Colloidal PTFE dispersion in commercial engine oil: Lubrication by Pluronic adsorption at the interface

•Pluronic block copolymers used as stabilisers for PTFE particles in engine oil.•Dispersion stability is governed by molecular weight and HLB of Pluronics.•Low molecular weight Pluronic shows best efficiency for PTFE stabilization.•Tribology tests evidenced agreement with dispersion stability parameters.•Adsorption of polymer chains as loops and tentacles presumably drives the stabilization. PTFE particles with an average size of ∼300 nm were dispersed in20w40 commercial engine oil using Pluronic® surfactant. The role of series of different Pluronics with varying molecular weight and HLB was investigated. The dispersion stability was checked by UV-Vis-NIR spectrophotometer and by force transducer. The result indicates significant dispersion stability for low molecular weight and low HLB Pluronic, attributed to faster diffusion at PTFE-oil interface and resultant steric stability. L92 based formulation with less than 10% sedimentation even after 48 hrs, was evaluated for further tribological tests, i.e. wear, friction and pressure profile. Hydrodynamic oil film pressure profile using journal bearing showed significant increase in the load carrying capacity owing to PTFE dispersion in engine oil. Four ball tester depicted decreases in wear scar diameter for L-92 stabilised dispersion. Plausible molecular mechanism is proposed based on adsorption of polymers bilayer around PTFE particles through tail-tail interactions between PEO chains.