Effect of Additives on the Rheological Properties of Fast Curing Epoxy Resins

Abstract

rapid resin transfer molding (rtm) process is suitable for high-throughput manufacturing of complex-shaped composite parts. ideally the epoxy system should exhibit low viscosity and long gel time at room temperature for quick mold filling, and very fast curing once the resin is inside the heated mold. the present research was performed on different epoxy formulations by varying the concentrations of diluent and catalyst. rheological studies were carried out to measure the flow viscosity and to determine the gel time at different temperatures. it is noted that the addition of diluent effectively decreases the viscosity of formulation, and the addition of imidazole affects the rate of epoxy cure. several epoxy resin formulations were studied and compared with the commercially available infusion-grade epoxy system of Araldite Ly 8601/Aradur 8602. the results show that epoxy systems such as that containing 5% imidazole and 10% reactive diluent are suitable for the rapid rtm process with balanced flow and cure characteristics.

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

“…Figure 8 shows the dynamic storage modulus (G ) and loss modulus (G") versus temperature during heating at a heating rate of 2 • C/min. These rheograms confirm that curing processes are time-and temperature-dependent [18,29]. Although the shapes of the curves obtained for elastic and viscous modulus are similar for all formulations, the curing reactions start at considerably different temperatures (i.e., times).…”

“…Time-dependent FT-IR absorbance measurements during temperature treatment of coatings (Figures 4-6) enables insight into the crosslinking by observation of decreasing intensity of the epoxy mode at 915 cm −1 [28]. Rheology (Figures 7 and 8), on the other hand, gives quite a piece of information on changes in consistency during the transformation of the formulation into a crosslinked structure [18,29]. When the obtained results are observed in parallel experiments, designed to approach to the same conditions as much as possible, they can throw light to the curing processes that lead to the formation of highly crosslinked protective coatings.…”

“…However, G or G" tend to final values of the order of magnitude 3 × 10 5 Pa (G ) and 10 4 Pa (G") for all formulations, respectively. The evolution of the elastic G modulus, which is proportional to the rigidity of the cured epoxy, indicate the formation of molecular networks through the formation of chemical bonds (crosslinking) in the either of the investigated epoxy systems [29].…”

“…This parameter is defined as a ratio between the lost and the stored deformation energy, which means the ratio between the viscous and the elastic contribution to the viscoelastic behavior. Namely, the proper balance between the viscous and the elastic contribution in the viscoelastic formulation before the deposition of the coatings is of particular importance when our aim is the deposition of the protective coatings with excellent barrier properties [18,29]. Specifically, the phase angle δ shows the time delay between the determined sinusoidal parameters and the measured characteristics G and G".…”

Solvato-morphologically controlled, reversible NIPAAm hydrogel photoactuators

“…All samples were exposed to white light and the storage modulus recorded. The storage modulus increases with time and in most cases (AI, AII, AIII, BI, BII and CI) reaches a plateau indicating no further significant growth of elastic structures due to the crosslinking 33 . It was observed that the plateau region of the storage modulus was dependent on the polymerisation solvent used (Fig.…”