Effect of structural ordering on the physicochemical properties of oils

The relaxation times T-1a and T-2a, proton populations P-i, and physicochem ical parameters (dynamic viscosity eta and density rho) of oils were determ ined by using the pulse NMR in conjunction with modeling. A relationship be tween the relaxation times and the molecular weight and concentration of as phaltenes and resins was found. The dependences obtained showed kinks at et a = 5-6 cP (rho = 840-850 kg/m(3)). A model of oil structure was proposed t o explain the experimental results. The model was based on the assumption o f a long-range order in oils. The viscosity was calculated by using a speci al radial distribution function R(r) = (1/n)Sigma N-k delta(r - r(k))/4 pi r(k)(2) and a special pair potential U(r) = 4 phi(0)[(a/r)(12) - Aexp(-alph a r)\cos(beta(r))\].