Working Mechanism of Organic Friction Modifiers on Steel and Paper Materials

The effect of organic Friction Modifiers (FMs) on friction properties at steel and paper clutch materials is investigated, and their working mechanisms are assessed by the observation of reaction and adsorption films formed on the surface. FMs are essential additives for drivetrain lubricants to manage friction properties. Recently developed fuel efficient transmission systems such as Continuously Variable Transmission (CVT) require precise and complicated friction control. As a result it is extremely important for the detailed behaviour of the FMs and in particular their reactions with the surfaces to be elucidated. In this study, friction properties of organic friction modifiers, oleic acid, oleyl alcohol and glycerol mono-oleate, were evaluated by TE77 and MTM using steel and paper specimens, which simulate two major components of CVT; a steel belt-pulley mechanism and a paper clutch system. The surface films on the post-test materials were studied by SEM, EDX, XPS and ATR-FTIR to assess the influence of the FMs. The results indicate that the friction properties are strongly affected by the substrate material and test temperature as well as the chemical structure of the FMs. In addition, interactions between the FMs and the other additives play an important role for the friction modification mechanism. In order to discuss the working mechanism of the FMs, the relationship between the friction properties and the chemical nature of the surface films was considered. Furthermore, the chemical structure of the FMs and its formulation suitable for CVT fluids are discussed

Properties of Polyol Esters for Low GWP Refrigerants

HFC (Hydrofluorocarbon) refrigerants, whose ODP (Ozone Depletion Potential) is 0, are used in refrigeration and air conditioning equipments recently. It is known that HFCs are high GWP (Global Warming Potential) refrigerants. In October 2016, Kigali Amendment to the Montreal Protocol was stated to achieve the phase-down of HFC refrigerants to prevent global warming. Transition of current HFCs to low GWP refrigerants would be accelerated around the world. HFO (Hydrofluoroolefin) refrigerants such as R1234yf, R1234ze etc. are low GWP refrigerants. Refrigerant manufacturers are introducing not only HFO itself, but also mixture of HFC and HFO. HFO is known to be less chemically stable compared to HFC since there is double bond in its molecular structure. Also, HFOs tend to dissolve well with refrigeration oil compared to HFCs. As a result, amount of refrigerant dissolving in the oil increase and the kinematic viscosity of the oil decrease. We investigated ways to solve problems which may occur by using HFOs. In particular, it is important to maintain the stability and lubricity of oil. To improve stability, we optimized the amount of the stabilizer. To improve lubricity, since the kinematic viscosity of the oil decrease because the refrigerant dissolve in the oil more than necessary, we applied original base oil formulation to prevent the refrigerant from dissolving too much to the oil. In the presentation, properties of POE refrigeration oils which solve problems of low GWP refrigerants by investigating appropriate base oil and additive formulation are introduced

Advanced Control of Frictional Properties on Paper Clutch Materials by a Combination of Friction Modifiers

This study proposes a novel approach for controlling frictional performances at paper clutch systems by a combination of organic friction modifiers (OFMs). The OFMs are commonly used for modifying the frictional properties at the paper clutch. Although the effect of the OFMs tends to be dependent on temperature due to their working mechanism based on the surface adsorption, the frictional properties are preferable to be stable in all the operating temperature for the consistent and precise clutch control. Aiming to modify the temperature dependence of the OFM effect, an OFM with an Advanced Concept (FMAC) was newly developed, and the impact on the clutch frictional performance was investigated using Low Velocity Friction Apparatus (LVFA). Only with the conventional OFM, the friction values experienced excessive reduction at 80 or 120°C, while an optimal property was achieved at 40°C. In the presence of the FMAC, it was possible to inhibit the conventional OFM selectively at the high temperature conditions preventing the friction reduction, leading to the ideal frictional property in all the temperature conditions. The surface analysis revealed that the FMACs were capable of adsorbing on the substrate more intensively at high temperature, which should be the reason of the temperature dependent competitive effect of the FMACs