Radiation grafting of polyethylene onto conductive carbon black and application as a novel gas sensor

Radiation grafting of polyethylene (PE) onto carbon black was carried out by gamma-ray irradiation of PE-adsorbed carbon black. The percentage of PE grafting and decomposition temperature of PE grafted onto the surface were determined by thermogravimetric analysis. At low irradiation temperature, the percentage of grafting was very small in spite of higher irradiation dose. On the contrary, at high temperatures near or above the melting point of PE, the grafting of PE onto the carbon black surface proceeded and the percentage of grafting exceeded 90% when the irradiation dose reached to 200 kGy. The results indicate that the adsorbed PE was completely grafted onto the carbon black surface. The decomposition temperature of the grafted PE on the surface was higher than both free (unadsorbed) PE and adsorbed PE on the carbon black surface, indicating that there is a covalent bond between the carbon black and PE molecule. Using the PE-grafted carbon black and PE, conductive PE/PE-grafted carbon black composite was prepared. Electric resistance suddenly increased in cyclohexane vapor over 101 times, and returned to initial resistance when transferred to air, indicating that the composite can be used as a novel gas sensor.