The effects of cyclic deformations such as bending and compressive flexing, temperature and pressure on electrical and dynamic mechanical properties of conductive polydimethylsiloxane (PDMS) composites have been investigated. Conductive elastomeric composites were prepared by incorporating various carbon blacks in insulating PDMS matrix. Electrical conductivity was measured against varying concentration of different carbon blacks to assess the percolation threshold of the composites. AC and DC conductivity was found to increase with an increase in some bending flex cycles. However, with compressive flexing, DC conductivity initially dropped but later started increasing with an increase in flex cycles. The variations in electrical conductivity and dynamic mechanical modulus due to bend flexing are found to be similar, i.e. both characteristics show an increase in magnitude with an increase in some flex cycles. DC resistivity was found to increase with heating–cooling cycles, and this change in resistivity did not follow the same path leading to electrical set and hysteresis. © 2017 Society of Chemical Industry

Effects of different mechanical deformations such as cyclic bending and compressive flexing and temperature on electrical and dynamic mechanical properties of elastomeric composites have been investigated. Conductive elastomeric composites were prepared by incorporating different carbon blacks in an insulating polychloroprene (CR) rubber matrix. The filler loading was varied between 10 and 110 phr (parts per hundred rubber) i/r/o different carbon blacks to assess the percolation threshold of different composites. Due to the spatial arrangement of conductive filler particles at certain critical concentration, some conducting networks are formed leading to abrupt increase in conductivity of polymer composites. This critical concentration is known as percolation threshold. The increase in conductivity well below and above percolation threshold is relatively less compared to that around percolation. The variation of electrical conductivity and dynamic mechanical modulus due to bending and compressive flexing are found to be similar, that is, both characteristics show a drop in magnitude with increase in number of flex cycles. The conductivity of system changes when composites are subjected to changes in temperature. This is mainly due to the destruction of existing conducting networks as well as formation of some new conducting networks. The net change depends on the degree of formation or destruction of networks. It is interesting to see that conductivity does not follow the same path during heating–cooling cycles thereby causing electrical hysteresis. POLYM. COMPOS., 39:3912–3923, 2018. © 2017 Society of Plastics Engineers