The effect of micro and nano-sized particles on mechanical and adhesion properties of a clear polyester powder coating

In this study, the effect of various micro and nano-sized particles on the mechanical and adhesion properties of a commercial non-pigmented polyester-TGIC powder coating was studied. Different coating formulations containing various wt.% of aluminum hydroxide (alumina) particles, TiO2 and two different types of fumed silica nanoparticles were prepared via a two-stage process. Tensile strength measurements, DMTA analyses and vertical pull off adhesion test were conducted to evaluate mechanical and adhesion properties of the powder coating samples. The results revealed that the mechanical properties of the powder coating samples were improved with respect to the particles loading up to 2 wt.%. The extent of this effect depends on the weight fraction and size of the particles. The fumed silica nanoparticles with dimethyl dichlorosilane treatment revealed to be more effective to enhanced mechanical and adhesion properties due to relatively better dispersion and plausible chemical interactions between silane treatment on the nanoparticles surface and polymeric matrix. The fluctuation in the mechanical properties was also observed as the particles content further increased up to 3 wt.% due to an undesirable dispersion of the particles and in turn to the presence of aggregates, air pockets as well as discontinuity in the film. Eventually, the results revealed that pre-dispersion of nanoparticles in an appropriate solvent such as ethanol with the aid of ultrasonic irradiation, is a useful and applicable method before addition to a powder coating formulation. In fact, applying ultrasonic irradiation facilitates breaking down of nanoparticles aggregations to possible primary particles. (C) 2013 Elsevier B.V. All rights reserved.