Slide 1

Nanolatex based nanocomposites: control of the filler structure and reinforcement. A. Banc 1 *, A-C. Genix 1, C. Dupas, M. Chirat 1, S.Caillol 2, and J.Oberdisse 1 1 Laboratoire Charles Coulomb, Universit Montpellier 2, Montpellier, France 2 Institut Charles Gerhardt, Montpellier, France Slide 2 Mechanical reinforcement in nanocomposites ? M ICROSTRUCTURE Filler network Diluted regime Filler Percolation threshold Composite properties Filler properties + Matrix properties M ECHANICAL PROPERTIES Jouault et al. F ILLER - FILLER INTERACTIONS F ILLER - MATRIX INTERACTIONS Slide 3 Model nanocomposites with tunable filler structure si30 nm Collodal silica + Drying Annealing Water evaporation Particles deformation Polymer diffusion Nanocomposite TUNABLE nanostructure: f( Si, Si / PEMA, M w ) PolyEthylMethacrylate (PEMA) Tg>Tamb Nanolatex PEMA 30 nm OR 200nm Mw 20, 50 or 160 kg/mol Slide 4 E FFECT OF R latex / R si Slide 5 Small Angle Scattering kiki ksks Wave vector q= - ksks kiki I(q)= f( , , P(q), S(q)) = Volume fraction = Scattering objects - matrix = Scattering lengh density P(q) = Form factor S(Q)= Structure factor q( -1 ) P(q) S(q) I(q) Silica nanoparticles P(q) =14 nm =0,11 q max d P(q)*S(q) q -df df= fractal dimension Slide 6 0% 1% 3% 5% 10% Structure R silica ~R latex ~14 nm Q -2,4 Colloidal solutions R silica Structure: 10% nanocomposites d* d*=2 /q* Model cubic network Silica networks whose the characteristic size decreases with Mw => decrease of the wall thickness 20 000g/mol 50 000g/mol 160 000g/mol Slide 14 PEMA50 PEMA160 PEMA20 1%3%10% 500 nm Structure: overview d* =12% >20% df=2,4 df=2,3 Slide 15 Rheological properties: matrices PEMA160 PEMA50 PEMA20 G G G G GNGN Master curve at annealing temperature (180C): Filler mobility: PEMA20 > PEMA50 > PEMA160 Slide 16 Rheological properties: nanocomposites Two filler volume fraction regimes: - < threshold viscoelastic material - > threshold elastic material Filler effect: -G at low frequency threshold d* At > threshold Fractal aggregates reinforce much more than the well dispersed filler. Power law ? Slide 19 Conclusions - Prospects => Dynamical approaches of the mechanical reinforcement Model nanocomposites Various nanoparticle dispersions: well dispersed / fractal aggregates / porous network => Novel structures with mixtures of latex bead sizes Mechanical reinforcement Mostly at low frequency aggregated filler reinforce better than the well dispersed one Quantitative description of the filler structure : D IRECT SPACE R ECIPROCAL SPACE TEM SAXS Image analysis + Simulation => Behavior at large strains?