Effects of composition of hardener on the curing and aging for an epoxy resin system

Abstract

Effects of composition of hardener on the curing and aging for an epoxy resin system Wu, Lixin; Hoa, Suong V.; Ton-That, Minh-Tan Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. ABSTRACT: Different mixture ratios of Shell Epon 828 (based on diglycidyl ether of bisphenol A, DGEBA) and Shell EPI-CURE 3046 (based on triethylenetetramine, TETA) were evaluated under different environments of isothermal curing at 80°C in DSC, room temperature curing in air, and aging in water at 45°C. The curing reactions were monitored using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and infrared spectroscopy (IR). It was shown that the initial curing rate increased with the amount of hardener. However, the epoxy groups in samples with excess hardener were prone to reaction with primary amines located at the ends of TETA molecules, resulting in a less dense epoxy network. During aging in water at 45°C, significant effects of water on the postcure and the increased water absorption with an increase of hardener amount were observed. The DMA results show that the samples with hardener around stoichiometric composition have the greatest storage modulus while curing in air environment. However, the samples with hardener much less than stoichiometric composition have greater storage modulus under aging in water at 45°C.

Epoxy/Silica Nanocomposites: Nanoparticle‐Induced Cure Kinetics and Microstructure

“…[11] However, for epoxy-rich systems, the etherification reaction might dominate the curing reaction after most of the secondary amines are consumed during the initial curing stage. [12] During the later reaction stage, the conversion rate of the nanoparticle-filled systems becomes lower than that of the neat system, showing almost stepwise behaviour for the higher filled epoxies AF3 and AF5. This behaviour is similar to that of an epoxy-rich system.…”

Synthesis and Characterization of Epoxy/MCDEA Networks Modified with Imidazolium‐Based Ionic Liquids

“…FTIR analysis constitutes a powerful tool for evaluating the cure reaction of epoxy pre-polymers [28][29][30][31][32][33] and was also employed in this study to monitor the reaction between DGEBA and IL. Figure 7 illustrates the spectra of [DiOImid][I] (curve A), DGEBA (curve B) and their blends containing 20 phr of IL prepared at room temperature (curve C) and at 100 8C for 10 min (curve D).…”

Epoxy-based nanocomposites for electrical energy storage. I: Effects of montmorillonite and barium titanate nanofillers

“…Figure 11 shows the dielectric strengths of all composites, i.e., of the single filler epoxy/BT and epoxy/oMMT, and of the dualfiller epoxy/BT/oMMT composites, as quantified by the Weibull ␣ w parameter. 54,[80][81][82] Also, fillers such as oMMT provide low or none dielectric mismatch between the filler and matrix and, thus, are not expected to introduce problems associated with local field enhancements at the polymer-filler interfaces. This result is easily understood by simply considering the field enhancement at the interface of the high permittivity BT filler, which is encapsulated inside a much lower permittivity epoxy matrix: As the concentration of the BT filler increases, the average interparticle distance decreases, and consequently the electric field concentration at the polymer-filler interfaces is amplified; this creates more points of initiation of local breakdown channels ͑i.e., creating a divergent field that may propagate the breakdown channel through the local weakest links͒.…”