SILICA-LIKE MALLEABLE MATERIALS Group 10 Kristen Losensky Tzu-Hao Yen 11-16-12 1.

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SILICA-LIKE MALLEABLE MATERIALSGroup 10

Kristen Losensky

Tzu-Hao Yen

11-16-12

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Summary: How It Works• Thermoplastics

• Flow when heated• Can be extruded shaped and molded

• Thermosetting / Cross-linked Polymers• Can not be reprocessed by heat or solvent• Dimensional stability• High-temperature mechanical, thermal, and

environmental resistance

• Make covalent links reversible• High Temperature: exchange reactions enable stress

relaxation and malleability• Low Temperature: exchanges become essentially stop,

producing a solid system• Reversible topology fixing controlled by kinetics

Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): 965-68. Web. 11 Nov. 2012.

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Summary: Research Performed

• Synthesis of both hard and soft epoxy networks with rearrangable topology• Exchange reactions without depolymerization. • Insoluble and processable• Gradual viscosity variations

• Examination of thermal and mechanical properties

Thermosetting Polymers

• Thermosetting materials• Irreversible• Liquid prior to curing• Good mechanical

properties• Solvent resistant• Cured by heat and

radiation

http://sp.life123.com/bm.pix/how-to-change-brake-pads.s600x600.jpg

Cross-Linked Materials• Cross-linking

• Un-polymerized resin + Crosslinking agents• Difficult to break• Most materials when heated may degrade or burn

• Commercial plastics

http://chemistry2.csudh.edu/rpendarvis/thermoplas.GIF

Thermoplastic Polymers• Thermoplastic materials

• Reversible • Remold and reforms• Weaker mechanical

properties• Solvent soluble• Recyclable http://images.wisegeek.com/stack-of-legos.jpg

http://chemistry2.csudh.edu/rpendarvis/thermoplas.GIF

Reversible Malleable Material Issues

• Depolymerization-repolymerization equilibria

• Degradation of combined materials

• Unavoidable termination reactions

http://images.clipartof.com/small/1047648-Royalty-Free-RF-Clip-Art-Illustration-Of-A-Cartoon-Black-And-White-Outline-Design-Of-A-Man-

Carrying-A-Heavy-Problem-Rock.jpg

High Silica Materials

• Amorphous silica• Thermally insulated• Inert to chemical

reagents• Resistance to organic

acids• Electrical insulation• Easily molded

http://image.made-in-china.com/2f0j00zBQTMaICHFcK/High-Purity-Silicon-Dioxide-Coating-Material.jpg

Stress & Strain Diagram

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Previous Work

• Radical Systems• Photoinduced plasticity in cross-linked polymers• Thermally/ Photochemically induced reparability• Unavoidable Termination Reactions

• Chemical Equilibrium• Heating

• Drives equilibrium towards depolymerization• Increases rate of bond breaking/reforming

• Prevent flow by using glass transition• Increased fluidity and processability• Network is less stable and sensitive to solvents

molle.k.u-tokyo.ac.jp

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Materials and Methods

• Soft Networks• Fatty acids and Catalyst Zn(Ac)2, 2H2O heated from 100

°C to 180°C under vacuum• Diglycidal ether of bisphenol A (DGEBA) is added to

fatty acid mixture and stirred at 130°C • Mixture is poured into brass mold with anti-adhesive

silicone paper

http://chemsrv1.uwsp.edu/macrog/lab/epoxyqc.htm

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Materials and Methods

• Hard Networks• Zinc Acetylacetonate Dihydrate Catalyst dissolved in

DGEBA by heating• Glutaric Anhydride added• Poured into brass mold • Cured at 140°C for 12 h

http://www.sigmaaldrich.com/catalog/product/FLUKA/49670?lang=en&region=US

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Results: Soft Network Synthesis • DGEBA and fatty dicarboxylic and tricarboxylic acids

• Epoxy/COOH has 1:1 stoichiometry• Zinc Acetate Catalyst Zn(Ac)2

• Complete conversion of epoxy groups

• Transesterification Reactions


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Results: Soft Network Properties• Elastomeric behavior • Modulus of 4 MPa• Elongation and stress at break 180%, 9 MPa • Number of ester links does not change with heating


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Results: Soft Network Solubility

• The network swells but does not dissolve


Fig. 2 Flow and insolubility properties of an epoxy network with 5 mol% Zn(Ac)2 catalyst. (A)Swelling during immersion in trichlorobenzene

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Results: Soft Network Malleability• Can completely relax stresses at high temperatures

• η(T) follows Arrhenius law• 100 °C relaxation time of 58 h• Room temperature relaxation time of 6 yr

• Can easily make complex shapes without mold


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Results: Hard Network Synthesis• DGEBA with glutaric anhydride

• Zinc Acetyl Acetonate Zn(AcAc)2

• Epoxy/Acyl stoichiometry is 1:1

• Transesterification Reactions


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Results: Hard Network Solubility

• Sample swells but does not dissolve• 16 h in trichlorobenzene at 180 °C

• Number of ester links does not change with temperature


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Results: Hard Network Properties• Behavior is similar to

typical hard epoxy resins• Glass Transition Tg 80 °C

• Modulus of 1.8 GPa• Stress at break of 55 MPa• Transesterification

reactions allow network to flow• Viscosity of 1.2 x 1010 Pa s• η(T) follows Arrhenius

equation


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Results: Hard Network Malleability

• Can be reprocessed• Compression molding at

high temperature• 3 min at 240 °C

• Can form complex shapes without molds


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Results: Topology• Systems with exchangeable links behave as a viscoelastic

fluid • Above Tg exchange reactions occur slowly

• Material properties depend on thermal history

• During cooling ramp:• Topology rearrangements become too slow, network appears

quenched• Further cooling freezes local monomer motion


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Results: Dilatometry Experiments• Cross-linked polymers have lower expansion coefficients• Increasing catalyst concentration increases expansion

coefficients• Topology freezing is well separated from Tg

• Topology freezing and Tg shift to higher temperatures when the heating rate is increased


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Results: Broadness of Tg

• Rate of change of η at Tg

• “Strong” Glass Formers show broad Arrhenius-like variations• Silica• P2O5

• “Fragile” Glass Formers show rapid η increase upon cooling• Organic and Polymer liquids


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Assessment• Synthesized both soft and hard polymer networks with

reversible covalent links• Transesterification Reactions• Mechanical Properties• Insoluble• Arrhenius-like variation in viscosity

• Separate topology freezing and glass transitions


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Further Research• Ability to control or fine tune temperature of topology

freezing transition

• Ability to control or fine tune glass transition temperature

• Choice of starting materials

http://www.bestchemshows.com/

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References (Pictures)1. molle.k.u-tokyo.ac.jp

2. http://chemsrv1.uwsp.edu/macrog/lab/epoxyqc.htm

3. http://www.sigmaaldrich.com/catalog/product/FLUKA/49670?lang=en&region=US

4. http://www.bestchemshows.com/

5. http://sp.life123.com/bm.pix/how-to-change-brake-pads.s600x600.jpg

6. http://image.made-in-china.com/2f0j00zBQTMaICHFcK/High-Purity-Silicon-Dioxide-Coating-Material.jpg

7. http://images.clipartof.com/small/1047648-Royalty-Free-RF-Clip-Art-Illustration-Of-A-Cartoon-Black-And-White-Outline-Design-Of-A-Man-Carrying-A-Heavy-Problem-Rock.jpg

8. http://chemistry2.csudh.edu/rpendarvis/thermoplas.GIF

9. http://chemistry2.csudh.edu/rpendarvis/thermoplas.GIF

10. http://me.aut.ac.ir/staff/solidmechanics/alizadeh/Tensile%20Testing_files/image011.gif

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References

1. Montarnal, Damien, Mathieu Capelot, Francois Tournilhac, and Ludwik Leibler. "Silica-Like Malleable Materials from Permanent Organic Networks." Science 334 (2011): 965-68. Web. 11 Nov. 2012.

2. Callister, William D., and David G. Rethwisch. Fundamentals of Materials Science and Engineering: An Integrated Approach. Hoboken, NJ: Wiley, 2012. Print.

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Questions?

SILICA-LIKE MALLEABLE MATERIALS Group 10 Kristen Losensky Tzu-Hao Yen 11-16-12 1.

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