silica for interior and exterior automotive coatings
TRANSCRIPT
Silica for interior and exterior
automotive coatings
European Coatings Conference
Automotive Coatings
Berlin, November 24. - 25, 2011
The Importance of
Particle Design in
Scratch Resistant
Coatings
Dr. Rüdiger Mertsch
Dr. Günther Michael
Dr. Sven Hill
Seite | 3
Particels
SiO2
Al2O3
TiO2
ZnO, CeO2, ITO
Mixed oxides
Si(CH3)3 (CH3)3 Si
Surface treatment
Silane
Siloxanes
Organic molecules
Multi treatment
Encapsulation
Structure
modification
Granulation
Mechanical treatment
Chemical treatment
Technical diversity of possible
materials
Dispersions
Water based
Solvent based
Reactive thinner
(on request)
Seite | 4
Fumed silica and oxides
• SiO2 (1940)
• Al2O3 (1950)
• TiO2 (1950)
• Fumed mixed oxides (1950)
• Surface modificated silicas (1960)
• ZrO2 (1990)
• ZnO (2000)
• CeO2 (2004)
• In2O3/SnO2 ITO
• SiO2/Fe3O4 MagSilica
Fumed silicas & metal oxides
Seite | 5
Primary particle, Aggregate and
Agglomerate
0 20 40 60 80 100
Residence time / ms 90 20 50
Primary particles form immediately aggregates and micro sized
agglomerates
mean p
rim
ary
part
icle
siz
e
Seite | 6
Surface Chemistry of fumed silica and
metal oxides
• High purity
• Low porosity
• Easy accessible surface
• Si-OH groups on the surface ( 2 - 3 per nm²)
Seite | 7
Examples for surface modified
fumed silica
3
3
Si -O
CH
CH -O
-O ( Si- -) n
CH 3
CH 3
O Si 8
C H 17
-O
-O
-O
Si
CH 3
CH 3
CH 3
-O
Si 16
C H 33
-O
-O
-O
Si
-O
-O
-O
(CH2)3-O-C(O)-C(CH3)=CH2
Seite | 8
Review of Structure Modification
• Bulk density:
Comparison of a conventional
fumed silica and a
Structure Modified Silica (SMS)
Both measuring cylinders
hold the same weight of each
type of material
Conventional
New SMS
Seite | 9
Structure modified fumed SiO2
Conventional structured fumed SiO2
Properties
• Tapped density: 130 – 230 g/l
• Excellent processability
• Low thickening effect
• High loading levels possible
• Scratch resistance improved due
to increased inorganic particle
content
TEM Comparison of
Fumed Silica Aggregate Structure
Seite | 10
0
5000
10000
15000
20000
0,1 1 10 100 1000
Shear Rate [s-1
]
Without fumed silica
Vis
co
sit
y [
mP
a s
]
Physica rotary viscosimeter
Rheology of an UV – Varnish using
structure modified silica (Polyester Acrylate)
Seite | 11
0
5.000
10.000
15.000
20.000
0,1 1 10 100 1000
Shear Rate [s-1
]
5 % hydrophobic, non-structurallymodified fumed silica
Without fumed silica
Vis
co
sit
y [
mP
a s
]
Physica rotary viscosimeter
Rheology of an UV – Varnish using
structure modified silica (Polyester Acrylate)
Seite | 12
0
5.000
10.000
15.000
20.000
0,1 1 10 100 1000
Shear Rate [s-1
]
5 % hydrophobic, non-structurally modifiedfumed silica
10 % hydrophobic & structure modifiedfumed silica
Without fumed silica
Vis
co
sit
y [
mP
a s
]
Physica rotary viscosimeter
Rheology of an UV – Varnish using
structure modified silica (Polyester Acrylate)
Seite | 13
40
45
50
55
60
65
70
75
80
85
90
1 2 3 4 5
20
° G
los
s
w/o silica 5 % fumed silica w/o silica 5 % fumed silica
Elcometer 1720
(wet scratching)
Gloss before scratching
Gloss after scratching
Crockmeter
(Dry scratching)
Gloss before scratching
Gloss after scratching
2 pack high solid formulation
Crockmeter with abrasive paper
Elcometer® 1720: 40 double strokes with pig's bristles; 0.15 % Quarz-Slurry
Scratch Resistant Coatings with
Structure Modified Hydrophobic Silica
Seite | 14
Dispersion based on structure modified
fumed silica
• Dispersion of
• Fumed silica in 1-methoxy-2-propylacetate (MPA)
• Fumed silica concentration: 30%
• With a special additive combination (no silicones)
• to control viscosity
• Dispersion stability
• to improve the aggregate fineness and morphology
Scratch resistant top coats
with excellent optical properties
Seite | 15
2C Clear Coat based on structure
modified fumed silica Dispersion
105,0 Total
19.0 Desmodur N 3390**
16.0 Fumed silica dispersion
3.0 Butyl glycol acetate
4.0 Solvesso 100
4.0 Xylene
4.0 Butyl acetate
5.0 MPA
50.0 Desmophen A 870, BA *
wt.%
* Bayer AG, Material Science
** Bayer AG, Material Science or Vestanat HT 2500 L (Evonik Degussa)
Seite | 16
Application results Scratch Test (2C Clear Coat)
50
60
70
80
90
Without structure modified fumed
silica
With structure modified fumed
silica
Wet Scratching
Dry Scratching
Resid
ual
Glo
ss %
2C Clear coat formulated using a fumed silica dispersion
Seite | 17
Detailed Mode of Action
5µm 5000 : 1
500nm 50000 : 1
Aggregates of the structure modified fumed silica are
homogenously distributed throughout the film
Seite | 18
Structure modified fumed silica in
UV-Coatings, wet scratching
0
10
20
30
40
50
60
70
80
90
without
SMS
With SMS
powder
SMS in
TPGDA
LAD
SMS
powder
SMS in
TPGDA
LAD
Haze,
Glo
ss
Gloss before
Gloss after scratch
Haze before
Haze after scratch
Laromer PE44 (BASF), TPGDA (BASF), Darocur 1173 (Ciba),
Fumed silica loading: 8,7% (total)
Bead mill
ZrO2, 1 mm
Seite | 19
Structure modified fumed silica in
UV-Coatings, Dry Scratching
0
10
20
30
40
50
60
70
80
90
w/o SMS SMS
powder
SMS in
TPGDA
SMS
powder
SMS in
TPGDA
Haze,
Glo
ss
gloss before
gloss after scratch
haze before
haze after scratch
Bead mill
ZrO2, 1 mm
Laromer PE44 (BASF), TPGDA (BASF), Darocur 1173 (Ciba),
Fumed silica loading : 8,7% (total)
Seite | 20
Improvement of Scratch Resistance
• To improve the scratch resistance of coatings a loading with fumed
silica of 5 – 15 % (based on binder) is necessary
• With standard-hydrophilic or with standard-hydrophobic fumed silica at
these concentrations the viscosity of the coating system is too high
• (Only) structure – modified hydrophobic fumed silica meets these
requirements
Scratch Resistant Coatings with
Structure Modified Hydrophobic Silica
Matted
Soft Feel Coatings
Hr. Hans-Dieter Christian
Hr. Andreas Feller
Dr. Sven Hill
Page | 22
What is a Matting Effect? Reflection of light on a glossy (left) and
matted (right) surface.
Page | 23
Example of a Car Interior
Leather
Not
matted Matted
Page | 24
CH3 CH3 CH3 CH3
CH3 CH3 CH3
Si Si Si Si
x y
A A
A
A = (CH2)3(OC2H4)n(OC3H6)mO - CH2 - CH - CH2
O O O
O
TEM photo of an elastomer
(PDMS)
Coating of Silicas with Elastomers
Based on PDMS
Page | 25
What Is Feel?
the study of tactile sensations
( psychology )
tactile :
capable of being touched or felt
New Webster’s Dictionary
of the English Language
“ The study of sensing
and manipulation through touch ” (MIT)
True to touch:
artificial finger feels
quality
Page | 26
Subjective Test of Soft-Feel Coatings
10 Test persons 0 = No soft feel
10 = excellent soft-feel effect
0123456789
10
1 2,4 8,8 4,6
untreated wax-treated PDMS treated Thermal silica
Matting agents
sc
ore
Page | 27
Universal Surface Tester UST®
Examination of Friction and Micro Friction
Force measurement system for high-sensitive measurement
of the tribological force form, as well as static and sliding friction.
Page | 28
Micro Frictional Forces Measured on Different Surfaces (Case Studies)
Page | 29
PU Coating with Thermal Silica
Thermal solica / Friction and Micro Friction
Surface Profile
Coeffi-
cient of
friction μ
Coefficient of Friction
Measure-
ment Settings
Starting position Scanner
Ball
Load
Friction force
Measured length
Pre-stress and post-stress
Speed
Measuring spacing
Range of measurement
Statistics Number of measurements
Mean
Standard deviation
User: Innowep
Comment: TS100 (PHT)
Microfriction
Page | 30
Surface Profile Measure-
ment
Coefficient of Friction
Coeffi-
cient of
friction μ
Microfriction
Scanner
Ball
Starting position
Measured length
Pre-stress and post-stress
Speed
Load
Friction force Measuring spacing
Range of measurement
Statistics Number of measurements
Mean
Standard deviation
User: Innowep
Comment: Acematt 3300 (PHT)
PU Coating with Surface Treated
Thermal Silica / Friction and Micro Friction
Page | 31
20µm2000 : 1
20µm2000 : 1
20µm2000 : 1
Clear coating
(unmatted)
Clear coating
(thermal silica)
Clear coating
(surface treated thermal silica)
Cut-Away Photo of Soft-Feel Coatings
(2000:1)
Page | 32
Hommel Tester Topographic Photograph
of the Soft-Feel Formulation with Thermal
Silica
Page | 33
Hommel Tester Topographic Photograph of the
Soft-Feel Formulation with PDMS-Modified Thermal
Silica
Page | 34
In Summary We as Evonik Industries Can Significantly
Contribute to the Demand of the Car Makers
Page | 36
Application results Optical Properties (2C Clear Coat)
20°
-Glo
ss
Haze
Without structure
modified fumed silica
With structure modified
fumed silica
2C Clear Coat formulated using a fumed silica dispersion