Dynamic and steady state viscoelastic behavior and morphology of MAPP treated PP/sisal composites

The present paper summarizes an experimental study on the molten viscoelastic behavior of PP/sisal composites under steady and dynamic state. Variations in melt viscosity and die swell of the composites with an increase in shear rate, fibre loading and coupling agent concentration have been investigated using capillary rheometer. It was observed that with the addition of sisal fibers and MAPP, the melt viscosity of the composites increased due to improved fiber–matrix interfacial adhesion. Further the dynamic viscoelastic behavior measured, employing parallel plate rheometer revealed an increase in the storage modulus (G′) indicating higher stiffness in case of fibre filled composites as compared with the virgin matrix. Time temperature superposition was applied to generate various viscoelastic master curves. The fiber–matrix morphology of the extrudates was also examined using scanning electron microscopy, which corroborated the findings of the rheological properties. The extrudate cross sections of the composites displayed uniform distribution of fibers within the PP matrix with lesser surface irregularities at high shear rates.     

凹凸棒土/ 聚丙烯/ 聚碳酸酯三元复合材料的力学性能及增韧机理

通过两步法熔融共混工艺制备了具有核壳特征凹凸棒土(AT) / 聚丙烯( PP) / 聚碳酸酯( PC) 三元复合材料。利用TEM 观察复合体系的亚微相态。使用万能材料拉力机、冲击实验仪等手段测试了复合材料的力学性能, 并对三元复合体系的增韧机理进行了探讨。结果表明, PC 连续相中形成了以AT 为核、PP 为壳的分散相。这种核2壳结构特征相包容粒子对PC 具有良好的增韧效果, 且强度较PP/ PC 二元共混体系有所提高。结合冲击断面形貌的SEM 分析, 认为AT/ PP/ PC 三元复合体系中的增韧机制主要是界面脱粘、空化作用和AT 对分散相的增强作用。      

表面改性对聚丙烯/纳米氢氧化镁复合材料性能的影响

研究了表面处理剂(钛酸酯和硅烷偶联剂)对聚丙烯/纳米氢氧化镁(MH)阻燃复合材料性能的影响。通过高压毛细管流变仪、LO I、力学测试、DSC和SEM对PP/纳米MH复合体系的结构与性能进行了研究。结果表明,所选偶联剂能有效地降低复合体系的表观黏度,改善体系的流动性。未改性的纳米MH对PP基体有异相成核作用;而表面改性剂能削弱填料对基体的异相成核作用。改性后的纳米MH粒子以独立形式均匀分散在基体中,PP与纳米MH界面的粘接力得到了加强,复合材料的拉伸性能和冲击强度有较大幅度的提高,阻燃性能也得到了改善。     

Morphology evolution of a liquid crystalline polymer in polycarbonate matrix enhanced by the addition of glass beads

Polycarbonate (PC)/liquid crystalline polymer (LCP)/glass bead (GB) composites filled with various volume fractions of GB were melt blended and characterized with rheological measurements and morphological observation. The study showed that the morphology evolution of LCP droplets from spheres and ellipsoids to long fibrils during the flow was enhanced by the addition of GB. Increasing shear rate also promoted the fibrillation of LCP. At the first glimpse, increasing the apparent shear rate significantly decreased the viscosity ratio (p) and increased the capillary number (Ca), which facilitated the deformation and fibrillation of LCP, while adding GB affected these parameters less. But a 5% incorporation of GB produced a more pronounced fibrillation effect than an 8-time increase of the apparent shear rate. Image analysis and model establishment were conducted to demonstrate that a high local shear, existing between the closely nearby rotating spheres, increased Ca effectively and promoted the LCP fibrillation even at lower apparent shear rates.     

云母/聚丙烯共混物熔体的拉伸流变性能

采用双料筒毛细管流变仪和Haul-off牵伸设备, 研究了云母(Mica)/聚丙烯(PP)共混物在拉伸流场中的流变性能。结果表明: Mica/PP共混物熔体拉伸流动属于拉伸变稀型, 随着云母含量的增加, 熔体的表观拉伸黏度逐渐增大。熔体的拉伸应力和表观拉伸黏度均随温度的升高而下降。随着拉伸应变速率的提高, 熔体的拉伸应力增大, 表观拉伸黏度减小, 熔体拉伸流动活化能呈下降趋势。云母微粒的加入使聚丙烯熔体的拉伸模量明显增大, 但随着拉伸速度的提高, 共混熔体的拉伸模量下降显著。为了提高Mica/PP共混物的纺丝稳定性, 应严格控制好拉伸速度和加工温度。     

铋粉对PP熔融流变性能及成纤性能的影响

采用熔融共混法制备铋/聚丙烯共混材料(Bi/PP),利用旋转流变仪对其熔融流变特性进行测试分析。再通过熔融纺丝法制备初生纤维,采用扫描电镜、单纤维强力仪等对初生纤维的结构及性能进行表征。研究表明:共混材料表现非牛顿流体特性;共混材料的表观黏度与温度及剪切速率呈负相关;相同温度下,随铋粉含量增加,共混物的表观黏度也相应上升,铋粉在PP基体中的分散性较好但团聚增多,初生纤维内部孔隙结构增多,力学性能有所降低。     

聚合物熔体在压力振动场中的流变行为

在熔体的流动过程中叠加脉动的压力振幅,研究了压力振动场对聚合物熔体的流动性能的影响。表观黏度随着压力振幅、振频的增加而明显下降,当压力振幅为29.7 M Pa时,高密度聚乙烯(HDPE)、聚丙烯(PP)和丙烯腈-丁二烯-苯乙烯共聚物(ABS)表观黏度最大的降低幅度分别为99%、99%和94.3%;随着振频的增加,黏度迅速下降,当振频大于0.70 H z之后,增加振频对黏度的影响不大,HDPE、PP和ABS表观黏度随振频增加而降低,幅度分别为48.9%、82.9%、66.7%,可见压力振动场能明显地改善聚合物熔体的流动行为。     

Melt flow properties of polypropylene/EPDM/glass bead ternary composites

The flow properties of polypropylene(PP)/ethylene-propylene-diene monomer copolymer(EPDM)/glass bead (GB) ternary composites were measured in a wide scope of shear rates by using a Rosand capillary rheometer. The apparent shear rates varied from 10 to 10⁵ s^–1, and the test temperature was from 210 to 240°C. The results showed that the flow behavior of the composite melts may be considered to approximate that of a power law fluid although the slope of the melt flow curves somewhat varied around shear rate of 700 s^{– 1}. The dependence of the melt shear viscosity on the test temperature was roughtly consistent with the Arrhenius expression. The melt shear viscosity increased dramatically with increasing the volume fraction (_g) of GB under lower shear rate level, white it increased gently with an addition of _g under higher shear rate level. Furthermore, there were certain effects of the filler surface treatment on the melt shear viscosity and its sentivity to the filler content at higher concentration of the beads at lower shear rates.     

Effects of recycling on the microstructure and the mechanical properties of isotactic polypropylene

Polypropylene (PP) was injection moulded several times to mimic the effect of recycling procedures. The influence of the recycling was studied by following changes in chemical structure, melt viscosity, crystallisation behaviour, and tensile and fracture properties. The main effect of recycling is the lowering of the melt viscosity, which is attributed to molecular weight decrease. Recycled PP exhibits greater crystallisation rate, higher crystallinity and equilibrium melting temperature than those measured for virgin PP. Elastic modulus and yield stress increase with the number of recycling steps. However, elongation at break and fracture toughness decrease.     

Morphological, rheological and mechanical characterization of polypropylene nanocomposite blends

In the present work, the effectiveness of styrene/ethylene-butylene/styrene rubbers grafted with maleic anhydride (MA) and a metallocene polyethylene (mPE) as toughening materials in binary and ternary blends with polypropylene and its nanocomposite as continuous phases was evaluated in terms of transmission electron microscopy (TEM), scanning electron microscopy (SEM), oscillatory shear flow and dynamic mechanical thermal analysis (DMA). The flexural modulus and heat distortion temperature values were determined as well. A metallocene polyethylene and a polyamide-6 were used as dispersed phases in these binary and ternary blends produced via melt blending in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in shear viscosity, melt elasticity, flexural or storage moduli and heat distortion temperature values were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene phase exhibited better toughness, lower shear viscosity, flexural modulus, and heat distortion temperature values than that prepared with polyamide-6 as dispersed phase. These results are related to the degree of clay dispersion in the PP and to the type of morphology developed in the different blends.     

PC/HBPS共混物的流变性能

通过熔融共混法制备了PC/HBPS共混物,研究了其流变特性。结果表明,此共混物属于假塑性流体,随着HBPS含量的增加,非牛顿指数增加;随着剪切速率的增加,表观黏度下降,但下降趋势较缓慢;随着温度的增加,表观黏度下降,但下降趋势很快;共混物的粘流活化能都比纯PC的粘流活化能高;随着HBPS含量的增加,表观黏度下降。     

PP毛细管微挤出的表面变形及熔体黏度

使用毛细管流变仪系统研究了微通道中润滑剂用量及润滑剂结构对聚丙烯微挤出的表面变形及熔体黏度的影响。结果表明:(1)随石蜡用量增加,聚丙烯表面变形/黏度逐渐减小;加入正戊烷与加入石蜡的情况相同;随硅油用量增加,聚丙烯的表面变形程度/黏度先减小后增加,当加入m(硅油)/m(PP)=2/100时达到最小值。(2)180℃时加入的润滑剂为m(润滑剂)/m(PP)=2/100,石蜡和正戊烷比硅油对聚丙烯微挤出的影响大,能更好地减小聚丙烯表面变形及熔体流动的黏度。     

氯化原位接枝改性CPVC流变行为的研究

采用氯化原位接枝技术制备了苯乙烯(St)、甲基丙烯酸甲酯(MMA)、丙烯酸-2-羟基乙酯(HEA)、丙烯酸-2-羟基丙酯(HPA)和丙烯酸丁酯(BA)等五种单体改性的CPVC.用毛细管流变仪测定了它们的流变行为.讨论了CPVC和改性CPVC的熔体粘度与剪切速率、剪切应力以及温度的关系.结果表明:CPVC和改性CPVC熔体均为假塑性流体,改性CPVC的假塑性增强,熔体表观粘度低于CPVC的熔体表观粘度.在190～205℃温度范围,两者的对数表观粘度与1/T呈非线性关系.CPVC-g-PMMA对温度和剪切应力更加敏感,CPVC-g-PHEA熔体的流动性明显高于CPVC及其他四种单体改性的CPVC.     

丁醛等离子体处理填料对填充聚烯烃熔体流变性的影响EI

用毛细管流变仪研究了经丁醛等离子体处理的云母粉填充高密度聚乙烯熔体(160℃)和聚丙烯熔体(180℃)的流变性。数据表明,处理削弱了非填充聚烯烃熔体流动的非牛顿性,熔体流动的牛顿指数随等离子体处理时间的延长而增大。处理降低了填充聚烯烃熔体在低切变速率下的表观粘度,提高了其在高切变速率下的表现粘度,发生转变的临界切变速率对填充聚乙烯和聚丙烯分别为150s^(-1)和50s^(-1)。扫描电镜观察熔体形态证实,处理对熔体粘度的复杂影响,是处理改善填料在熔体中的分散性和提高填料与基体界面结合力两者综合作用的结果。     

Online shear viscosity and microstructure of PP/nano-CaCO<Subscript>3</Subscript> composites produced by different mixing types

In this work, the online melt shear viscosity of polypropylene/nano-calcium carbonate composites was measured during the compounding to investigate the relationship between their rheological behavior and microstructure. Effects of dispersive mixing, distributive mixing, and chaotic mixing on online shear viscosity and microstructure of nanocomposites were analyzed. The results showed that the online shear viscosity of nanocomposites is lower than that of pure PP, when the nano-CaCO₃ content is lower than 5, 10, and 15 wt%, compounded by high dispersive mixing, dispersive/distributive mixing, and dispersive/distributive/chaotic mixing, respectively. This is greatly related with the dispersion of nanoparticles in PP matrix. It is deduced that there exists a critical percentage (Φ_cr) of the nano-CaCO₃ with size lower than 100 nm and a critical mean diameter (d _cr). The shear viscosity is lower than that of pure PP when the percentage is higher than the critical percentage and the mean diameter is lower than the critical diameter. In this work, the critical percentage is 80% and critical mean diameter is 60 nm.     

离子聚合物改性木粉/HDPE复合材料流变特性

为了提高木塑复合材料（WPC）的加工流动性能,利用离子聚合物改性WPC,通过HAAKE Minilab微量混合流变仪研究了离子聚合物改性木粉/高密度聚乙烯（HDPE）的毛细管流变特征。结果表明：添加与未添加离子聚合物的木粉/HDPE均为非牛顿流体中的假塑性流体,均呈现出“剪切变稀”的效应;随着钠离子聚合物含量的增加,改性木粉/HDPE的剪切应力和表观黏度均随着剪切速率的增大呈现降低的趋势,表明钠离子聚合物的加入可以显著改善聚合物熔体的流动特性;添加4wt%的钠离子聚合物和4wt%的锌离子聚合物的木粉/HDPE剪切应力和表观黏度均要低于添加4wt%的偶联剂马来酸酐接枝聚乙烯（MAH-g-PE）的WPC的值,表明与MAH-g-PE相比,离子聚合物更能够改善WPC的流动性能,减小熔体流动时HDPE与木粉之间的摩擦阻力;SEM分析表明,添加离子聚合物后HDPE塑料对木粉有很好的包覆效果,没有明显的界面缝隙,且在WPC断面上存在大量的毛刺纤维。     

振动共混对聚丙烯/聚碳酸酯流变性能的影响

在传统转矩流变仪上叠加机械振动制成了振动共混流变仪。实验证明，振动共混降低了70／30聚碳酸酯／聚丙烯共混物的粘度和储存模量，随着制备时的振动振幅和频率的提高，这种效果更加突出。但过大振幅振动中，低剪切与高剪切间的频繁更换，特别是明显的低剪切下相翻转转慢，导致形成了部分不稳定“双连续”相态，这时共混物粘度和模量反而比小振幅振动下制备的共混物的高。一个描述该体系表面张力／液滴半径之比与剪切速率关系的经验表达式较好地分析了流变参数与微观相形态之间的关系，说明了振动促使分散相粒子的破碎和两相的分散，确实影响共混物的相形态。振动共混对聚丙烯／聚碳酸酯流变性能的影响上海交通大学化学化工学院高分子材料研究所，上海　200240振动共混　聚丙烯　聚碳酸酯　流变性能　影响　转矩共混流变仪　相形态在传统转矩流变仪上叠加机械振动制成了振动共混流变仪。实验证明，振动共混降低了70／30聚碳酸酯／聚丙烯共混物的粘度和储存模量，随着制备时的振动振幅和频率的提高，这种效果更加突出。但过大振幅振动中，低剪切与高剪切间的频繁更换，特别是明显的低剪切下相翻转转慢，导致形成了部分不稳定“双连续”相态，这时共混物粘度和模量反而比小振幅振动下制备的共混物的高。一个描述该体系表面张力／液滴半径之比与剪切速率关系的经验表达式较好地分析了流变参数与微观相形态之间的关系，说明了振动促使分散相粒子的破碎和两相的分散，确实影响共混物的相形态。     

Effect of transcrystalline morphology on interfacial adhesion in cellulose/polypropylene composites

A study was conducted on the effect of cotton cellulose fibres on the crystallization behaviour of isotactic polypropylene (PP) from the melt and the resulting morphology. When the PP was allowed to crystallize isothermally at 131° C, the cotton fibres acted as nucleating agents and a transcrystalline phase was created around the fibres. Quench cooling of the melt prevented the occurrence of such a phase. Transcrystalline layers of different thicknesses were created by interrupting the isothermal crystallization at certain intervals and quenching the melt. The effect of these morphologies on interfacial shear stress transfer was investigated using the single-fibre fragmentation test. It was found that the transcrystalline morphology at the fibre/matrix interface improved the shear transfer considerably when a tensile load was applied in the fibre direction. One mechanism is proposed to be particularly responsible for this increase: slow cooling favours the kinetics of the approach of PP molecules, and hence interfacial adsorption, which yields an ordered transcrystalline PP interphase having a high density of intermolecular secondary bonds with the cellulose surface. An increase in the shear transfer efficiency with increasing thickness of the transcrystalline layer was also observed.     

Rheological behavior of short sisal fiber-reinforced polystyrene composites

The rheological behavior of short sisal fiber-reinforced polystyrene composites containing short sisal-fiber has been studied using an Instron capillary rheometer. The effect of fiber length, fiber loading, shear rate, shear stress and temperature on the rheological behavior of the composites was studied. Unlike other short fiber-reinforced thermoplastics at lower temperature the melt viscosity of polystyrene(PS)-sisal composites are lower than that at higher temperatures. At 180°C the viscosity of the composite is governed by wall-slip, which decreases the viscosity and at 190°C the viscosity is governed by fiber melt interaction that increases the viscosity. The morphology of the extrudate was studied using optical and electron microscopy.     

改性滑石粉填充聚丙烯/高密度聚乙烯复合体系的流变性能

研究了纯滑石粉和插层、偶联等方法改性处理的滑石粉填充聚丙烯／高密度聚乙烯(PP／HDPE)复合体系的流变性能,探讨了含量、温度、切变速率等因素对复合体系粘度特性的影响。结果表明,复合体系总体上有切力变稀的特性。体系表现切粘度随纯滑石粉和插层处理的有机滑石粉含量的升高而有不同程度的增加;随温度升高、切变速率升高而下降;理论上分析了复合体系中各组分之间的微观相作用。