Surface Energetics Evolution during Processing of Epoxy Resins

Low‐Surface‐Free‐Energy Materials Based on Polybenzoxazines

“…According to previous studies, [25,26] the surface free energy in an epoxy system increases upon increasing the curing time, whereas in this study we found that the surface free energies of the polybenzoxazine systems (at 180 8C) generally decrease upon increasing the curing time. We believe that these polybenzoxazines possess lower surface free energies than the epoxy systems due to the presence of strong intramolecular hydrogen bonding.…”

Enthalpic, Entropic, and Square Gradient Contributions to the Surface Energetics of Amine-Cured Epoxy Systems

“…Furthermore, the work in Ref. (6) disregards any fluctuation in composition, while the density gradient is recognized as playing an important role in surface phenomena (7). Therefore, this paper aims at a more detailed understanding and modeling of the surface evolution process during the polymerization 121 0021-9797/02 $35.00 of epoxy resins.…”

“…As far as interfaces are concerned, a direct and well-known consequence of this process is the adhesion of epoxy-based systems to a given substrate, which is an increasing function of the degree of polymerization. In a previous work (6), the link between the internal energy of the bulk and the surface energetics during the cure of various amine-cured epoxy resins was demonstrated and modeled for a wide range of conversion. In that approach, the increase in surface energetics was directly expressed as a function of the increase in internal bulk energy with conversion.…”

Prediction of the adhesive fillet size for skin to honeycomb core bonding in ultra-light sandwich structures

“…Furthermore, with the known meniscus size, the assumption that gravity can be disregarded in calculating meniscus shape can be verified. By considering a fillet radius of 0.5 mm, and with the epoxy surface tension according to Page et al [35], the Young-Laplace equation (11) gives DP = 70 Pa. In comparison, the pressure exerted by gravity with a 0.5 mm epoxy column is…”

“…When the Bond number is zero, the drop is a truncated sphere. To estimate the Bond number in the present case, and as the surface tension of the adhesive is not known, values of surface tension of an epoxy resin system (Ciba, LY 5082) as measured by Page et al [35] using the Wilhelmy slide method [28,30] were used. They ascertained a surface tension of about 35 mJ/m 2 for the uncured resin at room temperature.…”