Preparation Of Conductive Silicone Rubber Composites And Study Of The Strain Sensing Behavior

The use of conductive polymer composites (CPCs) as strain sensors has been widely investigated. Wide strain sensitivities and high repeatability are vital for different applications. In this paper, the relations of the conductive filler network and the strain sensing behavior and electrical stability under fatigue cycles are concerned systematically based on the conductive polymethylvinylsiloxane (PMVS) composites filled with both carbon nanotubes array (CNTA) and carbon black (CB). The dependence of the conductive filler network and the strain sensing behavior and electrical stability on the filler contents and the volume ratio of CNTA/CB is carefully studied. And we aim to prepare a kind of conductive polymer composite which show high sensitivity, high repeatability and electrical stability under fatigue cycles at the same time.First, three volume fractions of nanofillers, which represent the volume fractions corresponding to the start of the percolation threshold (1.5vol.%), the end of the percolation threshold (3vol.%), and that far exceeding the percolation threshold (6vol.%), are used for comparison. The volume ratio of CNTA/CB is 0:10,4:6,10:0, respectively. The electrical and mechanical properties are studied. It is noted that the strain to failure of all composites could reach above 78% strain, illustrating the composites can bear large strain when used for strain sensing. The conductive filler network is analyzed with Rubber Process Analyzer (RPA) and microscope, and the relations of the conductivity and the filler contents and the volume ratio of CNTA/CB is explained.With the increase of filler contents and the volume ratio of CNTA/CB, the sensitivity of composites decreases; while the repeatability and electrical stability under fatigue cycles of composites improve with the increase of filler contents. For composites either filled with granular or fibrous fillers, the strain sensitivity is highest near the percolation threshold, but repeatability and electrical stability under fatigue cycles is the worst; on the other hand, at the region that far exceeding the percolation threshold, it is just the opposite. The percolation threshold of the CNTA composites is lower than that of the CB composites for higher aspect ratio of carbon nanotubes (CNTs). But electrical stability under fatigue cycles of the CNTA composites is the worst, as the bond between CNT and matrix is relatively poor, and CNTs are easier to aggregate after fatigue tests. So it is difficult to achieve high sensitivity and repeatability and electrical stability simultaneously relying on a single CNTA or CB conductive network.The CNTA/CB/PMVS composite with 3vol.% content of fillers show high sensitivity (GF is 10 at 60% strain), high repeatability (the RSD of the max R/Ro value is 3.58%) and electrical stability under fatigue cycles (value range of R/Ro is 1.62 to 1.82) at the same time due to the synergistic effects of the CNTs and CB dual conductive network. For the volume fractions of CB and CNTA have just exceeded the percolation threshold, both CB and CNTs form conductive network respectively to get a dual conductive network. It could still form conductive network in the composite although the destruction-regeneration of the dual conductive network occur under strain, therefore the composite show high repeatability and electrical stability.