Investigation On The Gas Sensitivity Of Carbon Black/Polyethylene Conductive Polymer Composites

Dispersion of carbon black (CB) into an insulating polymeric matrix yields conductive composite material characterized by a sharp decrease of its electrical resistivity when the filler content exceeds a critical value called percolation threshold. For the composites having sufficiently high conductivity, a significant increase in their electrical resistance can be seen when the composites are contacted with organic solvents or vapors. Swelling or dissolution of the polymer matrix and the resultant destruction of the conduction paths within the composites should take the responsibility. Based on this feature, the composites are capable of acting as chemiresistors or electronic noses to detect, distinguish and quantify various solvents or solvent vapors and might find applications in many fields.In the present thesis, we successfully fabricated Carbon Black/Polyethylene (PE) conductive polymer composites by solution blending. With materials'microstructure analyzing (Field Emission Scanning Electron Microscope), the composite material had porous structure after curing. The comb-shaped electrode was produced by screen printing, which had good consistent. We chose plastics as substrate material, in order to avoid cracks.The filler concentration in the composites notably influences the resistance of the composites. It can be seen that a minimum value resistance appears when the content of CB increases to a certain extent and the value of this optimum CB content is higher than the related percolation threshold.Properties of solvent that influence the composites gas sensibility are investigated, such as vapor concentration, polarity and solubility parameter. Referring to the values of standard deviation and relative error as the evaluating parameters, the consistency of gas sensing components was analyzed via 40 times repetitious experimental data. All the composites prepared in this thesis show a good sensibility to Volatile Organic Compounds having some solvency ability to matrix and also have a good stability and reuse ability, such as xylene and chloroform. When adulterating CB/PE with EVA (ethylene-vinyl acetate resin), the CB / PE-EVA was sensitive to weak polarity and polarity organic solvents (ethanol, formaldehyde) but had more"NVC"(Negative Vapor Coefficient) phenomenon.All of the experimental results indicate that the PE/CB composites prepared by polymerization filling exhibit good gas sensing properties, demonstrating the promising application potential.