Natural rubber filled SiC and B₄C ceramic composites as a new NTC thermistors and piezoresistive sensor materials

Abstract

A novel electrically conductive composite for NTC thermistor and piezoresistive sensor was successfully fabricated by homogeneously dispersing conductive SiC and B4C in an insulating natural rubber (NR) matrix. The morphology of the composites was investigated by means of scanning electron microscopy, cross linking density (n), volume fraction of rubber (Vr), and interparticle distance among conductive phases (rp). The influence of the filler concentrations on the mechanical properties such as modulus of elasticity (E); hardness shore A (H), and elongation at break (EB) were studied in details. The dependences of volume resistivity of NR based composites filled with B4C and SiC as a function of fillers concentration was investigated. Temperature dependencies of volume resistivity were also measured to examine the possible application of the composites to polymer linear negative temperature (NTC) thermistors. Furthermore, the temperature dependencies of dielectric constant of the composites were studied. For practical application, the thermal stability of the composites was examined by means of resistivity temperature and pressure hysteresis cycle. In parallel, the conduction mechanism of conductivity of the composites was interpreted in terms of the computed the activation and hopping energy. The applicability of the composites to piezoresistive sensor was examined too. The good mechanical properties and thermal stability of NR composites behavior can be utilized for fabricating various electronic devices as NTC thermistors and piezoresistive sensor (i.e. transducers in pressure sensors). POLYM. COMPOS., 29:109–118, 2008. © 2007 Society of Plastics Engineers

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“…The cross‐linking density of the polymer composites was estimated by using the solvent swelling method with acetone as the solvent [20]. The crosslinking density ( n ) is dependent on the molecular weight between crosslinks as shown in Eq .…”

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