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

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.…”

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 °C) 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.…”

Void formation model and measuring method of void formation condition during hot pressing process

“…1 , resin surface tension can restrain void growth, the extent of which depends on the radius of the bubble and the evolution of resin surface tension before resin gelation. It has been proven that resin surface tension will increase slightly as resin cures [34–36], and the maximum surface tension before resin gelation, as measured by the Wilhelmy method, ranges from 40 to 50 mN/m for our studied epoxy and bismaleimide resins [36]. In addition, the average radius of voids under the optical microscope is larger than 10 μm for less than 1% porosity, which is even bigger for higher porosity.…”