Electrical and Mechanical Properties of Poly (Methyl Methacryrate)/Carbon Black Composites

Poly (methyl methacrylate) (PMMA)/carbon black (CB) composites were prepared by thermal molding after mixing of PMMA and CB by a vibration ball mill. The electrical conductivity, dielectric constant and mechanical tanδ of these composites were investigated as functions of CB content, temperature and degree of distribution of PMMA particle size. The observation using a microscope revealed that the increase of CB particles on the surface of PMMA particles resulted in the formation of conductive chains from the aggregation state, which leads to the formation of a network structure in the composite film. The critical volume fraction of CB (Vc) corresponding to the jumping of conductivity increased with the decrease of the degree of distribution of PMMA particle size. At a small CB content, the mobility of the matrix increased inspite of mixing, which was assumed to be due to the action of CB as a plasticizer. Besides gaining about 1010S·cm-1 of conductivity, PMMA/CB composites appear to retain the mechanical characteristics of PMMA owing to the composite effect with CB particles.