Influence of organic diluents and a solvent on rheological properties of PVC plastisols

The results of rheological investigations of poly(vinyl chloride) plastisols with dibutyl phthalate, di(2-ethylhexyl) phthalate or dibutyl sebacate as plasticizers, with addition of diluent (xylene, alpha-butyl acetate or butanol) and a solvent (cyclohexanone) are presented. Dependence of viscosity of a composition (measured using Hoppler viscometer) on shearing stress was described by Ostwald-de Waele equation. Maximal viscosity (h(0)) and pseudoplasticity factor H were determined using this equation (Table 2 and 3). Activation energy of viscous flow (Table 5 and 6) has been calculated from Arrhenius-Guzman equation. It was found that introduction of diluent into the plastisol decreases both (n(0)) and (n). However increasing amount of cyclohexanone causes at first increase in viscosity and pseudoplasticity and then they decrease (Fig. 3). It was also found that rheological properties of plastisols are highly influenced by the processes of plastisol particles' association and interactions between the components of a composition leading to formation of spatial structures. The phenomena proceeding on the surface of particles, in the solvation layer, play significant role. Their mechanisms were interpreted on the basis of the values of miscibility coefficients for the pairs of particular components of the composition (Table 7).