Surface modification of wood with
functionalized alkoxysilanes
Elisa Cappelletto, Rosa di Maggio
Department of Materials Engineering and Industrial Technology
University of Trento
Workshop “Basics for Chemistry of Wood SurfaceModification" 25 April-Kuchl
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
WOOD
COATING
Why? Enhancing wood durability
What? Alkoxysilanes different functionalized
How? Surface modification of wood throught immersion
Lignin
Hemicellulose
Cellulose
Material and Method
Sol-gel precursors
Solvents
Ethanol, Chloride acid and Ammonium solutions as catalytic agent
Substrate
Larch and Pine
Application by immersion
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Tetraethoxysilane
Si(OC2H5)4
Dimethyldiethoxysilane
(CH3)2Si(OC2H5)
Perfluorooctyltriethoxysilane
(C14H19F13O3Si) Phenyltriethoxysilane
(C6H5)Si(OC2H5)3
Preparation of Samples
Substrate: Larch and Pine
Coatings: wT, wM2, wPhtes
Residential Time: 3, 5,10, 20 min
Characterization: SEM-EDX
Time of deposition 20 min: presence of cracks
Conclusion:
Residential Time
single layer: 10 min
double layer: 3 min First Layer on Larch
5 min Fisrt Layer on Pine
10 min Second Layer
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
List of the SAMPLES
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Samples Substrate First Layer Second Layer Weight of coating per unit of surface g/m2
wM2 wood (CH3)2Si(OC2H5) 33
wTM2 wood Si(OC2H5)4 (CH3)2Si(OC2H5) 41
wTM2b wood Si(OC2H5)4 (CH3)2Si(OC2H5) 30
wTPFOS wood Si(OC2H5)4 (C14H19F13O3Si) 56
wTPhtes wood Si(OC2H5)4 (C6H5)Si(OC2H5)3 37
b= basic catalysis
Characterization of Treated Wood
SEM-EDX
FT-IR
NMR
Contact Angle Measurement
Fire Test
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Distribution on the surface
Coated wood
Untreated wood
Profile
EDX spectrum of Silicon
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
SEM-EDX
EDX spectra of Silicon
FT-IR (ATR)
IR spectra of treated samples show the strong Si-O-Si stretching band (1029 cm-1).
The treatments decrease the amount of –OH on the surface
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Solid State NMR investigation
Evaluation of the degree of condensation of
siloxane coatings
Structural Unit:
Q4 (Si(OSi)4), Q3 ROSi(OSi)3), Q2 (RO)2Si(OSi)2)
T3 RSi(OSi)3), T2 RSi(OSi)2OR’, T1 RSi(OSi)2(OR’)2
D2 R2Si(OSi)2, D1 R2Si(OSi)R’
High Degree of Condensation (DOC), matrix are
stable
DOC≈90
Deconvolution of Peaks
29Si CPMAS spectrum of treated samples
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
DOC=((4xQ4+3xQ3+2xQ2+Q1)/4+(3xT3+2xT2+T)/3+(2xD2+D1)/2+M)
where capital letters are the areas under the peaks obtained by
deconvolution
T2 T3
CONTACT ANGLE TEST(Vieca Method*)
The treatments increase hydrophobic behaviour of wood. Double layer
samples have higher equilibrium CA values respect to monolayer (≈90°)
0
20
40
60
80
100
120
untr
.woo
d
wM
2
wTM
2
wTM
2b
WTP
FOS
wTP
HTE
S
Theta STATIC CONTACT ANGLE
EQUILIBRIUM CONTACTANGLE
Untreated wood
vibration
Coated sample
*C. Della Volpe, D. Maniglio, M. Morra, S. Siboni, The determination of a “stable-equilibrium” contact
angle on heterogeneous and rough surfaces, Colloids Surf. A 206 (2002) 46–6
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Reaction to Fire (Cone Calorimeter Test)
s (MJ/m²) MLR t
Sample Time of ignition Total Heat Release Mass Loss rate
Untreated wood 13,33 156,65 445,000
Commercial prod. 14,00 156,51 235,000
WM2 13,33 157,33 428,333
WTM2a 15,33 145,22 30,000
WTM2b 16,67 151,75 31,667
WTPFOS 14,67 151,92 185,000
WTPHTES 18,00 148,46 35,00
Cone Calorimeter
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Time of ignition
Total Heat Release Mass Loss rate
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
SEM-EDX and FT-IR OF BURNED SAMPLES
SEM images of burned samples
EDX spectrum of burned sample
FT-IR (ATR) Treated wood and burned samples
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento
Conclusion
- The Modification of wood surface through immersion improves some properties of material
- Increase of the hydrophobic barrier
- Good Fire retardant properties ( taking into account the small amount of material deposited)
- Stable matrix on surface, and partial penetration on the bulk of wood
- No alteration of optical properties
- The results obtain with fluorinated treatments are comparable to those obtained with methylated
series. Methylated compounds are cheaper
- Good results with phenyltriethoxysilane
Work in Progress
- Biological test against fungi
- Application by impregnation
CNR-Ivalsa (Istituto per la Valorizzazione del Legno e delle Specie Arboree)
- Sesto Fiorentino (FI): Biological Test
- S.Michele all’Adige (TN): Flame Retardant Test
Acknowledgment The Trento Provincial Authority is gratefully acknowledged for funding (PAT – CENACOLI
project).
Collaborations
Elisa Cappelletto, Surface modification of wood with functionalized alkoxysilanes, University of Trento