Viscosity index. I. Evaluation of selected copolymers incorporating n‐octadecyl acrylate as viscosity index improvers

Abstract

SynopsisCompositionally and structurally varied copolymers all containing n-octadecyl acrylate were prepared and evaluated as viscosity index improvers in a common base oil under conditions of low shear. Systems evaluated over a range of copolymer and blend composition were: copolymers of n-octadecyl acrylate with, respectively, methyl methacrylate, 2-ethylhexyl acrylate, and n-dodecyl acrylate; and homopolymers of poly(n-octadecyl acrylate), prepared with a wide range of molecular weights. Properties were compared with those of blends of commercial methacrylate copolymers (acryloids) which had been freed of their entraining liquid. Mixtures of base oil with copolymers of n-octadecyl acrylate and methyl methacrylate, compared at fixed SAE viscosities, were the most efficient of all blends studied. They had the smallest rate of change of viscosity with temperature (as measured by their ASTM slopes), particularly in the composition region of incipient polymer precipitation at room temperature. Efficiency of certain of these compositions was somewhat greater than that of the acryloids. A parameter that related concentration and weight-average molecular weight was used to correlate all of the data for ASTM slope and viscosity. Empirical relations developed by using this parameter enabled rheological data to be estimated that agreed within 6% of experimental values for the case of thermodynamically good base oil solvents. These data demonstrated the relatively small contributions of copolymer structure to viscosity index improvement.

Triple Function Lubricant Additives Based on Organic–Inorganic Hybrid Star Polymers: Friction Reduction, Wear Protection, and Viscosity Modification

“…Unsurprisingly, the VI increases with increasing the polymer concentration from 1 to 2 wt % and is mainly attributed to a significant elevation of the kinematic viscosity (ν) at 100 °C (Figure , stripped columns), while the low-temperature viscosity remains relatively unaffected (Figure , solid columns). This observation is consistent with the generally accepted mechanism for polymethacrylate-based viscosity improvers, which involves temperature-enhanced coil swelling. ,,− This behavior is beneficial for typical (automotive) engine environments since it safeguards efficient lubrication at elevated service temperatures (≈ 100 °C), while practically retaining the cold-starting facility of the neat base oil …”

“…beneficial for typical (automotive) engine environments since it safeguards efficient lubrication at elevated service temperatures (≈ 100 °C), while practically retaining the cold-starting facility of the neat base oil. 8 Evaluating the differential dependence of viscosity index improvement on polymer topology reveals a decreasing trend in VI with increasing degree of branching of the polymeric additives. Although in principle the differences in measured VI will also depend on variations in the molecular weights of the employed additives, we attribute these variations to polymer architecture due to the relatively narrow range of molecular weights.…”

“…The mechanisms by which polymers modulate the temperature dependence of the viscosity vary between different classes of viscosity-improving polymers. Nevertheless, a vast body of literature suggests that the most efficient (polymethacrylate-based) viscosity-improving additives rely on a reversible, temperature-induced chain swelling, where the expanded chains have increased contribution to the solution viscosity when compared to their collapsed state analogues at low temperatures. ,− Evidently, the viscosity-improving performance is closely related to their molecular weight and architecture. Linear polymeric chains are theoretically the most efficient viscosity-improving additives since these macromolecules are topologically unconstrained allowing for the most pronounced dimensional differences between the collapsed and expanded states.…”

Preparation and chemical properties of soluble π‐conjugated poly(aryleneethynylene) consisting of azabenzothiadiazole as the electron‐accepting unit

“…Fig. 4) is assigned to a side‐to‐side distance of loosely packed alkyl side chains 24, 25. The d 3 distance (3.4 Å) is assigned to the layer‐to‐layer stacking distance, and it is shorter than that ( d 3 ′ = 3.8 Å or 2θ = 23.9°) observed with PAE‐BzTdz .…”

Role of Architecture on Thermorheological Properties of Poly(alkyl methacrylate)-Based Polymers

“…To date, a large number of polymeric thermorheological modifiers have been reported for oil-based media. The majority of these polymers are based on poly­(meth)­acrylates, olefin copolymers, and (hydrogenated) poly­(styrene- co -dienes) with varying architectures. ,,− However, the physical mechanism underlying their action has been the topic of debate for decades, with this lack of fundamental understanding hampering the rational design of next-generation rheological modifiers. A commonly accepted mechanism that was first proposed in the late 1950s by Selby et al relies on a reversible, temperature-induced coil expansion .…”