Mechanism of thermoviscoelasticity driven solid-liquid interface reducing friction for polymer alloy coating

High-temperature ablation is a common failure phenomenon that limits the service life of the transmission parts on heavy-duty machines used in heavy load, high temperature, high shock conditions due to in-sufficient supply of lubricating oil and grease. Traditional self-lubricating coatings prepared by inorganic, organic or organic-inorganic hybrid methods are prone to be oxidated at high temperatures to lose their friction reducing function, so that it is difficult to meet the engineering requirements of high-temperature lubrication. We design viscoelastic polymer coatings by a high-temperature self-lubricating and wear-resistant strategy. Polytetrafluoroethylene (PTFE, T m = 329 °C) and polyphenylene sulfide (PPS, T g = 84 °C, T m = 283 °C) are used to prepare a PTFE/PPS polymer alloy coating. As the temperature increases from 25 to 300 °C, the PTFE/PPS coating softens from glass state to viscoelastic state and viscous flow state, which is owing to the thermodynamic transformation characteristic of the PPS component. Additionally the friction coefficient ( µ ) decreased from 0.096 to 0.042 with the increasing of temperature from 25 to 300 °C. The mechanism of mechanical deformation and surface morphology evolution for the PTFE/PPS coating under the multi-field coupling action of temperature ( T ), temperature-centrifugal force ( T - F ω ), temperature-centrifugal force-shearing force ( T - F ω - F τ ) were investigated. The physical model of “thermoviscoelasticity driven solid-liquid interface reducing friction” is proposed to clarify the self-lubricating mechanism determined by the high-temperature viscoelastic properties of polymers. The high-temperature adjusts the viscosity ( η ) of the coating, increases interface slipping and intensifies shear deformation ( τ ), reducing the friction coefficient. The result is expected to provide a new idea for designing anti-ablation coatings served in high temperature friction and wear conditions.