Study on rheological behavior of polypropylene/clay nanocomposites

Polypropylene/montmorillonite nanocomposites (PPCN) were prepared by melt intercalation with maleic anhydride modified low isotactic polypropylene as the compatibilizer. The linear and nonlinear rheological properties of polypropylene/montmorillonite nanocomposites were studied. The deviation from linear behavior occurred at a strain of 10⁰ that was quite less than that for the polymer matrix. The results of dynamic frequency scan showed that the percolation threshold of PPCN was near 3 wt %. Having been subjected to steady preshear, the tactoids could be oriented preferentially in the shear direction, and the percolation network was ruptured. The magnitudes of the stress overshoots observed in the reverse flow experiments were strongly dependent on the rest time, which indicated that the ruptured network could be reorganized even under quiescent conditions. Furthermore, PPCN displayed a strain‐scaling stress response to the startup of steady shear. The maxima of the stress overshoots appeared at the stain of 10⁰, which was consistent with the strain where the deviation of linear viscoelastic behavior started. It might imply that subjected to the deformation less than 10⁰, the network structure could be regard as elastic one. Additionally, the analogous strain‐scaling stress response to the startup steady shear elucidated the structural analogy between PPCN and liquid crystal polymer solution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3609–3617, 2003     

改性剂对聚丙烯流变性能和发泡行为的影响

在改性聚丙烯PPFP1920中加入丙烯酸类树脂改性剂(记作G200)进行共混改性,制备了PPFP1920/G200复合材料,研究了G200含量对聚丙烯流变性能、发泡行为的影响.结果表明:随着G200含量的增加,复合材料的熔体流动速率大幅降低,复数黏度和低频储能模量提高,低频损耗因子降低,熔体弹性变好,复合材料可发泡性提...     

含杂环共聚芳香族聚酰胺溶液的动态流变特性

采用锥板流变仪,研究了含杂环共聚芳香族聚酰胺溶液的动态流变特性.结果表明:含杂环共聚芳香族聚酰胺溶液为假塑性流体;溶液浓度越高,相对分子质量越大,其储能模量(G')和损耗模量(G″)越大,但G'和G"随温度的升高而降低;随着含杂环共聚芳香族聚酰胺相对分子质量的增大,其相对分子质量分布越宽,溶液中大分子缠结网增强.     

Dynamic rheological behavior of reactively compatibilized polypropylene/polyamide 6 blending melts

The dynamic rheological behavior is measured by small amplitude oscillatory shear on rotational rheometer for polypropylene/polyamide 6 (PP/PA6) blends compatibilized by a polypropylene grafted maleic anhydride (PP‐g‐MAH). Scanning electron microscope (SEM) results show that the PP/PP‐g‐MAH/PA6 (=100/6/40wt) is sea‐island structure, the PP/PP‐g‐MAH/PA6 (=100/6/60wt) blend is semi‐cocontinuous. Coarse PA6 zones can be observed when the weight ratio is 100/6/80. At low frequency the complex viscosity, dynamic modulus of the PP/PP‐g‐MAH/PA6 (PP/PP‐g‐MAH = 100/6wt) blends first increase then drop with the increase of PA6 weight content in the range of 0–100, the maximum value arrives at the weight content of 60. The Cole–Cole plots as well as the weighted relaxation spectra of the blends have a main arc and a tail when the weight ratio of PP/PP‐g‐MAH/PA6 is in the range of 100/6/20–100/6/60, but have different shapes when the weight ratio increases to 100/6/80 and 100/6/100. The possible reason is the weight ratio of 100/6/80 and 100/6/100 is close to the phase inversion point. In fitting the storage modulus data at low frequency, Palierne's model with two parameters interfacial tension and interfacial shear modulus is better than Bousmina's model. Palierne's model with only one parameter of interfacial tension can not fit the data well. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42091.     

Steady flow and dynamic viscoelastic behavior of nylon 1313 using parallel‐plate rheometer and capillary rheometer

In this study, a novel nylon with long alkane segments (also called nylon 1313), which was synthesized using 1,13‐tridecanedioic acid in our laboratory, has been characterized. Different rheological behaviors of nylon 1313 have been presented using steady shear, creep recovery, and dynamic tests. The time‐temperature effects have also been investigated. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1643–1651, 2005     

EPDM橡胶的流变特性实验研究

为了研究橡胶熔体流变性能对其加工成型的影响，利用毛细管流变仪对三元乙丙橡胶（EPDM）的流变特性进行了实验研究。实验结果表明：EPDM橡胶在毛细管挤出时，剪切速率对剪切应力、剪切粘度和挤出胀大的影响最大；挤出温度对三者有一定的影响；在长径比相同时，毛细管半径对剪切应力和剪切粘度几乎没有影响，但对挤出胀大影响较大。     

Anomalous rheological behavior of polyethylene melts in the gross melt fracture regime in the capillary extrusion: Effect of long‐chain branching

During a capillary extrusion with several different polyethylenes, we observe an abnormal rheological behavior. The nominal viscosity of some polyethylene melt in the gross melt fracture regime does not change with the temperature. Several metallocene‐catalyzed linear low density polyethylene are investigated. Among them, polyethylenes, which have long‐chain branches in their main chain, show this abnormal rheological behavior. By capillary extrusion experiments with various dies of different L/D ratios, it is inferred that the abnormal rheological behavior is originated in the die land, not die entrance nor die exit. From various experiments, we notice that this abnormal phenomenon may be used to detect long‐chain branch of PE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

毛细管内多相脉动流动的格子-Boltzmann模拟

基于伪势模型理论,建立毛细管内汽液两相工质脉动流动的等温格子-Boltzmann模型。将利用该模型取得的静态液滴形态以及表面张力、大空间和窄空间内气泡浮升运动时的形态模拟结果与文献的研究结果进行对比,验证了模型的可靠性。对毛细管内泡状流和柱塞流两种流型在边界正弦压力波作用下绝热脉动流动情况进行了数值模拟。通过模拟研究了毛细管内不同压力波振幅下液相Reynolds数和气泡位移幅度周期性变化规律;获得了汽液界面形态在脉动过程中的变化;观察到在边界液相速度方向发生改变时,边界附近区域的Reynolds数振荡现象;分析了重力对脉动运动过程的影响。模拟结果为分析以毛细管为主要构件的脉动热管内汽液两相工质的工作过程提供了一定依据。     

SIS型热熔压敏胶的粘接性能及动态流变行为研究

以SIS(苯乙烯-异戊二烯-苯乙烯三嵌段共聚物)作为基体树脂制备HMPSA(热熔压敏胶)。研究了不同类型增塑剂与SIS基体的相容性对压敏胶(PSA)性能及动态流变行为的影响,并探讨了PSA性能与动态流变行为之间的关系。结果表明:当增塑剂与SIS中PS(聚苯乙烯)相的相容性较好时,相应HMPSA在低频(1 Hz)时的储能模量较低,初粘力较好;当增塑剂与SIS中PI(聚异戊二烯)相的相容性较好时,相应HMPSA在高频(100 Hz)时的损耗模量较高,剥离强度较大。     

纳米铜粉/PP复合材料的流变性能及动态力学性能研究

将纳米铜粉经硅烷偶联剂KH550处理后,按不同的配比与聚丙烯(PP)混合,经螺杆挤压制得纳米铜粉/PP复合材料,研究了纳米铜粉在PP复合材料中的分散性以及PP复合材料的流变性能和动态力学性能。结果表明:经改性后的纳米铜粉均匀分散在PP中;纳米铜粉/PP复合材料为非牛顿假塑性流体;在低剪切速率下,复合材料熔体的黏度高于纯PP的,随着纳米铜粉的含量增加,复合材料体系的表观黏度增大,高剪切速率时,纳米铜粉的添加量对复合材料的流动性能影响较小;当复合材料体系中纳米铜粉的质量分数小于或等于0.5%时,其熔体流动性能提高,储能模量小于纯PP的,当纳米铜粉质量分数大于0.5%时,其储能模量提高并高于纯PP的。     

Study on degradation and crosslinking of impact polypropylene copolymer by dynamic rheological measurement

The structural stability of impact polypropylene copolymer (IPC) melt under high temperatures was explored by dynamic rheological measurement. The structure changes including degradation and crosslinking of IPC were discussed through examining the influence of temperature and additive antioxidant on dynamic rheological functions. A plateau of dynamic storage modulus (G′) appeared in low frequency region at high temperatures under air atmosphere. Furthermore, when IPC sample was annealed at 230 °C, its viscoelasticity presented a dramatic change. The time dependences of G′ for pure IPC at different temperatures were investigated. At 190 °C, a slight drop and a succedent rise of G′ for IPC0 appeared. The decrease period of G′ generally shorted and the increase of G′ became more remarkable with the increase of temperature. The decrease of G′ was ascribed to the degradation in IPC and the G′ increase was due to the crosslink reaction. Through incorporation of antioxidant into IPC, the crosslinking in IPC could be effectively inhibited, and the degradation and crosslinking in IPC were believed to result from PP component.     

液体聚异戊二烯橡胶动态流变性能的研究

采用动态流变仪研究液体聚异戊二烯橡胶(LIR)的动态流变性能。频率扫描证明,LIR的粘度对剪切频率的敏感性很弱,只有在剪切频率较高时粘度才会发生变化;温度扫描证明,LIR的流变行为对温度非常敏感,而且在较高温度(130℃左右)下,LIR开始出现轻微的交联,导致粘度显著升高;Arrhenius方程可以描述LIR粘度与温度的关系,利用不同温度下的零切粘度计算得到的LIR流动活化能为39.27 kJ.mol-1。     

Melt rheological properties of polypropylene–maleated polypropylene blends. I. Steady flow by capillary

Melt rheological properties of blends of polypropylene (PP) and PP grafted with maleic anhydride (PP‐g‐MA) are studied using a capillary rheometer. A pseudoplastic flow behavior is observed. The pseudoplasticity of the melt reduces with an increase of PP‐g‐MA content and/or temperature. The PP‐g‐MA component in the blend acts as decreasing melt viscosity, especially in the lower shear rate region, while the addition of PP‐g‐MA to PP does not cause obvious increase of die swell ratio. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1641–1648, 1999     

Measurement of dynamic capillary pressure and viscosity via the multi-sample micro-slit rheometer

We develop two direct methods to simultaneously measure the dynamic capillary pressure and the viscosity of fluids by application of differential forces during flow into micro-channels. In the first method, a series of external pressures is applied in conjunction with the dynamic capillary pressure and a “Bagley analysis” is applied to the flow front velocity, and in the second, we utilize differential gravitational forces. By explicitly measuring the dynamic capillary pressure, the measurement window of the recently developed multi-sample micro-slit rheometer is extended to the regime where capillary forces are significant. These measurement methods will be useful in understanding filling flows encountered in diverse areas such as microfluidics, oil recovery and biological transport.     

Thermal degradation of polypropylene in a capillary rheometer

Melt viscosity of a polypropylene (PP) resin was measured in a capillary rheometer between 220 and 260°C. The melt viscosity showed a power law behavior with strong shear rate dependence. The effects of temperature and shear rate on the degradation were studied in the rheometer by heating at 260 and 280°C, and extruding at shear rates up to 10000 sec ?1 . Melt flow index (MFI) of samples after shearing and heating treatment was measured to characterize the molecular weight change. An increase in MFI was found for PP sheared at high temperature. Heating for longer time also increased MFI. Increase of shear rate had a small effect on increasing MFI at 260°C but produced a larger effect at 280°C. A constant increment in MFI was observed in PP subjected to high temperature processing and was attributed to degradation due to oxygenated products.     

MTA合成PET的流变性能研究

采用英国Rosand公司RH7-2X型毛细管流变仪对自制的MTA合成PET样品的流变性能进行了研究。结果表明:同常规PET相比,MTA合成的PET样品的熔体同属于假塑型非牛顿流体;MTA合成的PET样品的非牛顿指数n值较高,而且随着温度的提高,其n值增长趋势更加明显;在低剪切速率条件下,MTA合成PET样品的黏流活化能ΔEη较高,熔体剪切黏度对温度比较敏感,在高剪切速率(20000s-1左右)条件下,两者ΔEη的差距逐渐减小。     

UHMWPE／UHMWPP冻胶体系的流变行为研究

研究了超高相对分子质量聚丙烯（UHMWPP）的加入对超高相对分子质量聚乙烯（umfwPE）冻胶体系粘性行为、非牛顿指数、结构粘度指数的影响。结果表明：UHMWPP在UHMWPE／UHMWPP共混体系中起到了润滑剂的作用,使体系的表观粘度降低,非牛顿指数升高,结构粘度指数下降。其中,UHMWPP添加量为5％时,冻胶体系的可纺性最佳。     

Dynamic rheological behavior and morphology near phase-separated region for a LCST-type of binary polymer blends

The dynamic rheological properties and morphology in the vicinity of phase-separated region for poly(methyl methacrylate) (PMMA)/poly(styrene-co-acrylonitrile) (SAN) blends with lower critical solution temperature (LCST) behavior were investigated. When temperature was above the phase separation temperature, i.e. cloud point (T_c) for some PMMA/SAN blends, the slope of plotting versus decreased at low frequencies (terminal region), indicating the appearance of phase-separation and existence of heterogeneous structure. We employed a model dealing with complex modulus of the two phases mixture proposed by Kopnistos et al. for describing the dynamic rheological behaviors of PMMA/SAN blends, according to the assumption that the interfacial tension between the matrix and the dispersed phase was independent of local shear and variation of interfacial area, and that the dispersed spherical droplets were nearly monodispersed. It is found that the predicted results were in qualitative agreement with the experimental data of this study. The ratio of interfacial tension α to the size of dispersed phase R, α/R, was obtained for 80/20 and 60/40 PMMA/SAN blends, and the two different morphology were also observed.     

Mechanical properties and morphological behavior of calcium carbonate‐filled polypropylene in dynamic injection molding

A custom‐made electromagnetic dynamic injection molding machine was adopted to study the mechanical properties and morphological behavior of calcium carbonate‐filled polypropylene (PP) in a dynamic injection molding process. The influence of vibration amplitude and frequency on the mechanical properties and morphological behavior of samples was investigated using tensile tests, notched Izod impact tests, differential scanning calorimetry, and scanning electronic microscopy. The tensile stress and the impact stress for all samples investigated were found to increase in a nonlinear manner with increasing vibration amplitude and frequency. The tensile stress reached a maximum value at about 8 Hz and 0.15 mm for neat PP and PP filled with 3, 20, and 30 wt% CaCO₃. For PP filled with 40 wt% CaCO₃, the tensile stress reached a maximum value at about 12 Hz and 0.2 mm. The impact stress reached a maximum value at about 12 Hz. From DSC experiments it was shown that the melting temperature slightly increased, but no new polymeric crystalline peak appeared under the vibration force field. The CaCO₃ particles were diffused easily and distributed evenly in the PP melt under the vibration force field, so it is very useful in improving the quality of injection products. Copyright © 2006 Society of Chemical Industry     

Ultrasonic improvement of rheological behavior of polystyrene

The effects of ultrasonic oscillation on die pressure, productivity of extrusion, melt viscosity, and melt oscillating flow of polystyrene (PS) as well as their mechanism were studied in a special ultrasonic oscillations extrusion system developed in our lab. The experimental results show that in the presence of ultrasonic oscillations, the PS melt oscillating flow or surface distortion of PS extrudate is inhibited or disappears. The surface appearance of PS extrudate gets greatly improved. The die pressure, melt viscosity, flow activation energy, and consistency efficiency of PS decreased and the productivity of PS extrudate increased in the presence of ultrasonic oscillation. The shear sensitivity of PS melt viscosity is decreased because of the increase of its power law index in the presence of ultrasonic oscillation. Introduction of ultrasonic oscillation into PS melt can greatly improve the processibility of PS. Their possible mechanism is also proposed in this article. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2451–2460, 2002