Study on laminar viscosity and zero shear viscosity of latex systems.

The flowing nature and rheological properties of polymethyl methacrylate latex systems in a coaxial cylinder viscometer were studied on the basis of laminar shear flow model and rheological experimental data. The physical meaning of laminar viscosity (ηi,j) and zero shear viscosity (η0) were described. We assumed that laminar shear flows depended on position and shear time, so microrheological parameters were the function of position and shear time. ηi,j was the viscosity of any shear sheet i between two neighboring laminar shear flows at time t; j was denoted as j=t/Δt; and Δt was the interacting time of two particles or two laminar shear flows. τi,j and γi,j were shear stress and shear rate of any shear sheet i at j moment. According to Newton regulation τi,j=ηi,jγi,j, apparent viscosity ηa should be a statistically mean value of j shear sheets laminar viscosity at j moment, i.e., ηa=∑i=jηi,jγi,j/∑i=jγi,j. η0 was defined as shear viscosity between a laminar shear flow and a still fluid surface, i.e., η0=(τi,j/γi,j)j–i→0. These new ideas described above may be helpful in the study of the micromechanisms of latex particle systems and worthy of more research.