Preparação e caracterização de compósitos de borracha natural pré-vulcanizada e negro de fumo com vistas para utilização como sensor mecânico de alta deformação

Abstract

Elastomers are materials that have high deformation when subjected to a mechanical action, and are traditionally electrical insulators. However, there are cases where considerable electrical conductivity and certain mechanical deformation are required in the same material, for applications such as the monitoring of structures. The combination of pre-vulcanized natural rubber (PNR) with carbon black (CB) results in a conductive polymeric composites or also called extrinsic conductive polymers with suitable elasticity to be integrated into systems as piezo-resistive sensors with large deformations, which may be applied to robots surfaces and different structures, such as buildings, bridges, tunnels, dams, airplanes, ships, wind turbines, and many others that require daily monitoring to avoid accidents. In this work we present a development of materials with potential to be used as piezo-resistive sensors based on conductive polymer composites. Their electrical, mechanical and morphological properties was characterizes and a study of their performance as a sensor (piezo-resistive test), was performed. The percolation threshold (existence of at least one electric conduction path in the sample) in the composites, in which, along the surface, was reached at 5% CB into the polymer matrix. The strain-strain tests showed that with the increase in charge concentration (CB) in the polymer matrix, the rupture deformation remains close to 400%, however there is an increase in the Young's modulus, which implies that the CB particles served as reinforcement in the PNR matrix. Scanning Electron Microscopy images shared several aggregates and agglomerates, forming conductive paths in the samples with higher CB contents. Increasing the CB loads, the material becomes more fragile. The composite presented a change of linear electric resistance with change of the mechanical deformation, which, associated an electrically conductive film with high deformation, shows great potential for the use as electromechanical sensor.