Goodbye, Space Elevator: Earth-Based Nanotech

Transcription

1 Goodbye, Space Elevator: Earth-Based Nanotech Asst. Prof. Daniel F. Schmidt Department of Plastics Engineering / Nanomanufacturing Centers at UML

2 2 What is Nano?

3 3 What is Nano?

4 4 What is Nano?

5 5 Some Thoughts on our Discourse Nano = billionth Nano- =??? Nano is the new Turbo (metacool.typepad.com,, Sept. 12, 2005) In the sciences, nano- is most meaningful when: A system contains features that are really small (with at least one dimension of ~100 nm or less) The system behaves in a fundamentally different manner as a direct result of nanosized features

6 6 Some Thoughts on our Discourse The development of science and technology Revolution vs. evolution The novel and the familiar Hype and the next big thing The incentive to sell (Telling a good story is how you get places!) The long-term consequences (Overselling, dismissal, fatigue, confusion, fear, ignorance) Reality tends to be more mundane ( and it s s hard to sell mundane or is it?) Case Study: Polymer Nanocomposites

7 7 Case Study: Polymer Nanocomposites Polymer = Plastic, more or less Polymer implies many repeating units Plastic implies something, formable, i.e. polymer or polymer plus additives Nanocomposite = Type of composite A composite is a combination of at least two different phases of matter In a nanocomposite,, at least one phase has at least one dimension of <100 nm

8 8 Classical Composites The Rule of Mixtures OR 1 / (Composite( Property) ) = (Fraction Red) ) / (Red( Property) ) + (Fraction Green) ) / (Green( Property) (Composite Property) ) = (Fraction Red) ) x (Red( Property) ) + (Fraction Green) ) x (Green( Property) This approach can predict composite stiffness, electrical and thermal conductivity, and thermal expansion.

9 9 Implications of nano in Nanocomposites Interphase = polymer at or near an interface (different!) = Bulk polymer COMPOSITE ~6% of area covered by particles ~4% of area covered by interphase NANOCOMPOSITE ~6% of area covered by particles ~45% of area covered by interphase

10 10 Nanocomposite Dimensionality Nanoparticles Metal oxides Carbon black Polymer colloids Carbides (Si, W) Nitrides (B, Si) Block copolymers POSS 0-D 1-D Nanorods Carbon nanotubes MO z nanowhiskers MO x nanotubes BN nanotubes Block copolymers Nanolayers 2:1 Phyllosilicates Hydrotalcite Block copolymers 2-D 3-D Nanonetworks IPNs Block copolymers

11 11 Common Phyllosilicates (phyllo = lat. leaf) Weathering Volcanic activity Mica (micare = lat. to shine) Vermiculite (vermiculus = lat. little worm) Montmorillonite, a.k.a. Bentonite (Montmorillon, France; Fort Benton, Wyoming) Talc ( Soapstone ) (talq = Arab. mica) Kaolin ( China Clay ) (kaoling = Chin. high cliff) NANOCLAY!

12 12 Why Nanoclay? Readily available Found in dirt, rivers worldwide Nano when dispersed in a medium; otherwise primarily micron-sized sized Hydrophilic, but easily modified to give polymer compatibility Alkylammonium modifiers typical Bio-derived & biodegradable Long safety record in detergents, fabric softeners, etc. Inexpensive (~$2.50-$3.50/lb) $3.50/lb) compared to other nanofillers Low toxicity, good sustainability relatively green as well? ~ nm (image courtesy of D. Shah, Cornell University) ~1 nm

13 13 Nanoclay Dispersion and Nanocomposite Structure Thermodynamics Thermodynamics and Processing IMMISCIBLE INTERCALATED EXFOLIATED CONVENTIONAL COMPOSITE NANOCOMPOSITE

14 14 Property Impetus for Study Mechanical Properties Nylon-6 Nylon-6 Nanocomposite STIFFNESS Elastic Modulus (GPa( GPa) STRENGTH (IN TENSION) Tensile Strength (MPa( MPa) STRENGTH (IMPACT) Impact Strength (kj/m 2 ) THERMAL EXPANSION Thermal Expansion Coefficient (strain / C) DISTORTION TEMP. ( C)( WATER UPTAKE (wt%) (From work by the Toyota Corporation, 1993) 10-5

15 15 Impetus for Study Barrier Properties 1.0 Relative Permeability PCL Nanocomposite B A PCL Composites (conventionally filled) Volume Fraction Silicate (Messersmith and Giannelis, 1995)

16 16 Impetus for Study Thermal Properties Nanocomposites can display improved thermal stability Heat output during nanocomposite burning is lower The formation of a char layer protects underlying material Nanocomposites can display self-extinguishing extinguishing behavior Large Heat Release Decomposing Polymer Virgin Polymer Polymer Nanocomposite Small Heat Release Protective Char Layer Charring Polymer Virgin Polymer (Gilman and Giannelis, 1998)

17 17 Commercial Applications Wilson Double Core tennis balls (Davis Cup) (InMat Air D-Fense) Butyl rubber NC for gas barrier GM Safari / Astro step assist 2004 Chevrolet Impala body side molding 2005 Hummer H2 SUT cargo bed (Basell nano-tpo / Profax) 2004 Acura TL seat back (Noble Polymers Forte PP NC) Polyolefin NCs for reduced density and cycle time, improved impact strength, surface quality, and dimensional stability Honeywell Aegis ColorMatrix Imperm Lanxess Durethan KU NYCOA nanoseal Polyamide NCs for barrier properties

18 18 Summary & Conclusions Nano means many things to many people For scientists it implies fundamental changes in behavior as a direct result of nanoscopic features The term has nevertheless been abused for many reasons Polymer nanocomposites represent a realisitic, down-to to-earth application of nanotechnology In optimized polymer nanocomposites,, we can Make materials stiffer, stronger and tougher all at once Reduce the permeability of the material Reduce flammability and improve heat stability Retain transparency (as particles are so small) Produce thinner parts faster and with less energy One of the first real large-scale commercial successes of the nanotech era!