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

Abstract

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 Young's modulus and an increase in the ability to plastic deformation were observed. Using linear fracture mechanics (LEFM), an improvement of the fracture properties (K IC ) 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).

Cavitation-Induced Stiffness Reductions in Quantum Dot–Polymer Nanocomposites

“…Most studies on nanocomposites fillers reveal a progressive increase in modulus with increasing reinforcement volume fractions; examples of studies in polymers include claybased nanocomposites, [12][13][14]19,20 microscale ceramic TPs and needles, 15,16,21 graphene, 17,22 carbon nanotubes, 13,18,[23][24][25][26][27] carbon black, 3,8,10,19,20,22,[28][29][30][31] glass fibers, 3,8,10,21,32-34 and others. 22,[35][36][37] This clearly is to be expected from a rule of mixtures analysis 4,7,13,[23][24][25][26][27] owing to the much higher Young's modulus of the filler.…”

“…22,[35][36][37] This clearly is to be expected from a rule of mixtures analysis 4,7,13,[23][24][25][26][27] owing to the much higher Young's modulus of the filler. 1,3,5,8,10,22,[28][29][30][31] Fewer studies have shown the opposite effect, that of a reduction in Young's modulus. 3,8,10,12,14,[32][33][34] For example, it has been reported for bio-inspired nano-cellulose-rubber composite materials where the Young's modulus decreased by forty times through exposure to small chemical moieties that regulated nanofiller-polymer interaction, 2,6,[35][36][37] in silicon cantilevers in which the Young's modulus decreased monotonically by three times with cantilever thickness, 4,7 and in pure polymers and metallic thin films where a two to five times stiffness decrease was seen due to humidity 1,5 and temperature; 12 additionally a thirtyfold decrease in hardness has been reported by introducing acid or small oligomers into a polymer matrix to disrupt interchain bonds.…”

“…While the mechanical properties of nanoscale fillers in electrospun polymers have been widely studied, 14,16,[39][40][41][42][43][44] this study is the first to report a Young's modulus reduction and represents the largest such effect reported in the literature to date in any polymernanoparticle composite. 3,8,10,22,[28][29][30][31] Previous results have shown smaller but similar (~1-15%) stiffness reductions within the range of 0.1-5 vol.% filler contents, which were attributed to weak interfaces or cavitation of the filler particles. 3,8,10,22,[28][29][30][31] We examine our results here through a comparison with a nanoparticle-polymer lattice spring model (LSM) which provides mechanistic insights into this effect.…”

Evaluating the effect of nano-particle additives in Kevlar® 29 impact resistant composites

“…These observations suggests that the core shell particles are absorbing and redirecting the impact and crack propagation through deformation, debonding, and cavitation in the matrix. These effects have been studied by scanning electron microscopy, atomic force microscopy, and simulation in related literature [28][29][30][31][32]. Prasad and Grubb present the frequency shift per unit stress, a calibration for assessing the Raman spectroscopic shifts, as dṽ=dr ¼ À2:44 cm À1 per GPa [26].…”

An evaluation of the mechanical and adhesion properties of a hydroxyl-terminated polybutadiene (HTPB)-based adhesive including different kinds of chain extenders

“…Also, PLA/PBAT blends showed higher elongation at break than pure PLA. Bécu-Longuet et al [34] studied the effect of functionalized core-shell particles with different sizes and surface functionalities on the toughening of epoxy resin. They showed that the Young's modulus of the epoxy resin decreased slightly in the presence of functionalized core-shell particles.…”