Effect of extensional cyclic strain on the mechanical and physico-mechanical properties of PVC-NBR/graphite composites

Abstract

Abstract. The variation of electrical resistivity as will as the mechanical properties of PVC (polyvinylchloride)-NBR (acrylonitrile butadiene rubber) based conductive composites filled with different concentrations of graphite were studied. These samples were studied as function of the constant deformation fatigue test. When the specimen was subjected to a large number of rapidly repeating strain cycles, and different strain amplitudes, the conductivity, σ(T), shows an initial rapid fall followed by dynamic equilibrium. Increasing the number of cycles and strain amplitudes, the conductivity remains almost constant over the temperature range 30-140°C. The equilibrium state between destruction and reconstruction of graphite particles has been detected for all strains of certain values of strain cycles (1000, 2000, 3000, and 4000 cycles for 30% strain amplitude). A preliminary study was done to optimize the possibility to use Conductive Polymer Composites (CPC) as a strain sensor and to evaluate its performance by an intrinsic physico-mechanical modification measurement. The electromechanical characterization was performed to demonstrate the adaptability and the correct functioning of the sensor as a strain gauge on the fabric. The coefficient of strain sensitivity (K) was measured for 50 phr graphite/PVC-NBR vulcanized at 3000 number of strain cycles and 30% strain amplitude. There was a broad maximum of K, with a peak value of 82, which was much higher, compared to conventional wire resistors. A slight hysteresis was observed at unloading due to plasticity of the matrix. A good correlation exists between mechanical and electrical response to the strain sensitivity. Mechanical reinforcement was in accordance with the Quemada equation [1] and Guth model [2] attested to good particle-matrix adhesion. It was found that the viscous component of deformation gradually disappeared and the hardening occurred with increasing strain cycles. The modulus, fracture strength, and elongation at break increased with increasing filler volume fraction up to 40 phr of graphite particles.

A study on electrical and thermal conductivities of ethylene–octene copolymer/expandable graphite composites

“…Several researchers have studied the conductivity properties of EOC composites using different fillers such as carbon black, polyaniline, and multiwall carbon nanotubes [10–12]. Conducting polymer composites (CPC) with elastomeric polymer matrices have applications in the field of sensors, e.g., temperature sensors [13] and strain sensors [14].…”

Polydimethylsiloxane-integratable micropressure sensor for microfluidic chips

“…23,25 However, in our case, the sensor undergoes a transverse deformation including both bending and stretching processes, which are more complicated analyses mathematically. Hence, we introduce a theoretical perspective to understand the action of length under pressure.…”

Mechanical properties of styrene butadiene rubber-/ethylene propylene diene monomer rubber-based conductive blends

“…As seen, the correlation between experimental data and equation (8) is also not good enough. On the other hand, equation (8) enables to predict elongation at break of electroconductive composites from the knowledge of percolation concentration determined from an independent measurement of electrical conductivity and therefore its utilization is more advantageous.…”

“…1,2 Carbon black (CB)-filled conductive rubbers have wide applications, such as pressure sensitive sensors, which can be used for shock proof switches, 3 sensors for the measurement of vehicle weights to collect toll tax on roads, 4 smart flexible sensors adapted to textile structures, able to measure their strain deformations, 5 and tactile sensor that is thin and flexible and able to attach to a curved surface and will make the robot operate in unstructured environments. [6][7][8] The elastomer blends consisting of compatible elastomer pairs are very useful in achieving a high degree of conductivity because of their well-defined interface. 9 Accumulation of the black at the interface has the effect of increasing the number of contact points or decreasing the gap width, and higher loading or poorer dispersion is also obtained.…”