Pressure Sensibility of Conductive Rubber Based on NBR- and Polypyrrole-Designed Materials

Abstract

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Conductive rubbers combine features such as elasticity and electrical conductivities. Here, we developed an elastic conductive material based on nitrile rubber (NBR) and polypyrrole (PPy) by melt processing. PPy was also synthesized in three different media as silver (PPy-Ag), organomontmorillonite (PPy-OMt), and silver-organomontmorillonite (PPy-Ag-OMt) before mixture with NBR. Chemical structure, morphology, and stress–strain properties were evaluated. Pressure sensibility was evaluated in the range of 0–67 MPa during 10 cycles. During the compression and expansion processes, the electrical conductivity changes from high to low values and the difference of loading and unloading cycles demonstrates the repeatability and low hysteresis. The organomontmorillonite clay improves the homogeneity of particles into the matrix, and based on SEM images, the dispersity follows the sequence PPy-OMt, PPy-Ag-OMt, and PPy-Ag-OMt. This behavior affects the electrical conductivity and mechanical and electromechanical properties. The higher elastic modulus for composites compared to neat NBR is assigned to the reinforcing effect of the fillers. NBR/PPy-Ag-OMt (5 wt.%) is the best material in the absolute value of Scomp (46.3%/MPa) and the Scomp/hysteresis ratio (8.5%). In spite of different formulations displaying the best performance on the evaluated criteria (highest absolute conductivity, the highest percentage change in conductivity, lowest hysteresis, and lack of sample disruption), we can suggest that a lower amount of conducting particles benefits the reticulation process (as observed by the gel fraction values). Additionally, the possibility of using mechanical processing to obtain large-scale pressure sensor materials is without a doubt the most important outcome of this research area.

Keywords

• conducting polymer
• conductive rubber
• melt processing
• montmorillonite
• silver