LLDPE在挤出加工中的弹性现象研究

使用Brabender PLD 651 挤塑仪配不同长径比、不同材质的毛细管流变口模,测定了几种LLDPE在一定温度下的挤出物胀大和熔体破裂的临界剪切应力,同时用Instron 3211毛细管流变仪做了对比实验。结果表明,毛细管口模的长径比达到一定值后,挤出物胀大随剪切速率的变化关系与长径比无关。这一长径比值又随毛细管口模材质而有所不同。对于一定长径比的毛细管流变口模,熔体破裂的临界剪切应力与挤出温度、口模材质无关。通过实验可知,采用提高口模温度、增加口模长径比或改变口模材质均能推迟熔体破裂现象的发生,从而提高了挤出加工的生产量。     

高填充性聚丙烯基纳米复合材料挤出胀大行为研究

使用毛细管流变仪考察了3种高填充聚丙烯（PP）纳米复合材料的挤出胀大行为,研究了口模温度、剪切速率、熔体压力、纳米粒子填充比例和纳米粒子形貌对PP纳米复合材料熔体挤出胀大比的影响。结果表明,3种PP纳米复合体系熔体的挤出胀大比均随口模温度的增加而减小,且大致呈线性关系;随着剪切速率的增大而增加,且随着填料填充比例的增加有减小的趋势;随着熔体压力的增大而增加,并且随着熔体压力的增加,其挤出胀大比随填料填充比例的增加而减小的幅度下降;3种颗粒形貌纳米粒子填充体系中,在相同的体积分数和温度下,片状结晶纳米氢氧化镁［Mg（OH）2］填充体系熔体挤出胀大比最小,球状纳米碳酸钙（CaCO3）填充体系熔体挤出胀大比最大,棒状粒子埃洛石纳米管（HNTs）填充体系熔体挤出胀大比介于两者之间。     

挤出条件对PP/硅藻土口模膨胀行为影响

应用熔体流动速率仪测定了3种粒径硅藻土(体积分数为10%)填充聚丙烯(PP)复合材料的口模膨胀比(B),考察口模直径和挤出工艺条件对复合体系口模膨胀行为的影响.结果表明.复合体系的B随着剪切应力和剪切速率的增加而非线性增大,且随着温度的上升而线性下降;当载荷及温度一定时,B随着口模直径增加呈非线性提高,随着口模长径比增加呈非线性减小.     

聚甲醛共混物及复合材料挤出胀大行为的研究

采用共混方法制备了聚甲醛(POM)/高密度聚乙烯(HDPE)共混物和POM/HDPE/纳米碳酸钙(nano-CaCO3)复合材料,在温度(T)为170~220℃和载荷(F)为1.2~12.5 kg的条件下,应用流动速率仪考察了温度、载荷及HDPE用量(φ)等对共混物和复合材料熔体挤出胀大行为的影响。结果表明,复合材料的挤出胀大比(B)随着温度的升高而近似线性下降;挤出胀大比随着载荷的增加而非线性提高;挤出胀大比随着HDPE用量的增加而提高,两者间呈非线性关系。     

回收料制备人造草丝熔体的流变性能研究

采用聚合物动态流变测试仪研究了含回收料的人造草丝熔体的流变性能,探讨了回收料用量、温度、口模长径比对熔体表观黏度和挤出胀大比的影响。结果表明,人造草丝熔体属于假塑性熔体,其表观黏度随剪切速率和回收料用量的增加而降低。在剪切速率500s-1时,回收料用量越低,熔体的表观黏度降低越明显;剪切速率1800s-1时,熔体的表观黏度变化平缓且较为接近。对于100%回收料草丝熔体,其表观黏度随温度的升高和口模长径比的减小而降低;挤出胀大比则随温度的升高和口模长径比的增大而降低。     

EPDM/PP热塑性弹性体的制备及其流变特性

以聚丙烯(PP)和三元乙丙橡胶(EPDM)等为原料,采用完全动态硫化共混技术制备EPDM/PP热塑性弹性体(TPV),使用毛细管流变仪对TPV熔体的流变特性进行测试。分别研究了剪切速率、挤出温度对黏度、剪切应力和挤出胀大比的影响,以及不同条件下熔体流过毛细管口模时流速对压力降的影响。结果表明,TPV熔体是假塑性流体,其剪切应力随剪切速率增大而增大,随挤出温度的升高而降低;黏度随剪切速率和挤出温度的增大而降低;挤出胀大比则随剪切速率和挤出温度的增大而增大;毛细管口模的压力降也随流速和毛细管口模长度的增大而增大。     

聚合物熔体在任意长径比圆锥口模的挤出胀大唯象研究

深入讨论了聚合物熔体在不同长径比、不同角度圆锥口模的挤出胀大现象及机理。对口模长径比较小的挤出胀大,由于熔体入口拉伸弹性变形来不及松弛,产生较大的挤出胀大;对长径比较大的口模,熔体在平直流道内停留时间较长,入口弹性形变逐渐松弛,这时主要是流动剪切应变引起的弹性变形,产生较弱的挤出胀大,比长径比小的挤出胀大来得小,并且聚合物熔体的挤出胀大随着长径比的增大而趋向一恒定值。结果还表明:聚合物熔体在圆锥口模的挤出胀大受到挤出口模入口角影响。当L/D较小时,挤出胀大与口模入口角有关;当L/D较大时,口模入口角对挤出胀大影响较小。     

ABS/HGB与PP/HGB挤出流动中弹性性质的研究

应用XNR-400A型熔体流动速率测定仪,比较了ABS/HGB及PP/HGB复合材料的弹性性质。结果表明:ABS/TK 70及PP/TK 70体系熔体的挤出胀大比B均随着剪切应力τw的增大而增大。对ABS/TK 70体系,当τw>120 kPa时,其熔体的挤出胀大比增幅明显增大。ABS/TK 70体系的挤出胀大比随着温度的上升而增大;而PP/TK 70体系的挤出胀大比随着温度的上升而减小。相同剪切应力下ABS/TK 70体系挤出胀大比随着HGB的体积分数增加而增大;而PP/TK 70体系的挤出胀大比随着HGB的体积分数增加而减小。     

POE/纳米碳酸钙复合材料的流变性能研究

试验研究聚烯烃弹性体（POE）／纳米碳酸钙复合材料的流变性能。结果表明，随着剪切速率的增大，复合材料的剪切粘度和非牛顿指数逐渐减小，挤出胀大比和零口型入口压力降增大，挤出物外观变差；随着纳米碳酸钙用量的增大，复合材料的剪切粘度对剪切速率的敏感性下降，非牛顿指数增大，挤出胀大比总体上呈下降趋势，零口型入口压力降变化较小，在相对低的剪切速率下，挤出物外观得到改善。     

内胎胶料的挤出胀大行为

用Monsanto毛细管流变仪,在100～130 ℃及流动速率1.02～254.00 mm/min的条件下,考察了内胎胶料的挤出胀大行为.结果表明,在一定温度下,挤出胀大比(B)随着壁面表观剪切速率的增加而增大,两者之间呈非线性函数关系,而B与壁面剪切应力则大致上呈线性函数关系;当表观剪切速率一定时,B随着温度的升高而非线性下降.在一定的挤出条件下,B随着流道直径比的增加而有所增大,两者之间近似呈线性函数关系.     

Preparation and properties of HDPE/CaCO3/OMMT ternary nanocomposite

A series of binary composites based on HDPE (high density polyethylene) and nanoinorganic particles such as nano‐CaCO₃ and OMMT (organic montmorillonite) were prepared. Their properties including tensile, impact strength, and some thermal properties were tested. The results showed that binary composite has partial improvement in mechanical properties compared with pure HDPE. A ternary composite nano‐CaCO₃/OMMT/HDPE was prepared and characterized. It was found that the mechanical and thermodynamic properties of this ternary composite have been enhanced greatly compared with both pure HDPE and binary composites. The tensile strength, Young's modulus, flexural strength, elastic modulus, and impact strength of nano‐CaCO₃/OMMT/HDPE were increased 124.6%, 302.7%, 73.86%, 58.97%, and 27.25%, respectively. The DMA test results showed that the mechanical properties of ternary composite were increased because of the limitation on the movement of HDPE due to inorganic particles. The synergistic effect introduced by nanoparticles may play an important role in all these processes. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

HDPE/蒙脱土纳米复合材料流变性能的研究

采用两种不同口模厚度的窄缝流变仪研究了高密度聚乙烯（HDPE）/蒙脱土（MMT）纳米复合材料及其基体HDPE的流变性能，测试了不同温度下熔体的流变曲线，非牛顿指数；分析了温度，剪切应力对剪切粘度的影响在所研究的剪切应力。剪切速率及温度范围内，两者均属于假塑性流体，呈现剪切变稀行为。在较高温度和较低剪切速率下，HDPE/MMT纳米复合材料的熔体表现为类牛顿性流体行为。与HDPE相比，HDPE/MMT纳米复合材料熔体具有较高的温度敏感性。     

有机MMT对高密度聚乙烯改性的研究

采用十二烷基三甲基氯化铵、十六烷基三甲基氯化铵、十六烷基三甲基溴化铵和双十八烷基二甲基氯化铵4种阳离子表面活性剂对钠基蒙脱土(MMT)进行有机化处理,制备了有机MMT(OMMT)。将OMMT与高密度聚乙烯(HDPE)进行熔融插层制备了HDPE／OMMT纳米复合材料,研究了OMMT的层间距同季铵盐烷基链的关系。结果表明,OMMT的层间距随烷基链长度的增加而增大;随着OMMT含量的增加,HDPE／OMMT纳米复合材料的断裂伸长率和拉伸强度降低,弯曲弹性模量增加,弯曲强度出现极大值,使该纳米复合材料的力学性能得到了一定的改善。     

废旧PE-HD/OMMT纳米复合材料热氧老化性能和燃烧性能研究

以废旧高密度聚乙烯（PE-HD）和蒙脱土（MMT）为原料,采用熔融插层法制备纳米复合材料,考查制备工艺对该材料热氧老化性能和燃烧性能的影响。结果表明,PE-HD复合MMT或有机蒙脱土（OMMT）后,抗热氧老化性能显著降低,阻燃性能增强;十六烷基三甲基溴化铵（CTAB）、OMMT、马来酸酐（MAH）和过氧化二异丙苯（DCP）加入量分别增加时,PE-HD/OMMT纳米复合材料的抗热氧老化性能无显著变化,阻燃性能呈现先增强后降低或稳定的趋势;当CTAB加入量为1 %、OMMT加入量为3 %、MAH和DCP加入量为1.5 %时,PE-HD/OMMT纳米复合材料的极限氧指数达到19.4 %,阻燃性能最好。     

Influence of nano‐organomontmorillonite on the viscoelasticity of the poly(trimethylene terephthalate)/glass fiber/organomontmorillonite hybrid nanocomposites materials

The influences of organically modified montmorillonite (OMMT) on the viscoelasticity of poly(trimethylene terephthalate)/glass fiber/OMMT (PTT/GF/OMMT) hybrid nanocomposite materials at liquid, elastic and glassy states, respectively, were investigated by using the rotational rheometer and dynamic mechanical analyzer (DMA). The viscoelasticity results suggest that OMMT has many important influences on the structure, modulus and toughness of the hybrid nanocomposite materials. At melton state, the shear‐thinning phenomena of the hybrid composite melts become remarkable with increasing OMMT content. At low frequency, the shear storage modulus (G′) and shear loss modulus (G″) of the melts increase with increasing OMMT content. The melt's elastic response increases by OMMT, and OMMT improves the creep resistance of the melts; in addition, the stress relaxation of the hybrid composite melts become slow with increasing OMMT content, and the stress leavings becomes much higher with increasing OMMT content. At glassy state, the storage modulus of the hybrid nanocomposites increases with increasing OMMT content, while the materials' loss modulus increases first and then decreases with increasing OMMT content; therefore, OMMT nanosheets have reinforcement effect on the composites, and it also has definite toughening effect on the hybrid composite when the OMMT content is no >2 wt%. At rubbery state, the hybrid composites show lower decreasing storage modulus but have lower cold‐crystallization ability than that of pure PTT and PTT/GF composite. POLYM. COMPOS., 35:795–805, 2014. © 2013 Society of Plastics Engineers     

季铵盐插层剂对高密度聚乙烯性能的影响

采用季铵盐阳离子作为插层剂与钠基蒙脱土层间的无机阳离子进行离子交换,制备系列有机化蒙脱土,利用红外光谱对蒙脱土的结构进行表征,结果表明,插层剂已进入蒙脱土的层间.同时将有机化蒙脱土与HDPE进行熔融插层,制备了纳米聚乙烯复合材料,研究了插层剂对其部分力学性能的影响.     

Linear low-density polyethylene/high-density polyethylene blends: Effect of high-density polyethylene content on die swell and flow instability

This work aimed to evaluate the effect of high-density polyethylene (HDPE) content and of shear rate on the die swell and flow instability of linear low-density polyethylene (LLDPE)/HDPE blends. The results showed that the die swell of the LLDPE/HDPE blends increased with the increase in the shear rate. At high shear rates, the increase in the HDPE content led to an increase in the die swell of LLDPE/HDPE blends. The surface morphology analysis of the extrudates by optical and scanning electron microscopy revealed the presence of sharkskin and stick–slip flow instabilities in LLDPE and LLDPE/HDPE blends at the shear rates investigated. These instabilities were attenuated with the addition of HDPE and almost disappeared in the LLDPE/HDPE blend containing 50 wt% of HDPE.     

聚合物/有机蒙脱土纳米复合材料分散形态的制备影响因素

选择不同种类的有机蒙脱土（OMMT）和不同聚合物种类,采用不同加工条件和工艺,利用机械混炼法或挤出法制备出了不同亚微观形态的聚合物/有机蒙脱土纳米复合材料。首先通过研究具有不同的改性层间距的OMMT,发现改性后层间距的增大有利于聚合物分子的插层及蒙脱土片层的剥离,有利于制备剥离型纳米复合材料,并用示意图简要说明了形成过程;而同一种OMMT在具有不同分子结构的聚合物中,利用实例（高密度、低密度、线型低密度聚乙烯）以及简易示意图说明了聚合物分子链结构对于制备的纳米复合材料的亚微观形态的影响机理。在加工工艺条件中,加工过程中的剪切力大小是主要影响因素,通过以挤出法和机械混炼法制备的PP/OMMT与EPDM/OMMT纳米复合材料的TEM结果对比分析,说明剪切力的增大有利于蒙脱土片层的分离,更倾向于制备出剥离型纳米复合材料。     

In situ synthesis and characterization of polypropylene/polyvinyl acetate‐organophilic montmorillonite nanocomposite

A novel polymer‐nanoclay hybrid nanocomposite based on polyvinyl acetate (PVAc)‐organophilic montmorillonite (OMMT) has been reported via an in situ intercalated polymerization technique. The hybrid material was synthesized by one‐step emulsion polymerization of vinyl acetate in the presence of OMMT using polyvinyl alcohol as the stabilizing agent. The intercalated polymerization was characterized by X‐ray diffraction (XRD). The XRD patterns show that the interlayer spacing of OMMT after polymerization increased from 2.64 to 3.78 nm, indicating that the large macromolecular chain of PVAc was formed in the OMMT interlayer space. The Fourier transform infrared spectrum showed the characteristic absorption of PVAc in the OMMT particles separated from the nanocomposite, and the position of peaks shifted to high wave numbers. This showed that there was an interaction between PVAc and OMMT nanoparticles. A two‐fold blend composed of PVAc‐nano‐OMMT/PP was prepared by the melt‐blending technique. XRD and transmission electron microscopy images of the PVAc‐nano‐OMMT/PP composite further confirmed the formation of a partially delaminated nanocomposite structure. Thermogravimetry results showed that the thermal stability of PVAc‐nano‐OMMT/PP was greater than that of either polypropylene (PP) or Nano‐OMMT/PP blend. PVAc‐nano‐OMMT/PP had better toughness, as the mass fraction of OMMT was 5 wt %. The flame retardancy of PP, Nano‐OMMT/PP, and PVAc‐nano‐OMMT/PP composites was also studied. According to the limiting oxygen index (LOI) data and Cone calorimeter test, the addition of PVAc‐OMMT resulted in higher LOI and lower heat release rate, effective heat of combustion, smoke release course, and better flame retardancy and barrier properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012