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  • Polymer (nano)composites : key-role of chemistryH Thc HuyKhoa Ha - HKHTN

  • OutlineI.Polymer microcomposites filled with microparticlesI.1.Mechanical melt blendsI.2.Importance of polymer/filler interface (tension and adhesion) I.3."Polymerization-filled composites" PFC's II.Polymer nanocomposites filled with nanoparticlesII.1. Layered silicate as nanofillers -Polymer-clay nanocomposites : melt blending vs. in situ polymerization-Polyolefinic matrices : role of matrices and compatibility-Polyester matrices : role of clays and organo-modificationII.2. Carbon nanotubes as nanofillers-Polymer-CNTs composites : production and properties-Melt blending technique, e.g., in elastomeric matrices- in situ polymerization, e.g., in thermoplastic matrices III. General conclusions et outlook

  • Chapter 1 :

    Polymer microcomposites filled with microparticles

  • Typical example : polyethylene filled with reinforcing inorganic particles

  • (From Prof. G. Marosi)

  • Effect of particulate fillers on mechanical properties * High density polyethylene (Mw ~ 90K)*

  • NB : mechanical properties for a semi-crystalline thermoplastic like HDPE measured by tensile testing (in between Tg and Tm)RigidityLimit of elastic behavior: Strength experienced by the materials per initial section (constraint): Length elongation compared toinitial length of the deformed zone

  • Solutions ?1) Decrease the hydrophilicity of the filler surfaceChemical treatment of the filler surface(alkoxysilane, alkylamine, Al carboxylates,)Improvement of the dispersionPoor adhesionLess brittle composite materials

  • Filler or coating

    composition

    Filler

    content

    Elongation

    at break

    Impact

    strength

    (wt%)

    (%)

    (kg m/m)

    Reference materials

    Unfilled HDPE

    0

    1045

    2.77

    + Kaolin

    20

    218

    1.24

    Kaolin + surface agents

    0.6 n-hexylamine

    20

    291

    1.38

    5.0 triethoxysilane

    20

    162

    1.92

    5.0 octadecyl

    triethoxysilane

    20

    668

    1.38

    2.5 oxylaluminum-

    2-ethylbutyrate

    20

    300

    1.91

  • 2) (Polymer) grafting reaction onto filler surface via chemical treatment of filler surface with coupling agents (vinylic or methacrylic alkoxysilanes, aluminum methacrylates,) followed by polymer grafting all along melt blending/processing

    Improved dispersionReinforced adhesion =>Mechanical rupture within the matrix !Rigidity and resistance to break significantly improved

  • Filler or coating

    composition

    Filler

    content

    Elongation

    at break

    Impact

    strength

    (wt%)

    (%)

    (kg m/m)

    Reference materials

    Unfilled HDPE

    0

    1045

    2.77

    + Kaolin

    20

    218

    1.24

    Kaolin + coupling agents

    2.0 3-(trimethoxysilyl)propyl

    methacrylate

    20

    277

    1.96

    2.0 vinyltriethoxysilane

    + 3.0 amyl-triethoxysilane

    20

    71

    1.58

    1.5 oxyaluminum

    methacrylate

    20

    420

    2.79

    1.5 oxyaluminum-methacrylate

    + 2.5-bis-(t-butylperoxy)

    -2,5-dimethylhexane (a)

    20

    430

    3.04

    (a) Peroxide content was 0.05 wt% kaolin.

  • Filler - Polymer Dispersion / Interaction

  • Polymerization-Filling Technique ENIKOLOPIAN N.S., USSR Pat. 763,379 (1976)HOWARD E.G., US Pat. 4,104,243 and 4,097,447 (1978)

  • Polymerization-Filling Technique Mainly developed for Ziegler-Natta catalysts (transition metal complexes )

  • Metallocenes : Single Site Catalysts in Olefin Polymerization

  • PFT via Metallocene CatalystsfillerMAOCompositeMetalloceneMonomerDeagglomerationof the filler

    Fixation possible on basic, acidic, organic, metallic surfaces

    Protection of active catalystImmobilization of the active species throughelectrostaticinteractions

    Homogeneousdispersion of the filler

  • PFT with metallocene/MAO complexes : experimental procedure Filler treatment :

    MAO fixation

    * filler dispersion in heptane followed by contact with (TMA-depleted) MAO * solvent evaporation and thermal treatment (150C)

    * (unreacted MAO washed out with toluene)

    Metallocene activation

    * treated filler suspended in heptane and contacted with the catalyst :

    * transfer in the polymerization reactor and addition of ethylene (10 bars) and hydrogen when needed

    * composite isolated by precipitation from acetone.

    (Tert-butylamido)dimethyL(tetramethyl-h5-cyclopentadienyl)silane titanium dimethyl (CGC1)

  • Polymerization from the filler surface uniform distribution of the filler throughout the matrix

    optimum polymer adsorption and wetting

    only process for the preparation of UHMWPE-based compositesAdvantages towards melt blending :

  • Characteristic features of PFT via metallocene catalysis (Dubois, Jrme et al., Chem. Mater., 13, 236 (2001)) Polymer growth from the filler surface and open pores :Glass beads coated by 7wt% of an ethylene-octene copolymerHighly porous silica (160m/g) with 38wt% of HDPE

  • Characteristic features of PFT via metallocene catalysis

    Strong filler-polymer adhesion :

  • PFT via metallocene catalysis : some applications Filler precoating : Dispersion of coated glass beads in HDPE

  • ConclusionsHomogeneous polyolefinic-based compositesVersatility of microsized fillers : - acidic (kaolin, silica, ...) - basic (magnesium hydroxide,...) - organic (graphite, cellulose,) - metallic (nickel, iron,)metallocene-based catalysts : Ti,Zr,(Hf),...

    Allows for control over the molecular parameters - Mn (hydrogen as transfer agent) - composition (a-olefin copolymerization) high catalytic efficiency performant mechanical properties : stiffness and toughness (even at high filling) filler deagglomeration homogeneous filler dispersion (encapsulation) enhanced interfacial adhesion

    PFC via metallocene-based catalysts

  • Chapter 2 :

    Polymer nanocomposites filled with nanoparticles

  • Chapter 2 :

    Polymer nanocomposites filled with nanoparticlesPart I. Layered silicates as nanofillers

  • Layered Silicate Nanocomposites : Brief History 1950 First US Patent by Carter L.W. et al. (US 2,531,396)(assigned to National Lead Co.)

    1976 Polyamide nanocomposites by S. Fujiwara S. et al. (Ja Appl. 109,998) (assigned to Unitika K.K.)

    1993 Polyamide-6 organophilic clay nanocomposites by Okada A. et al. (Toyota Research) (Mater. Res. Soc. Proc., 171, 45, 1993)

    Claim : dramatic improvement of mechanical, barrier and thermal properties (at low clay content)

    International academic and industrial research KICK OFF!!!

    Currently : huge interest for layered silicate nanocomposites based on thermoplastics, elastomers and thermosets

  • Polymer Layered Silicate Nanocomposites : Bibliographic Statistics From CAS and Medline Databases via Scifinder Scholar 2004 research toolScientific articles, reviews and communications

    Graph1

    2

    5

    12

    19

    16

    26

    73

    128

    213

    352

    531

    564

    Year

    Number of publications

    Feuil1

    19932

    19945

    199512

    199619

    199716

    199826

    199973

    2000128

    2001213

    2002352

    2003531

    2004564

    Feuil2

    Feuil3

  • Polymer Layered Silicate Nanocomposites : the most cited matrices NB : 1061 hits concern montmorillonite (~65%) !

  • Layered Silicate Nanocomposites : Bibliographic Statistics From CAS Database via Scifinder Scholar 2004 research toolInternational patents1PP 22% 2PA-6 19 3PE 18 4PS 17 5PET15 6PA-6,6 97EPR 7 8PA-12 7EVA 7 10SBR 6NB : ~68% concern montmorillonite!

    Graph1

    3

    0

    1

    3

    1

    14

    17

    46

    53

    84

    80

    74

    Year

    Number of publications

    Feuil1

    19933

    19940

    19951

    19963

    19971

    199814

    199917

    200046

    200153

    200284

    200380

    200474

    Feuil2

    Feuil3

  • Nanocomposites : Definition and Generalities

  • Classification :Erik T.Thostenson et al.; Composite Sci. Technol. 65(2005)491-516.

  • Polymer Layered Silicate Nanocomposites molecular distribution of (alumino)silicate layers into a (polymer) matrix

    usually obtained starting from smectite clays (montmorillonite, saponite, hectorite,)

  • Building the PhyllosilicatesSilicon-Oxygen Tetrahedron Aluminum-Oxygen Octahedron

  • Kaolinite [Al2Si2O5(OH)4]Pyrophyllite [Al2Si4O10(OH)2] (ideal)1:1 Clay MineralOctahedral LayerTetrahedral Layer2:1 Clay Mineral

  • Crystal SystemsMMT

  • Montmorillonite : Origin and Resources * Nax(Al4-xMgx)Si8O20(OH)4

  • Montmorillonite : main characteristic features Surface area~ 750 m/g Density ~ 2.6 Aspect ratio~ 100-500 CEC 1)~ 70 120 meq./100gCationic Exchange Capacity = maximum amount of cations, e.g. NH4+, that can be taken up per unit mass, in H2O at pH 7 (1meq/g is 96.5 Coulombs/g in SI units)

  • m-size Particle > thousands Platelets The Processing ChallengePolymer

  • Modification of CLAY, Why???????

  • MMTs modification methods : I/ Alkyl ammonium salts Alkyl phosphonium salts