Curing of epoxy resin by ultrafine silica modified by grafting of hyperbranched polyamidoamine using dendrimer synthesis methodology

Abstract

Hyperbranched polyamidoamine-grafted silica was prepared according to dendrimer synthesis methodology. The modified silica was dispersed uniformly in epoxy resin, and the curing of epoxy resin proceeded successfully by heating in the presence of the modified silica; the gel fraction of the epoxy resin cured by the hyperbranched polyamidoamine-grafted silica (grafting ϭ 80.2%) reached 77% at 170°C after 48 h. The gel fraction increased with increasing terminal amino group content of the hyperbranched polyamidoamine-grafted silica. In addition, the curing ability of the silica increased by complexation of the terminal amino groups of the grafted polyamidoamine with boron trifluoride. The modulus of elasticity of the curing materials obtained using the modified silica as a curing agent was lower than that using conventional a curing agent such as ethylenediamine in the presence of untreated silica. On the other hand, the heat resistance of the curing product using the modified silica was superior to that using ethylenediamine, but no difference in glass-transition temperature was observed. It is expected that hyperbranched polyamidoamine grafted-silica is incorporated uniformly with chemical bonds in the matrix of the epoxy resin.

Assembling hyperbranched polymerics

“…131,132 These researchers also applied this methodology for the grafting of hyperbranched polymers onto silica nanoparticles preliminary treated with 3-glycidoxypropyl trimethoxysilane. 133,134 Scale-up synthesis of hyperbranched PAMAM grafted onto ultrafine silica nanoparticles was successfully achieved by Murota et al 135 Furthermore, the postgrafting polymerization of different monomers onto PAMAM-modified silica nanoparticles resulted in polymer-inorganic nanoparticles with high surface grafting density. 136,137 Tsubokawa et al have broadened applications for the grafting of hyperbranched PAMAM by exploring carbon black and PS surfaces.…”

Learning about novel amine-adduct curing agents for epoxy resins: Butyl-glycidylether-modified poly(propyleneimine) dendrimers

“…9B) which decreases gradually with increasing the number of the bonded BGE segments of the curing agents. In contrast, these cured epoxy resins are much more thermally stable than that cured with PAMAMs [14] or silica-supported PAMAMs [13], in which cases the obvious weight loss can be detected in a much-lower temperature range (∼160 • C).…”

“…For example, Tande et al [12] used ester-terminated poly(propyleneimine) dendrimers to plasticize polyvinyl chloride (PVC) with the decreased glass-transition temperature found, which is due to the additional free volume provided by the dendrimers. Other reports indicated that PAMAMs and these of similar molecular structures [13][14][15][16][17] could effectively crosslink epoxy resins. These dendrimers also exhibit the advantages of lowered vapor pressure, alleviated toxicity, reduced unfavorable odor, retarded carbonation in air, and improved compatibility with epoxy resins over the conventional linear-aliphatic-amine curing agents of low molecular weights (e.g., ethylenediamine).…”

Cross-linking of cationically polymerised epoxides by nanoparticles

“…Afterwards a condensation of the formed silanols with each other and with the silanol groups present on the particle surface takes place. The curing of epoxy resins by fumed silica grafted with hyperbranched polyamidoamine was recently examined by Okazaki et al [11]. Most likely the observed curing reaction was a combination of a polyaddition and an anionic polymerisation induced by the amine.…”