Preparation and electrical conductivity of nutural rubber/polypyrole/montmorillonite nanocomposites

The natural rubber (NR) /polypyrrole (PPy) composites were prepared by the chemical oxidative polymerization of pyrrole in aqueous solution of natural rubber latex. The reactions were carried out at 0 ºC for 1 hour using FeCl3 solution as an oxidant with constant FeCl3:pyrrole mole ratio of 2.5. The amount of PPy in the composite was weight determined from 60 ºC oven-dried material. The electrical conductivities of the composites were measured with a home-made four-point probe set up. Parameters affecting the electrical conductivity of the composites were studied, i.e. the amount of pyrrole monomer, types of solvent, the addition of surfactant, the amount of montmorillonite (MMT), and types of organically modified montmorillonite (oMMT). It was found that loading of pyrrole gave the composites with increasing electrical conductivities, with the highest value of which was 4.44 Scm-1 for 15 wt% of PPy. Higher electrical conductivity (7.16 Scm-1) was obtained with addition of sodium dodecylbenzene sulfonate(SDBS). In the presence of MMT, the nanocomposites exhibited higher electrical conductivity with increasing MMT content. The electrical conductivity of the nanocomposites prepared with sodium dodecylbenze sulfonate montmorillonite modifier gave the highest value of 7.38 Scm-1. An XRD pattern showed an increase in d-spacing of MMT from 1.26 nm to 1.84 nm of NR/PPy/MMT nanocomposite, confirming the intercalation of conducting PPy into MMT layers. The use of organic modifier increased the d-spacing of MMT to 2.80 nm. The thermal stabilities of NR/PPy, NR/PPy/MMT, and NR/PPy/oMMT composites were found to be higher than pristine PPy.