Preparation of Highly Exfoliated Epoxy/Clay Nanocomposites by “Slurry Compounding”:  Process and Mechanisms

Abstract

Epoxy/clay nanocomposites with a high degree of exfoliation were achieved using a so-called "slurry-compounding" process with which the dispersed state of clay in water can be successfully transferred to an epoxy matrix. In this process sodium montmorillonite was first exfoliated and suspended in water. This suspension was further treated with acetone to form a clay-acetone slurry followed by chemical modification using silane. The modified slurry was then mixed extensively with epoxy to form epoxy/nanoclay composites. It has been shown that the morphologies of clay before and after curing are quite similar and the exfoliation process is termed "slurry compounding". Furthermore, the amount of organic modifier used is only 5 wt % of clay, in contrast to conventional organoclays which normally contain at least 25-45 wt % of organic surfactant. The resulting epoxy/nanoclay composites exhibit a high degree of clay exfoliation and a better thermal mechanical property.

Interface-tuned epoxy/clay nanocomposites

“…In contrast, clay is a stiff, 1-nm thick layer which produces a significantly restricting effect on the matrix chain movement, leading to improved T g s. However, previous studies regarding the improvement of T g s of epoxy/clay nanocomposites are inconsistent. With addition of clay, some reported an increment of T g s [39e41], while there are reports of reduced [42e44] or no change of T g s [45,46]. This may be caused by inappropriate ratio of epoxy to hardener, variations of curing condition and excessive surfactants left by modification.…”

Silylation of montmorillonite surfaces: Dependence on solvent nature

“…In fact, the swelling property of the silylated clay minerals is a key factor for intercalation of macromolecules and exfoliation of the silylated clay minerals layers [23,24].…”

Locking effect: A novel insight in the silylation of montmorillonite surfaces

“…In the resultant hybrids, the linkage between organic components and layered silicates via covalent bonds enables a durable immobilization of the reactive organic groups, preventing their leaching in the surrounding medium when the silane grafted clays are to be used in solutions [6]. More importantly, by introducing special functional groups in the used silanes, the adsorption selectivity of the resultant materials to contaminants could be greatly improved [3], and novel clayepolymer composites with excellent mechanical property can be obtained [2,7]. Especially, in the resultant clayepolymer composites, silane is the key bridge between clay filler and polymer matrix, which provides silanol to condensate with SieOH and AleOH on the clay surface, and the introduced special functional groups (e.g.…”