New approaches to characterize polymeric oil additives in solution based on pyrene excimer fluorescence

Abstract

Maleated polyolefins (MaPOs) such as maleated ethylene propylene copolymers or polyisobutylene terminated at one end with a succininic anhydride can be used as polymeric dispersants in engine oils after reaction with polyamines while unmodified EP copolymers improve the viscosity index of oils. MaPOs can also be labeled with pyrene derivatives to generate pyrene-labeled polyolefins (PyLPOs) as fluorescent mimics of oil additives and pyrene excimer fluorescence (PEF) can be applied to probe their behavior in solution. This review describes new methodology that was recently implemented to characterize the complex fluorescence signal emitted by PyLPOs by using steady-state and time-resolved fluorescence. This methodology enables one to gain quantitative information about the level of clustering of the succinic pendants along a maleated polyolefins and intra-and intermolecular aggregation of polyolefins in solution. Such information is relevant to scientists aiming to characterize polymeric oil additives used in engine oil.

Probing the Interactions between Mimics of Pour Point Depressants (PPDs) and Viscosity Index Improvers (VIIs) in Engine Oil Using Fluorescently Labeled PPDs

“…VIIs are polymers such as ethylene−propylene (EP) copolymers that accomplish this task by undergoing a coil expansion upon increasing the temperature. 7,14,15 The different oil additives used in the industry all have a specific purpose, PPDs and VIIs being designed to lower the PP and control the VI of the oil, respectively, and they need to achieve their task optimally without detrimental interactions with one another. For this reason, techniques that provide information about the level of interpolymeric interactions between polymeric additives used by the oil industry are particularly interesting.…”

“…As wax crystals grow in size as the temperature decreases, they aggregate and form a 3D network. , Expansion of this network of wax crystals in the oil results in the formation of a gel which prevents oil flowa regime that can lead to engine failure . The control of wax crystal growth and engine oil viscosity is handled by using respectively pour point depressants (PPDs) and viscosity index improvers (VIIs), which are the two main polymeric additives employed in engine oils. − …”

“…The lowest temperature at which the oil is still capable of flowing is called the pour point (PP). − Additives used to lower the PP of an engine oil are termed PPDs. Alkyl aromatic polymers and poly­(alkyl methacrylate)­s (PAMAs) − are two important families of PPDs used by the lubricants industry.…”

“…By contrast, VIIs are meant to counteract the inherent decrease in oil viscosity that occurs upon increasing the oil temperature. ,, The magnitude of the decrease in oil viscosity upon increasing temperature is called the viscosity index (VI), a low VI corresponding to an oil whose viscosity decreases substantially with increasing temperature. Because the good operation of an engine depends on the even flow of the oil regardless of temperature, the oil industry is interested in controlling the oil viscosity within a narrow range, hence the need to increase the VI of the oil by using VIIs.…”

“…Because the good operation of an engine depends on the even flow of the oil regardless of temperature, the oil industry is interested in controlling the oil viscosity within a narrow range, hence the need to increase the VI of the oil by using VIIs. VIIs are polymers such as ethylene–propylene (EP) copolymers that accomplish this task by undergoing a coil expansion upon increasing the temperature. ,, …”