| abstract |
A method is provided to determine the predisposition of a polymer to form network or gel in a lubricating oil which comprises obtaining a composition of a polymer in a diluent, measuring the shear stress as a function of shear rate, determining the yield stress using the Herschel-Bulkley equation and assessing the yield stress. A method is also provided to determine the predisposition of a polymer to form network or gel in a lubricating oil which comprises obtaining a composition of a polymer in a diluent, determining at least one of (i) the storage modulus G′ and loss modulus G″ of the composition by subjecting the composition to sinusoidal (oscillating) stress or strain of certain amplitude and frequency, (ii) the phase lag (angle) of the response strain or stress δ, or (iii) the tangent (tan) δ, and (c) assessing at least one of the G′, G″, δ, or tan(δ) determined. |