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

Abstract

IntroductionEpoxy resins are well known as thermally and environmentally stable materials with applications ranging from adhesives to coatings and matrix resins of composites. Anhydride-cured epoxy resins are key components of electrical insulators. Important objective in epoxy resin chemistry is to improve the toughness/stiffness/strength balance without sacrificing processability, dimensional stability and electrical properties. [1] While microfillers are being used extensively to modify epoxy resin properties, the use of nanofillers is rather limited because of dispersion problems and viscosity build-up relating to strong interparticle interactions of nanofillers. [2] Moreover, nanofillers require special handling due to health hazards relating to inhalation problems. Therefore, it is a very attractive approach to generate nanofillers in-situ. For example, water swellable layered silicates are rendered organophilic via cation exchange of intergallery sodium cations for alkylammonium cations to produce much smaller intercalated and exfoliated nanoparticles. Such in-situ formation of organoclay nanosilicates was reported to afford unusual property combinations such as improved stiffness, strength, thermal stability, flame retardency, and barrier performance. [3][4][5] Although first attempts to exploit organoclay-filled epoxy resins [6] date back to 1965, remarkable progress has been made to tailor epoxy nanocomposite using various organophilic layered silicates. For example, Giannelis and coworkers [7][8][9][10][11][12] applied organoclays modified with bis(hydroxyethyl)methyldodecylammonium chloride in the presence Full Paper: 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. k:/3b2/jobs/eng/280/41_h.3d 26. 7. 2000 Hallal/Witte Young's modulus and tensile strength of nanocomposites containing 10 wt.-% of C12A compatibilized with DDS (wt.-% with respect to total mass of HY 925 and DDS) 42 C. Zilg, R. Thomann, J. Finter, R. Mülhauptof methylnadic anhydride-cured epoxy resin to achieve significant increases of stiffness at low silicate content of 4 wt.-%. However, the performance was found to depend on formulation components and cure conditions. A...

Mode I interlaminar fracture behavior and mechanical properties of CFRPs with nanoclay-filled epoxy matrix

“…The clay agglomerates and/or non-uniformly distributed clays may present at high clay contents, and these agglomerates can act as crack initiation sites, causing the nanocomposite to fail prematurely at a low failure stress/strain. It was also suggested that different cure speeds between the bulk epoxy and the silicate interfaces may induce internal stresses, leading to a substantial loss of strength [14].…”

Environmental degradation of epoxy-organoclay nanocomposites due to UV exposure: Part II residual mechanical properties

“…Different cure speeds in the bulk epoxy and at the silicate interface region may also generate significant internal stresses, inducing a loss in strength [11]. Meanwhile, the incorporation of clay could increase the viscosity of the mixture and make the degassing process more difficult, introducing significant amount of nano-or micro-voids.…”

Performance of epoxy-nanocomposite under corrosive environment

“…Understanding and controlling the various factors that govern the making of exfoliated thermoset/layered silicate nanocomposite is rather complex, several research projects have focused and made contribution to understand some of these issues [4][5][6]. Nanocomposites have the ability and the potential to reduce the permeability of polymer composites against ingress of corrosive substances.…”