Xavier Kornmann

Synthesis of epoxy-clay nanocomposites : Influence of the nature of the clay on structure

Abstract Epoxy–clay nanocomposites were synthesised using two montmorillonite clays (MMT) with different cation-exchange capacities (CEC) (94 and 140xa0meq/100xa0g). The purpose was to investigate the influence of the CEC of the clay on the synthesis and structure of epoxy–clay nanocomposites. The dispersion of the 1xa0nm thick clay layers was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Although XRD data did not show any apparent order of the clay layers in the nanocomposite, TEM revealed parallel clay layers with interlamellar spacing of 90xa0A (MMT of high CEC) and 110xa0A (MMT of lower CEC) and the presence of remnant multiplets of non-exfoliated layers. A mechanism responsible for the influence of CEC on nanocomposite interlamellar spacing is discussed. The dispersion of the clay was investigated by SEM and found to be finer in the nanocomposites as compared with in conventional composites although the nanocomposites still have clay aggregates at the microscale rather than a monolithic structure.

Synthesis of epoxy–clay nanocomposites. Influence of the nature of the curing agent on structure

Epoxy-clay nanocomposites were synthesised by swelling an organophilic montmorillonite in a diglycidyl ether of bisphenol A resin with subsequent polymerisation. Three different curing agents were used: an aliphatic diamine and two cycloaliphatic diamines. The cure kinetics of these systems was evaluated by differential scanning calorimetry and the structure of the nanocomposites was characterised by X-ray diffraction and transmission electron microscopy. Successful nanocomposite synthesis was dependent not only on the cure kinetics of the epoxy system but also on the rate of diffusion of the curing agent into the galleries because it affects the intragallery cure kinetics. The nature of the curing agent influences these two phenomena substantially and therefore the resulting structure of the nanocomposite. The curing temperature controls the balance between the extragallery reaction rate of the epoxy system and the diffusion rate of the curing agent into the galleries. Thus, the choice of curing agent and curing conditions controls the extent of exfoliation of the clay in the material.

Toughening of electron-beam cured acrylate resins

The aim of this study was to improve the toughness of EB-cured acrylate thermost resins by using hyperbranched aliphatic polyesters as additives to obtain a liquid-liquid phase-separated resin. The ...

Stiffness Improvements and Molecular Mobility in Epoxy-Clay Nanocomposites

Conventional composites filled with clay as well as intercalated nanocomposites, and exfoliated nanocomposites based on a glassy epoxy matrix have been synthesised. Flexural moduli of these materia ...