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The influence of small compositional and structural differences in ethylene/propylene copolymers as a lubricating oil rheology modifier on their solution viscometric behavior

The influence of the composition and structure of amorphous ethylene-propylene copolymer, EPC on viscometric behavior of mineral lubricating oils was examined and described. It is shown that even small differences in composition and structure of the same polymeric product, which are unavoidable consequence of the statistical nature of polymerization reactions, can display significant changes related to viscosity and thickening efficiency. Molecular weight of the additive has the most significant effect on viscosity since their very small increase causes a substantial increase in viscosity of olefin copolymer (OCP) solutions. Composition and distribution of comonomer sequences are important parameters, but do not show explicit nor linear effect on the solution viscosity. The interdependence of ethylene content, molecular weight and viscosity of additive solutions is expressed by an empirical function which is calculated using the Marquardt-Levenberg iterative algorithm. Understanding of the dependencies between the composition and structure together with the application characteristics is necessary for the formulation of lubricants and for achieving the optimal performance of a polymeric additive.

amorphous ethylene-propylene copolymer ; composition ; structure ; viscosity

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