Abstract

One reason for using polymeric additives is to obtain a product which has better viscosity-temperature characteristics than a comparable pure mineral oil. Measurements of the viscosity-temperature behaviour of motor oils with and without polymer addition show the necessity of a revision of the generally accepted concept of the mechanism of VI improvement. By addition of polymer the better viscosity-temperature characteristics of light oils, which are however of limited value for lubrication of engines, can bemaintained partially in the region of higher viscosities. So it becomes obvious how it is possible to produce multigrade oils from polymers the polymer coil dimensions of which either expand or contract with increasing temperature. Coil expansion promotes VI improvement to some extent, but in no way does this effect play a decisive part

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