Viscosity index improvers and thickeners

Stambaugh, R. L.

doi:10.1007/978-1-4615-3554-6_5

Cited by 6 publications

(8 citation statements)

References 18 publications

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“…In comparison with the vast pool of studies documenting the interactions between wax and PPDs, much less seems to be known about the interactions between waxes and VIIs such as the EP copolymers studied herein. In particular, interactions between waxes and EP copolymers having a high ethylene content were found to be reduced at low temperatures as illustrated in Figures C,D contrary to reported expectations . The suggestion that waxes do not cocrystallize with long polyethylene stretches of the EP(78) copolymers at low temperature is supported by studies of the interactions of waxes with PE–PEP.…”

Section: Resultsmentioning

confidence: 57%

“…The ethylene-to-propylene molar ratio defines the quality of a given EP copolymer as a VII. , The presence of long ethylene sequences in EP copolymers induces polymer crystallinity that changes the hydrodynamic volume of the polymer coil in a way that yields desirable lubrication properties for an engine oil as a function of temperature. But polymer sequences with higher ethylene contents are also expected to interact strongly with wax present in the engine oil at very low temperatures . The interactions between wax and EP copolymers are expected to affect V h of the EP copolymers coil and thus the viscosity of the EP copolymer solution.…”

Section: Introductionmentioning

confidence: 99%

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Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil

Pirouz

Duhamel

Sheng³

et al. 2017

Macromolecules

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A new methodology based on pyrene excimer fluorescence (PEF) was applied to quantitatively measure the actual level of intermolecular association between ethylene-propylene (EP) copolymers in toluene in the presence of wax, an intrinsic component of engine oils. EP copolymers are commonly used as viscosity index improvers (VIIs) in engine oils. Unfortunately waxes in engine oils thicken the oil and are suspected of associating with VIIs at low temperature.In this study, four EP copolymers were maleated to yield EP−MA and then fluorescently labeled with 1-pyrenemethylamine to yield Py-EP. Successful maleation and pyrene labeling were confirmed by Fourier transform infrared (FTIR) and UV-Vis absorption spectroscopy. The solution behaviour of the EP copolymers in the presence of wax was characterized by PEF, which was used to quantitatively measure the molar fraction of intermolecular interactions (finter) between EP copolymers in the absence or presence of wax. The fraction finter was determined through the analysis of the fluorescence spectra of the Py-EP solutions acquired as a function of temperature.Upon excitation, the Py-EP solutions generated excimer upon encounter between an excited and a ground-state pyrene. The ratio of the excimer fluorescence intensity (IE) over that of the monomer (IM) yielded the IE/IM ratio which was employed to determine finter. Plots of finter as a function of temperature provided a description of the solution behaviour of a given VII with or without wax present in solution. The results of this study indicate that wax in solution binds onto EP copolymers dissolved in toluene, which increases macromolecular associations as reflected by an increase in finter. The formation of microcrystals between semicrystalline EP copolymers however induces strong polymer-polymer interactions that result in the dissociation of the wax from the polymers.

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Section: Resultsmentioning

confidence: 57%

Section: Introductionmentioning

confidence: 99%

Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil

Pirouz

Duhamel

Sheng³

et al. 2017

Macromolecules

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“…The self-assembly of block copolymers into micelles is essential for a variety of applications, including viscosity modification of oils, , the formation of complex block polymer phases, and controlled drug release. − Many of these applications require micelles to maintain a dynamic equilibrium. Importantly, chain exchange is a fundamental process of micelle relaxation which has been shown theoretically to be the dominant mechanism close to equilibrium. , However, despite substantial experimental progress, understanding of the molecular level details of the process remains incomplete.…”

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confidence: 99%

Free Energy Trajectory for Escape of a Single Chain from a Diblock Copolymer Micelle

2021

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We use umbrella sampling to compute the free energy trajectory of a single chain undergoing expulsion from an isolated diblock copolymer micelle. This approach elucidates the experimentally unobservable transition state, identifies the spatial position of the maximum free energy, and reveals the chain conformation of a single chain as it undergoes expulsion. Combining umbrella sampling with dissipative particle dynamics simulations of A 4 B 8 micelles reveals that the core block (A) of the expelled chain remains partially stretched at the transition state, in contrast with the collapsed state assumed in some previous models. The free energy barrier increases linearly with the Flory−Huggins interaction parameter χ up to large interaction energies, where the structure of the otherwise spherical core apparently deforms near the transition state.

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“…Polymer additives are also dissolved in base lubricant oils and used as friction modifiers. 14 In most cases, polymer additives are used to reduce the change in the bulk viscosity of the base oils against temperature change (this type of additive is referred to as "viscosity index improver"). Recently, block copolymers with functional groups have been receiving attention as friction modifiers; they are expected to adsorb on surfaces and restrain the decrease of lubricant film thickness.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Polymer additives are also dissolved in base lubricant oils and used as friction modifiers . In most cases, polymer additives are used to reduce the change in the bulk viscosity of the base oils against temperature change (this type of additive is referred to as “viscosity index improver”).…”

Section: Introductionmentioning

confidence: 99%

Low-Friction Adsorbed Layers of a Triblock Copolymer Additive in Oil-Based Lubrication

et al. 2015

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The tribological properties of the dilute solution of an ABA triblock copolymer, poly(11-acrylamidoundecanoic acid)-block-poly(stearyl methacrylate)-block-poly(11-acrylamidoundecanoic acid (A5S992A5), in poly(α-olefin) (PAO) confined between mica surfaces were investigated using the surface forces apparatus (SFA). Friction force was measured as a function of applied load and sliding velocity, and the film thickness and contact geometry during sliding were analyzed using the fringes of equal chromatic order (FECO) in the SFA. The results were contrasted with those of confined PAO films; the effects of the addition of A5S992A5 on the tribological properties were discussed. The thickness of the A5S992A5/PAO system varied with time after surface preparation and with repetitive sliding motions. The thickness was within the range from 40 to 70 nm 1 day after preparation (the Day1 film), and was about 20 nm on the following day (the Day2 film). The thickness of the confined PAO film was thinner than 1.4 nm, indicating that the A5S992A5/PAO system formed thick adsorbed layers on mica surfaces. The friction coefficient was about 0.03 to 0.04 for the Day1 film and well below 0.01 for the Day2 film, which were 1 or 2 orders of magnitude lower than the values for the confined PAO films. The time dependent changes of the adsorbed layer thickness and friction properties should be caused by the relatively low solubility of A5S992A5 in PAO. The detailed analysis of the contact geometry and friction behaviors implies that the particularly low friction of the Day2 film originates from the following factors: (i) shrinkage of the A5S992A5 molecules (mainly the poly(stearyl methacrylate) blocks) that leads to a viscoelastic properties of the adsorbed layers; and (ii) the intervening PAO layer between the adsorbed polymer layers that constitutes a high-fluidity sliding interface. Our results suggest that the block copolymer having relatively low solubility in a lubricant base oil is effective at forming low-friction adsorbed layers in oil-based lubrication.

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Viscosity index improvers and thickeners

Cited by 6 publications

References 18 publications

Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil

Using Pyrene Excimer Fluorescence To Probe the Interactions between Viscosity Index Improvers and Waxes Present in Automotive Oil

Free Energy Trajectory for Escape of a Single Chain from a Diblock Copolymer Micelle

Low-Friction Adsorbed Layers of a Triblock Copolymer Additive in Oil-Based Lubrication

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