Jürgen Finter

Morphology and toughness/stiffness balance of nanocomposites based upon anhydride‐cured epoxy resins and layered silicates

Basic correlations between polymer morphology, silicate superstructures, glass temperature, stiffness and toughness of thermoset nanocomposites were investigated as a function of layered silicate type and content. The nanocomposites were based upon hexahydrophthalic anhydride-cured bisphenol A diglycidyl ether and layered silicates such as synthetic fluoromica (Fmica), purified sodium bentonite and synthetic hectorite, all of which were rendered organophilic by means of ion-exchange with various mono- and difunctional alkyl ammonium ions. Enhanced toughness was associated with the formation of dispersed anisotropic laminated nanoparticles consisting of intercalated layered silicates. Nanocomposite superstructures were imaged by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM).

The influence of silicate modification and compatibilizers on mechanical properties and morphology of anhydride-cured epoxy nanocomposites

Resin composition, silicate filler modification, and curing agents were varied systematically in order to improve the performance of anhydride-cured epoxy nanocomposites based upon organoclay. The filler component was fluorohectorite which was rendered organophilic by means of cation exchange of intergallery sodium cations for protonated alkylamines with chain lengths variable from butyl (C4), hexyl (C6), octyl (C8), decyl (C10), dodecyl (C12), hexadecyl (C16), octadecyl (C18) to 12-aminododecanoic acid (C12A). The alkyl chain length must exceed six C atoms to afford increased interlayer distances, accompanied by increased stiffness. Compatibilizer addition such as epoxidized and maleinated soy bean oil or dodecenylsuccinate afforded improved tensile strength without sacrificing stiffness and toughness. Morphology development, determined by means of transmission electron microscopy, and fracture behavior were examined.

Organic/inorganic hybrid materials and nanocomposites based upon layered silicates modified with cyclic amidines

Various cyclic amidinium cations were used to exchange intergallery sodium cations of water swellable fluorohectorite in order to produce novel families of organic/inorganic hybrid materials. Oligomeric cyclic amidinium cations, such as mono(imidazolinium) terminated oligostyrene, oligostyrene-co-oligo(acrylonitrile), and oligo(methyl methacrylate) with number-average molecular masses around 3000 g/mol afforded effective exfoliation during melt processing. Morphology and dynamic mechanical properties were measured as a function of silicate content and silicate modification.