Effect of modified bentonites on the crosslinking process of epoxy resin with alifphatic amine as curing agent

Abstract

In this work the influence of modified bentonites on the process of epoxy crosslinking with triethylenetetramine (TETA) was investigated. Bentonites (BS) modified with quaternary phosphonium (QPS) and ammonium (QAS) salts were used as a nanofiller in the epoxy matrix (EP) in the amounts of 1 and 3 wt %. Gel time of the compositions was investigated using rotational rheometer at 30, 45 and 60 °C and activation energies of the compositions were determined. The storage G' and loss G" moduli crossover criterion was used to determine the nanocomposites gel time variation. On the basis of the obtained results, it was found that the addition of modified aluminosilicates decreased the gel time of epoxy compositions at 30 and 45 °C, while at 60 °C it increased compared to unmodified epoxy resin. The obtained results indicate that the amount of modified aluminosilicate and the type of salt influence the reactivity of epoxy compositions. Among the tested systems, the most reactive was the composition of EP+3%BSQPS1, because the gel time at 30 °C and activation energy decreased by 1500 s and 8 J/mol, respectively, in relation to the unfilled EP resin. A more catalytic effect was observed in the case of bentonites modified with quaternary phosphonium salts, which may be associated with lower phosphorus electronegativity in relation to nitrogen and a lower viscosity of these systems.

Biochar as an Effective Filler of Carbon Fiber Reinforced Bio-Epoxy Composites

“…Among the natural additives for polymers, plant, animal and mineral origin can be distinguished. They may occur in the form of powder, microparticles or nanoparticles, or long and short fibers [2][3][4]. The use of such modifiers as biochar [5][6][7], carbon nanotubes [8][9][10], basalt powder [11][12][13][14], lignin [15,16], and ground waste from the agricultural [17][18][19] and food industries [20][21][22] in polymer composites has been the subject of many scientific papers in recent years.…”

Compositions of unsaturated polyester resins used for facing layers of laminates

“…As a results of the gel time study, the values of the loss modulus G", storage modulus G', complex dynamic viscosity η* and loss tan δ from the time t s were obtained (Table 2). The gel time was determined on the basis of the intersection of the curves G' and G'' [20].…”

The effect of the heat treatment on the crosslinking of epoxy resin for aviation applications

“…An important challenge for all technical applications of epoxy resin based com-posites, particularly aviation constructions, is the need to manufacture materials with significantly reduced flammability [26][27][28][29]. However, fillers can reduce the gel time of the resin [30,31], and therefore alter the manufacturing process. For example, it was found that water contained in fillers may cause an acceleration of the resin/hardener reaction [32].…”