Nanofibrillated Cellulose
as Additive for Wood Coatings
Franziska Grüneberger, Tina Künniger, Anja Huch,
Martin Arnold, Ingo Burgert, Tanja Zimmermann
Laboratory for Applied Wood Materials
Empa – Swiss Federal Laboratories for Material Sciences and Technology
COST Action FP1105 Meeting
Zürich, 31.08.2015
Introduction
COST Action FP1105 Meeting – 31.08.2015
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Idea of Project
NFC network with nanoparticles
to increase e.g. UV
or fungi resistance
1 µm
10 µm
NFC network structure
to counteract mechanical
impacts (cracking/hail damage)
10 µm
NFC network in coating
COST Action FP1105 Meeting – 31.08.2015
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Project structure
Different polymer matrices

Compounding with
unmodified NFC
successful fibrillation of NFC
and quality assessment/
control via rheology

differences between acrylic
and alkyd binders

testing with regard to coating
application
NFC isolation
Possible
NO
YES
Modification of NFC


liquid suspensions: rheology
dry films: tensile tests;
artificial aging
NFC polymer compound
Tests
Functionalization of NFC
with different active substances
(NFC as carrier substance)
Reinforced & functionalized
wood coating
COST Action FP1105 Meeting – 31.08.2015
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Rheology of NFC-acrylate suspensions
▪ tunable viscosity by NFC addition
▪ NFC dominates the flow behaviour of NFC-acrylate suspensions
▪ no/only little influence of acrylate type  behaves like conventional thickener
Grüneberger et al. (2014) Cellulose, 21, 1313-1326
COST Action FP1105 Meeting – 31.08.2015
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Mechanical properties of free films
neat polymer
composite with 2.5% NFC
▪
▪
▪
▪
mechanical reinforcement of polymeric binders after NFC addition
big variation of mechanical properties depending on binder type
remarkable changes of mechanical properties during aging, esp. for alkyds
effect bigger than the effect of NFC addition beforehand
Grüneberger et al. (2014) J. Mater. Sci., 49, 6437-6448
COST Action FP1105 Meeting – 31.08.2015
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Project structure
Different polymer matrices

Compounding with
unmodified NFC
successful fibrillation of NFC
and quality assessment/
control via rheology

differences between acrylic
and alkyd binders

testing with regard to coating
application
NFC isolation
Possible
NO
YES
Modification of NFC


NFC polymer compound
Tests

liquid suspensions: rheology
dry films: tensile tests;
artificial aging
functionalization with UV
absorbers:


inorganic ZnO
organic UV absorber
Functionalization of NFC
with different active substances
(NFC as carrier substance)
Reinforced & functionalized
wood coating
COST Action FP1105 Meeting – 31.08.2015
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Functionalization with ZnO
after sonication
+
5 µm
50 µm
NFC
unstabilized, powdery ZnO
NFC/ZnO compound
addition to binder
▪ homogeneous distribution of unstabilized ZnO into NFC network,
also after storage of the liquid coating formulation
▪ NFC prevents sedimentation of ZnO during the curing process of the coating
Grüneberger et al. (2015) Prog. Org Coat. 87, 112-121
COST Action FP1105 Meeting – 31.08.2015
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Functionalization with ZnO
transmission [%]
100
coating with ZnO (no NFC)
80
60
40
increasing ZnO content
20
0
200
400
600
800
wavelength [nm]
gloss at 60°
100
coating with NFC and ZnO
no NFC
80
60
NFC
40
20
0
0
2
4
6
8
10
ZnO content in coating [wt%]
▪ reduced UV-transmission of ZnO-containing free coating films, no influence of NFC
▪ NFC serves as matting agent: reduced gloss
▪ reduced crack formation in ZnO-containing coating in presence of NFC depending on binder
Grüneberger et al. (2015) Prog. Org Coat. 87, 112-121
COST Action FP1105 Meeting – 31.08.2015
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Functionalization with ZnO
50
increasing ZnO content
reference without ZnO
different sample series
with and without NFC
∆E*
40
30
20
increasing
ZnO content
10
0
0
50
168 h of artificial weathering
1512 h of artificial weathering
∆E*
commercial ZnO product
for UV protection
1600
reference without ZnO
40
0 h of artificial weathering
400
800
1200
weathering time [h]
30
different sample series
at 2.4% ZnO
20
10
0
0
400
800
1200
weathering time [h]
1600
▪ increased colour stability with increasing ZnO concentration, no effect of NFC on colour
▪ stabilizing effect of NFC/ZnO-system was generally insufficient
▪ but: commercial ZnO product underperformed, as well
Grüneberger et al. (2015) Prog. Org Coat. 87, 112-121
COST Action FP1105 Meeting – 31.08.2015
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Implementation: Prototypes for NEST
NEST building
after 7 month of natural weathering
untreated
org. UVA
+ HALS
NFC
+ org. UVA
+ HALS
NFC
+ commercial ZnO
NFC/ZnO
NFC/ZnO
+ org. UVA
+ HALS
▪ Empa internal project NEST (Next Evolution in Sustainable Building Technologies)
▪ module “Vision Wood” (“Vision Holz”)
▪ 6 wooden façade elements as prototypes are currently installed for pre-tests in natural weathering
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Summary

NFC = potential new component for wood coatings
significant impact of NFC on viscosity: like a conventional thickener
 effect of film aging on mechanical properties bigger than effect of NFC
addition, esp. for alkyds

NFC improved dispersion/stabilization of unstabilized ZnO in the coating
 NFC reduced crack formation of coatings with ZnO
 colour stabilizing effect of ZnO insufficient and was not improved by NFC

COST Action FP1105 Meeting – 31.08.2015
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THANK YOU to
SNF for founding
 Prof. Ingo Burgert (doctoral supervisor)
 Martin Arnold, Dr. Tanja Zimmermann, supervisors at Empa
 co-workers of Applied Wood Materials Lab @ Empa

and to YOU!
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