Rheology of PVAc–MMT–STAB

Polyvinyl acetate (PVAc) is considered to be an acceptable environmental friendly adhesive, and montmorillonite (MMT) is a cheap and accessible natural nano-mineral. In this work, MMT was first organically activated by octadecyl trimethyl ammonium bromide (STAB). The intercalated nano-composite, MMT–STAB, was then polymerized with VAc. The influence of various additions of MMT–STAB on the rheology of PVAc–MMT–STAB was analysed using the power-law function equation and the Cross–Williamson model viscous equation. The results showed that MMT–STAB was able to improve the rheology of PVAc. The PVAc and PVAc–MMT–STAB all were pseudo-plastic non-Newtonian fluids, with a flow index (i) of 0.93. The apparent viscosity (η), fluid consistency (Ï), characteristic time of materials (ζ), zero shear viscosity (η 0), weight average molecular weight (M w), number average molecular weight ( M n) and the solid content (O), all increased with increasing additions of MMT–STAB as a result of the polymerization process. All properties, apart from ζ, showed a maximum with the addition of 2.0 wt%. The limiting viscosity (η ∞) was 0 mPa s for all samples of PVAc or PVAc–MMT–STAB. Their storage stability was found to be excellent. The reasonable addition of MMT–STAB in polymerization was found to be no more than 2.0 wt% of VAc. In addition, both PVAc and PVAc–MMT–STAB exhibited the normal stress effect (or Weissenberg effect), also known as the 'pole-climbing phenomenon'.