Effects of binder polymers on rheological properties and coating characteristics of magnetic suspensions

概要

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The relations between magnetic properties of coating films and dispersion state of magnetic particles in the suspension are investigated with the aid of a rheological method. Suspensions of maghemite particles were prepared in two dispersing systems VAGH/RE610 system and MR110 system. VAGH is an ordinary binderpolymer based on a polyvinyl chloride derivative and RE610 is a dispersing agent consisting of an alkyl ether phosphate, while MR110 is a binder with polar groups, which adhere to the surface of the magnetic particles, in the molecular chains. Usually, dispersing agents are not necessary in the MR110 system.<BR>Dried film of a suspension of MR110 system show better surface smoothness in comparison with that of VAGH/RE610 system. Therefore, it is thought that dispersibility of particles in MR110 system is better than that in the VAGH/RE610 system. However, the viscosity of the MR110 system appeared to be higher than the VAGH system under relatively high shear rate, in contrast to ordinary suspensions, which show lower viscosity when particles are better dispersed.<BR>The mechanism of the peculiar rheological behaviors in the suspensions of magnetic particles was explained by a percolation model, in which elastic networks are constructed with elastic units, flocs, the mechanical property of which depends on the shear history of the system.
Japan Society of Colour Materialの論文