Sensing of liquids by electrically conductive immiscible polypropylene/thermoplastic polyurethane blends containing carbon black

Abstract

Immiscible polymer blends based on polypropylene/thermoplastic polyurethane (PP/TPU) are interesting host multiphase systems for the incorporation of low concentrations of conductive carbon black (CB) particles. The enhancement of conductivity (and the lower critical CB content for percolation) in the PP/TPU blend is achieved via double percolation, that is, structural and electrical. The CB particles form chainlike network structures within the TPU phase, which exhibit phase continuity of elongated particles within the PP matrix. Moreover, scanning electron microscopy and dynamic mechanical thermal analysis studies indicated that the incorporation of CB particles into the PP/TPU blend has a "compatibilizing" effect, resulting in an enhanced interaction between the two polymers. Extruded PP/TPU/CB filaments produced by a capillary rheometer process at various shear rates were examined as sensing materials for a homologous series of alcohols, that is, methanol, ethanol, and 1-propanol. All filaments displayed increasing resistance upon exposure to the various alcohols combined with excellent reproducibility and recovery behavior. An attempt is made to identify the dominant mechanisms controlling the sensing process in a CB-containing immiscible polymer blend characterized by a double-continuity structure. The interphase region, its quantity, and continuity played a significant role in the liquidtransport process. Blend composition, filaments' extrusion temperature, and production shear rate level were considered as significant parameters determining the structure and the resultant sensing properties.

Liquid sensing properties of melt processed polypropylene/poly(ε-caprolactone) blends containing multiwalled carbon nanotubes

“…The ability to draw fibers from carbon black filled systems is very limited, while with nanotubes the processability is much better. Thus, it seems to be interesting also to investigate composites and blends based on CNTs for liquid sensing purposes.For melt-processed biphasic polymer/ CB composites, Narkis et al reported the liquid sensing behaviour of [30][31][32][33][34]. In the immiscible polymer blends containing CB, like PP/PA6/CB, HIPS/EVA/CB, and PP/TPU/CB, the liquid sensing behaviours depended on their components, composition, and composite morphologies, which could be influenced by the melt-processing method and mixing conditions.…”

Polymer composites as sensing materials for liquid organic solvents – preliminary results

“…DC (direct current) electrical resistivity of these materials was found to be sensitive to benzene, n-heptane, methanol and methyl methacrylate [5]. Sensitivity to a mentioned liquids was also observed in a case of polymer blends of high impact polystyrene (as a matrix) and ethylene-co-vinyl acetate (as a dispersed phase) containing carbon black (electrically conductive filler) [6]. The filaments of thermoplastic polyurethane-carbon black compunds displayed an increase in resistance upon exposure to various alcohols (methanol, ethanol, and 1-propanol) [4].…”

“…A principle of operation these devices is based on a change of their electrical properties upon exposure to a studied sample. In a sensor technology both the intrisically conducting polymers (their conductivity can be changed by doping) and composites (electrically insulating polymer matrix with a conductive filler) are applied [1][2][3][4][5][6][7][8][9][10][11].…”

Polycarbonate/Carbon Nanotubes Nanocomposites as Liquid Sensors

“…This makes it possible to detect the exposure to the external condition. For example, CPCs can be used for sensing mechanical stress [4,5], temperature [6], gas [7,8] vapor [9,10], pH and liquid [11][12][13][14][15].…”