Influence of Nanoparticle s Surface Composition on the Properties of Epoxide Based Adhesives

Transcription

1 Influence of Nanoparticle s Surface Composition on the Properties of Epoxide Based Adhesives A. Hartwig, J. Trautmann, M. Sebald har@ifam.fraunhofer.de EUADH xford September 2008

2 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

3 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

4 Adhesives and nanocomposites are basically identical Adhesives: Adhesion / technical adhesion determined by interfacial chemistry Nanocomposites: Cohesion (adhesion between particles and polymer) determined by interfacial chemistry Similar: glass fibres, filler particles etc. bservation: Interfacial strength often higher than cohesive strength Integration of adhesion into bulk adhesive Influence of nanoparticles in adhesives?

5 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

6 Surface modification of fumed silica Condensation reaction between Surface-Si-H and Silanes in an organic solvent. Et Si Et Et Si Me Me Me (3-Glycidyloxypropyl)- trimethoxysilane (GLYM) Si(CH 3 ) 3 Si 2 ECHTM

7 Surface modification of fumed silica II esulting surface composition and structure depends strongly on: - Kind and amount of silane - Solvent - Process engineering: Stirring, temperature, time... - Utilized catalyst here bases as catalyst Silane should be selected according to chemistry of adhesive.

8 Effect of catalyst concentration on surface coverage Weight % of chemisorbed GLYM / 100 g Si [g] No effect Agglomeration 0 0,05 0,1 0,15 0,2 0,25 mmol base / mmol surface-sih ptimal catalyst concentration for the modification: 0,09-0,14 mol catalyst / mol Surface-SiH

9 Covalent bonding and physical adsorption 110 non cat. mod. Nano-Si base-cat. mod. Nano-Si C 1.5 wt.% C 30 wt.% 5 wt.% derivation (wt.%/ C) wt.% wt.% derivation (wt.%/ C) temperature ( C) temperature ( C) -0.5 Through catalysis: Three times more chemisorbed silane

10 Visualization of the polysiloxane shell EF-TEM image (Nanoparticle on graphite) Nanoparticles with 20 wt.% covalently bonded silane Polysiloxane shell detectible, 2-4 nm thickness 100 nm 100 nm C-X-Si

11 Fumed silica is homogeneously distributed in epoxy resin still agglomerated nanostructured nanoparticles

12 Particle properties Compared to commercial surface modified fumed silica: Thick silane layer Multifunctional partially cross-linked silane oligomers Basic catalyst Higher thermal stability ( stronger bond )

13 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

14 Cationic polymerisation of epoxy resins: base reactions 1. Formation of super acid by initiator decomposition 2. Initiation and addition of the first monomer H + H H H 3. Chain growth + + n n H H

15 4. Chain transfer by alcohol or water n + 'H n ' + H n ' + H + H H H SbF 6 - S + S Particles modified with ECHTM: Si(CH 3 ) 3

16 Cationic curing of epoxy resin with fumed silica Silica particles bear epoxy groups. Soluble, linear polymer by cationic polymerisation of cyclohexenoxide. Insoluble content increases with particle amount. Extraction esidue [wt-%] Cross-linking by particles Content mod. Si 2 [wt-%]

17 SEM-examination: fracture surface and extracted particles Particles covered with polymer Thickness of interphase ca. 9nm

18 Influence of modified fumed silica on T g Cationic cross-linking of cycloaliphatic epoxy resin. 30 T G decreases with amount of filler % filler 0% filler Glass transition range becomes broader. tan delta % filler Lower stresses. 5 Very hard particles surrounded with soft polymer within hard polymer T [ C]

19 Different behaviour for photo curing Same epoxy resin. Flexibilisation with 10% Polyole EL + 10% ECHTM EL + 10% GLYM EL+10% Aerosil200 EL+ Sarcat+ PEG, 20 C C 10% differently modified fumed silica. Curing at 20 C. Increasing and broadening of T G. Effects most pronounced for system with highest compatibility. Tan Delta C C C Temperature ( C) Universal V3.9A TA Instru

20 Application of modified fumed silica in addition curing epoxides Low viscosity bisphenol A diglycidylether and polyamidoamine esin: CH 3 CH 3 CH 3 H CH 3 CH 3 CH 3 Hardener: * H N 1 H N NH NH * 2 n 1 1

21 Influence of surface modification lap-shear-strength [MPa] : pure epoxide 2: + unmodified silica 3: + reactive silica 4: + non-reactive silica eactive particles with glycidyl groups strong increase Non reactive particles (phenyl groups) slight decrease

22 Effect of covalently bonded silane on the lap shear strength MPa % -4% 22% 36% 5 0 reference 10 wt.% cov. silane 10 wt.% cov. silane & 30 wt.% physisorb. silane 20 wt.% cov. silane

23 Peel strength is strongly enhanced 0,5 peel strength [N/mm²] 0,4 0,3 0,2 0,1 4x 0 reference 5 wt.% non mod. Nano-Si 2 5 wt.% GLYMmod. NanoSi 2

24 Fracture toughness increases tensile stress [N/mm²] eference adhesive adhesive with 5 wt.% mod. Nano-Si 2 5 wt.% GLYM-mod. Nano-Si 2 (20 wt.% cov. Silan) 40% greater fracture energy Increasing toughness with constant tensile strength Elongation [%]

25 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

26 Synergistic property improvements through the combination of two different kind of reactive-modified nano particles 36% lap shear strength [MPa] 3 2,5 2 1,5 1 0,5 reference 5 wt.% Nano-Si2 5 wt.% Nano- Silicone Particles 5 wt.% Nano-Si2 a. 5 wt.% Nano-Silicone Particles 0 36% 38% 87% peel strength [N/mm²] reference 5 wt.% Nano-Si2 5 wt.% Nano- Silicone Particles 0 4x 15x 22x 5 wt.% Nano-Si2 a. 5 wt.% Nano-Silicone Particles

27 Self-assembling structures are formed GLYM-modified fumed silica and Glycidoxy modified nano-silicone particles 5 wt.-% each esults depend strongly on process conditions during surface modification 10 µm 1 µm 0,2 µm

28 utline Introduction Surface modification of fumed silica Influence of nanoparticles on the properties of epoxide based adhesives Synergistic interaction between nanoparticles Conclusions

29 Conclusions Properties of adhesives are strongly influenced by nanoparticles The right surface composition is required for improvements Strength and toughness can be improved at the same time Combination of interacting nanoparticles lead to strong synergistic effects Property improvements by strongly agglomerated fumed silica shows that not single particle are important but a large interphase in the adhesive

30 Thank you for your most valuable your time and attention!