Polymers (Polyvinylpyrrolidones) As Active Additives Modifying the Lubricating Properties of Water

Abstract

Surface active compounds may act as effective additives modifying water lubricity. Their action mechanism consists in the formation of a lubricating film enriched with an active compound. The reasons for the choice of polyvinylpyrrolidones as additives were their physiological inertness and a lack of harmful environmental effects. The tests were carried out on the solutions of two polyvinylpyrrolidones with degrees of polymerization of 450 (PVP 450) and 14400 (PVP 14400). A significant effect of the polymer chain length on physicochemical (viscosity, surface tension, wettability of steel) and tribological properties (resistance to motion, wear, scuffing) has been found. PVP 14400 showed a considerably greater ability to thicken solutions. Over 10 times higher coefficients of viscosity relative to an analogous PVP 450 solution were observed already at a concentration of 5%. A slightly higher ability of PVP 14400 to reduce surface tension was observed. In the case of wettability of steel, a more effective decrease in the wetting angle was observed for PVP 450. However, the differences obtained were not large and usually did not exceed 20%. The measurements of resistance to motion and wear at three constant loads (2000, 3000, 4000 N) as well as tests on antiseizure abilities under a constant velocity increment of load (409 N/s) were carried out using a four-ball tester (T-02 tester). All friction pairs were made of bearing steel. Introducing additives to water significantly affects a decrease in resistance to motion and wear as well as an increase in the ability of a tribological system to prevent seizure. The system did not undergo seizure even at a load of 4 kN. A 2-fold decrease in the coefficient of friction (μ) and an over 30% decrease in the value of wear scar diameters (d) relative to water were observed for PVP 450 and PVP 14400 solutions at 2.0 kN. The use of water as a lubricant led to seizure of the tribological system already at above 2 kN. Addition of the polymers to water also results in a significant improvement in its antiseizure properties. The values of scuffing load (P t) and limiting pressure of seizure (p oz) for individual solutions were even 5 and 15 times higher, respectively, than the values for water. Seizure load (P oz) was also relatively high, and its level was almost two times higher than that for water. The results obtained indicate that polyvinylpyrrolidone used as an additive considerably improves the tribological characteristics of water as a lubricant base.

Polymer Molecular Weight Dependence on Lubricating Particle–Particle Interactions

“…5, 20 A 2-fold reduction in the coefficient of friction and a 30% reduction in the wear scar diameter relative to water were measured for PVP solutions under a normal load of 2 kN. 5 PVP also exhibits high degradation resistance, which is beneficial from a tribology perspective, confirming the polymer stability as a lubricant over extended periods of time.…”

“…4 Moreover, lubrication using more environmentally friendly, waterbased solvents is increasing in popularity. 5 Various systems, ranging from micro/nanoelectromechanical systems and biomedical devices, to articulating joints or the eye, require surfaces in contact to slide easily past each other in aqueous environments. 1,4 In particular, polymer coatings have been shown to be economic, versatile and convenient approaches to reduce the frictional forces between surfaces in an aqueous system, as they are able to sustain large normal loads while retaining a stable fluid interfacial layer.…”

Friction-lowering capabilities and human subject preferences for a hydrophilic surface coating on latex substrates: implications for increasing condom usage

“…The lubricating effect of PVP has been reported in the literature [27][28][29] and is used in several commercial hydrophilic lubricious coatings e.g. those found on a catheter [30][31][32].…”

The potential of the application of biodegradable and non‐toxic base oils for the formulation of gear oils — model and component scuffing tests

“…1 Because the potential market for ecological lubricants seems to be wide and because new EU regulations imposing the application of biodegradable lubricants in selected areas of technique can be expected, 2 many researchers have undertaken an effort to develop ecological lubricants. They include ecological oils, greases and cutting fluids [3][4][5][6][7] ; however, there is also a new approach related to the reduction of the content of toxic additives in lubricants by the application of scuffing-preventive hard, thin coatings on the mating machine parts. 8 The aim of this work was to assess natural and white oils as potential candidate bases of gear oils.…”