Fracture behavior of core‐shell rubber–modified clay‐epoxy nanocomposites

Abstract

Morphology and fracture mechanisms in two nanoclay‐filled epoxy systems were investigated using both microscopy and spectroscopy tools. Clay exfoliation was achieved using a series of sample preparation steps, and confirmed using wide angle X‐ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. Significant improvement in modulus was obtained when clay exfoliation was achieved. Incorporation of core‐shell rubber (CSR) in both caly‐filled epoxy systems leads to greatly enhanced fracture toughness. Optical microscopy and TEM observations of the CSR‐modified nanocomposites suggest that CSR cavitation. shear yielding of the matrix, clay layer delamination. CSR bridging, crack bifurcation. and crack deflection are among the operative toughening mechanisms observed, depending on the nature of the epoxy matrix utilized.

Mechanical properties of thermosets

“…A similar result was also reported for fully exfoliated epoxy/clay and nylon/clay nanocomposites. 30,31 This suggests that a nearly perfect exfoliation and dispersion of nanofiller in the polymer matrix will not necessarily improve fracture toughness of the polymer matrix. it is believed that the intercalated or agglomerated domains can help trigger some limited degree of toughening that is unachievable in the fully exfoliated systems.…”

Ethylene-octene copolymer (POE) toughened polyamide 6/polypropylene nanocomposites: Effect of POE maleation

“…It is also possible that polymer nanocomposites inherently contain incomplete dispersion of nanoparticles, which form aggregates that causes premature crack formation due to poor adhesion between nanparticles and matrix. The presence of exfoliated nanoparticles may also restrict molecular mobility of the surrounding matrix material, which in turn leads to the reduction of impact strength and toughness [21]. However, this drawback is believed to be overcome by the incorporation of a rubber phase.…”

Fish DNA-modified clays: Towards highly flame retardant polymer nanocomposite with improved interfacial and mechanical performance

“…These small tactoids are uniformly and randomly dispersed in the epoxy resin, demonstrating that the clay modification based DNA is an effective approach to enhance both the exfoliation and dispersion of clay. In addition to such argument associated with dispersion, as reported in literatures505152, under an effective load, most of microcracks are initiated within the intra-layer of semi-stacked clay rather than at epoxy-clay interfacial region. This phenomenon proves that higher contents of d-clay, e.g., 5 wt%, could result in lower reinforcing trend in tensile strength mentioned in mechanical section.…”