Nanoobjects in wood-protective coatings - Christian Lehringer (EMPA)

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Presentation from Christian Lehringer (EMPA) about the benefits and challenges ofincorportating nanoobjects into coatings designed to protect wood.

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  • Acrylate-resins and polyurethanes
    Outdoor and indoor application
    Fast and efficient manufacturing processes (application, spreading, drying time)
    Waterborn coating systems
  • Particle size, concentration, surface area, morphological structure, embedding into matrix
    Embedding of nanoobjects into polymer matrix specificially adapted to the different components
  • Nanoobjects in wood-protective coatings - Christian Lehringer (EMPA)

    1. 1. Nanoobjects in wood-protective coatings Christian Lehringer, Klaus Richter Empa, Swiss Federal Laboratories for Materials Science and Technology
    2. 2. University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    3. 3. Topics  Nano – where size does matter  Wood – a substrate with special characteristics  Application of engineered nanoobjects (ENOs) in wood coatings  Environmental, health and safety aspects  Conclusions University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    4. 4. Topics  Nano – where size does matter  Wood – a substrate with special characteristics  Application of engineered nanoobjects (ENOs) in wood coatings  Environmental, health and safety aspects  Conclusions University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    5. 5. Nano – where size does matter "Nano" = 1 to 100 nm University College of London, 04.11.2010, Christian Lehringer and Klaus Richter ISO/TS-27687 (2008)
    6. 6. Nanotechnology Use of nanomaterials Anorganic nanostructures Organic nanostructures Nanocomposites Nanoparticles for drug delivery ... Manipulation and assembly Nanoparticle manipulation Nanostructural architecture Nanomanufacturing Nanoelectronics ... Disciplines of Nanotechnology University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    7. 7. Topics  Nano – where size does matter  Wood – a substrate with special characteristics  Application of engineered nanoobjects (ENOs) in wood coatings  Environmental, health and safety aspects  Conclusions University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    8. 8. Wood – a substrate with special characteristics University College of London, 04.11.2010, Christian Lehringer and Klaus Richter  Bio-Composite-Polymer  Porous structure  Heterogenous  Anisotropic  Combustible  Hygroscopic  Biodegradable  Sensitive to UV-radiation  Density depends on species longitudinal
    9. 9. Topics  Nano – where size does matter  Wood – a substrate with special characteristics  Application of engineered nanoobjects (ENOs) in wood coatings  Environmental, health and safety aspects  Conclusions University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    10. 10. Key areas of wood surface coating University College of London, 04.11.2010, Christian Lehringer and Klaus Richter UV-protection Hydrophobation Easy-to-clean Antimicrobial Hardness Scratch resistance
    11. 11. Some ENOs currently used for wood coatings and their application area University College of London, 04.11.2010, Christian Lehringer and Klaus Richter *with hydrophobic functionalization Nanoobject Aluminum oxide (Al2O3) Iron(III) oxide (Fe2O3) Silver (Ag) Titan dioxide (TiO2) Zinc oxide (ZnO) Silizium dioxide (SiO2) Hardness x x Abrasion resistance x x Scratch resistance x x UV-Protection x x x Antimicrobial x x x Hydrophobation/ Easy-to-clean x*
    12. 12. UV-protection University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Schilliger 2010
    13. 13. UV-protection  Nanoscaled pigments of TiO2, Fe2O3, ZnO for transparent systems  Absorption and scattering of UV light  Substitute for organic UV-Absorbers (UVA)  Combination with lignin stabilizers and hindered amine light stabilizers (HALS)  Photocatalytic activity of nanoparticles requires combination with radical interceptors University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    14. 14. UV-protection University College of London, 04.11.2010, Christian Lehringer and Klaus Richter www.nanobyk.com
    15. 15. Hydrophobation/ Easy-to-clean University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    16. 16. Hydrophobation/ Easy-to-clean  Sol-gel-technology with organofunctional silanes or (poly)siloxanes  Effect: hydrophobic characteristic of substance + formation of hydrophobic nanostructure  Liquid water protection feasible, water vapor protection difficult University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    17. 17. Wood-inorganic composites by sol-gel process  Two stage process  Hydrolysis (here Silicic Acid Esters)  Condensation…. University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Si OEt EtO OEt Si OEt HO OH - 2 EtOH + 2 H2O OE Et O t Tetraethoxy silane (TEOS) OEt etc. + H2O 2 HO ..... (SiO2)nSi OEt OEt HO O OH OEt OEt SiSi OEt OH - H2O Silicate
    18. 18. 3-Isocyanatpropyl triethoxysilane β-(3,4 epoxycyclohexyl) ethyl trimethoxysilane vinyl trimethoxy silane Wood-inorganic composites by sol-gel process University College of London, 04.11.2010, Christian Lehringer and Klaus Richter  … in the cell wall
    19. 19. Antimicrobials University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Künniger 2010 Mold Blue stain Algae
    20. 20. Antimicrobials  Leach-resistance of Ag; TiO2; ZnO for long-term effect  Nanoobjects should be released systematically and preferably continuously in small amounts from an actively biocidal coating  Function possibly through ingestion, as contact poison, by photo-oxidative mechanism or binding to microbial DNA University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    21. 21. Antimicrobials University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Hochmannova 2010
    22. 22. Surface hardness/ scratch resistance  Silicones and nanosized alumina particles (Al2O3; SiO2) as additive  Surface modification of nanoparticles by trialkoxysilanes to improve the dispersibility of in acrylate media  In parquet industry, however, until now a broad application has not been realized University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    23. 23. Surface hardness/ scratch resistance University College of London, 04.11.2010, Christian Lehringer and Klaus Richter TEM picture of polyacrylate filled with 30 wt.-% nanosized silica. Bauer 2005
    24. 24. Surface hardness/ scratch resistance University College of London, 04.11.2010, Christian Lehringer and Klaus Richter www.nanobyk.com
    25. 25. Challenges and future research  Homogenous dispersion of nanoobjects in embedding matrix – avoid agglomeration  Long-term studies about leaching and mitigation  Balance between leach-resistance and systematic release of nanoobjects  Polymerization in the wood cell wall and covalent bonding University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    26. 26. Challenges and future research  Avoid crack formation, yellowing, depolymerization, improve gloss retention  Commercial application of sol-gel- technologies for wood impregnation  Reactivity of nanoobjects (e.g. Ag  Ag2S)  Renovation cycles (sanding, coating removal, new coating) University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    27. 27. Design for minimal exposition of engineered nanoobjects (ENOs) University College of London, 04.11.2010, Christian Lehringer and Klaus Richter “Factors of stability” Stability of ENO integration into coating system by trend higher by trend lower Location of ENOs in façade coating system in the bottom layers at the surface Binding type between ENOs and coating matrix covalent not covalent Property of ENOs in organic coating matrix not photocatalytic photocatalytic Property of ENOs in organic or mineral coating matrix wettability high wettability low Property of façade coating system resistance against exterior influ- ences (e.g. moisture, wind- abrasion, temperature changes) low resistance against exte- rior influences Som 2010 Stability of ENO integration into coating system by trend higher by trend lower in the bottom layers at the surface covalent not covalent not photocatalytic photocatalytic wettability high wettability low resistance against exterior influ- ences (e.g. moisture, wind- abrasion, temperature changes) low resistance against exte- rior influences “Factors of stability” Stability of ENO integrat by trend higher Location of ENOs in façade coating system in the bottom layers Binding type between ENOs and coating matrix covalent Property of ENOs in organic coating matrix not photocatalytic Property of ENOs in organic or mineral coating matrix wettability high Property of façade coating system resistance against exterior influ- ences (e.g. moisture, wind- abrasion, temperature changes)
    28. 28. Topics  Nano – where size does matter  Wood – a substrate with special characteristics  Application of engineered nanoobjects (ENOs) in wood coatings  Environmental, health and safety aspects  Conclusions University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    29. 29. University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Life cycle of nanocoatings
    30. 30. Estimated influences of ENOs on the environment, modified after Som et al. (2010) University College of London, 04.11.2010, Christian Lehringer and Klaus Richter ENVIRONMENT Ag c) ZnO c) TiO2 b) SiO2 a) Al2O3 a) Indication for hazardous effects (with realistic con- centrations) + + + -- -- Solution in water increases the toxic effects (+), re- duces toxic effects (-) ++ ++ 0 -- ++ Tendency for agglomeration and sedimentation (-) or no sedimentation (+) - - -- -/+ -- Waste water facility releases ENO into waters (+), does not release ENO into waters (-) - n.i. - - - Stable during waste incineration (+), burns during waste incineration (-) + + ++ ++ ++ legend: + applies;  weak indices available; - does not apply; n.i, not investigated (high degree of uncertainty) The indices represent the overall evaluation of the ENOs: a) rather harmless; b) big uncertainty due to lack of data; c) biological effect traceable, effect on environment to be expected. These estimations do not represent the effects of nanoobjects that were generated by unintended actions (e.g. traffic) *: mostly dependent from contaminants in the samples (transition metals such as Iron, Nickel, Cobalt etc.) #: Aluminum oxide hydroxide (AlOOH) in the lung was investigated.
    31. 31. Estimated influences of ENOs on the health on basis of different biological studies, modified after Som et al. (2010) University College of London, 04.11.2010, Christian Lehringer and Klaus Richter HEALTH Ag a) ZnO c) TiO2 a) SiO2 a) amorph Al2O3 # b) Chronic toxicity (long term effects to be expected, PNEC, PEC), threshold values known     n.i. Acute toxicity      Impairment of DNA     n.i. Brain damage: damage of the central nervous sys- tem n.i. n.i. n.i. n.i. n.i. Crossing and damaging tissue barriers (e.g. blood- brain barrier, placenta, lung) n.i. n.i.   # Skin     n.i. Gastrointestinal tract     n.i. Lung      legend: + applies;  weak indices available; - does not apply; n.i, not investigated (high degree of uncertainty) The indices represent the overall evaluation of the ENOs: a) rather harmless; b) big uncertainty due to lack of data; c) biological effect traceable, effect on environment to be expected. These estimations do not represent the effects of nanoobjects that were generated by unintended actions (e.g. traffic) *: mostly dependent from contaminants in the samples (transition metals such as Iron, Nickel, Cobalt etc.) #: Aluminum oxide hydroxide (AlOOH) in the lung was investigated.
    32. 32. The "Collingridge dilemma“ (Collingridge 1980) Decision making in uncertainity University College of London, 04.11.2010, Christian Lehringer and Klaus Richter Early phase of development Influence on innovations Technical "log-in effects" Costs for corrections Socio-economic “lock-in” effects Time and knowledge Late phase of developmentEarly phase of development Influence on innovations Costs for corrections Time and knowledge Late phase of development
    33. 33. Summary  Wood coating systems with considerable market relevance  Thorough risk assessment, life-cycle-analysis, material characterization, standardized metrology required  Public acceptance strongly depends on transparent security systems, consistent labeling of nanoproducts and honest communication University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
    34. 34. Thank you very much for your attention University College of London, 04.11.2010, Christian Lehringer and Klaus Richter

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