Exploitation of introducing of catalytic centers into layer galleries of layered silicates and related epoxy nanocomposites. I. Epoxy nanocomposites derived from montmorillonite modified with catalytic surfactant‐bearing carboxyl groups

Abstract

Montmorillonite (MMT) was modified with the acidified cocamidopropyl betaine (CAB) and the resulting organo‐montmorillonite (O‐MMT) was dispersed in an epoxy/methyl tetrahydrophthalic anhydride system to form epoxy nanocomposites. The intercalation and exfoliation behavior of the epoxy nanocomposites were examined by X‐ray diffraction and transmission electron microscopy. The curing behavior and thermal property were investigated by in situ Fourier transform infrared spectroscopy and DSC, respectively. The results showed that MMT could be highly intercalated by acidified CAB, and O‐MMT could be easily dispersed in epoxy resin to form intercalated/exfoliated epoxy nanocomposites. When the O‐MMT loading was lower than 8 phr (relative to 100 phr resin), exfoliated nanocomposites were achieved. The glass‐transition temperatures (Tg's) of the exfoliated nanocomposite were 20 °C higher than that of the neat resin. At higher O‐MMT loading, partial exfoliation was achieved, and those samples possessed moderately higher Tg's as compared with the neat resin. O‐MMT showed an obviously catalytic nature toward the curing of epoxy resin. The curing rate of the epoxy compound increased with O‐MMT loading. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1192–1198, 2004

Preparation and characterization of organoclays based on an amphoteric surfactant

“…Before the suspensions were acidified, the carboxyl groups were dissociated, as indicated by the pH range (8.0-8.3) of these suspensions, thus rendering the surfactant molecules electrically neutral. An earlier report on the intercalation of CAB into montmorillonite mentions acidifying the surfactant to an unspecified pH prior to mixing with the clay [14] and this is usual practice when working with alkylamines in the form of the free base [5]. Although it might be anticipated that a dissociated, negatively charged carboxyl group might hinder the uptake, these results indicate that greater uptake can result without acidifying the suspension.…”

“…Fully exfoliated epoxy-montmorillonite nanocomposites were obtained in which the betaine had a catalytic effect on the resin curing, as shown by the faster disappearance of the epoxy ring with increasing clay loading. It has been suggested that such interactions took place when CAB-organoclays were compounded with epoxy resin by in-situ intercalative polymerization [14] where the carboxyl group demonstrated a catalytic effect on polymerization, indicating that the carboxyl group can interact with the matrix. For this to occur requires that the carboxyl group should be protonated, which was ensured by acidifying the clay-surfactant suspension.…”

“…An organoclay based on CAB has been used as a nanofiller for an epoxy resin using in-situ polymerization [14,15]. In this study, the basal spacing of the organoclay used was 4.0 nm, although precise details of the clay:surfactant ratio used were not given.…”

Preparation and thermal characterisation of poly(lactic acid) nanocomposites prepared from organoclays based on an amphoteric surfactant

“…It has also been shown that the carboxyl group in CAB-MMT organoclay can catalyse curing in epoxy resins [12,13].…”

Morphology, thermal, and viscoelastic properties of poly(glycidyl methacrylate-co-methyl methacrylate)-based nanocomposites with various organo-modified clays

“…Hwu et al reported that the intercalated nanocomposite prepared by the solution method shows a higher glass transition temperature (T g ) and a higher T d [19]. On the other hand, the nanocomposites of acid anhydridecured epoxy resins can be prepared by essentially in situ intercalative polymerization method [20][21][22][23][24][25][26][27] because the cured polymers are non-fusible and insoluble. For example, Zhang et al reported that the nanocomposite prepared from diglycidyl ether of bisphenol A and 4-methyl-1,2-cyclohexanedicarboxylic dianhydride shows a higher T g , T d and storage modulus than the pure cured epoxy resin [21].…”