Preparation and tribological behaviour of poly(methyl methacrylate) (PMMA) microcapsules containing friction modifiers.

Aims: Microcapsules comprising of a poly(methyl methacrylate) (PMMA) shell and friction modifier (FM) core were prepared to reduce the friction and extend the service life of engine lubricating oil.Methods: Microcapsules containing both organic FM and molybdenum FM were produced via solvent evaporation technique. The friction coefficient, thermal stability, and chemical composition of microcapsules were investigated.Results: The incorporation of microcapsules in lubricating oil dramatically reduced the friction coefficient to be lower than that of virgin FM. Organic FM and molybdenum FM are compatible during the encapsulation process. The release of the FM inside the microcapsules was controllable by thermal degradation of polymeric shell at 150 °C or mechanical rupture at room temperature.Conclusions: This study provided a novel approach to improve the tribological properties of lubricating oil with long service life, facile fabrication and low cost and will find potential applications in lubrication industry for internal combustion engines.

Site-Selective Modification of Cellulose Nanocrystals with Isophorone Diisocyanate and Formation of Polyurethane-CNC Composites.

The unequal reactivity of the two isocyanate groups in an isophorone diisocyante (IPDI) monomer was exploited to yield modified cellulose nanocrystals (CNCs) with both urethane and isocyanate functionality. The chemical functionality of the modified CNCs was verified with ATR-FTIR analysis and elemental analysis. The selectivity for the secondary isocyanate group using dibutyl tin dilaurate (DBTDL) as the reaction catalyst was confirmed with (13)C NMR. The modified CNCs showed improvements in the onset of thermal degradation by 35 °C compared to the unmodified CNCs. Polyurethane composites based on IPDI and a trifunctional polyether alcohol were synthesized using unmodified (um-CNC) and modified CNCs (m-CNC). The degree of nanoparticle dispersion was qualitatively assessed with polarized optical microscopy. It was found that the modification step facilitated superior nanoparticle dispersion compared to the um-CNCs, which resulted in increases in the tensile strength and work of fracture of over 200% compared to the neat matrix without degradation of elongation at break.