Tailored Crosslinking Process and Protective Efficiency of Epoxy Coatings Containing Glycidyl-POSS

Abstract

Versatile product protective coatings that deliver faster drying times and shorter minimum overcoat intervals that enable curing at faster line speeds and though lower energy consumption are often desired by coating manufacturers. Product protective coatings, based on silsesquioxane-modified diglycidyl ether of bisphenol-A (DGEBA) epoxy resin, are prepared through a glycidyl ring-opening polymerization using dicyandiamide (DICY) as a curing agent. As silsesquioxane modifier serves the octaglycidyl-polyhedral oligomeric silsesquioxane (GlyPOSS). To decrease the operational temperature of the curing processes, three different accelerators for crosslinking are tested, i.e., N,N-benzyl dimethylamine, 2-methylimidazole, and commercial Curezol 2MZ-A. Differential scanning calorimetry, temperature-dependent FT-IR spectroscopy, and rheology allow differentiation among accelerators’ effectiveness according to their structure. The former only contributed to epoxy ring-opening, while the latter two, besides participate in crosslinking. The surface roughness of the protective coatings on aluminum alloy substrate decreases when the accelerators are applied. The scanning electron microscopy (SEM) confirms that coatings with accelerators are more homogeneous. The protective efficiency is tested with a potentiodynamic polarization technique in 0.5 M NaCl electrolyte. All coatings containing GlyPOSS, either without or with accelerators, reveal superior protective efficiency compared to neat DGEBA/DICY coating.

Investigation of the functional network modifier loading on the stoichiometric ratio of epoxy resins and their dielectric properties

“…While, in the above examples, C-O oxirane stretching was taken to result in absorption at 915 cm -1 , this wavelength is not ubiquitous and, rather, is dependent upon the local environment. For example, the equivalent vibrational mode has been observed at 907 cm -1 in tetraglycidyl diamino diphenyl methane and, of particular relevance to the work described in this publication, has been reported to be displaced to a wavenumber below 915 cm -1 in the same commercial octaglycidyl-POSS used here [31]. As such, we interpret the data shown in Fig.…”

“…This study concluded that, while the use of absorbance around 915 cm -1 is not straightforward during the final stages of curing, where the epoxy concentration is low and the accurate evaluation of the strength of the 915 cm -1 band is consequently challenging, this approach nevertheless ''gives most accurate results in mIR region''. The above conclusions were drawn using data published by Fraga et al [30], which reveal reduced absorption at 915 cm -1 with increased curing time, plus evidence of a relative increase in absorption around 935 cm -1 as curing proceeds; equivalent behaviour has also been reported in an FTIR study of the curing behaviour of DGEBA/octaglycidyl-POSS systems [31]. While, in the above examples, C-O oxirane stretching was taken to result in absorption at 915 cm -1 , this wavelength is not ubiquitous and, rather, is dependent upon the local environment.…”

“…Furthermore, comparison of the data obtained from 4 wt% GPOSS and 30 wt% GPOSS reveals not just an increase in the strength of the absorption peak in the latter system but also its displacement to lower wavenumbers. As it has been reported that the C-O oxirane stretching vibration occurs at a lower wavenumber in GPOSS than in DGEBA [31], this variation may indicate the preferential consumption of epoxide groups from the latter component.…”

Bio-Based Epoxy Adhesives with Lignin-Based Aromatic Monophenols Replacing Bisphenol A

“…Nevertheless, up to 85% of the world's epoxy resins are based on bisphenol A (BPA), known for its negative impact on the environment due to its estrogenic activity and acute toxicity to freshwater and marine species [3][4][5]. These environmental concerns, working towards the replacement of oil-based chemicals and avoiding the release of toxic materials into our society, are pushing researchers to search for alternative adhesive materials [6].…”

Polymer Processing and Surfaces

“…An excellent protective efficiency in the corrosion applications of various metal substrates is very important for coating manufacturers. Rodošek et al contributed to the field of epoxy coatings by developing a protective coating with a shorter drying time and shorter minimum overcoat intervals, allowing higher line speeds, which in turn led to a reduction in energy consumption in their study [ 13 ]. Octaglycidyl-polyhedral oligomeric silsesquioxane was used as a modifier for the diglycidyl ether of bisphenol-A epoxy resin, which was prepared by glycidyl ring-opening polymerization using dicyandiamide as a curing agent.…”