bài giảng polymer nanocomposite

Polymer (nano)composites : key-role of chemistry Hà Thúc Huy Khoa Hóa - ĐHKHTN Outline I. Polymer microcomposites filled with microparticles I.1. Mechanical melt blends I.2. Importance of «polymer/filler» interface (tension and adhesion) I.3. "Polymerization-filled composites" PFC's II. Polymer nanocomposites filled with nanoparticles II.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-modification II.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 Typical example : polyethylene filled with reinforcing inorganic particles inorganic particles Hydrophobic Hydrophilic-surface polyethylene Particulate fillers Fillers aggregation => mechanical brittleness Uniaxial constraint Generation of voids => propagation of the rupture Uniaxial constraint Generation of voids => propagation of the rupture (From Prof. G. Marosi) Materials Stiffness Brittleness (fast deformation) Brittleness (slow deformation) Young’s modulus Impact strength (IZOD test) Elongation at break (tensile test) (GPa) (J/m) (%) HDPE 0.7 80 900.0 HDPE + 40wt% kaolin 3.1 17 1.6 HDPE + 40wt% mica 6.5 20 0.3 HDPE + 40wt% CaSO 4 2.8 15 1.3 HDPE + 40wt% CaCO 3 2.7 21 3.0 Effect of particulate fillers on mechanical properties BRITTLENESS non-homogeneous mineral dispersion poor mineral-polymer interaction * High density polyethylene (Mw ~ 90K) * Stress at break Stress at yield Young modulus initial slope Elongation at yield point Elongation at break Elongation (%) Stress (MPa) NB : mechanical properties for a semi-crystalline thermoplastic like HDPE measured by tensile testing (in between T g and T m ) Rigidity Limit of elastic behavior : Strength experienced by the materials per initial section (constraint) : Length elongation compared to initial length of the deformed zone Solutions ? 1°) Decrease the hydrophilicity of the filler surface Chemical treatment of the filler surface (alkoxysilane, alkylamine, Al carboxylates,…) Improvement of the dispersion Poor adhesion Less brittle composite materials 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 dispersion Reinforced adhesion => Mechanical rupture within the matrix ! Rigidity and resistance to break significantly improved [...]... clays,… Classification : Nanocomposite particulaire (SiO2, Aluminium, Oxyde de métaux …) Nanocomposite lamellaire (argile et graphite) 3 ème 1 er 2ème Nanocomposite fibreux (nano fibre ou nano tube de carbone) 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 TEM : Montmorillonite... research KICK OFF!!! • Currently : huge interest for layered silicate nanocomposites based on thermoplastics, elastomers and thermosets… Polymer Layered Silicate Nanocomposites : Bibliographic Statistics Scientific articles, reviews and communications From CAS and Medline Databases – via Scifinder Scholar 2004 Polymer Layered Silicate Nanocomposites : the most cited matrices PP (13%) PA-6 (12%) PS (10%)... as transfer agent) - composition (α-olefin copolymerization)  high catalytic efficiency  performant mechanical properties : stiffness and toughness (even at high filling) - filler deagglomeration - homogeneous filler dispersion (encapsulation) - enhanced interfacial adhesion Chapter 2 : Polymer nanocomposites filled with nanoparticles Chapter 2 : Polymer nanocomposites filled with nanoparticles Part... PVC (2%) Other polymers (42%) NB : 1061 hits concern montmorillonite (~65%) ! Layered Silicate Nanocomposites : Bibliographic Statistics International patents 1 PP 22% 2 PA-6 3 PE 4 PS 5 PET 6 PA-6,6 7 EPR 8 PA-12 9 EVA 10 SBR 19 18 17 15 9 7 7 7 6 NB : ~68% concern montmorillonite! From CAS Database – via Scifinder Scholar 2004 research tool Nanocomposites : Definition and Generalities Nanocomposite. .. stiffness/toughness - costly ­thermally activated initiators (peroxydes)  • Polymerization from the filler surface POLYMERIZATION-FILLED COMPOSITES : PFC’s Polymerization-Filling Technique ENIKOLOPIAN N.S., USSR Pat. 763,379 (1976) HOWARD E.G., US Pat. 4,104,243 and 4,097,447 (1978 fixation of a Ziegler­Natta type catalyst onto the filler olefin polymerization from the filler  surface/pores Filled-Polyolefin Filler... with nanoparticles Part I Layered silicates as nanofillers Layered Silicate Nanocomposites : Brief History • 1950 • 1976 • 1993 First US Patent by Carter L.W et al (US 2,531,396) (assigned to National Lead Co.) Polyamide nanocomposites by S Fujiwara S et al (Ja Appl 109,998) (assigned to Unitika K.K.) Polyamide-6 organophilic clay nanocomposites by Okada A et al (Toyota Research) (Mater Res Soc Proc.,... 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 Ti N CH3 CH3 Polymerization from the filler surface Advantages towards melt blending : uniform distribution of the filler throughout the matrix optimum polymer adsorption and wetting only process for the preparation of UHMWPE­based ... metallocene catalysis • Strong filler -polymer adhesion : 10µm Weak interfacial adhesion PFC(22wt% glass  beads) Melt blend (20wt% glass beads) Strong interfacial adhesion PFT via metallocene catalysis : some applications Filler precoating : Dispersion of coated glass beads in HDPE • Precoating of glass beads by either polyethylene (HDPE) or ethylene/1-octene copolymer (LLDPE) and composites filled... Hf(BH4)4 Metallocenes : Single Site Catalysts in Olefin Polymerization  General structure – activation by methylaluminoxane MAO CH3 CH3 M X X + M Al O CH3 + X n M = Ti, Zr, Hf X = Cl, CH3, Al O n MAO for :  ­ methylation ­ cationization ­ protic scavenger action ­High catalyst activity ­Molecular weight control (sensitivity to hydrogen) ­Copolymerization with α­olefins (thermoplastic to elastomer)... Combination of HIGH STIFFNESS and HIGH  IMPACT RESISTANCE (even at high filler content, > 60 wt%) Characteristic features of PFT via metallocene catalysis • Polymer growth from the filler surface and open pores : 1µm 1µm Glass beads coated by 7wt% of an ethylene­octene copolymer Highly porous silica (160m²/g) with 38wt% of HDPE Filler and composite type silica silica melt blend PFC Content Impact of filler energy . nanofillers - Polymer- clay nanocomposites : melt blending vs. in situ polymerization - Polyolefinic matrices : role of matrices and compatibility - Polyester matrices : role of clays and organo-modification II.2 n MAO for : - methylation - cationization - protic scavenger action  Properties - High catalyst activity - Molecular weight control (sensitivity to hydrogen) - Copolymerization with α-olefins (thermoplastic. improved Filler - Polymer Dispersion / Interaction • Surface modification of the filler  Surface agents (monofunctional) : -silanes; -alkylamines; -Al carboxylates; -titanate esters;  Coupling