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

1. Nanoobjects in wood-protective coatings
Christian Lehringer, Klaus Richter
Empa, Swiss Federal Laboratories for Materials
Science and Technology

2. University College of London, 04.11.2010, Christian Lehringer and Klaus Richter

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. 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. 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. 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. 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. 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. 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. 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. 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. UV-protection
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
Schilliger 2010

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. UV-protection
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
www.nanobyk.com

15. Hydrophobation/ Easy-to-clean
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter

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. 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. 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. Antimicrobials
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
Künniger 2010
Mold Blue stain Algae

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. Antimicrobials
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
Hochmannova 2010

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. 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. Surface hardness/ scratch resistance
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
www.nanobyk.com

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. 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. 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. 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. University College of London, 04.11.2010, Christian Lehringer and Klaus Richter
Life cycle of nanocoatings

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. 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. 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. 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. Thank you very much for your attention
University College of London, 04.11.2010, Christian Lehringer and Klaus Richter