。其螺杆转数和加料装置转数可进行任意匹配组合,达到最优的混炼效果,挤出稳定,容易控制。B.为防止成型材料在挤出加工时温度上升,使用低转速大扭矩电机。C.配置有计量混合加料装置,能够使用100%的粉碎回收原料,保证挤出的稳定,得到优质发泡片材。D.发泡气体定量供给装置。可采用高压定量计量或低压定量计量方法。 相似文献
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道达尔石化公司近13开发出耐热结晶聚苯乙烯树脂新牌号CX5229。据称,道达尔利用其新工艺生产的这一新牌号,适用于挤出发泡片材、取向聚苯乙烯和吹塑薄膜等,结晶度高,且仍保留加工成型要求的关键性能——熔体强度。用常规挤出设备加工时,其成型压力和加工温度比传统牌号低10%-15%。 相似文献
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以自制的剥离高岭(MK)、原高岭土(K)以及聚丙烯(PP)和马来酸酐接枝聚丙烯(PP-g-MA)等作为基本原料,通过熔融挤出、注塑成型,制备PP复合材料。采用XRD、DSC、TG研究复合材料的非等温结晶行为、结晶动力学以及热降解性能。结果表明:高岭土的加入,使结晶温度、结晶度、热稳定性都有所提高,且结晶速率加快,具有异相成核作用。与原高岭土相比,改性高岭土更能促进PP复合材料的PP异相成核,促进PP稳态晶型(α晶型)的转变,结晶速率较快。与纯PP和PP/PP-g-MA复合材料相比,PP/改性高岭土复合材料的结晶峰温度、最大热降解温度分别提高了16.7、7.8、9.7、12.6℃。 相似文献
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采用自行研制的高熔体强度聚丙烯(PP),通过挤出片材发泡实验,研究了口模温度、挤出温度、螺杆转速等工艺条件以及PP熔体强度和发泡成核剂对片材发泡效果的影响。PP发泡片材最佳挤出工艺条件为:挤出温度210℃,口模温度160℃,螺杆转速40 r/min。PP熔体强度为13 cN,发泡成核剂用量为6 phr时,发泡片材密度最低(0.450g/cm~3),片材表面光滑平整,挤出发泡效果最好。 相似文献
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加工参数对PP/木粉复合材料结构和性能的影响 总被引:3,自引:0,他引:3
将聚丙烯(PP)与处理木粉混合,经双螺秆挤出机适粒后·混入微扎发泡母粒,经单螺杆挤出机塑化和片材口模成型PP/木粉复合微孔片材试样.通过改变挤出温度、螺杆转速、口模压力降以及冷却定型条件,测定试样拉伸性能、密度、孔隙率,扫描电镜(SEM)观察试样断面形貌,研究加工参数与PP/木粉复合微孔片材结构和性能的关系.结果发现,在挤出温度180℃,螺杆转速50 r/min,高的挤出压力时,泡孔尺寸小而均匀.对片材坯料给予的冷却定型可以固定泡孔结构防止泡孔合并和过度生长及塌陷. 相似文献
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Han-Xiong Huang 《Polymer Engineering and Science》1998,38(11):1805-1811
Continuous extrusion was studied of self-reinforced high density polyethylene (HDPE) sheets from flow-induced crystallization at die pressures varying from 30 to 60 MPa. Their morphology, thermal behavior, tensile strength, and light transmittance were tested. Flow fields of a polymer melt through a converging wedge channel were also investigated by direct visual observations in conjuction with a theoretical analysis. The extensional strain rate increased abruptly as the melt approached the exit of the converging channel, this resulting in a higher crystallization rate. So, achieving the crystallization of molecular chains just in front of the exit of the converging channel may favor to extrude the bulk polymeric materials having high properties under lower pressures (e.g., 40 MPa or lower), this having been realized in the present work. The tensile strength of the self-reinforced HDPE sheet prepared at a 40 MPa pressure was enhanced by a factor of 8. 相似文献
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D. M. Bigg 《Polymer Engineering and Science》1976,16(11):725-734
Linear crystalline polymers can be processed to high degrees of orientation sufficient to produce dramatic increases in tensile strength and modulus. Three processes have been identified for inducing such orientation: cold drawing, hydrostatic extrusion, and solution spinning. All three processes utilize a high elongational velocity gradient in a critical temperature range to produce a high strength crystalline morphology. Although the molecular superstructure may differ in each case, the mechanical properties are similar, An increase in strength is achieved either through the creation of new tie molecules between crystal lamellae or through the creation of an extended chain crystal substructure. Temperature and molecular weight are the prime variables in determining which morphology will develop. The optimum processing temperature for many of the specific techniques is the crystalline dispersion temperature. At this temperature, the crystal structure is particularly adaptable to forming a new crystal morphology. Ul-tradrawn polymers are more Hookean in behavior than isotropic polymers and have properties similar to steel and glass. Polyoxymethylene has been processed most closely to its theoretical strength. Polyethylene, which is the most difficult to process, has achieved the highest modulus of any common polyolefin polymer, about 7 × 1010 Pa. 相似文献
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使用电磁动态塑化挤出机,对HDPE/CaCO,复合材料的挤出片材做横向和纵向拉伸性能研究。振动力场能够有效地改善HDPE/CaCO,片材的拉伸强度和拉伸断裂伸长率,在本实验范围内,与稳态挤出制品相比,片材的横向和纵向拉伸强度分别提高了16.4%和15.6%,横向和纵向拉伸断裂伸长率分别提高了38.9%和44.0%;振动对材料横向的影响比对纵向更具有规律性。 相似文献
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系统介绍了导电型聚苯乙烯型胶带从粒料到最终产品的生产工艺,分析了各种工艺参数对导电型聚苯乙烯胶带的拉伸强度、柔韧性、表面电阻等性能及产品收率的影响。通过进一步的试验,优化了胶带片材挤出、片材分条及胶带成型的工艺参数。 相似文献
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BACKGROUND: The axial strength of a plastic pipe is much higher than its circumferential strength due to the macromolecular orientation during extrusion. In this work, a custom‐made electromagnetic dynamic plasticating extruder was adopted to extrude high‐density polyethylene (HDPE) pipes. A vibration force field was introduced into the whole plasticating and extrusion process by axial vibration of the screw. The aim of superimposing a vibration force field was to change the crystalline structure of HDPE and improve the molecular orientation in the circumferential direction to obtain high‐circumferential‐strength pipes. RESULTS: Through vibration extrusion, the circumferential strength of HDPE pipes increased significantly, and biaxial self‐reinforcement pipes could be obtained. The maximum increase of bursting pressure and tensile yield strength was 34.2 and 5.3%, respectively. According to differential scanning calorimetry and wide‐angle X‐ray diffraction measurements, the HDPE pipes prepared by vibration extrusion had higher crystallinity, higher melting temperature, larger crystal sizes and more perfect crystals. CONCLUSION: Vibration extrusion can effectively enhance the mechanical properties of HDPE pipes, especially the circumferential strength. The improvement of mechanical properties of HDPE pipes obtained by vibration extrusion can be attributed to the higher degree of crystallinity and the improvement of the molecular orientation and of the crystalline morphology. Copyright © 2008 Society of Chemical Industry 相似文献
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对等规聚丙烯(iPP)片材在退火固相拉伸过程中的晶体转变过程进行了研究。X射线衍射(XRD)表征了结晶衍射峰,定量计算出β晶的相对含量;二维小角X射线散射(2D-SAXS)揭示了α?β 晶型转变过程;差示扫描量热仪(DSC)揭示了iPP的熔融性能。结果表明,iPP片材在固相拉伸过程中发生了晶型转移,XRD衍射曲线中出现了β晶典型衍射峰β(300),2D-SAXS图中出现了取向串晶结构;在110 ℃拉伸作用下能够产生相对高β晶含量的iPP,最高含量为6.75 %;拉伸强度的增加幅度不大但其缺口冲击韧性显著提高;对固相拉伸作用后的iPP片材进行了退火处理,表明退火温度在110 ℃前串晶结构不会受到破坏,超过110 ℃退火后串晶结构被破坏再次形成球晶结构。 相似文献