临界状态下温度对挤出自增强PP片材结构性能的影响

采用楔形收敛流道挤出口模，临界挤出状态下获得了聚丙烯自增强片材。研究结果表明：PP自增强片材在此状态下挤出成型其纵、横向拉伸强度均有明显上升，其结晶形态为串晶互锁结构，而结晶的晶型与常规成型的PP片材相比则没有变化。     

聚乙烯在复合应力场中临界状态挤出成型的研究

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。     

聚乙烯在复合应力场中固态挤出成型的研究

采用具有复合应务场的挤出口模，固态挤出HDPE以获得双向自增强片材。研究表明，所得到的自境强片材的纵横向强度都有明显提高，微观测试表明，在试样内部生成大量百列有序、取向程度很高的微纤结构，这些微纤结构赋予材料极高的强度。     

自增强HDPE棒材的制备与结构形态

采用普通挤出设备,通过流动诱导结晶的方法制备了自增强HDPE棒材(直径5mm)。分析了自增强棒材的制备过程,并采用SEM观察与DSC分析,对其结构形态进行了研究。结果表明,流动条件、挤出压力与熔体温度是由聚合物熔体连续挤出方法成型自增强体型制品的重要影响因素;自增强棒材内形成了具有较高耐热性能的微纤结构,尤其是较高挤出压力(如60MPa)下制备的棒材。     

超高摩尔质量聚乙烯挤出成型技术及发展

引入了熔融理论、形态控制和自增强理论,详细地总结了超高摩尔质量聚乙烯的挤出成型方法,包括熔融挤出、近熔点挤出、固态挤出.发掘超高摩尔质量聚乙烯加工难题的求解历程与规律;并展望了超高摩尔质量聚乙烯连续挤压研究的历史趋势.     

超高相对分子质量聚乙烯固相挤出过程研究

采用一种新型超高相对分子质量聚乙烯成型技术—固相挤出成型。采用扫描电子显微镜观察了制品成型前后内部微观结构变化;采用差示扫描量热分析,研究了不同挤出温度与口模拉伸比对挤出制品热性能的影响。结果表明,相对熔融挤出成型,固相挤出成型制品光滑、透明、密度较大;制品内部产生大量的微纤结构,结晶度提高,分子链取向增强,拉伸强度提高了2.7～4.5倍,拉伸弹性模量提高了42倍;另外,熔点上升了3～5 ℃、熔融焓及结晶度分别提高了8~10个百分点。     

复合拉伸力场挤出HDPE片材的力学性能

利用收敛-发散口模挤出制备了高密度聚乙烯(HDPE)片材,研究了挤出温度对片材力学性能的影响.结果表明:在复合拉伸力场作用下,熔态挤出(140℃)片材的纵、横向屈服拉伸强度分别为28.3,27.0MPa,固态挤出(112℃)片材的纵、横向屈服拉伸强度分别为181.4,51.3 MPa,纵、横向屈服拉伸强度分别增加了540%和90%.与固态挤出相比,熔态挤出片材纵、横向断裂伸长率分别增加了760%和124%.扫描电子显微镜显示,熔态挤出HDPE片材由球晶结构构成;固态挤出片材由大量垂直于挤出方向规整排列的片晶组成,并有少量的串晶生成,片晶厚度增加,这种结构有利于改善制品的双向力学性能.     

两种加工方式炭黑在HDPE中的分布和抗静电性能研究

采用管材挤出和片材模压两种成型加工方式,制备了炭黑/高密度聚乙烯(HDPE)管材和炭黑/HDPE片材样品,测试了样品不同层面(表面层和中心层)的体积电阻率、摩尔质量和摩尔质量分布,并对样品不同层面进行了SEM观察。结果表明,管材挤出加工方式使HDPE摩尔质量较小组分向管壁富集,炭黑优先分布在管材表面层;片材模压成型中,HDPE摩尔质量不会发生富集分级效应。     

挤出比对固态挤出成型自增强木塑复合材料性能的影响

采用稳定、连续的固态挤出成型装置制备了高度取向的自增强木塑复合材料棒材,考察了其性能及结构。力学性能测试结果表明,随着挤出比的增大,复合材料的弯曲弹性模量从2400 MPa提高到5800 MPa,拉伸强度从20.7 MPa提高到81.6 MPa。扫描电子显微镜观察发现,复合材料内部形成了大量沿挤出方向有序排列的微纤结构。差示扫描量热分析结果表明,与常规挤出的复合材料相比,自增强复合材料的熔融峰向高温方向漂移,结晶度随挤出比的增大而明显上升。     

聚乙烯热收缩片材挤出拉伸一次成型工艺研究

利用高分子材料“取向—解取向”原理,实现了聚乙烯（PE）片材挤出拉伸一次成型,并探讨了通过三辊压光机对聚乙烯片材进行拉伸定型的方法,研究了辊筒温度、拉伸率、拉伸距离和拉伸速度对PE片材收缩率和截面厚度的影响。结果表明,拉伸率、拉伸距离对PE片材收缩率影响较大,提高拉伸率,降低拉伸距离均可提高片材收缩率,辊筒温度和拉伸速度对收缩率影响较小,提高辊筒温度、拉伸速度,能小幅增加收缩率;在辊筒温度60 ℃、拉伸率45 %、辊筒距离1.5 mm、拉伸速度2.4 m/min情况下,PE片材收缩率可达78 %（10 min,120 ℃）。     

新型PVC片材的力学性能和阻隔性能的研究

采用微层挤出技术制备了微层PVC片材,采用涂覆法制备了多层PVC/PVA复合片材,对其力学性能和阻隔性能进行了研究。结果表明:①多层结构有利于提高PVC/PVA复合片材的阻隔性能,涂覆PVA溶液增大了片材的拉伸强度。②微层PVC片材的分子链发生取向,沿挤出方向的拉伸强度明显高于垂直挤出方向;微层PVC片材的层数越多,取向作用越强,越有利于阻隔性能的提高。     

聚碳酸酯片材的挤出成型与应用

关于聚碳酸酯片材的挤出成型,诸如对树脂的要求、螺杆结构特性、机头类型、压延方法等作了详细的叙述,同时还论述了国内外片材挤出成型的应用领域。     

The modelling of large deformations of pre-oriented polyethylene

High temperature reversion tests have revealed a state of pre-existing molecular orientation in extruded polyethylene sheet. This state is related to differences in stress-deformation behaviour when specimens of the sheet are stretched along different angles with respect to the extrusion direction. An established large deformation, rate-dependent constitutive equation has been developed to model this material, by incorporating the pre-orientation by the addition of a strained Gaussian network. The level of pre-orientation is deduced from the dimensional changes on shrinkage. The constitutive equation is incorporated into the finite element package abaqus, and the shapes and drawing forces of tensile specimens extended at various angles to the extrusion direction are modelled.     

PVC卷帘门窗型材挤出技术

对PVC卷帘门窗型材挤出技术进行了研究。介绍了PVC卷帘门窗型材的配方设计要点、产品性能、生产工艺流程、重点工艺参数控制和挤出成型设备的性能特点。     

硬质PVC门窗异型材的高速挤出

简要介绍了硬质ＰＶＣ门窗异型材高速挤出技术的国内外现状，并对配方、工艺、挤出机、畏机及模具等影响高速挤出的要素作了一定的探讨。     

Thermoforming of liquid crystalline polymer sheets

Liquid crystalline polymer (LCP) extruded sheets were further processed by the conventional thermoforming method. The available processing temperature range was defined through the structural, thermal, and elevated temperature mechanical characterization of the extruded sheet. This temperature range was found for LCP to be quite narrow, in the proximity of the crystal-mesophase transition. The structural changes imposed on the LCP sheet during forming and its thermal stability were investigated using wide angle X-ray diffraction, mainly for the determination of the chain orientation distribution, DSC, and dynamic mechanical analysis. Thermoforming onto a symmetrical male mold was found to enhance the orientation in the extrusion machine direction and even change the preferred orientation in the extrusion transverse direction to orientation along the thermoforming direction. Annealing at the thermoforming temperature range results in a more ordered and thermally stable structure accompanied by just a slight orientation loss.     

异型材高速挤出关键技术的探讨

对挤出机、辅机、模具、配方等影响异型材高速挤出的关键技术作了一定的探讨。     

Structural,mechanical, and thermal properties of extruded sheets of a liquid crystalline copolyester

Structural, Mechanical, and thermal properties of extruded sheets of a liquid crystalline copolyester containing p-hydroxybenzoic acid and 2-hydroxynaphthoic acid were investigated using X-ray diffraction measurements, differential scanning calorimetry, rheovibron measurements, and scanning electron microscopic observation. The extruded sheets of the thermotropic copolyester are composed of layered structures containing skin and core layers. A skin layer comprises fine fibrils oriented almost parallel to the extrusion direction. A core layer contains poorly oriented thicker fibrils or platelike structures. The orientation function of sheets and their tensile dynamic modulus parallel to the extrusion direction increase with increasing draw-down ratio of the sheet. Annealing of the sheet caused the increases in the temperature and the heat of crystal—mesophase transition, the heat-resistance to the mechanical tensiles properties, and the inherent viscosity of the polymer. The effect of annealing on the structural properties of the extruded sheet was discussed. © 1993 John Wiley & Sons, Inc.     

PVC结皮低发泡宽幅门板挤出成型技术

介绍了PVC结皮低发泡宽幅门板的挤出成型技术。     

Mineral additive aids polyolefin production

Heritage Plastics, a privately-owned US-based company, is offering a new mineral additive range, Minapol^™, designed to improve the productivity, physical properties and profitability in polyolefin moulding and extrusion applications. The pelletized mineral concentrates can be used in applications such as polyethylene film extrusion, polyethylene blow moulding, polypropylene injection moulding and polyethylene sheet extrusion and thermoforming.Visit www.addcomp.com for the latest additives and compounding industry news