Influence of Polymer Modulus on the Percolation Threshold of Electrically
Y.S. Kim, J.B. Wright, J.C. Grunlan
Texas A&M University, US
Keywords: segregated network, percolation threshold, matrix modulus
Abstract:Monodispersed copolymer emulsions with different glass transition temperatures were synthesized to investigate the effect of room temperature polymer matrix modulus on the electrical properties of carbon black (CB) filled segregated network composites. The emulsion with highest modulus at room temperature produced composites with the lowest percolation threshold. The threshold for a composite made from a copolymer latex containing an equal ratio of butyl acrylate and methyl methacrylate (BA5) is 1.5 vol%, while the percolation threshold for the much lower modulus BA7 (7:3 BA:MMA ratio) is 4.9 vol %. The microstructure of each composite shows significant differences in the level of CB dispersion within the polymer matrix. Higher modulus polymer particles push the CB more efficiently into the interstitial space between them, resulting in a lower percolation threshold. This modulus effect was confirmed by increasing the drying temperature, where the modulus of latexes were more similar and the percolation thresholds for three composites also become closer to one another.