How Pressure Affects the Dynamic Viscosities of Two Poly(propylene glycol) Dimethyl Ether Lubricants

The dynamic viscosity of two poly(propylene oxide) dimethyl ethers with average molecular weights higher than 1.3 kg·mol−1 are the object of study in this work. The experimental measurements have been performed with a rotational automated viscometer and a high-pressure rolling-ball viscometer up to 60 MPa at five temperatures ranging from (303.15 to 373.15) K. We present other physical properties that affect the lubrication, such as the viscosity index, the pressure−viscosity coefficient, and the temperature−viscosity coefficient. Several Vogel−Fulcher−Tammann (VFT) type equations were used to fit the viscosity experimental values to the pressure and temperature. The viscosity data have also been fitted as a function of temperature and volume to the thermodynamic scaling model of Roland et al.