Determination of the viscosity of polyphenylene oxide lubricant with graphite and hexagonal boron nitride additives for AZ31 superplastic forming

Polyphenylene oxide (PPO) with graphite and hexagonal boron nitride additives was tested as a candidate lubricant for high-temperature superplastic forming (primarily blow forming) of AZ31 magnesium alloy. Several samples of PPO with varying quantities of graphite and hexagonal boron nitride additives were prepared according to the formulations listed in Table 1 below. The apparent viscosity of each formulation was to be measured as a function of temperature and shear rate.*;Ultimately, the samples were analyzed using the Rosand RH-2000 capillary rheometer and the ARES-LS2 rotational rheometer. The formulation containing 5% graphite and 5% hexagonal boron nitride exhibited the most uniform properties, with apparent viscosity ranging from 1*104 Pa*s to 8.04*10 4 Pa*s over the temperature range (275°C to 350°C) and the shear rate range (0.01s-1 to 1s-1).;However, the properties of this formulation are not as uniform as those of a rival candidate lubricant Poly Dimethyl Siloxane (PDMS). PDMS is Newtonian: its viscosity is constant with respect to shear rate, and so its behavior is easier to model and control. PDMS is therefore a more suitable candidate lubricant for AZ31 forming than any of the analyzed PPO/additive formulations.;*Please refer to dissertation for diagram.