Abstract: Experimental study was carried out on the melt viscosity of different types of PMMA. It showed that rheological behavior of three PMMA was different because their molecular was different, and under the same temperature and pressure, the higher the molecular weight, the larger the viscosity. With increasing extrusion pressure the shear rate increased, shear viscosity decreased, so the melt gave the characteristics of shear thinning. With increasing temperature, the shear viscosity decreased, and gradually become equal when the temperature reached 280 ℃.

Key words: PMMA, viscosity, flow rate