Fluoropolyether coatings: Relationships of electrochemical impedance spectroscopy measurements, barrier properties, and polymer structure

Abstract

Ten model coatings, selected and obtained from a family of fluorinated resins synthesized by the reaction of perfluoroether oligomeric diols of different molecular weights with polyisocyanurates of hexamethylenediisocyanate (HDI) and isophoronediisocyanate (IPDI), were characterized with differential scanning calorimetry, mechanical testing, and electrochemical impedance spectroscopy measurements. The electrochemical and chemico-physical measurements show that the glass-transition temperature of the starting isocyanate trimers greatly influences the properties of the final urethane coatings; the IPDI trimer gives harder coatings with lower water permeabilities than the corresponding HDI-based materials. Moreover, for each class of materials (from IPDI or HDI), the fluorine content plays a relevant role: the higher the fluorine percentage, the lower the water absorption into the coatings. Furthermore, the chain length of the polyols used for the synthesis of the prepolymers is a variable that exhibits great influence on the coating properties: coatings containing shorter perfluoropolyether segments show better barrier properties. orinated polyether to the cyclic trimers (polyisocyanurates) of hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI). The prepolymers can be self-cured by exposure to atmospheric moisture [monocomponent (MC), moisture-curing formulations] or crosslinked by the addition of stoichiometric amounts of ZDOL polyethers [BC (bicomponent) formulations]. Several properties of this new class of materials have been recently described, 1 including electrochemical impedance for TiO 2 -pigmented coatings. 2 PFPE coatings are characterized by high durability and peculiar surface properties and so are very interesting candidates for developing new anticorrosive protective systems for steel, concrete, and other engineering materials. As a matter of fact, the water permeability and barrier behavior of coating systems containing PFPE may depend

Fabrication of super-hydrophobic surfaces for enhanced stone protection

“…Acrylics and siloxanes have proved to be more suitable and are widely applied nowadays, but they still do not satisfy all the demands for an ideal protective coating for stone monuments and especially those of cultural heritage value. The partially fluorinated and perfluoropolymers were also investigated, since the introduction of fluorine atoms substantially reduces the surface energy of the polymer film [1, [10][11][12]. However, even perfluoroethers with the lowest surface energy of the film formed can assure water contact angle only up to 120° [13].…”

UV Curing of Perfluoropolyether Oligomers Containing Graphene Nanosheets to Enhance Water‐Vapor Barrier Properties

“…Moreover due to their high durability and toughness and their peculiar surface properties, UV‐cured PFPE coatings are very interesting candidates for developing high‐performance protective systems for different materials. The water permeability of coatings containing PFPE is generally low (good barrier behavior) due to the extreme hydrophobicity of the fluorinated chain and its very low glass transition temperature.…”

Study of metal protective hydrophobic coatings from waterborne polyurethane ionomers

“…the volume fraction of water (v) in organic polymers can be calculated from the coating capacitance, which can be estimated through EIS measurements [4]. The volume fraction of electrolyte absorbed by the coatings is reported in Fig.…”

“…The voltage perturbation was applied to an aluminum panel coated with the fluorinated polyurethane coatings (working electrode, WE) through a platinum electrode (counter electrode, CE) at ambient temperature, at the open-circuit potential [12], using a Metrohm AUTOLAB PGSTAT30 [4]. Data collected in the frequency range between 1 and 40 kHz were used to evaluate the dielectric constants of the coatings [13,14].…”

“…Their surface properties like hydrophobicity and cleanability can be improved by introducing low surface tension fluorinated monomers or macromers, like in case of fluorinated polyether containing polyurethanes [2][3][4]. In these products it was observed that water permeability, barrier properties and durability are largely affected by phase segregation phenomena involving the apolar fluoroether segments and polar urethane moieties [2].…”