In the area of coating development,
it is extremely difficult to
find a substitute for bisphenol A diglycidyl ether (DGEBA), the classical
petroleum-based raw material used for the formulation of epoxy thermosets.
This epoxy resin offers fast curing reaction with several hardeners
and the best thermal and chemical resistance properties for applications
in coatings and adhesive technologies. In this work, a new biobased
epoxy, derived from poly(limonene carbonate) oxide (PLCO), was combined
with polyetheramine and polyamineamide curing agents, offering a spectrum
of thermal and mechanical properties, superior to DGEBA-based thermosets.
The best formulation was found to be a combination of PLCO and a commercial
curing agent (Jeffamine) in a stoichiometric 1:1 ratio. Although PLCO
is a solid due to its high molecular weight, it was possible to create
a two-component partially biobased epoxy paint without the need of
volatile organic compounds (i.e., solvent-free formulation), intended
for use in coating technology to partially replace DGEBA-based thermosets.
Biobased epoxy-derived raw materials will be essential for future coating and adhesive designs in industry. Here, a facile approach is reported towards the incorporation of limonene into an epoxy-functionalized polycarbonate and its crosslinking with a polyamine curing agent to obtain a thermoset material. For the first time, a solvent-borne adhesive with excellent filmforming, mechanical and adhesion strength properties is described.
In this work, the use of ZrO2 nanocoating in aluminum substrates, generated by controlled electrochemical chronoamperometry in hexafluorozirconic acid solutions (H2ZrF6·5H2O), resulted in a lower porous films than that obtained by chemical conversion coating. After the application of an epoxy coating, long-term cyclic immersion corrosion tests and scratch tests proved the superior protection of the dual system and the coating lifespan, thanks to the enhanced adhesion of ZrO2 intermediate layer and the organic coating. As zirconium-based electrolytes are considered more friendly bath if compared to that of other conversion coating processes, like chromating, phosphating or anodizing processes, the study opens new insights to the protection of structural metals in sectors such as automotive, naval and aerospace industries. The main advantages are the employment of lightweight intermediate pre-treatment (nanoscale), compared to conventional ones (microscale), and reduction of waste slurry (electrolyte bath free of additives).
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