Effects of stearic acid coated talc,CaCO3, and mixed talc/CaCO3 particles on the rheological properties of polypropylene compounds

The effect of the stearic acid coated fillers and their geometry on the shear/dynamic viscosity and complex viscosity has been investigated using polypropylene (PP) compounds filled with stearic acid uncoated and coated talc, calcite, and mixed talc/calcite particles. The viscosity was measured over a wide range of shear rates (10^?8 to 10³) using a capillary, cone‐plate and sandwich rheometer. Overall, the rheological properties of the compounds exhibited different behavior upon different filler systems, stearic acid involvement, shear stress or strain, and frequencies due to stearic acid involvement. This implies that the stearic acid lowers the interfacial force between the filler surface and the resin matrix, followed by a favorable processing. In addition, at very low shear stresses, the viscosity of talc(un) compounds was higher than calcite(un) ones; at very high shear stresses, on the other hand, talc compounds became lower than calcite(un) compounds. This is interpreted as due to the different geometry between talc and calcite. The yield value as a function of shear stress was observed for all filler systems and exhibited lower than that obtained from the extrapolation. Furthermore, the Cox–Merz relation between the complex and shear viscosity for both the stearic acid uncoated and coated compounds is found not valid. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2105–2113, 2004     

Ternary Blends to Improve Heat Distortion Temperature and Rheological Properties of PVC

Summary: Binary and ternary blends of PVC mixed with α‐methylstyrene/acrylonitrile‐butadiene‐styrene copolymer (AMS‐ABS) and ethylene/vinyl acetate/carbon monoxide terpolymer (EVA‐CO) are investigated, with the aim to obtain a new PVC based material with an improved heat distortion temperature and good processability. Dynamic Mechanical Thermal Analysis (DMTA) reveals that ternary PVC/AMS‐ABS/EVA‐CO blends exhibit two glass transition temperatures: the lower T_g corresponds to a PVC/EVA‐CO phase and the higher one to a PVC/AMS‐ABS phase. An analysis of PVC respective interactions with AMS‐ABS and EVA‐CO leads to assert that the distribution of PVC in the ternary PVC/AMS‐ABS/EVA‐CO system is basically controlled by the binary immiscible blend composition, taken as Φ AMS‐ABS/Φ EVA‐CO ratio. The inclusion of AMS‐ABS and EVA‐CO to form ternary blends based on PVC, allows to improve heat distortion temperature (owed to the presence of AMS‐ABS), maintaining a low viscosity in the molten state, due to the plasticizing effect of EVA‐CO.

Viscosity function obtained at T = 170 °C from extrusion capillary measurements.     

Influence of binder composition on the rheological behavior of injection-molded microsized SiC suspensions

The influence of four kinds of binders consisting of paraffin wax （PW）, random-polypropylene （RPP）, high-density polyethylene （HDPE）, and stearic acid （SA） on the theological behavior of injection-molded SiC feedstocks was investigated over a temperature range of 150℃ to 180℃ and a shear rate range of 4 s^-1 to 1259 s^^-1. The results showed that all the feedstocks exhibited pseudoplastic flow behavior. The wax-based binder of multipolymer components （PW-RPP-HDPE） exhibited better comprehensive rheological properties compared with the binder of monopolymer components （PW-RPP or PW-HDPE）. The addition of 5wt% SA to the binder could reduce the viscosity of the feedstock but enhance the rheological stability by improving the wettability between the binder and the SiC powder. The binder of 65wt% PW ＋ 15wt% HDPE ＋ 15wt% RPP ＋ 5wt% SA was found to be a better binder for microsized SiC injection molding.     

Liquid rheology study on refined rapeseed oil

The rapeseed oil extracted from the mature seeds was purified by refining processing,and the rheological characteristic analysis of the viscosity and dynamic shear rate at gradient temperatures was made.The result shows that at 20,40,60 and 80 ℃ respectively,when the shear rate gradually rises,the torque increases accordingly but its viscosity does not vary distinctly.The result suggests that when rapeseed oil is used as the raw of edible oils and industries,the working procedures at high temperature will n...     

骑跨采动压巷道围岩稳定性数值模拟

针对巷道围岩遇水膨胀软化、岩石流变特性显著及长期受采动支撑压力作用的特点,应用FLAC数值软件分析骑跨采动压巷道在不同垂距及水平距离下巷道围岩的稳定性,并研究巷道围岩应力场、变形场及塑性区的变化特征.研究结果表明：巷道围岩变形表现为以底鼓变形最大,两帮变形次之,顶板变形量相对较小的特点;受支撑压力的影响,巷道围岩的应力、变形及塑性区分布呈现明显的不对称性;随着垂距及水平距离的增加,巷道围岩应力及变形呈现出不同程度的减小趋势.     

大岗山水电站坝区辉绿岩流变特性的三轴试验研究

为解决大岗山水电站坝基的辉绿岩的流变力学问题,利用RLW-1000三轴流变仪进行了不同应力路径下的三轴流变试验,得到了各工况下的应力-应变-时间曲线。结果表明：辉绿岩是典型的硬脆性岩石,存在明显的流变门槛值,破坏时表现为突发性的脆性破裂。在破裂应力水平下表现出减速蠕变、等速蠕变和加速蠕变,减速蠕变和加速蠕变历时都十分短暂。临近破裂时的横向蠕变速率均不同程度的大于轴向,这是导致岩石扩容的主要原因。由于流变过程中损伤不断发展,导致岩石整体强度下降,因此流变破坏强度普遍低于常规三轴压缩试验瞬时破坏强度。辉绿岩存在一定的蚀变现象,蚀变矿物呈细鳞片状集合体。由于蚀变带的存在,使得岩块的强度受到影响,岩石破裂极易发生在结晶程度较差的矿物颗粒部位或胶结程度较差的两种矿物接触部位。     

坝区辉绿岩体的长期剪切流变强度分析研究

岩体长期剪切流变强度是进行岩体工程长期运行稳定分析的重要基础。以大岗山水电站坝区辉绿岩现场剪切流变试验数据为基础,分别采用等时应力-应变曲线法、非稳定蠕变判别法和稳态蠕变速率法计算获得坝区辉绿岩的长期剪切流变强度,并进行了对比分析。采用等时应力-应变曲线法分析坝区辉绿岩的长期剪切流变强度较为科学合理。与岩体瞬时抗剪强度相比,长期剪切流变强度因裂隙损伤扩展有所降低,坝区岩体长期剪切流变的内摩擦角衰减了30.7%,长期剪切流变的粘聚力衰减了22.6%。     

Melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites. I. Untreated fibers

The melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites was studied with an Instron capillary rheometer. The variation of melt viscosity with shear rate and shear stress at different temperatures was studied. The effect of relative composition of component fibers on the overall rheological behavior also was examined. A temperature range of 130 to 150°C and shear rate of 16.4 to 5470 s^?1 were chosen for the analysis. The melt viscosity of the hybrid composite increased with increase in the volume fraction of glass fibers and reached a maximum for the composite containing glass fiber alone. Also, experimental viscosity values of hybrid composites were in good agreement with the theoretical values calculated using the additive rule of hybrid mixtures, except at low volume fractions of glass fibers. Master curves were plotted by superpositioning shear stress and temperature results. The breakage of fibers during the extrusion process, estimated by optical microscopy, was higher for glass fiber than sisal fiber. The surface morphology of the extrudates was analyzed by optical and scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 432–442, 2003     

水煤浆的滑移速度修正模型

在煤水混合物的流动过程中存在着滑移效应,但是在用传统的Mooney方法和Jastr- zebski方法对高浓度水煤浆的滑移特性进行分析时,没能得出一致的结果。笔者基于前人对滑移的假设,通过多管径管流试验。研究了高浓度水煤浆管内流动的滑移现象,分析了滑移引起的附加流量对总流量的影响,提出了选取最佳滑移指数确定水煤浆真实流变特性的本构模型和方程。指出高浓度浆态非牛顿流体存在屈服应力。     

Rheology of typical emulsifiers and effects on stability of emulsion explosives

Structure of emulsifiers or functionality and molecular weight determines its rheology,emulsification and stability of emulsion explosives.Rheology of typical emulsifiers was studied by automatic rheometer.Relations between rheology and structural properties of typical emulsifiers were analyzed.Experimental results show that viscosity of emulsifiers didn’t change with shear rate at room temperature and appeared properties of Newtonian fluid.Viscosity of different component emulsifiers declines with temperature in different modes.The change of strain doesn’t affect modulus of emulsifiers.Loss modulus increases linearly with the increase of frequency in oscillation and storage modulus does non-linearly.The higher the temperature is,the lower change amplitude of loss modulus with frequency will be.The emulsifiers with imide and amide functionality for emulsion explosives have better shear properties at high temperature and better shapingness and stability at room temperature than other emulsifiers with ester and Sorbin Monoleate(SMO)functionality.