Henry Sautereau

Epoxy networks toughened by core–Shell particles: Influence of the particle structure and size on the rheological and mechanical properties

The core–shell particles considered were poly(butyl acrylate) core/epoxy groups functionalizing the poly(methyl methacrylate) shell. Physical and thermomechanical properties of benzyl dimethylamine (BDMA)-catalyzed diglycidyl ether of bisphenol A (DGEBA)/dicyandiamine epoxy networks toughened with core–shell particles were studied. The blends were prepared under well-defined processing conditions. The resulting properties were found to depend on the state of the dispersion of the particles in the prepolymer matrix before crosslinking. These particles were dispersed at different volume fractions in order to vary the interparticle distance. The relationships between the size of the core–shell particles and the level of toughening are reported. Static mechanical tests were performed in tension and compression modes on these core–shell polyepoxy blends. A slight decrease in the Youngs modulus and an increase in the ability to plastic deformation were observed. Using linear fracture mechanics (LEFM), an improvement of the fracture properties (KIC) was measured. By varying the volume fraction of core–shell particles, an optimum toughness improvement was found for an interparticle distance equal to 400 nm (with an average particle size of 600 nm).

Kinetic of a thermoplastic-modified epoxy-aromatic diamine formulation: modeling and influence of a trifunctional epoxy prepolymer

Abstract The influence of a trifunctional epoxy prepolymer (triglycidylparaaminophenol, TGpAP) on kinetic reactions of a diepoxy prepolymer, diglycidylether of bisphenol A, DGEBA/diamine 4,4′-methylenebis[3-chloro 2,6-diethylaniline] MCDEA system was investigated as the influence of the addition of an initially miscible thermoplastic (polyetherimide, PEI or polyethersulfone, PES). The reaction mechanism between an amine and TGpAP is very complex so a phenomenological kinetic model is used. A reactive epoxy-amine system with TGpAP shows a faster reaction rate increase with temperature than a system containing only DGEBA because cyclization and etherification reactions are favoured with temperature in the case of TGpAP. A large discrepancy between theoretical value and experimental conversions at the gel point insoluble fraction was observed and can be explained by the fact that three epoxy groups of TGpAP have quite different reactivities due to different structures and substitution effects and also by the fact that other side reactions as cyclizations tend to result in gelation conversions higher than those expected from Florys equation. After vitrification, the glass transition temperature of systems containing TGpAP goes on, increasing significantly because of intermolecular etherification reactions. Before any phase separation, a nonreactive thermoplastic (polyetherimide) was found to have no influence on reaction rate whereas polyethersulfone with terminal reactive phenoxy groups was found to accelerate the reaction rate. Similar behaviors were observed after phase separation.

Introduction of a Rubbery Interphase in Glass/Epoxy Composite Materials: Influence of the Interlayer Thickness on the Viscoelastic and Mechanical Properties of Particulate and Unidirectional Composites

From a concept developed on micromechanical models, a crosslinkable elastomeric adduct based on a liquid reactive rubber and an epoxy prepolymer is deposited on glass beads and glass fibers reinforcing an epoxy DGEBA-DDA matrix. Model composites made from glass beads coated with various thicknesses of elastomer are studied in terms of viscoelastic behavior and mechanical properties (elastic, pre-yielding, plastic and fracture). Mechanical properties (for example fracture toughness) are enhanced for an optimum thickness of coating in agreement with theoretical models developped in literature. The presence of the thin layer of elastomer in the composites is displayed by dynamic mechanical analysis. A transposition on unidirectional glass fibers composites (GFRP) is made. An optimum interlayer thickness exists which leads to an improvement in impact and fatigue properties without any losses in elastic and thermal behavior of GFRP.

TEMPO-Mediated Oxidation of Lignocellulosic Fibers from Date Palm Leaves: Effect of the Oxidation on the Processing by RTM Process and Properties of Epoxy Based Composites

© 2012 Kaddami et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. TEMPO-Mediated Oxidation of Lignocellulosic Fibers from Date Palm Leaves: Effect of the Oxidation on the Processing by RTM Process and Properties of Epoxy Based Composites