挤出成型微晶聚烯烃片材和管材

通过熔体形变法在特殊的工艺条件下挤出ＨＤＰＥ和ＰＰ片材和管材,产品由常规挤出的白色不透明状态变为无色透明状。其纵向,横向拉伸强度同步提高,ＨＤＰＥ的纵向拉伸强度提高１０倍,ＰＰ则提高了６倍以上;ＨＤＰＥ的横向拉伸强度可提高５０％,ＰＰ约提高９３％。     

塑化过程振动参数对制品力学性能的影响

采用自制新型液压脉振式注塑机,在塑化过程引入液压脉动,探讨振动参数对制品力学性能的影响。结果表明:施加振动后,低密度聚乙烯、聚丙烯拉伸强度分别提高6.1%,9.8%;密度分别增大0.33%,0.30%;加工能耗分别降低6.8%,6.3%,且呈现一定的变化规律。     

振动力场下聚合物塑化挤出技术研究

介绍玫种将电磁场引起的机械振动力场引入聚合物塑化挤出全过程的塑料电磁动态塑化挤出设备,讨论了它的原理、结构及应用,实验与生产表明,塑料电磁动态塑化挤出设备在加工聚烯烃时能耗降低２０％～５０％,挤出熔体温度降低２０℃以上,制品拉伸强度提高１６％以上,对无机填料充体系的兴旺聚散效果提高。     

振动挤出对聚烯烃流变行为的影响

利用自行研制的振动挤出装置研究了振动挤出对聚烯烃流变行为的影响。结果表明:振动场能使高密度聚乙烯(HDPE)和聚丙烯(PP)熔体的表观黏度降低;振动场和熔体表观黏度的关系受振动频率、口模温度、螺杆转速的影响。     

振动挤出对LDPE熔员结晶行为的影响

通过对低密度聚乙烯毛细管动态挤出进行测试分析,探讨了振动力对聚合物挤出物融结晶行为的影响,发现在ＬＤＰＥ熔体流动过程中叠加适当的振动力场后,ＬＤＰＥ挤出物的熔融始态明显变化,结晶度不变的同时,晶粒大小有较大降低,并认为这是振动力场对聚合内部结构产生影响的结果,研究结果对聚合物动态成型加工新的的深入理论研究具有十分重要的意义。     

近熔点挤出HDPE片材结晶结构的研究

通过挤出工艺制备了高密度聚乙烯(HDPE)片材,并用二维广角X射线衍射(2D-WAXD)、二维小角X射线散射(2D-SAXS)和差示扫描量热法(DSC)研究了挤出温度和螺杆转速对HDPE挤出片材微观结构的影响。结果表明:在近熔点条件下,HDPE中残存的局部有序结构在微弱的剪切作用下并没有促使片材取向,但是结晶度、长周期和片晶厚度均有所增加。这主要是因为残存的局部有序结构不仅能够加快熔体的结晶动力学进程,还能使结晶起始时间提前,从而使HDPE熔体有更长的时间进一步结晶,进而得到了更完善的晶体。另外,在相同挤出温度下,结晶度、长周期和片晶厚度均随螺杆转速的增加而减小,这归因于熔体在料筒中的剪切时间变短。     

振动挤出对HDPE/碳纤维复合材料流变行为和性能的影响

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。     

振动挤出对HDPE管材耐慢速裂纹增长性能的影响

使用自制的电磁动态塑化挤出机挤出高密度聚乙烯(HDPE)管材。对稳态挤出和振动挤出的HDPE管材耐慢速裂纹增长性能进行了测试。采用DSC、WAXD分析研究了振动力场对HDPE管材耐慢速裂纹增长性能的影响。结果表明:振动挤出的HDPE管材结晶度提高,熔点升高,晶片变厚,晶粒尺寸变大,结晶完善,耐慢速裂纹增长性能提高。     

含氟弹性体对聚烯烃挤出性能的改善

熔体破裂是挤出成型中遇到的最严重的问题。在树脂中掺入适量的含氟弹性体,是减轻甚至消除熔体破裂的有效措施。PPA2231及FKM-A是较有代表性的两种含氟弹性体。本文介绍了物料制备及实验的方法,利用毛细管流变仪的大量实验结果,详尽分析了这两种含氟弹性体对LLDPE、HDPE及PP这三种聚烯烃树脂挤出性能的效应。并简述了在挤出加工时,含氟弹性体还可降低熔体温度,减小机头压力,提高挤出效率。     

振动挤出HDPE管材的结构与力学性能

使用自制的电磁动态塑化挤出机和螺旋芯棒式机头挤出高密度聚乙烯(HDPE)管材.采用爆破压力测试,拉伸性能测试,差示扫描量热法分析等研究振动频率和振幅对HDPE管材结构与力学性能的影响.振动挤出的HDPE管材周向强度显著提高,实现了管材的双向自增强.与稳态相比,振动挤出的HDPE管材结晶度提高,熔点升高,结晶完善;爆破压力最大提高了34.2%,轴向拉伸屈服应力最大提高了5.3%.     

Structure and Properties of Vibrating Extruded High-Density Polyethylene Sheet

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.     

Effect of vibration extrusion on the structure and properties of high‐density polyethylene pipes

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     

Effect of Vibrating Extrusion on the Structure and Mechanical Properties of Isotactic Polypropylene

An electromagnetic dynamic plasticating extruder, invented by the authors, was used to prepare isotactic polypropylene (PP) sheets. Tensile and impact tests show that the extruded samples can simultaneously be reinforced and toughened along the flow and transverse directions in a moderate frequency and amplitude range. The microstructures of the obtained samples were characterized by differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD), and scanning electron microcopy (SEM). The results indicate that the vibration plasticating extrusion affected the morphology of the PP extrudate, it especially resulted in finer spherulites, and move tie molecules, which account for the enhancement of the tensile strength and impact toughness of PP sheets in both extrusion and transversal directions.     

Study on the Effect of Axial Vibration of Screw in Plasticating Process (Extrusion Part)

To improve the conformation of polymers, axial vibration is offered in the entire polymer process. Two sections, the axial shearing section and the axial pressing section, exert the effects of vibration on the melt. In the axial shearing section, with the effect of vibration, molecular chain orientations in the direction of flow and vibration produce the network frame, which ameliorates the mechanical properties, especially in the transverse direction, of the polymer product. The vibration can promote the disentanglement of molecular chains, which leads to a decrease in the viscosity and an increase in the flowability of melt. At the same time, it can ameliorate the blend quality of the filling system. Some experiments on extruded film, sheet, pipe, foam, and filling systems prove that the analyses are correct.     

振动改善全同立构聚丙烯注塑试样的力学性能

为了研究振动场对全同立构聚丙烯力学性能的影响，研制了压力振动注射装置，研究了不同熔体温度下，振动频率、振动压力对iPP F401注塑试样的拉伸强度、冲击强度和断裂伸长率的影响，并进行了WAXD和DSC测试。结果表明：振动除了提高试样结晶度外，还会诱导晶型的变化，即除α晶，还有β晶生成。随着振动频率和振动压力的增加，振动试样的拉伸强度和冲击强度得到明显改善，其最大增幅分别为26．1％和168％。     

氟碳弹性体对HDPE挤出性能的影响

利用不同长径比的毛细管流变仪，研究了加入不同份数的氟碳弹性体对HDPE挤出性能的影响，得到了剪切速率与剪切应力的关系曲线和180℃时表观粘度与剪切速率的关系曲线。结果表明，分别在HDPE 5000S中加入0．125份氟碳弹性体和HDPE 6098中添加0．1份氟碳弹性体后，挤出物表面的光洁度得到改善。物料的粘度和粘流活化能均降低，显著提高了挤出的效率。     

PP／LDPE共混物熔体流动特性的研究

将两种熔融流动指数（ＭＦＩ）相差大的聚丙烯（ＰＰ）分别与一低密度聚乙烯（ＬＤＰＥ）进行共混，用熔体流动速率仪测定其流动特性。发现ＭＦＩ值高的ＰＰ，当共混比ＰＰ／ＬＤＰＥ为５０／５０时，其熔体流动速率（ＭＦＲ）为最大，本文对此作了初步的分析和讨论。     

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

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.     

LLDPE／LDPE共混物熔体挤出流动性的研究

应用毛细管流变仪，考察了挤出条件下ＬＬＤＰＥ／ＬＤＰＥ共混物熔体的流动性及其影响因素。结果表明，末端压力损失随着ＬＬＤＰＥ质量百分含量ＬＬ的增加而有所增大；熔体的剪切流动基本上服从指数律，其非牛顿性随着ＬＬ的改变而发生波动。