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Conductive and rheological behavior under heat treatment of conductive polymer composites

Author: CaoQing
Tutor: ZhengQiang;SongYiHu
School: Zhejiang University
Course: Polymer materials
Keywords: Conductive polymer composites Carbon black Conductive Behavior Rheological behavior Synchronization test Seepage
CLC: TB324
Type: Master's thesis
Year: 2010
Downloads: 136
Quote: 3
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Excellent overall performance, conductive polymer composites have been widely used in anti-static, pressure sensors and self-limit temperature materials. Wherein, based on the self-limiting temperature of the positive temperature coefficient (PTC) effect material can be applied particularly extensive, but the effect of the negative temperature coefficient (NTC) is a disadvantage of such materials. So far, NTC mechanism has been subject to controversy. Black (CB) as the conductive filler, the agglomeration process of the CB particles in the process of heat treatment in the polymer melt to provide evidence for the NTC MECHANISM. HDPE / CB, PP / CB, PS / CB and PMMA / CB composite system heat treatment temperature zone in the NTC effect, simultaneous measurement of the electrical conductivity and rheological behavior of the composite system. Found that the percolation phenomenon of dynamic resistance and modulus of CB content and heat treatment temperature on the dynamic seepage. Be the CB particle gathered a dynamic model of dynamic percolation model is introduced to classical percolation theory. The study found that the resistor aggregation kinetics constant and independent of the CB content CB particles gathered in the polymer melt and the CB particles contents, primarily reflecting the movement of the viscous flow of the polymer molecular chain. At the same time, the introduction of a CB aggregation kinetics model mechanical percolation model, the dynamic modulus percolation model. Modulus the aggregation kinetics constant and CB content independent of temperature. This is because, at elevated temperatures, the exercise capacity of the viscous flow of the molecular chain enhanced, while also facilitating its attachment of the CB particles moving together, thus accelerating CB particles form aggregates. These two processes competing with each other, to cause the modulus of the aggregation kinetics constant and independent of temperature. Dynamic resistance percolation index close to 2.0, as the temperature increases and the CB content increases gradually dimensional CB conductive path is formed in the system gradually. Modulus seepage index with increasing temperature, the CB content increased gradually close to 0.4, indicating that the contribution of CB modulus gradually dominant role. CB aggregation driving force from the interfacial tension between the CB particles and polymer molecules in the polymer melt. Model according CCA, CB skeleton with the heat treatment temperature increased, Paper No. CB content increases, the heat treatment time and constantly improve the heat treatment process can be seen as an isolated the CB small particles or aggregates to imperfect CB skeleton movement and form a perfect skeleton of CB process. Relaxation Behavior of heat treatment on the end of the composite system, found little effect of heat treatment on the relaxation time of the end of the HDPE / CB and PP / CB system, indicating that the CB slow gathered in these two systems, and the formation of aggregates is not yet limit the movement of molecules. PS / CB and PMMA / CB after heat treatment caused the end of the relaxation time limit increases CB gather faster, the degree of aggregation. High CB content HDPE / CB composite system at higher temperatures for a long time when the heat treatment of the conductive and the rheological behavior and found that the heat treatment results modulus \a high degree of agglomeration, the motion greatly reduced capacity so that the molecular chain of the polymer; the same time, the resistance with the heat treatment time increases, which is the height reunion CB makes CB conductive network damage.

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