Effect of the hardener to epoxy monomer ratio on the water absorption behavior of the DGEBA/TETA epoxy system

Abstract

SbstractThe water absorption behavior of the DGEBA/TETA epoxy system was evaluated as a function of the epoxy monomer to amine hardener ratio. Weight gain versus immersion time curves were obtained and the experimental points were fitted using Fickian and Non-Fickian diffusion models. The results obtained showed that for all epoxy monomer to hardener ratios analyzed water diffusion followed non-Fickian behavior. It was possible to correlate the water absorption behavior to the macromolecular structure developed when the epoxy/ hardener ratio was varied. All epoxy/hardener ratios present a two-phase macromolecular structure, composed of regions with high crosslink density and regions with lower crosslinking. Epoxy rich systems have a more open macromolecular structure with a lower fraction of the dense phase than the amine rich systems, which present a more compact two-phase structure.

Carbon nanotube-reinforced glass fiber epoxy composite laminates exposed to hygrothermal conditioning

“…Lastly, studies have reported that such behavior could also be a result of stress relaxation which occurs due to swelling after water absorption [48][49][50]. Overall, the water absorption behavior reported in the present study shows a different trend which has not previously been reported in the literature for GFRP composites.…”

Analysis of properties of epoxy compositions that operate in contact with water and oil products

“…There are many ways for directed modification of epoxy solutions. They include a use of fillers, variation of types and amounts of a curing agent [6], plasticization, a use of combinations of various epoxy resins and hardeners [7]. Paper [8] shows disadvantages of protective polymer solutions.…”

Star-shaped lactic acid based systems and their thermosetting resins; synthesis, characterization, potential opportunities and drawbacks

“…Often, 1-2 wt% of the initiator is utilized for the thermal curing. Using excess amount of the curing agent or applying high temperatures for curing may result in higher exotherms, faster gelation and more shrinkage due to excessive thermal zoning [52,60]. Moreover, the NMR technique can also be used for measuring the chain length of the branches [5], the percentage of the LA in forms of reacted with the core molecule as well as the percentage of the LA reacted into free oligomers [4,52].…”

“…Different factors are involved in the free radical curing reactions which are often employed for curing of the S-LA systems, including the nature of the initiator, initiator: resin ratio, applied heat regimes, retention times and cooling strategies. Using excess curing agent or applying high temperatures for the curing may result in higher exotherms, faster gelation and more shrinkage due to excessive thermal zoning [52,60].…”

“…The tuning of curing parameters, including temperatures, pressures, time, etc [90]. is of importance, especially in thermosets, as it affects the properties of the final product and applying improper conditions for curing, may result in higher exotherms, faster gelation and more shrinkage due to excessive thermal zoning[52,60].Understanding of the cure process is substantially important, especially for more complex systems such as industrial formulations, as a variety of additives are interfering in the curing procedure, resulting in a more complex cure kinetics. These factors indicate that an excellent control over curing process is required for production of thermosets with desired properties[70,71].…”