Melt Rheological Properties of Silver-Powder-Filled Polypropylene Composites

The melt rheological properties of titanate coupling-agent-treated particulate silver powder (varying from 0 to 5.6 vol% of Ag) were investigated. The effect of filler concentration on shear stress, shear rate, melt viscosity, and melt elasticity parameters were determined by using a piston-type capillary rheometer. The study shows that the materials follow a power law in viscous behavior over the entire range of shear rates and temperatures investigated. The melt viscosity decreases with filler content up to 4.1% and increases with a further increase in filler content. Interestingly, the viscosity of the composition was lower than that of unfilled polypropylene. The melt elasticity decreases with an increase in Ag content in the composites up to 4.1%; beyond that, it increases. The effect of temperature on the viscoelastic properties of filled polypropylene was also investigated.     

PVC通信电缆绝缘料流变行为的研究

本文采用毛细管流变仪对聚氯乙烯电缆料的加工流变性能进行了研究，分析并讨论了影响ＰＶＣ流变性能的各种因素。结果表明：在试验温度下，增塑ＰＶＣ的剪切应力均随剪切速率的增加而增大，但当剪切速率增加到一定程度后，剪切速率对剪切应力的影响变小；改性剂ＰＭ－１的加入可以大大降低在相同剪切速率下的剪切应力。改性剂ＰＭ－１使电缆料的剪切敏感性减小，牛顿性增强。虽然ＰＭ－１不能改变临界剪切应力值，但却使当临界剪切应力相应的熔体粘度减小，即临界剪切速率增大，这在实际生产过程中是十分有用的，即可以提高挤出速度而不致于产生熔体破裂。分子量减小，熔体表观粘度明显减小。熔体表观粘度随温度的升高而逐渐减小。     

Melt rheological properties of nickel powder filled polypropylene composites

The melt rheological properties of nickel powder filled polypropylene composites were investigated. The effect of filler concentration on shear stress-shear rate data, melt viscosity and melt elasticity parameters were determined by using a capillary rheometer. The study shows that the materials follow a power law in viscous behavior over the entire range of shear rates investigated and that the viscosity increases and elasticity decreases as filler concentration is increased up to a critical value. However, beyond the critical filler content melt viscosity decreases while melt elasticity increases. The effect of temperature on the viscoelastic properties of filled polypropylene was also investigated.     

Melt flow behavior of blends from poly(vinyl chloride) and epoxidized natural rubber

Blends from poly(vinyl chloride) (PVC) and epoxidized natural rubber (ENR) were prepared in a Brabender plasticorder by the melt blending technique. The melt flow behavior of these blends with respect to blend ratio and temperature has been examined using a melt flow indexer and capillary rheometer. ENR decreases the Brabender torque, increases the melt flow index (MFI), and decreases the melt viscosity of PVC in the blends. Arrhenius plots were used to study the effect of temperature on melt flow index (MFI) and viscosity. Moreover, the flow behavior index (n′) obtained from capillary rheometer data was found to be dependent on temperature and blend ratio.     

双螺杆挤出机螺杆组合对聚丙烯/纳米CaCO3复合材料在线流变性能的影响

采用啮合型同向旋转双螺杆挤出机制备聚丙烯(PP)/纳米碳酸钙(nano-CaCO3)复合材料,制备过程中在双螺杆挤出机末端连接Haake在线流变仪进行在线流变性能测试。研究了两种螺杆组合结构、纳米CaCO3含量对PP/纳米CaCO3复合材料在线剪切黏度的影响,比较了在不同聚合物加工流场下PP/纳米CaCO3复合材料的在线流变性能。结果表明,引入分布混炼有利于降低复合材料的剪切黏度,复合材料剪切黏度随纳米粒子的加入先呈下降趋势,当达到某一含量后,再提高纳米粒子含量会使黏度提高。     

Rheological behavior and mechanical properties of PVC/MAP‐POSS nanocomposites

The polyhedral oligomeric silsesquioxanes which contains methylacryloylpropyl groups (MAP‐POSS) was synthesized. The MAP‐POSS/PVC nanocomposites were prepared. The influences of composition, shear rate' shear stress on melting rheological behavior of MAP‐POSS/PVC nanocomposites were discussed. The dynamic mechanical properties, mechanical properties, and morphology were determined by DMA, material tester and SEM, respectively. The result shows that the plastic times decreases and melt viscosity increases with increasing MAP‐POSS content. The n has a maximal value at 5 wt% MAP‐POSS content, but have best impact strength at 3%. MAP‐POSS can use as process aid and impact aid of PVC at appropriate contents. POLYM. COMPOS., 31:1822–1827, 2010. © 2010 Society of Plastics Engineers.     

The significance of capillary rheology testing temperature for predicting PVC extrudability

A rheological investigation of the saturated fatty acids as lubricants for PVC was made in a Sieglaff-McKelvey rheometer over a wide temperature range. Results reveal that with an increase in carbon chain, fatty acids became more effective in reducing the melt viscosity of PVC. It was also discovered that the maximum viscosity variation due to these materials was observed at 350°F. At test temperatures of 400°F and above, no major viscosity differences were observed. Furthermore, the changes in the melt viscosity were more pronounced at shear rates less than 200 sec^?1. The usefulness of the measured viscosity variations at the critical test temperature of 350°F was shown by extrusion. An excellent correlation between the apparent melt viscosity and extrusion melt temperature was found. The criticalness of the test temperature in assessing the effect of lubricants on PVC flow is discussed.     

硬质PVC挤出发泡材料的塑化性能研究

采用Haake转矩流变仪测定了挤出发泡PVC混合料的恒温、升温熔融塑化性能，结果表明：随着PVC树脂聚合度增加，塑化时间和加工转矩增加；随着ACR加工助剂用量和分子质量的增加，塑化时间缩短，转矩增加；ACR抗冲改性剂具有类似ACR加工助剂的塑化改良行为；添加填充剂碳酸钙促进PVC熔融塑化；ADC发泡剂可延缓PVC混合料的塑化速率、提高熔体粘度，添加发泡剂NaHCO3将大大延缓混合料的塑化速率。     

CPE对发泡PVC/木粉复合材料熔体流变性能的影响

采用旋转流变仪,应用小振幅流变测试法研究了抗冲击改性剂氯化聚乙烯（CPE）对发泡聚氯乙烯(PVC)/木粉复合材料熔体流变性能的影响。实验结果表明：角频率（ω）在0.1～100 rad/s之间时,随ω的增大,发泡PVC/木粉复合材料熔体的复数黏度（η*）降低,表现出"剪切变稀"效应,熔体的储能模量（G′）和损耗模量（G〞）随ω的增大而增加;加入5份CPE时,复合材料熔体的G〞明显提高,G′变化幅度较小,熔体的η*增加,促进了PVC的凝胶化;继续增加CPE的用量到10份,发泡PVC/木粉复合材料熔体的G〞和G′降低,η*也降低;随着ω的增加,加入CPE使样品的损耗角正切明显降低,熔体的弹性响应增加。加入10份CPE时,发泡PVC/木粉复合材料的冲击强度提高20 ％。     

Calcium stearate–stearic acid as lubricants for rigid poly(vinyl chloride) (PVC). Capillary rheometer measurements and extrusion properties

Capillary rheometer measurements show that stearic acid can be characterized as a normal lubricant. If the content of stearic acid is increased in rigid PVC formulations, the melt viscosity will decrease. This leads to a corresponding increase of shear rate and volumetric flow rate. The influence of calcium stearate is opposite to the normal characteristic of a lubricant. Increasing amounts of calcium stearate lead to an increased melt viscosity and a decreased shear rate and volumetric flow rate. In the extrusion of rigid PVC, the apparent “lubricating” effect of calcium stearate is probably due to the increased friction with resulting heat evolution and higher mass temperature, leading to a decreased viscosity of the plastic melt. This is in agreement with the results of the extrusion experiments. Both mass temperature and power consumption decrease when stearic acid is added and increase when calcium stearate is added to the formulation.     

Melt rheology of semirigid PVC compounds

This paper describes a statistical experiment on the melt behavior of semirigid PVC compounds using a capillary rheometer. Three formulating variables, viz., PVC resin inherent viscosity, internal lubricant concentration, and external lubricant concentration, and two processing variables, viz., shear rate and temperature, were examined. The dependent variables tested were melt viscosity and critical shear rate. The regression equations relating the formulating variables with dependent variables were obtained at various temperatures. Melt distortion free formulations can thus be determined from the contour plots of the dependent variables. Depending on formulation and processing conditions, a discontinuity in the flow curves is observed Melt irregularity of extrudates was observed to occur not only at very high shear rates but also at very low shear rates and at the discontinuity of flow curve.     

聚烯烃弹性体的结构与熔体黏度关系的研究

采用凝胶渗透色谱仪和核磁共振仪表征了一系列聚烯烃弹性体（POE）样品的结构,并用毛细管流变仪考察了其挤出稳定性、剪切依赖性和黏温依赖性,分析了熔体黏度与聚合物结构的关系。结果表明,随着剪切速率的提高,高相对分子质量的POE熔体易出现不稳定流动,挤出物表面发生畸变;相对分子质量越大、温度越低、共聚单体含越高,发生不稳定流动的临界剪切速率c越低;POE的剪切黏度很大程度上受相对分子质量的影响,与共聚单体的含量关系不大;不同相对分子质量及组成的POE熔体的黏流活化能相近,约为2.8×10^4 J/mol。基于Carreau、Cross和Arrhenius等方程,分别建立了关联熔体零切黏度与聚合物重均相对分子质量和温度关系的半经验式、关联熔体表观黏度与零切黏度和剪切速率关系的半经验式;两式可用于预测POE熔体的黏度,其适用范围为温度为130~190 ℃,剪切速率为10~2 000 s-1,重均相对分子质量（Mw）为4.2×10^4~1.24×10^5 g/mol。     

The effect of polypropylene/polyamide 66 blending modification on melt strength and rheologic behaviors of polypropylene

Common linear polypropylene (PP) was modified by blending with polyamide 66 (PA66) under the act of compatibilizer in a twin-screw extruder in an attempt to improve the melt strength (MS) of PP. The MS of pure PP and modified PPs were measured by MS testing unit at three temperature of 190, 210, and 230 °C, and the MS improvement of PP was verified. The MS of the modified PPs increased with increasing the content of PA66. The steady- and dynamic-shear rheological behaviors of pure PP and modified PPs were investigated using a capillary rheometer and a parallel-plate rotating rheometer. The steady-shear rheological analysis results revealed that modified PPs had higher melt shear viscosity, stronger non-Newtonian behaviors, and higher zero shear-rate viscosity. The dynamic-shear rheological analysis showed modified PPs had higher melt complex modulus and smaller phase angle, which indicated that the melt viscosity and melt elasticity of PP were also enhanced. The modified PPs was characterized by DSC. DSC results revealed that the PA66 phase and PP phase of the modified PPs were in state of crystallization. The enhancement of MS, melt viscosity, and melt elasticity of modified PPs could be due to undisaggregated PA66 crystallization phase within the melt of PP blends.     

Effect of Mechanochemical Degradation on Rheological Behavior of PVC

The rheological behavior of mechanochemically degraded poly(vinyl chloride) (PVC) was studied through a Brabender plasticorder and capillary rheometer. The experimental results show that the degraded PVC has a much shorter plasticizing time, higher plasticizing rate, and lower melt viscosity and glass transition temperature as compared with undegraded PVC. The results provide a theoretical base for using the low molecular weight PVC prepared by the mechanochemical method as plasticizer for high molecular weight PVC.     

高等级HDPE管材树脂毛细管流变性能研究

采用单管毛细管流变仪,在不同温度下对高等级高密度聚乙烯(HDPE)管材树脂的熔体流动行为进行了研究,考察了剪切应力(τ<,w>)、剪切速率(γ)、挤出胀大及温度之间的关系.结果表明,高等级HDPE管材树脂熔体的剪切流动基本上服从幂律定律;熔体的表观黏度(η<,a>)对温度的依赖性大致上符合Arrhenius方程;η<,a>随τ<,w>和γ的增加而非线性减小;挤出胀大比随温度的升高而下降,随γ的增加呈非线性增大.     

Poly (alpha-methylstyrene) as a processing aid for rigid poly (vinyl chloride)

Poly (alpha-methylstyrene) (PAMS) is a new approach to process improvement in rigid poly (vinyl chloride) (PVC)—the use of a low molecular weight polymer as a process aid. PAMS can reduce fusion time, melt viscosity and improve heat stability of rigid PVC compounds. The reduced melt viscosity allows the addition of fillers to PVC without adverse effect on extrusion rates. This polymer also improves the resistance to melt fracture and shear “burning” at high shear rates. When used within the optimum concentration range, physical properties such as tensile strength, Izod impact and heat distortion are maintained. In addition, PAMS gives, improved production rates in both pipe extrusion and injection molding processes without sacrifice in properties.     

Effect of diatomite/polyethylene glycol binary processing aid on the melt fracture and the rheology of polyethylenes

The influence of polyethylene (PE) glycol (PEG), diatomite, and diatomite/PEG binary processing aid (BPA) on the rheological properties and the sharkskin melt fracture of three PEs was studied using a capillary rheometer. When diatomite or PEG is added to the PE matrix, they have little effect on the viscosity reduction of PEs, while the diatomite/PEG BPA shows a synergetic effect on the viscosity reduction of PEs. The incorporation of small amount of BPA was found to increase the shear‐thinning behavior and decrease the melt viscosity significantly. Meanwhile, the critical apparent shear rate for the onset of sharkskin melt fracture of PEs is increased. The mechanism for BPA to improve the rheological properties and the melt flow instability of PEs was discussed. POLYM. ENG. SCI., 45:898–903, 2005. © 2005 Society of Plastics Engineers     

聚丙烯/丙烯-乙烯共聚物共混体系的流变行为研究

采用毛细管流变仪和旋转流变仪研究了聚丙烯(PP)纤维专用料/丙烯-乙烯共聚物(PEC)共混体系的流变行为,探究了剪切速率、温度、共混物组成对熔体流变行为的影响。结果表明,随着剪切速率的增加,PP、PP/PEC和PEC均表现出"剪切变稀"行为;随着温度的升高,聚合物的表观黏度逐渐降低,特别是在低剪切速率下的这种现象更明显;随着PEC含量的增加,体系的非牛顿指数增加,黏流活化能降低,黏度对温度的敏感性降低,熔体剪切模量增加,熔体弹性增加。     

PVC/M-80共混体系的流变性能研究

本文采用高压毛细管流变仪及HAKKE转矩流变仪对PVC/M-80共混体系的流变性能进行了研究。探讨了原料组分比,以及加工工艺参数对PVC/M-80共混体系流变性能的影响。结果表明,PVC/M-80共混体系熔体是典型的非牛顿假塑性流体;随着M-80组分比的增加,共混体系熔体的平衡扭矩和熔体温度均呈明显的降低趋势;共混体系熔体的平衡扭矩随加工温度的增加呈线性降低;在常用加工转速范围内,转速对共混体系流动性的影响不明显。     

PE-LLD/乙烯基笼形倍半硅氧烷共混熔体的流变行为与力学性能

采用毛细管流变仪研究了线形低密度聚乙烯( PE-LLD)与乙烯基笼形倍半硅氧烷(E-POSS)共混物熔体的流变行为;讨论了共混物的组成、剪切应力、切变速率及温度对熔体流变性、非牛顿指数和挤出膨胀比的影响;测定了共混物的屈服应力、断裂应力和断裂伸长率对E-PUSS含量的依赖性。结果表明,E-PUSS加人量在J%以内和实验温度低于160℃熔体的流动性随切应力增大而变好,假塑性增强,超过3%和高于160℃假塑性降低。PE-LLD/E-PUSS共混物的强度在E-PUSS含量为3%时达到最大。