The electrical and mechanical behavior of carbon black filled poly(vinyl acetate) latex-based and solution-based polymer composites was examined. A set of experiments were performed to distinguish composites with a segregated network (emulsion-based) from those with random dispersion (solution-based) of the filler. The percolation thresholds for the emulsion-based composites were near 1.2 vol% carbon black, while the solution-based composites were around 8.2 vol% carbon black. This difference is due to the segregated network formation, which leads to excluded volume effects in emulsion-based systems. This excluded volume created by the solid polymer particles forces the carbon black particles into conductive pathways at low concentration. In the solution-based case, fully solvated polymer results in a random dispersion of carbon black. The segregated network composite also shows significant improvement in both electrical conductivity and storage modulus with low carbon black loading, while the solution-based composite achieves significant property enhancements at higher carbon black loading because of the greater percolation threshold. The effect of clay in both emulsion and solution-based composites with carbon black was also studied by preparing composites with three clay concentrations (0.2, 0.4 and 2 wt%). In emulsion-based composites, low clay concentration reduced the percolation threshold from 1.2 vol% to 0.8 vol% carbon black, but with solution-based composites clay increased the percolation threshold from 8.2 vol% to 11.7 vol% carbon black. It is assumed that clay helps to force the carbon black particles into the conductive pathways in the emulsion-based composites. In solution-base composites, clay improves the dispersion of carbon black, thereby destroying the carbon black network and reducing conductivity and storage modulus. The storage modulus in emulsion-based composites improved with 0.2 wt% clay but greater clay concentration resulted in a drop in modulus due to porosity from excess excluded volume effects.
| Identifer | oai:union.ndltd.org:TEXASAandM/oai:repository.tamu.edu:1969.1/ETD-TAMU-1566 |
| Date | 15 May 2009 |
| Creators | Miriyala, Sethu M. |
| Contributors | GRUNLAN, JAIME C., BALBUENA, PERLA, ZHANG, XINGHANG |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | thesis, text |
| Format | electronic, application/pdf, born digital |
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