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《Composite Interfaces》2013,20(3-4):169-176
The water sorption properties of Precipitated Calcium Carbonate (PCC) formulations have been studied in relation to the rheological behaviour. Uncoated mineral fillers (median diameter 0.85 μm) have been dispersed in an organic liquid used as plasticizer, a dioctylphthalate (DOP), at a concentration of 25% by weight (volume fraction of about 11%). Water sorption isotherms onto PCC in air and in the organic matrix have been constructed. Measurement of water concentration in the DOP permits a complete evaluation of water exchanges at the inorganic (mineral)/organic (plasticizer) interface. Evolutions of yield stress, storage modulus and loss modulus have been determined as functions of the water activity in the system. A drastic change of rheological properties has been observed for water activities above 0.3. 相似文献
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采用流变学法系统地考察了部分水解聚丙烯酰胺(HPAM)/Cr(III)交联体系的 反应动力学。HPAM溶液的粘性模量G”大于弹性模量G’,且其数值随时间不发生变 化,体系为粘性溶液。而HPAM/Cr(III)体系的G’和G”的数值都随时间变化,G” 在反应开始阶段大于G’,当反应进行一段时间后,G’超过G”占据主要地位,体 系成为弹性体系。交联过程可分为三个阶段:第一上升阶段,平缓上升阶段和第二 上升阶段。利用G’~ t曲线可以推测反应机理。实验发现成胶速率随反应物HPAM 和Cr(III)的浓度的增加而增加,而成胶时间缩短。在羧基浓度过量的情况下,交 联反应对Cr(III)浓度的反应级数是1。凝胶的有效弹性交联密度随聚合物浓度的增 加而增,且随凝胶反应的进行而增加。凝胶的交联点间的平均分子量随Cr(III)浓 度的增加和交联反应的进行而下降。 相似文献
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DYNAMIC RHEOLOGICAL BEHAVIOR OF POLYPROPYLENE FILLED WITH ULTRA-FINE POWDERED RUBBER PARTICLES 总被引:2,自引:0,他引:2
QiangZheng Yan-xiaCao MiaoDu 《高分子科学》2004,(4):363-367
Dynamic rheological characteristics of polypropylene (PP) filled with ultra-fine full-vulcanized powdered rubber (UFPR) composed of styrene-butadiene copolymer were studied through dynamic rheological measurements on an Advanced Rheometric Expansion System (ARES). A specific viscoelastic phenomenon, i.e. “the second plateau“, appeared at low frequencies, and exhibits a certain dependence on the amount of rubber particles and the dispersion state in the matrix. This phenomenon is attributed to the formation of aggregation structure of rubber particles. The analyses of Cole-Cole diagrams of the dynamic viscoelastic functions suggest that the heterogeneity of the composites is enhanced on increasing both particle content and temperature. 相似文献
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二氧化硅悬浮体和水解聚丙烯酰胺体系的流变性 总被引:6,自引:0,他引:6
研究了二氧化硅悬浮体的流变性。在固体含量较少的情况下, 体系呈Newton型;固体含量达到一定程度以后, 产生三维结构, 为假塑性体系。三维结构的固体含量与pH值有关。实验证实, 在等电点(i,e, p)附近三维结构最为疏松。还研究了水解聚丙烯酰胺(HPAM)对悬浮体流变性能的影响。HPAM破坏了二氧化硅粒子聚集体结构, 呈絮凝体结构, 并出现触变性。当高聚物在固体表面覆盖一半时, 具有最大触变性和动剪切力。HPAM的水解度达到一定程度, 由于对固体粒子由“强”吸附转变为“弱”吸附, 固体粒子“屏蔽”了高分子间的相互作用, 出现了负触变性现象。在流动时粒子会脱附, 静止以后又产生吸附, 这种吸附与脱附是产生负触变性的主要原因。HPAM水解过度或用量过多, 均会减弱负触变性现象。 相似文献
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《Composite Interfaces》2013,20(7-9):685-698
Polymer composites filled with natural organic fillers have gained a significant interest during the last few years, because of several advantages they can offer compared with properties of inorganic-mineral fillers. However, these composites (based, in most cases, on polyolefins) often show a reduction in some mechanical properties. This is mainly due to the problems regarding dispersion of the polar filler particles in the non-polar polymer matrix and their interfacial adhesion with polymer chains. In this work, polypropylene–wood flour composites were prepared and the effect of the addition of a maleated polypropylene was investigated. The two materials were compounded by an industrial co-rotating twin screw extruder, with two different compositions, without and with addition of Licomont AR504® (maleic anhydride-grafted polypropylene wax). The extruded material was then compression molded, which provided the specimens for tensile and impact tests. Water uptake was measured; the morphology of the fracture surfaces of the samples coming out from mechanical tests was investigated through SEM analysis. Rheological characterization was carried out as well. The addition of the adhesion promoter allowed a decrease in water uptake; mechanical properties were improved as well, especially elastic modulus and tensile strength; impact strength increased in the case of unnotched samples, while notched ones did not show remarkable differences. SEM analysis of the fracture surfaces also showed an overall change in the morphology as a consequence of the utilization of the adhesion promoter. 相似文献
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壳聚糖浓溶液流变学性质研究-溶剂性质的依赖性 总被引:4,自引:0,他引:4
用不同pH值的HCOOH, CH~3COOH, HCl,0.1mol.dm^-3CH~3COONa+0.2mol.dm^-3CH~3COOH水溶液为溶剂, 进行了壳聚糖浓溶液的流变学性质研究。实验结果表明, 溶剂pH值相同时, 壳聚糖在各种酸中的溶解性和溶液沾度差别较大。同一种酸中, 在可溶范围内, pH值增加, 溶剂变劣, 粘度-浓度的幂律方程指数α增大。外加盐使溶剂变劣程度增加。在任何一种酸中, 浓溶液粘度都随存放时间的延长而下降, 流动指数n减小, 流动活化能基本不变。 相似文献