Effect of Nanoalumina on the Electrochemical and Mechanical Properties of Waterborne Polyurethane Composite Coatings

Abstract

A nanocomposite coating was formed by incorporating nanoalumina pigment in a waterborne polyurethane dispersion (WPUD) to different loading levels (0.1% and 1.0% by weight). Electrochemical performance of the nanocomposite coating was evaluated by applying these nanomodified coatings on mild steel substrate and exposing them to salt-spray, humidity, and accelerated UV weathering. The surface morphology of the composite coating was evaluated using various analytical techniques. SEM and AFM were used to investigate the dispersion of nanoalumina pigment and surface morphological changes of the nanomodified coating, before and after exposure to the test environment. Mechanical properties like scratch resistance were studied by using nanoscratch technique (Nanoindenter TI-900, Hysitron Inc, USA) and hardness using pencil hardness test method. The results showed an improvement in the corrosion, UV weathering, and mechanical properties of the coatings at lower concentration (0.1% by wt), indicating the positive effect of addition of nanoalumina pigment to the coating.

Effect of Nanosilica Filled Polyurethane Composite Coating on Polypropylene Substrate

“…To obtain the same coating thickness of around 3 micrometers for all samples, 1 g of the mixed suspensions was then directly coated on each PP substrate using Rod Mayer technique. The coating thickness is mainly determined by the withdrawal speed, by the solid content, and by the viscosity of the liquid [19]. The consistency of the coating thickness was controlled by monitoring the three factors above.…”

Developments in aqueous polyurethane and polyurethane-acrylic dispersion technology. Part II. Polyurethane-acrylic dispersions and modification of polyurethane and polyurethane-acrylic dispersions

“…Therefore, addition of pigment dispersants and thickeners as well as applying special techniques like e.g. using ultrasonic treatment [70][71][72] were recommended to achieve good suspension of fillers in APUD and it was found [70,72] that this method was the most effective in terms of achieving good film properties when fillers were added to water in which prepolymer-ionomer was emulsified. Addition of fillers to polyol before synthesis of APUD is also a good way to reach good stability of filled dispersion.…”

“…APUAD modified with graphene oxide were also recently studied [80,81] and it was found that just 0.015 % of that nanofiller was sufficient to obtain much improved water resistance of the film while higher amounts were not as effective in that regard. Other nanofillers -nano ZnO and superparamagnetic iron oxide (SPIO) were also used for modification of APUD [71,82] and nanosilver was used for modification of 2-component waterborne polyurethane based on water-dispersible polyol -water-dispersible polyisocyanate system [83]. In a study reported in [71] coatings produced from APUD containing two different amounts of nano ZnO (0.1 % and 1 %) were tested and (similarly as it was shown for graphene oxide modified APUAD) it was found that a very small amount of nanofiller (it was 0.1 % in case of nano ZnO) was sufficient to get all substantial coating properties (abrasion resistance, hardness and water resistance) significantly improved as compared to unmodified APUD while the properties of coatings containing 1 % of that filler were not as good.…”

“…Other nanofillers -nano ZnO and superparamagnetic iron oxide (SPIO) were also used for modification of APUD [71,82] and nanosilver was used for modification of 2-component waterborne polyurethane based on water-dispersible polyol -water-dispersible polyisocyanate system [83]. In a study reported in [71] coatings produced from APUD containing two different amounts of nano ZnO (0.1 % and 1 %) were tested and (similarly as it was shown for graphene oxide modified APUAD) it was found that a very small amount of nanofiller (it was 0.1 % in case of nano ZnO) was sufficient to get all substantial coating properties (abrasion resistance, hardness and water resistance) significantly improved as compared to unmodified APUD while the properties of coatings containing 1 % of that filler were not as good. In another study published very recently [82] was admixed with prepolymer ionomer before emulsifying in water and chain extension has been completed, so APUD containing SPIO particles could be obtained.…”

“…More details on various coating applications of APUD and APUAD can be found in e.g. [19,53,55,59,71,[93][94][95][96][97][98][99][100][101][102][103][104]. Other important current and potential applications of APUD and APUAD include, inter alia:…”