Polyalkylene Glycol Research Articles

Kinematic Viscosity Prediction of Polyalkylene Glycol in a Deep-Sea Environment from Molecular Dynamics

Kinematic Viscosity Prediction of Polyalkylene Glycol in a Deep-Sea Environment from Molecular Dynamics

Degradation of Polyalkylene Glycol: Application of FTIR, HPLC, and TGA in Investigating PAG Oil Thermal Stability and Antioxidant Reaction Kinetics

Degradation of Polyalkylene Glycol: Application of FTIR, HPLC, and TGA in Investigating PAG Oil Thermal Stability and Antioxidant Reaction Kinetics

Chemical stability investigation of haloolefin refrigerants and their blends with lubricants

This paper examines the findings of highly accelerated life tests (HALT), conducted according to ASHRAE Standard 97 sealed glass tube methodology for R-123 like, R-134a like and R-410A/R-404A like lower global warming potential (GWP) alternatives. Additionally, possible chemical breakdown pathways are reviewed for the new haloolefin refrigerants. Note, compositions for the following blends are shown as percent by weight. For R-123 like refrigerants, R-1336mzz(Z), R-1336mzz(E), R-514A (74.7% R-1336mzz(Z)/25.3% R-1130(E)), R-1233zd(E), and R-1224yd(Z) were examined with and without lubricants. R-1233zd(E) and R-1224yd(Z) were evaluated with mineral oil and the rest were evaluated with polyalkylene glycol (PAG), polyolester (POE) and polyvinyl ether (PVE) lubricants. For R-134a like refrigerants, R-1234ze(E), R-450A (42% R-134a/58% R-1234ze(E)), R-515B (91.1% R-1234ze(E)/8.9% R-227ea), R-1234yf, R-513A (56% R-1234yf/44% R-134a), and R-516A (77.5% R-1234yf/8.5% R-134a/14.0% R-152a) were examined with and without PAG, POE, and PVE lubricants. For R-410A/R-404A like, R-454B (68.9% R-32/31.1% R-1234yf), R-454C (21.5% R-32/78.5% R-1234yf), R-455A (3.0% R-744/21.5% R-32/75.5% R-1234yf), and R-468A (3.5% R-1132a/21.5% R-32/75.0% R-1234yf) were also examined with PAG, POE and PVE lubricants. R-466A (49% R-32/11.5% R-125/39.5% CF3I) was part of this study but will not be covered since it does not contain a haloolefin component.

Optimising Two-Stage Vacuum Heat Treatment for a High-Strength Micro-Alloyed Steel in Railway Spring Clip Application: Impact on Microstructure and Mechanical Performance.

The heat treatment process is a vital step for manufacturing high-speed railway spring fasteners. In this study, orthogonal experiments were carried out to obtain reliable optimised heat treatment parameters through a streamlined number of experiments. Results revealed that a better comprehensive mechanical performance could be obtained under the following combination of heat treatment parameters: quenching temperature of 850 °C, holding time of 35 min, medium of 12% polyalkylene glycol (PAG) aqueous solution, tempering temperature of 460 °C, and holding time of 60 min. As one of the most important testing criteria, fatigue performance would be improved with increasing strength. Additionally, a high ratio of martensite to ferrite is proven to improve the fatigue limit more significantly. After this heat treatment process, the metallographic microstructure and mechanical properties satisfy the technical requirements for the high-speed railway practical operation. These findings provide a valuable reference for the practical forming process of spring fasteners.

Dynamic desorption characteristics of propane and polyalkylene glycol lubricants

Natural refrigerant propane has a saturated-liquid density that is only about half that of HFC refrigerants. Compared with traditional refrigerants, the absorption/desorption characteristics of propane with lubricants show great differences. Studies on the dynamic characteristics of refrigerant/lubricant mixtures have mainly focused on the absorption process, especially the absorption process of high-density refrigerants. The desorption of refrigerant from the mixture has been less studied. In this paper, an experimental apparatus was built to observe and measure the dynamic characteristics of refrigerant desorption. The effects of the refrigerant/lubricant combinations, the depressurization rate, the ambient temperature, and the initial concentration on the desorption process driven by depressurization were analyzed. The depressurization rate is the main factor influencing the desorption mass flow rate. As the pressure dropped, the refrigerant solubility decreased fast, causing the supersaturation degree to rise rapidly, which is the main driver of refrigerant desorption. Moreover, the correlation between the desorption mass flow rate and the supersaturation degree was obtained by the experimental results. The absolute deviations between the experimental and simulated concentrations were less than 2.5%.

Thermal, rheological, and tribological characterization of graphene–polyalkylene glycol nanolubricant for improving the overall efficiency of refrigeration systems

Thermal, rheological, and tribological characterization of graphene–polyalkylene glycol nanolubricant for improving the overall efficiency of refrigeration systems

Heat Transfer Coefficient of 7050 Aluminum Alloy under Different Quenching Medium Parameters

In this study, the heat transfer coefficients of 7050 aluminum alloy under different water temperatures, polyalkylene glycol aqueous solution concentrations and quenching medium types are calculated by an iterative method, and the heat transfer coefficient of the aluminum alloy under different quenching medium parameters was compared and the difference was discussed in detail. The results show that with the increase of water temperature, the heat transfer coefficient of 7050 aluminum alloy gradually decreases; with the increase of polyalkylene glycol aqueous solution concentration, the heat transfer coefficient gradually decreases; the order of heat transfer capacity of quenching medium is disclosed among the studied medium types.

Influence of water content on elastohydrodynamic friction and film thickness of water-containing polyalkylene glycols

Lubricants with a functional water portion have demonstrated a drastic reduction in friction under elastohydrodynamic lubrication conditions. With water-containing polyalkylene glycols, superlubricity with coefficients of friction <0.01 have been measured in model and gear contacts. In addition to the low friction, their calorimetric properties make them particularly interesting for application in electrified vehicles because the liquid can simultaneously serve as lubricant for the gearbox and coolant for the electric motors and the power electronics. In this study, the influence of water content between 8 wt% and 40 wt% of water-soluble polyalkylene glycols on friction and film thickness in elastohydrodynamically lubricated rolling-sliding contacts such as in gears and bearings is investigated. A polyalphaolefine oil is used as a reference. Friction has been measured on a ball-on-disk tribometer and film thickness on an optical tribometer. For a water content of 40 wt%, superlubricity with coefficients of friction down to 0.004 are found. The decrease in friction is up to 95% compared to the polyalphaolefine reference. The measured film thickness decreases with increasing water content. For a water content of 8 wt%, the film thickness is similar to that of the polyalphaolefine reference while at the same time friction is still reduced by 81%. Depending on the friction and film thickness requirements of a specific tribosystem, the water content of a water-containing polyalkylene glycol can be chosen accordingly.

Running-In Effects of Lubricated Polyether Ether Ketone on Steel for Different Spreading and Sorption Tendencies

Polyether ether ketone is a highly resilient thermoplastic that can withstand as an unfilled or filled polymer tribological high loads in high-temperature applications, as it has a high glass and melting temperature. Currently, it attracts interest as a lubricated material for drive systems to minimize noise, as a lightweight solution improving the CO2 balance, or in combination with novel lubricants. We have produced friction and wear maps with pin-on-disk tests on steel axial bearing rings and investigated the interaction and running-in behavior with different lubricants, such as different polyalkylene glycols, polyalphaolefin, and various esters. In general, the behavior of polyether ether ketone is hardly influenced by the frictional heat when loaded at room temperature. It shows a lubricant-specific polymer transfer and surface softening. This running-in impact is enhanced if a loading strategy with initial high friction power is applied. The beneficial transfer forms on the track in mixed lubrication on the rough counterpart until an increasing adhesive contact limits this effect. The appearance of a minimal wear coefficient was found below the glass temperature with lubricants strongly sorbing in polyether ether ketones, such as polar polyalkylenglycol or trimellitic acid ester-based lubricants. Using the interfacial energy of the system to derive an energy term describing the tendency to form a stable transfer, systematic trends in the tribological behavior of polyether ether ketone and polyketone could be identified that can be projected on other systems.

Viscosity and Friction Reduction of Double-End-Capped Polyalkylene Glycol Nanolubricants for Eco-Friendly Refrigerant

In sustainable tribology, researchers are investigating methods to enhance tribological performance by incorporating nanoparticles into lubricants. However, one potential drawback of this strategy is increased lubricant viscosity. The current study aimed to assess the impact of these nanoparticles on the viscosity and coefficient of friction (COF) of the nanolubricants. Three different nanolubricants were synthesized through a two-step process, including mono-nanolubricants (Al2O3/DEC PAG and SiO2/DEC PAG) and hybrid nanolubricants (Al2O3-SiO2/DEC PAG), at volume concentrations between 0.01% and 0.05%. The viscosity and shear flow behavior of these nanolubricants were evaluated using a digital rheometer, while the COF was measured using a Koehler four-ball tribometer. All the nanolubricants showed Newtonian behavior during the experiments. The dynamic viscosity velocity increment of SiO2/DEC PAG was found to be the lowest (1.88%), followed by Al2O3-SiO2/DEC PAG (2.74%) and Al2O3/DEC PAG (3.56%). The viscosity indices of all the nanolubricants were improved only at higher concentrations. At a volume concentration of 0.03%, the Al2O3-SiO2/DEC PAG nanolubricant reduced the COF by up to 8.1%. The results showed that the combination of nanoparticles, temperature, and volume concentration significantly influenced the viscosity and COF of nanolubricants. This study provides essential information for developing high-performance nanolubricants with improved viscosity and COF and advancing environmentally friendly tribology solutions.

Stability and Thermal Conductivity of Mono and Hybrid Nanoparticles Dispersion in Double-End Capped PAG Lubricant

Stable nanolubricant mixtures are interrelated with thermal conductivity enhancement, thus improving heat transfer performance in automotive air conditioning (AAC) systems. This paper studies the stability and thermal conductivity of double-end capped polyalkylene glycol (PAG)-based nanolubricants specially designed for R1234yf refrigerant. Mono nanolubricants (Al2O3/PAG and SiO2/PAG) and hybrid nanolubricants (Al2O3–SiO2/PAG) were prepared using a two-step preparation method at different volume concentrations of 0.01 to 0.05%. The stability of these nanolubricants was observed by visual, UV-Vis spectrophotometer, and zeta potential. Thermal conductivity (k) was measured from 30 to 70 °C using a C-Therm thermal properties analyser. The results from the stability analysis show that all nanolubricants were confirmed in excellent stability conditions for more than six months with minimum visual sedimentation, more than 70% concentration ratio, and zeta potentials greater than 60 mV. The Al2O3–SiO2/PAG samples recorded the highest values of thermal conductivity increment, followed by the Al2O3/PAG and SiO2/PAG samples with 2.0%, 1.7%, and 1.5% enhancement. Hybrid nanolubricants have been shown to have greater potential in the AAC system because of their excellent stability and better property enhancement in thermal conductivity.

Lubricant performance against white etching areas (WEAs) formation in AISI 52100 bearing steel under cyclic compressive loading

Premature bearing failures commonly occur in applications that operate under extreme boundary conditions. The lubrication engineers and tribologists are confronting a key challenge in these bearing failures associated with microstructure decay, such as White Etching Cracks (WECs) and White Etching Areas (WEAs). Lubricant degradation is one of the critical factors for the subsurface decay in the bearing steel. This work evaluates the performance of mineral oil (heavy paraffin oil) and synthetic poly alkyl glycol (PAG) against WEAs formation under pure sliding with cyclic compressive loading. The performance of lubricants was evaluated using Infrared Fourier Transform (FTIR) and Electron Spin Resonance (ESR) spectroscopy. The outcomes reveal that the free radical formation rate is higher for paraffin than PAG. This study found that WEAs formation in the bearing steel is delayed in the PAG tested samples compared to paraffin.

Elastohydrodynamic Film Formation and Sol/Gel Transition of Aqueous Fluids

One of the most widely used water soluble lubricants is PolyAlkylene Glycol (PAG). PAG aqueous solutions can form a gel depending on the concentration and temperature, which affects the formation and friction of lubricating films. This experimental work combined rheological measurements and in-situ film-forming analysis in pure rolling conditions using PAG aqueous solutions of various concentrations. It shows that the pure PAG behaved classically as a piezoviscous fluid, while its aqueous solutions behaved as isoviscous fluids. This was confirmed by the establishment of a film formation map. In addition, the aqueous solutions exhibited two behaviors, characteristic of either sol or gel. A detailed analysis of the film thickness evolution, based on Moes–Venner’s predictions, allowed us to calculate the effective viscosity in the inlet zone and to discuss the origin of the two families, sol vs gel.Graphical

Polymerization of poorly water-soluble monomers in the presence of ethoxylated polyalkylene glycol Laprol 6003, an ethoxylated product of alcoholate copolymerization of propylene oxide with glycerol

The paper shows the similarity of kinetic regularities of vinyl monomers polymerization in the presence of Laprol 6003, regardless of the degree of solubility of the monomers in water. It is assumed that this feature of polymerization is due to the same mechanism of formation of polymer-monomer particles (PMP) – from monomer microdroplets. The interfacial adsorption layer of PMPs, the main site of polymerization, is formed from a surfactant adsorbed from the bulk of the monomer phase and a polymer formed in the adsorption layer upon initiation of polymerization. The formation of complex structures in the interfacial adsorption layer of particles, the incompatibility of the surfactant and the resulting polymer, and high viscosity cause the formation of a strong interfacial layer that ensures the stability of polymer suspensions from the early stages of polymerization.

Experimental study of a domestic refrigerator using (SiO 2 /PAG oil/R- 134a) nano-refrigerant as a replacement for pure R-134a

This research studies the influence of using SiO2 nano-particles of 50nm in a Vapor Compression Refrigeration System (VCRS), along with Poly-alkylene Glycol (PAG) oil and R-134a mixed to create a nano-refrigerant. In this work, the nano-particles were performed in three different concentrations (0.1%, 0.3%, and 0.5%) and mixed with 200ml of PAG oil. AVCR system was built at the mechanical engineering department laboratory in Al-Qadisiyah University to study the Coefficient of Performance (COP) and the consumed energy by the compressor in the two cases of adding the nano-particles and using a pure refrigerant. The paper showed an increase in the system's COP from 2.3 to 2.81 when using a concentration of 0.5% of SiO2/PAG oil/R-134a, increasing the refrigeration effect and decreasing the consumed power.

Adjustable superlubricity system using polyalkylene glycol with various acid aqueous solutions

Polyalkylene glycol (PAG) aqueous solutions have recently been demonstrated to exhibit an ultralow friction coefficient (COF, μ < 0.01). However, the prolonged running-in period and low bearing capacity have limited its widespread application. In this study, we determined that the running-in period can be decreased by more than 75% when the pH value of the lubricant is controlled at 3 by introducing various acid solutions. Additionally, less time was required to realize stable superlubricity with inorganic acid at lower pH values. This was mainly attributed to the acceleration effect of hydrogen ions around the contact region. In case of PAG aqueous solution with organic acid, the wear loss between sliding solid surfaces was reduced, and thus the bearing pressure during the superlubricity period was significantly improved from approximately 30 to 160 MPa. Furthermore, the organic acid molecules were considered to form strong hydrogen bonds with PAG macromolecules and solid surfaces. This in turn strengthened the structure of the adsorption layers. The unique effect of different acids in aqueous polymer lubrication can potentially significantly aid in advancing the study of polymer tribology and broadening industrial applications.

Lubrication Performances of Polyalkylene Glycols at Steel Interface under External Electric Fields.

This work studied the lubrication performances of polyalkylene glycols, which are insulating oils, at the steel interface under external electric fields. The results show that external electric fields greatly affect the lubrication performances of polyalkylene glycols, and there is an optimal voltage (−1.0 V) for the improvement in friction reduction performance. The surface analysis and experiment results indicate that the polyalkylene glycol adsorption film and the reduction in the amount of FexOy and FeOOH in the tribochemical film contribute to improved friction performance under the negative voltage condition. This work proves that the lubrication performances of insulating oils can be affected by external electric fields as well. A lubrication model was proposed, hoping to provide a basic understanding of the lubrication mechanisms of ether-bond-containing insulating oils in the electric environment.

A multifunctional additive for heavy concretes

Introduction. Faster construction and commissioning of industrial and civil facilities is a main factor affecting their operational characteristics at the stage of construction due to high-quality multifunctional additives, having plasticizing properties, coupled with the accelerated curing of composite materials in cement binders. The article addresses a study on the influence of a new multifunctional additive on the physical and mechanical properties of heavy concretes, that determines its plasticizing properties and affects concrete strength.&#x0D; &#x0D; Materials and methods. The study focuses on concrete B30. The Vicat apparatus was used to test the cement paste to identify its normal density and setting time according to GOST 310.3. The strength of cubic specimens was tested using hydraulic press P-120 according to GOST 1080-90.&#x0D; &#x0D; Results. The multifunctional additive was obtained by synthesizing caprolactam mixed with polyalkylene glycol and amino alcohols. The test on the setting time of the cement paste has proven that the multifunctional additive plasticizes, if added to heavy concrete mixes. The impact of the concentration of the multifunctional additive on the setting time, compressive strength and slumping of the concrete mix has been identified. These new data were applied to find the optimal interval of concentrations of the multifunctional additive, added to the concrete mix to make densely reinforced concrete products. The optimal concentration interval is 0.2–0.3 % of the cement mass.&#x0D; &#x0D; Conclusions. The multifunctional additive made of domestic chemical products as a result of the study, improves physical and mechanical characteristics of concrete mixes to be used in the construction of civil and industrial construction facilities.

Mutual diffusivities of difluoromethane and 2,3,3,3-tetrafluoropropylene dissolved in polyalkylene glycol lubricant

In this work, the mutual diffusivities of difluoromethane (R32) and 2,3,3,3-Tetrafluoropropylene (R1234yf) dissolved in Polyalkylene glycol (PAG) lubricant were studied experimentally based on the principle of dynamic light scattering. The pressure range of mutual diffusivity measurement is from 0.142 MPa to 3.371 MPa, and the temperature range is from 293.15 K to 353.15 K. The experimental data were correlated as the equation of temperature and pressure. The average relative deviation between the experimental data and the model is less than 1.34%. The results show that when the temperature is constant, mutual diffusivities of R32/PAG and R1234yf/PAG mixture decrease with the increasing of the solubility of refrigerants. The mutual diffusivity of R1234yf/PAG is less than that of R32/PAG at the same temperature and solubility. This may be due to the longer length of the R1234yf molecule and greater polarity, which results in the difficult diffusion in the lubricant. The molecular radius (0.164 and 0.299 nm) for the mutual diffusivity of R32 and R1234yf in PAG lubricants were obtained according to the Einstein-Stokes equation. The obtained radius values are within a reasonable order of magnitude compared to literature values. Since the molecular radius of R32 is smaller than that of R1234yf, which is also consistent with the experimental results in this work that the mutual diffusivity of R32 dissolved in PAG is larger than that of R1234yf.

Experimental study of a domestic refrigerator using (SiO2/PAG oil/R-134a) nano-refrigerant as a replacement for pure R-134a

This research studies the influence of using SiO2 nano-particles of 50nm in a Vapor Compression Refrigeration System (VCRS), along with Poly-alkylene Glycol (PAG) oil and R-134a mixed to create a nano-refrigerant. The methodology used in this work, the nano-particles were performed in three different concentrations (0.1%, 0.3%, and 0.5%) and mixed with 200ml of PAG oil. A VCR system was built at the mechanical engineering department laboratory in Al-Qadisiyah University. In order to study the Coefficient of Performance (COP) and the consumed energy by the compressor in the two cases of adding the nano-particles and using a pure refrigerant. The paper showed an increase in the system's COP from 2.3 to 2.81 when using a concentration of 0.5% of SiO2/PAG oil/R-134a, increasing the refrigeration effect and decreasing the consumed power.