Download Determination of Dispersive Properties of Silicas by Inverse Gas

Materials Transactions, Vol. 48, No. 6 (2007) pp. 1548 to 1553
#2007 The Japan Institute of Metals
EXPRESS REGULAR ARTICLE
Determination of Dispersive Properties of Silicas by Inverse Gas
Chromatography: Variation with Surface Treatment
Young-Cheol Yang and Pyoung-Ran Yoon
Department of Mineral Resources & Energy Engineering, Chonbuk National University, Jeonju 561-756, South Korea
The application of inverse gas chromatography (IGC) to the examination of the surface properties of untreated crystalline and fused silica
and surface-treated silicas with silane coupling agents is discussed. The carbon content of the silane coupling agents adsorbed on the surface of
the silicas was determined by means of a Carbon Determinator. If the assumption is made that each silane coupling agent molecule occupies an
area of 0:51 nm2 , the adsorption amounts show that multilayers are generally adsorbed onto the silica surfaces. This paper presents and
discusses the dispersive properties expressed by SD , the dispersive component of the surface free energy, as determined at various temperatures.
At the same temperature of IGC measurement, the values of SD determined by IGC were lower for the crystalline silica than for the fused silica.
This means that crystalline silica is more stable than fused silica. The silica surface-treated with -methacryloxy propyl trimethoxy silane
(MTMS) shows a relatively high SD value(42.75 mJm2 at 160 C). This means that this sample should be compatible with polyester(27 3 mJm2 at 290 C) at high temperature. The silicas that were surface-treated with -glycidoxy propyl trimethoxy silane (GMS) and
-mercapto propyl trimethoxy silane (MCMS) exhibit SD values that are in close agreement with those of almost all resins(30 mJm2 at 160 C).
The SD value of the silica surface-treated with -amino propyl triethoxy silane (AES) is similar to that of epoxy resin(40 mJm2 at 80 C). This
means that this sample is compatible with epoxy resin at relatively low temperatures.
[doi:10.2320/matertrans.MER2007046]
(Received February 22, 2007; Accepted March 27, 2007; Published May 25, 2007)
Keywords: inverse gas chromatography(IGC), silica, dispersive component of the surface free energy(SD ), multilayer
1.
General
1.1 Introduction
Silica has a broad variety of applications in industry. Silica
has been treated with surface-modifying agents to obtain
improved dispersibility, mechanical and electrical properties,
water resistance and reinforcement in plastics systems.1) In
this study, we used silane coupling agents as surfacemodifying agents for silica.
The mechanical performance of a composite material
strongly depends on the properties of the filler-matrix
interface and, in particular, on the level of adhesion between
the matrix and the reinforcing filler. The level of adhesion is
determined by the surface energies of both adherents. The
surface free energy, which describes the interaction potential
of a given surface, has two components: the dispersive
component originating from dispersive or London interactions, and the specific component due to all other types of
interactions.
Inverse gas chromatography (IGC) at infinite dilution
conditions may be successfully applied to the determination
of the surface properties of various solids.2) IGC allows the
detection of the solid surface properties, using molecules of
known properties, or probes, which are injected into a
chromatographic column filled with the solid of interest.
In this study, we chose IGC for the detection of the
possible differences in the SD values of untreated crystalline
and fused silica and silicas surface-treated with silane
coupling agents. The IGC results are reported in this paper.
1.2
Theory of inverse gas chromatography (IGC) at
infinite dilution
In IGC under infinite dilution conditions, the retention
volume VN is computed from the following expression (1):
VN ¼ ðtR t0 ÞjDC
ð1Þ
where tR is the retention time of the probes, t0 the zero
retention time measured with a nonadsorbing probe such as
methane, j the compressibility factor depending on the
pressures at the column inlet and outlet, and DC the corrected
flow rate. Practically, the retention time and the retention
volume VN can be determined as in a current chromatographic experiment: a larger VN will correspond to a higher
affinity of the probe for the chromatographic support.
In expression (1), j was calculated by the following
expression (2):3)
ðpi =p0 Þ2 1
j ¼ 1:5
ð2Þ
ðpi =p0 Þ3 1
where pi is the inlet pressure of the carrier gas, and p0 the
outlet pressure of the carrier gas which usually equals
atmospheric pressure.
For a test substance, the free energy of adsorption, GA , is
the sum of the energies of adsorption attributable to the
dispersive and specific interactions. The adsorption of nonpolar probes such as n-alkanes occurs through dispersive
interactions, whereas, for polar probes, both London and
acid-base interactions contribute to GA . In this study, we
used the model of Donnet et al., because the injected probe is
in the gas state.4) In this model, GA is given by the
following expressions:
SP
½GA ¼ ½GD
A þ ½GA ð3Þ
¼ ½RT ln VN þ C
¼ ½K ðhS Þ
þ
1=2
½GSP
A 0S ðhL Þ
ð4Þ
1=2
0L ð5Þ
SP
where GD
A and GA are the dispersive and specific
components of the free energy of adsorption, respectively.
The value of the constant, C, in expression (4) depends on the
arbitrarily chosen reference state of the adsorbed molecule.
In expression (5), K is a constant, h Plank’s constant, and 0
Determination of Dispersive Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment
Table 1
Chemical
composition
(mass%)
Physical
properties
Crystalline
silica
Fused
silica
Crystalline
silica
Fused
silica
Table 2
Expressions
in this paper
Chemical compositions and physical properties of samples.
SiO2
Al2 O3
Fe2 O3
Na2 O
99.7
0.1561
0.0098
0.0214
SiO2
Al2 O3
Fe2 O3
Na2 O
99.89
0.0285
0.005
0.0033
Maximum
diameter(mm)
Mean
diameter(mm)
BET Surface
Area(m2 /g)
Average Pore
Diameter(nm)
180
13.55
2.2654
4.9484
180
14.21
2.9894
7.3271
Chemical names and structures of the silane coupling agents.
Chemical name
Structure
CH3 O
MTMS
γ −Methacryloxy propyl
trimethoxy silane
GMS
γ −Glycidoxy propyl
trimethoxy silane
MCMS
γ −Mercapto propyl
trimethoxy silane
HS(CH2)3Si(OCH3)3
AES
γ −Amino propyl
triethoxy silane
NH2(CH2)3Si(OC2H5)3
the deformation polarizability of the molecules. Subscripts S
and L refer to solid and liquid, respectively. In the case of nalkanes, GA is equal to the free energy of adsorption
corresponding to the dispersive interactions, GD
A , only, i.e.,
1=2
½GSP
¼
0
in
expression
(5).
The
term
[K
ðh
0S ]
SÞ
A
is characteristic of a given solid surface and is related to
GD
A . Consequently [RT ln VN þ C], between an adsorbate
and an adsorbent, appears as a linear equation of the parameter [ðhL Þ1=2 0L ], and [K ðhS Þ1=2 0S ] becomes the
slope of the linear equation.
The above method has been used to characterize silicas,
modified silicas, oxides, various minerals and solid polymers.5–11)
2.
1549
Experimental
2.1 Materials
Natural crystalline and fused silica were used in this work,
and the chemical compositions and physical properties of
these silicas are shown in Table 1. The chemical names and
structures of the silane coupling agents used in the adsorption
experiment are shown in Table 2. The silane coupling agents
contain three hydrolysable substituents on the right side of
each silicon center(Table 2), which, in principle, would
enable the formation of a chemisorbed crosslinked siloxane
network by the condensation of adjacent adsorbed silantriols
with each other as well as with the surface hydroxyl groups as
shown in Fig. 1. The silane coupling agents also contain one
or more nonhydrolyzable alkyl or aryl groups which are used
to provide compatibility with organic matrices. These may
also contain substituent groups that can provide reactive
CH2
CH2
C
CO(CH2)3Si(OCH3)3
CH2O(CH2)3Si(OCH3)3
CH
O
R
O
H
O
Si
H
O
R
H
Si O
HO
H
HO
H
O Si O
R
O Si OH
H
H
O
O
R
H
H H
H
Silica Surface O
O
Si
Si
O
H
O
Si
Si
O
n
O
Fig. 1 Schematic diagram for the reaction of alkoxy silanes with
hydroxylated silica surface.
centers for graft formation between a polymeric matrix and
the mineral surface. These reactive substituents can be
tailored for specific applications and include vinyl, acrylate
and methacrylate, chloro, amino, epoxy, and mercapto
groups.12)
2.2 Adsorption experiment
We used methanol and distilled water as the solvent and
acetic acid as the catalyst to hydrolysis. The experiment
designed to modify the crystalline and fused silica surface
was performed as follows. Solvent (100 mL), silane coupling
agents (0.2, 0.3, 0.4, 0.6, 0.8, 1.0 and 2.0 g) and silicas (30 g)
were stirred by a magnetic bar stirrer for an hour and then
separated into solid and liquid components by a centrifugal
1550
Y.-C. Yang and P.-R. Yoon
Table 3 Adsorption experimental conditions.
Silane coupling agent
MTMS
Solution
Remarks
3:533:58
Acetic acid
catalyzed
5:666:88
Natural
4:724:76
Acetic acid
catalyzed
9:9510:66
Natural
Methanol(80 v.%)
Distilled water(20 v.%)
GMS
MCMS
pH
Distilled water
Methanol(80 v.%)
Distilled water(20 v.%)
AES
Distilled water
Silica weight
30 g
Table 4 Carbon content of four silane coupling agents adsorbed on the surface of silicas.
Sample
Crystalline
silica
Fused
silica
Silane coupling agent
Experimental
concentration
C content
(w/w%)
The number of
adsorption layers
0.0009
MTMS
1.0 g/100 mL
0.2109
3:336:67
GMS
1.0 g/100 mL
0.2005
3:77:4
MCMS
1.0 g/100 mL
0.0748
2:765:52
AES
1.0 g/100 mL
0.0905
3:346:68
0.0000
MTMS
1.0 g/100 mL
0.1364
1:633:27
GMS
1.0 g/100 mL
0.1466
2:054:1
MCMS
1.0 g/100 mL
0.1518
4:258:49
AES
1.0 g/100 mL
0.1139
3:186:37
separator. A suitable amount of acetic acid specially was
added before stirring in accordance with the type of coupling
agents to obtain a reasonable pH value for hydrolysis,
because the pH value is the most important factor in the
hydrolysis of silane coupling agents.13) The conditions used
in the adsorption experiment are shown in Table 3. The
separated silicas were then dried for 8 hours at 105 C. The
various samples were prepared in this way for the IGC study
at infinite dilution viz. the untreated crystalline and fused
silica, four types of silane coupling agents-treated crystalline
and fused silicas.
alkanes, C5 to C10 , were used as the probe in the IGC
experiment.
2.4 Analysis instruments
We used a Mastersizer of Malvern Co. for the particle size
analysis, an ICP-7500 of Shimadzu Co. for the chemical
analysis of the samples, an ASAP 2010 of Micromeritics for
the BET surface area, a WR-112 Carbon Determinator of
Leco Co. for the carbon analysis and an HP 6890 Plus of
Hewlett Packard Co. for the IGC experiment.
3.
2.3 IGC experiment conditions
Since the particle size of the silica was too small to make
chromatographic supports, silica disks were prepared by
compression of the powders in an IR die under a pressure of
108 Pa. The disks were then hand-crushed and sieved to select
the fraction of particles having diameters between 250 and
425 mm. Particles of the correct size were introduced into a
stainless steel column, 50 cm long and 3.17 mm in diameter.
Approximately 1 g of each sample was used as the filling of
the chromatographic column. Each column, filled with the
sample, was conditioned at 200 C for 24 hours to remove any
impurities in it. The IGC measurements were performed with
a Hewlett Packard 6890 GC system equipped with a highly
sensitive flame ionization detector (FID). The carrier gas was
nitrogen (N2 ) and the flow rate was 10 mL/min. The
temperature of the IGC measurement was varied from 70
to 180 C. Very small amounts of the probes were injected
using the following stratagem: 1 to 5 mL of the probe was
introduced via a septum into a 1L flask, which was flushed
with N2 , after which about 0.3 mL of the diluted probe was
injected into the GC system. A homologous series of n-
Results and Discussion
3.1 The number of adsorption layers
We performed the hydrophobic experiment of all of the
samples to generally examine that which concentration was
achieved monolayer adsorption at. It was found that the
MTMS- and MCMS-treated samples with a concentration of
0.8 g/100 mL and above completely floated on the water.
However, the hydrophobic experiment of the samples surface-treated with GMS and AES was unable to be performed,
because both of these samples have hydrophilic properties.
Consequently, we chose the samples at a concentration of
1 g/100 mL as the standard samples for the IGC experiment,
because it was considered that higher than monolayer
adsorption of the silane coupling agents was achieved at this
concentration.
We performed the carbon analysis to calculate the number
of layers adsorbed on the surface of the standard samples.
The carbon analysis results of the standard samples are
presented in Table 4. The molecular possession area of silane
coupling agents is approximately 0.5 to 1 nm2 .14,15) If we
choose the crystalline silica surface-treated with MCMS,
Determination of Dispersive Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment
That is, the mole number per 1 g of the crystalline silica
surface-treated with MCMS ¼ 20:8 106 mol
This can be changed to molecular numbers as follows.
20:8 106 mol 6:02 10
mol
23
¼ 125:22 1017
125:22 10 50 10
20
4
-1
2
CH2
∆GA
0
-2
-4
-6
4
5
6
7
8
9
10
11
Carbon number of the probe
2
Fig. 2 Determination of the GCH
value.
A
If the molecular possession area of the silane coupling
agent(0.5 to 1 nm2 ) is 0.5 nm2 , the total molecular possession
area is:
17
6
RT ln VN (kJ·mol )
because its carbon content is the lowest, the number of
adsorption layers can be calculated as follows.
BET surface area of crystalline silica = 2.2654 m2 /g
(Table 1)
Mass of carbons in functional group of MCMS: C3 ¼ 36
g/mol
Carbon content per 100 g of the crystalline silica surfacetreated with
MCMS ¼ 7:48 102 g (Table 4)
This can be changed to mole numbers as follows.
mol
7:48 102 g 0:208 102 mol
36 g
¼ 20:8 104 mol
1551
2
CH2 ¼ 35:6 þ 0:058ð293 TÞ in mJm2
ð7Þ
2
m ¼ 6:261 m /g
Finally, the number of adsorption layers is as follows.
total molecular possession area of MCMS
BET surface area of crystalline silica
¼ 6:261 m2 =g 2:2654 m2 /g 2:76 layer
If the molecular possession area of the silane coupling agent
is 1 nm2 , the number of adsorption layers will be twice that.
The number of adsorption layers calculated using the above
method is presented in Table 4. That is, the results presented
in Table 4 suggest that the above monolayer adsorption of the
silane coupling agents was achieved for all of the samples. A
schematic diagram of the multilayer is shown in Fig. 1. The
surface properties of the samples reflect the innate characteristics of the functional group of each silane coupling agent,
regardless of the number of adsorption layers, because the
functional groups protrude from the layer as shown in Fig. 1.
3.2
The dispersive component of the surface free energy
(SD )
The dispersive component of the surface free energy, SD , is
obtained by injecting a homologous series of n-alkanes into
the column and determining their retention characteristics.
Dorris and Gray used the incremental amount of free energy
of adsorption corresponding to the adsorption of one CH2
D 2)
2
group, GCH
A , to determine the value of S :
"
#2
2
1
GCH
A
D
S ¼
ð6Þ
4CH2 N aCH2
where CH2 is the surface energy of a solid composed solely
of -CH2 - groups, i.e., a surface analogous to polyethylene, N
Avogadro’s number, and aCH2 the cross sectional area of an
adsorbed -CH2 - group (0.06 nm2 ).2) The variation of CH2
with the temperature is given by:
where T is the temperature in K.
Generally, the logarithm of VN varies linearly with the
number of carbon atoms of the injected n-alkanes. Therefore,
it becomes possible to define the free energy of adsorption,
2
GCH
A , of one methylene group, which no longer depends on
the arbitrary choice of the reference state:
nþ1 VN
2
GCH
¼
RT
ln
ð8Þ
A
VNn
where R is the ideal gas constant, T the absolute temperature,
and VNnþ1 and VNn the net retention volumes of n-alkanes
having n þ 1 and n carbon atoms, respectively.
In the IGC experiment, the retention time and volume are
associated with the SD of the solid. That is, RT ln VN varies
linearly with the number of carbon atoms of the injected nalkanes, as shown in Fig. 2.
2
In Fig. 2, GCH
is the slope of the line obtained from
A
expression (8). Therefore, the SD values of the solid are
computed by expression (6).
Figures 3 and 4 display the variation of [RT ln VN ] vs. the
carbon number of the n-alkanes used to probe the surface
properties of the untreated crystalline and fused silica.
Figures 5 and 6 display the variation of [RT ln VN ] vs. the
carbon number of the n-alkanes used to probe the surface
properties of the crystalline and fused silica surface-treated
with MTMS. Each line in the above graphs indicates the
variation according to the temperature of the IGC measurement. The SD values of the untreated crystalline, fused and
surface-treated silicas were computed by the above method
for each line.
The SD values of the samples were computed at various
measuring temperatures between 70 and 180 C. The calculated values of SD are presented in Table 5. The range of
temperature used for the IGC measurement was different for
each sample, as shown in Table 5. This means that the range
of temperature which is suitable for the IGC measurement is
1552
Y.-C. Yang and P.-R. Yoon
8
8
Untreated crystalline silica
70°C
80°C
90°C
100°C
110°C
120°C
130°C
140°C
4
2
-1
2
-1
RT ln VN (kJ·mol )
4
MTMS−treated crystalline silica
130°C
140°C
150°C
160°C
170°C
180°C
6
RT ln VN (kJ·mol )
6
0
-2
-4
0
-2
-4
-6
-6
-8
-8
-10
-12
-10
4
5
7
6
9
8
10
5
11
6
7
8
9
10
Carbon number of the probe
Carbon number of the probe
Fig. 3 Variation of [RT ln VN ] vs. the carbon number of the n-alkanes used
as molecular probes for the untreated crystalline silica.
Fig. 5 Variation of [RT ln VN ] vs. the carbon number of the n-alkanes used
as molecular probes for the crystalline silica surface-treated with MTMS.
8
12
Untreated fused silica
70°C
120°C
80°C
130°C
90°C
140°C
100°C
110°C
-1
RT ln VN (kJ·mol )
6
4
-1
8
MTMS−treated fused silica
130°C
140°C
150°C
160°C
170°C
180°C
6
RT ln VN (kJ·mol )
10
4
2
0
-2
-4
2
0
-2
-4
-6
-6
-8
-8
-10
5
-10
4
5
6
7
8
9
10
6
7
8
9
10
Carbon number of the probe
Carbon number of the probe
Fig. 4 Variation of [RT ln VN ] vs. the carbon number of the n-alkanes used
as molecular probes for the untreated fused silica.
different for each sample because their surface properties are
different.
The SD values of the crystalline and fused silica are lower
than those of the other fillers.11) There have been several
papers that presented the SD values for synthetic silica. The
SD values of crystalline and fused silica in this paper are
similar to those of these previous studies. The SD values of
synthetic silica were as follows: 40 4 mJm2 at 80 C,16)
40 mJm2 at 150 C,17) 46 mJm2 at 80 C.18)
The SD values of the untreated fused silica shown in
Table 5 were slightly higher than those of the untreated
crystalline silica at the same measuring temperature. This
means that crystalline silica is more stable than fused silica.
The SD values of the silicas surface-treated with MTMS were
Fig. 6 Variation of [RT ln VN ] vs. the carbon number of the n-alkanes used
as molecular probes for the fused silica surface-treated with MTMS.
higher than those of the silicas surface-treated with the other
silane coupling agents at the same measuring temperature.
The MTMS agent is compatible with polyester, having a SD
value of 27 3 mJm2 at 290 C.19) The SD values of the
silicas surface-treated with GMS were approximately
30 mJm2 at 160 C. It is considered that the GMS agent is
suitable for most polymers, because it has a SD value of
around 30 mJm2 at 140 C.20) It is estimated that the MCMS
agent is also suitable for most polymers, because the SD value
of the crystalline silica surface-treated with MCMS was
about 30 mJm2 at 150 C. The SD values of the silicas
surface-treated with AES were around 30 mJm2 in the
relatively low temperature range. Consequently, the AES
agent is compatible with epoxy resin, having a SD value of
40 mJm2 at 80 C.21)
Determination of Dispersive Properties of Silicas by Inverse Gas Chromatography: Variation with Surface Treatment
1553
Table 5 Dispersive component(SD ) of the surface free energy of untreated and silane coupling agents-treated silicas at various
temperatures.
Silane
none
MTMS
GMS
MCMS
AES
4.
SD (mJm2 )
Concentration
70 C
80 C
90 C
100 C
110 C
120 C
130 C
140 C
Crystalline
silica
54.10
49.42
45.59
43.88
41.62
36.92
33.63
31.78
Fused
silica
58.93
55.28
53.08
48.20
47.25
44.49
41.33
37.81
Crystalline
silica
1.0 g/100 mL
54.69
Fused
silica
1.0 g/100 mL
Crystalline
silica
1.0 g/100 mL
49.65
Fused
silica
1.0 g/100 mL
49.07
Crystalline
silica
Sample
150 C
160 C
170 C
180 C
51.72
46.13
42.75
35.18
29.16
50.78
47.45
44.82
37.32
35.27
28.87
44.36
41.40
35.23
32.31
30.43
45.98
43.87
39.19
38.49
33.54
1.0 g/100 mL
40.22
35.21
33.03
29.99
28.85
Fused
silica
1.0 g/100 mL
54.05
48.29
44.69
38.22
34.33
31.3
29.23
Crystalline
silica
1.0 g/100 mL
40.12
36.72
32.69
28.61
Fused
silica
1.0 g/100 mL
38.60
35.65
32.80
28.32
Conclusions
Crystalline and fused silica were subjected to surface
treatment with four types of silane coupling agent: MTMS,
GMS, MCMS and AES. The treatment of the crystalline and
fused silica by these silane coupling agents modified their
surface. We examined the number of layers adsorbed on the
surface of the silicas by carbon analysis and the surface
properties of these silicas according to SD using IGC. The
present study produced the following conclusions:
(1) By assuming that the molecular possession area of the
silane coupling agent is 0.5 to 1 nm2 , it was determined
that multilayer adsorption was achieved on the surface
of the silicas by carbon analysis.
(2) The values of SD decreased with increasing IGC
measuring temperature in all cases. Silica is an oxide
with a relatively low surface energy. The SD values of
the crystalline silica were lower than those of the fused
silica at the same measuring temperature. This means
that crystalline silica is more stable than fused silica
from the surface energetic point of view.
(3) The SD values of the silicas surface-treated with MTMS
were higher than those of the others, while the SD
values of the silicas surface-treated with AES were the
lowest at the same measuring temperature. This result
indicated that while the AES-surface-treated silica is
suitable for polymers such as epoxy resin, the MTMSsurface-treated silica is suitable for polymers such as
polyester. The silicas surface-treated with GMS and
MCMS are suitable for most polymers, because their SD
value is close to that of almost all resins at
160 C(30 mJm2 ).
REFERENCES
1) H. S. Katz and J. V. Milewski: Handbook of Fillers and Reinforcements
for Plastics (Litton Educational Publishing Inc. 1978) 136.
2) G. M. Dorris and D. G. Gray: J. Colloid and Interface Sci. 77 (1980)
353–362.
3) A. T. James and A. J. P. Martin: The Biochemical J. 50 (1952) 679.
4) J. B. Donnet, S. J. Park and H. Balard: Chromatographia 31 (1991)
434–440.
5) H. Balard, M. Sidqi, E. Papirer, J. B. Donnet, A. Tuel, H. Hommel and
A. P. Legrand: Chromatographia 25 (1988) 712–716.
6) E. Papirer, H. Balard, Y. Rahmani, A. P. Legrand, L. Facchini and
H. Hommel: Chromatographia 23 (1987) 639–647.
7) M. Sidqi, H. Balard and E. Papirer, A. Tuel, H. Hommel and A. P.
Legrand: Chromatographia 27 (1989) 311–315.
8) M. M. Chehimi and E. Pigois-Landureau: J. Mater. Chem. 4 (1994)
741–745.
9) U. Panzer and H. P. Schreiber: Macromolecules 25 (1992) 3633–3637.
10) A. Voelkel, E. Andrzejewska, R. Maga and M. Andrzejewski: Polymer
34 (1993) 3109–3111.
11) Y. C. Yang and P. R. Yoon: Korean J. Chem. Eng. 24 (2007) 165.
12) D. H. Solomon and D. G. Hawthorne: Chemistry of Pigment and Fillers
(John Willey & Sons 1983) 108.
13) M. R. Rosen: J. Coatings Technology 50 (1978) 70–82.
14) O. K. Johannson, F. O. Stark, G. E. Vogel and R. M. Fleischmann:
J. Composite Materials 1 (1967) 278–292.
15) C. H. Chiang and J. L. Koenig: J. Colloid and Interface Sci. 83 (1981)
361–370.
16) H. Hadjar, H. Balard and E. Papirer: Colloids and Surfaces A:
Physicochemical and Engineering Aspects 99 (1995) 45–51.
17) A. Khalfi, E. Papirer, H. Balard, H. Barthel and M. G. Heinemann:
J. Colloid and Interface Sci. 184 (1996) 586–593.
18) C. Perruchot, M. M. Chehimi, M. Delamar, S. F. Lascelles and S. P.
Armes: J. Colloid and Interface Sci. 193 (1997) 190–199.
19) G. L. Gaines: Polymer Eng. Sci. 12 (1972) 1.
20) S. Wu: J. Macromol. Sci.-Revs. Macromol. Chem. C10 (1974) 1.
21) J. Schultz, L. Lavielle and C. Martin: J. Adhesion 23 (1987) 45–60.