The effect of mechanical stress on four viscosity improver polymers

The effect of a Bosch injector on the mass distribution function of four viscosity improver (VI) polymers has been studied. Two of these, hydrogenated styrene—isoprene (HSI) and hydrogenated styrene—butadiene (HSB), are di-block polymers, whereas the others are either comb-like, polyalkyl methacrylate (PMA), or linear, olefin copolymer (OCP). Measurements were performed by light scattering and viscometric techniques before and after application of mechanical stress. Only slight modifications in the physical properties were detected for HSB and HSI, which can be explained by their micellar behaviour. Conversely, a large variation in mean size and viscometric properties was observed for PMA and OCP. Finally, a model is proposed which links the variation of the mass distribution function to the intrinsic viscosity loss.