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陈雨泉

铁虫 (小有名气)

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虫号: 2031260
注册: 2012-09-26
性别: GG
专业: 高分子合成化学

[求助] 论文翻译，求大神给翻译一下

Phase structure and mechanical and adhesion properties of
epoxy/silica hybrids
M. Ochi*, R. Takahashi, A. Terauchi
Department of Applied Chemistry, Faculty of Engineering, Kansai University,3-3-35 Suita-shi, Osaka 564-8680, Japan
Received 10 October 2000; accepted 6 December 2000
Abstract
Organic/inorganic hybrids containing 4± to 19.8 wt% of silica were synthesized from an epoxy resin diglycidyl ether of bisphenol-A
(DGEBA) and a g-glycidoxypropyltrimethoxysilane (GPTMS) or a tetramethylorthosilicate (TMOS) by utilizing a sol/gel process. In the
DGEBA/GPTMS hybrids, the storage modulus in the rubbery region increased and the peak area of the tan d curves in the glass transition
region decreased, respectively, with the hybrization of small amounts of silica. This may result from the suppression of the epoxy network
moiety with the incorporation of the silica network. Observation using transmission electron microscopy (TEM) revealed that the silica
networks are uniformity dispersed in the hybrids. Furthermore, the hybrids with GPTMS showed a very high adhesion strength for the
silicone rubber. Results from the X-ray microanalysis show that the silica networks are concentrated in the interfacial area of the adhesive
joints with silicone rubber. In the swelling test of silicone rubber with the epoxy resin containing GPTMS, the degree of swelling increased
with increasing GPTMS content. The high adhesion strength observed in the DGEBA/GPTMS hybrids was caused by the immersion of the
adhesives into the surface layer of the silicone rubber substrate, which was attributed to the good af®nity between GPTMS and the silicone
rubber. q 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Epoxy resin; Silica network; Organic/inorganic hybrid
1. Introduction
Organic polymers usually have some superior characteristics
with respect to their toughness, ˉexibility and processability.
On the other hand, inorganic polymers have high heat
resistance and good mechanical and optical properties.
Recently, organic/inorganic hybrid materials have been investigated
as promising materials by combination of the superior
properties of both the organic and inorganic polymers [1±4].
Sol/gel process [5] is a method for preparing inorganic polymers
at a low temperature. By using the sol/gel process, we
could combine the organic substances, which would be
decomposed at a relatively low temperature, with inorganic
substances, which have a high heat resistance.
Many organic/inorganic hybrids are formed by incorporating
a functional organic polymer into the matrix of an
inorganic network synthesized from the condensation polymerization
of some metal alkoxides. Chujyou et al.
[6,7]reported that the hybrids of an inorganic silica network
with organic polymers, which could form hydrogen bonding
between the inorganic and organic components, could
produce homogeneous and transparent glassy materials. It
has been clari®ed that the phase structure of hybrids
strongly depends on the interaction between the inorganic
and organic components. Huang et al. [8,9]studied hybrid
materials, which were prepared by the incorporation of a
silicone elastomer into a silica network. They reported that
the structure and mechanical properties of the hybrids are
signi®cantly affected by the process conditions, such as the
amount of catalyst, molecular ratio of inorganic/organic
compounds and molecular weight of organic compound.
The organic/inorganic hybrids in which an inorganic material
is incorporated into an organic polymer matrix have also
been studied by many investigators. Yano et al. [10] studied
the structure and mechanical properties of the poly(vinylalcohol)/
silica hybrid systems. They reported that the micro-
Brownian motion of the organic polymer is strongly restricted
by the inorganic silica network combined with the matrix on a
molecular scale and thus the mechanical strength of the hybrid
increases with an increase in the silica content.
In the present study, the epoxy-based organic/inorganic
hybrid materials were prepared using the bisphenol-A type
epoxy resin and silanealkoxide as the organic and inorganic
sources, respectively. The thermal mechanical properties and
the phase structure of the epoxy/silica hybrids were
Polymer 42 (2001) 5151±5158
0032-3861/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved.
PII: S0032-3861(00)00935-6
www.elsevier.nl/locate/polymer
* Corresponding author. Tel.: 81-6-6368-1121; fax: 81-6380-8032.
E-mail address: mochi@ipcku.kansai-u.ac.jp (M. Ochi).
investigated in detail. In addition, these hybrids showed a very
high adhesive bonding strength for silicone rubber whose
surface is extremely hydrophobic and is not suitable for adhering
with an epoxy resin. Thus, their bonding properties and
adhesion mechanism for silicone rubberwere also investigated.
2. Experimental
2.1. Materials
The epoxy resin used in this study was a commercial
grade of diglycidyl ether of bisphenol-A (DGEBA:Epikote
828, epoxy equivalent: 190 ^ 5Yuka-shell Epoxy Co.).
The curing agent used was tetraethylenepentamine
(TEPA, extra-grade, Tokyo Kasei Co., Ltd.).
H2N±…CH2±CH2±NH†
3±CH2CH2±NH2
The silane alkoxides used as inorganic sources were 3-
glycidoxy-propyltrimethoxysilane (GPTMS, extra-grade,
Kanto Chemical Co., Ltd.)
and tetramethoxysilane (TMOS, extra-grade, Tokyo Kasei
Co., Ltd.). The former Si(OCH3)4 alkoxide has a functional
(epoxy) group, which can react with the organic component.
Thus it is natural to consider that the magnitude of the
interaction between the organic and inorganic components
in the hybrids synthesized from the former silane alkoxide is
higher than that of the hybrids prepared from the later
alkoxide.
The substrate was a silicone rubber sheet (K-125, Togawa
Rubber Co.). All the reagents and silicone rubber sheet were
used as received.
2.2. Preparation of DGEBA/GPTMS hybrid materials
Prescribed amounts of GPTMS were added to DGEBA
with stirring at 808C. In addition, a stoichiometric amount of
curing agent for the epoxy group and 1 phr of H2O were
added and then the mixtures were vigorously stirred to
obtain homogeneous solutions.
The resulting homogeneous compounds were poured into
an aluminum container in order to prepare the epoxy/silica
hybrid plates. The compounds were ®rst cured at 60, 100
and 1508C, then ®nally cured at 1908C for 4 h during each
curing step. Table 1 shows the starting composition and the
percent silica (wt%) of the hybrid materials determined by
TGA.
2.3. Adhesion of DGEBA/GPTMS/TMOS hybrid materials
to silicone rubber
Several mixtures of DGEBA and silane alkoxides
containing 6 wt% of silica were prepared by controlling
the fraction of GPTMS and TMOS. In these systems, the
molecular weight of silica was estimated to be 52.1 (SiO3/2)
and 60.1 (SiO2)g mol21 for GPTMS and TMOS, respectively.
The silicone rubber sheets were coated with the
mixture of DGEBA and silane alkoxide to prepare the specimens
for the lap shear and 908 peel test (Fig. 1A and B). The
mixture used as adhesives were cured at 60, 100, 150 and
1908C for 4 h during each curing step. The silicone rubber
was not treated with any surface modi®er and was backed by
a metal plate to prevent any excessive deformation of the
substrate itself. As the adherend failure was observed in
several specimens and the bonding area could not be
measured exactly, the bonding strength of the specimens
were expressed by kgf.
2.4. Measurements
The conversions of the epoxy group of DGEBA and
5152 M. Ochi et al. / Polymer 42 (2001) 5151±5158
Table 1
Composition before curing and silica content of hybrid materials
Sample code Composition before curing (mol) Silica content
DGEBA TEPA GPTMS wt% (calc)a w% (expt)b
Unmodi®ed 1.00 0.286 ± 0.0 0.0
GPTMS-4 1.00 0.342 0.392 4.0 3.8
GPTMS-6 1.00 0.378 0.644 6.0 5.8
GPTMS-10 1.00 0.475 1.33 10.0 9.6
GPTMS-14 1.00 0.634 2.44 14.0 13.6
a Calculated from reactant stoichiometry.
b Experimentally determined from TGA measurements at 8008C in air.
methoxy group of GPTMS were followed by FT-IR (Spectra
2000, Perkin Elmer Co., Ltd.) measurements. The conversion
of the epoxy and alkoxide groups were calculated from
the changes in the magnitude of the adsorption peaks at 910
and 2836 cm21 with curing time, respectively.
The weight percent of silica of the hybrid materials was
determined by thermo-gravimetric analysis (TGA: THERMOFLEX
TAS-200 TG8110D, RIGAKU Co., Ltd.) by
heating in air over the temperature range of 20±10008C,
at the rate of 58C min21. The residual weight of all specimens
was kept a constant after heating over 8008C. Since
the organic component seems to have almost completely
decomposed in the temperature region over 8008C, the
values of the residual weight were used as the silica content
in the hybrid materials.
The ultra-thin sections of the DGEBA/GPTMS hybrids
were observed using a transmission electron microscope
(TEM: JEM-1210, JEOL Co., Ltd.) to study the microphase
structure of the hybrids. The specimens for the
TEM observations were prepared using an ultramicrotome
(REICHERT ULTRACUT E, Leica Co., Ltd.) with a
diamond knife. Prior to the TEM observations, the specimens
were not treated with any staining techniques.
The dynamic mechanical properties of the cured hybrid
materials were determined using a non-resonance forced
vibration viscoelastometer (DVE-4, Rheology Co., Ltd.)
in air. The frequency and amplitude of the vibration were
adjusted to 10 Hz and ^5 mm, respectively. The temperature
range was from 2150 to 2508C and the heating rate was
28C min21, respectively.
The lap shear and 908 peel strength of the joints (Fig. 1A
and B) were measured using an Instron-type tensile machine
(Shimazu Autograph, AGS-2000E) at a cross-head speed of
50 mm min21. For the lap shear strength of the joints with
the DGEBA/GPTMS hybrid materials, the temperature
range was from 25 to 1808C.
The Si distribution in the adhesive layer of the joints was
investigated using an X-ray microanalyzer (XMA:JED-
2001, JEOL Co., Ltd.). The specimen was coated with a
thin layer of carbon to improve the conductivity and prevent
charging.
A piece of silicone rubber (20 ￡ 10 ￡5 mm3) was swollen
in DGEBA or a mixture of DGEBA and GPTMS, which
contained different silica contents from 6 to 19.8 wt% at
608C for 3 days. In these swelling tests, the curing agent
was not added to all the mixtures. The degree of swelling
was de®ned as
Degree of swelling …wt%† ˆ …Wwet 2 Wdry
† ￡ 100=Wdry; …1†
where Wwet and Wdry are the weights of the swollen and
dried silicone rubbers, respectively.
3. Results and discussion
3.1. Preparation of DGEBA/GPTMS hybrid materials
The changes in the conversion of epoxy and silane alkoxide
groups with curing time in the epoxy/silica hybrid is
shown in Fig. 2. The conversion of these groups was estimated
from the changes in the peak area at 2836 (alkoxide)
and 910 cm21 (epoxy), respectively. The conversion of the
epoxy and silane alkoxide groups increased in almost the
same manner during curing. This means that the epoxy and
silica networks were almost simultaneously constructed to
form the hybrid system. In addition, the ®nal conversion of
both groups is over 90%. Very little unreacted epoxy and
M. Ochi et al. / Polymer 42 (2001) 5151±5158 5153
Fig. 2. Chemical conversion of epoxy and methoxy groups (GPTMS-6).
(X) epoxy group, (W) methoxy group.
Fig. 1. Shape and dimensions of adhesive joints in lap shear and 908 peel
tests.
alkoxide groups remained in the hybrid system after the
post-curing at 1908C. These results show that both the
epoxy resin and the silane alkoxide should form tightly
crosslinked networks.
The following reaction mechanisms are proposed for the
sol/gel reaction of the silane alkoxide:
Hydrolysis of the silane alkoxide ®rst occurs by the reaction
with water contained in the epoxy resin. The dehydration
and dealcohol condensation reactions then occur to
form the network structure. Matejka et al. [11] described
that the addition of an acid catalyst to the epoxy/silane
mixture should mainly accelerate the hydrolysis of the
silane alkoxide and the condensation reaction of the alkoxide
is signi®cantly promoted by the presence of a basic
catalyst. The aliphatic polyamine, which is added as a
curing agent in this study, has a relatively high basicity
and thus acts as a basic catalyst for the condensation reaction
of the silane alkoxide. As shown in Fig. 2, the conversion
of the alkoxide group is over 90%. This result means
that the silane alkoxide should form a densely crosslinked
network through the condensation reaction of the alkoxide
group.
3.2. Morphology of DGEBA/GPTMS hybrid materials
Unmodi®ed epoxy resin and several DGEBA/GPTMS
hybrid materials with different silica contents from 6 to
14 wt% were used as samples for the TEM observations.
Fig. 3 shows the morphology of the hybrid materials identi-
®ed by TEM. The unmodi®ed system has a uniform structure
over the entire area, while in the hybrid with 6 wt%
silica, very small dark spots in which the silica network is
highly concentrated, are observed over the entire area of the
hybrid material. It can be seen that the silica incorporated in
the hybrid is about 5±10 nm in size. It is well known that the
silica network spreads out like a hyper-branched cluster
under basic conditions [12]. In this report, TEPA, which
has a relatively high basicity, was used as the curing
agent. Therefore, the silica network probably formed a cluster
structure rather than a chain network. However, GPTMS
used as an inorganic source has an epoxy group and this
group reacted with TEPA. These results mean that the ®ne
silica particles observed by TEM (Fig. 3) are not the pure
silica network. It is natural to consider that the ®ne silica
particles are composed of silica and a part of epoxy network
5154 M. Ochi et al. / Polymer 42 (2001) 5151±5158
Fig. 3. Transmission electron micrographs of epoxy/silica hybrid systems.
xSi…OR† 1 H2O ! xSi…OH† 1 ROH …Hydrolysis†
xSi…OH† 1 …OH†Six ! xSi±O±Six 1 H2O …Dehydration condensation†
xSi…OH† 1 …RO†Six ! xSi±O±Six 1 ROH …Dealcohol condensation†
which should form an interpenetrating network structure
between the organic and inorganic components with a covalent
bond. Moreover, in the hybrid material containing
10 wt% silica, the area of the dark portions should mean
that the silica/epoxy interpenetrating network had increased.
However, a uniform microstructure was again observed in
the system containing 14 wt% silica. The number of silica
clusters containing the epoxy resin (dark spots) with the size
of about 10 nm increased with an increase in the amount of
GPTMS used as the inorganic source and covered the entire
area of the epoxy matrix with increasing silica content.
Matejka et al. [13] described that the dispersibility of the
silica network progressed with an increase in the interaction
as a covalent bond between the organic and inorganic
phases. Similarly, in this system, it is considered that the
silica network cluster containing some quantities of epoxy
resin was ®nely dispersed in the epoxy matrix along with the
formation of covalent bonds between the organic and inorganic
phases. The uniform microstructure observed in the
system containing 14 wt% silica was caused by the uniform
dispersion of the innumerable 10 nm dark spots over the
entire area of the matrix.
3.3. Dynamic mechanical properties of DGEBA/GPTMS
hybrid materials
The temperature dependence of dynamic mechanical
properties of the DGEBA/GPTMS hybrids containing
different amounts of silica network is shown in Fig. 4. In
the unmodi®ed system, the storage modulus was clearly
decreased in the glass transition region (Tg) and had a
very low value in the rubbery region. It is well known that
the decrease in the modulus in the Tg region is due to the
micro-Brownian motion of the network chains. However, in
the hybrid systems, the modulus in the rubbery region
increased with an increase in the silica contents and thus
the glass transition behavior became indistinct. This result
shows that the micro-Brownian motion of the epoxy
network is strongly restricted by the hybrization with the
silica network. The storage modulus of the hybrid systems
with over 10 wt% silica showed no decrement in the glass
transition region and kept at a high value even in the high
temperature region over 2008C. This means that the heat
resistance of the cured epoxy resin is signi®cantly improved
by the hybrization with a silica network and the DGEBA/
GPTMS hybrids (silica content: . 10 wt%) could maintain
the glassy state up to their decomposition temperature.
It is well known that a cured epoxy resin clearly shows a
large tan d peak in the glass transition region. Also, in this
study, the unmodi®ed epoxy system showed a large tan d
peak in the glass transition region. However, the area of the
tan d peak decreased with the hybrization of the silica
network into the epoxy resin. In the hybrids of DGEBA/
GPTMS (silica content: .10 wt%), the tan d peak in the
glass transition region completely disappeared and no
other tan d peaks appeared in the measured temperature
range. These results show that the silica network is
dispersed in the epoxy network in a molecular order and
the motion of network chains is strongly restricted in the
epoxy/silica hybrids. These phenomena were also observed
in other hybrid materials [14,15]. However, the complete
disappearance of the tan d peak was hardly achieved and
the hybrid material required the addition of large amounts of
inorganic components for the large change in the tan d peak.
However, as shown in Fig. 4, the molecular motion of the
network chains in the DGEBA/GPTMS hybrids was effectively
restricted by the hybrization with small amounts of
silica network. Thus, it is concluded that the epoxy and
silica networks in the hybrid system should be combined
in molecular order by covalent bonds.
3.4. Bonding properties and mechanism of DGEBA/GPTMS
hybrid materials
The adhesive bonding properties of the DGEBA/GPTMS
hybrids for silicone rubber were investigated. The lap shear
and the 908 peel strength were measured using the substrates
shown in Fig. 1A and B. Fig. 5 shows the lap shear strength
during the curing process of the silicone rubber joints
bonded with the DGEBA/GPTMS hybrids containing different
amounts of the silica network. The bonding strength of
all the cured systems increased with curing. However, the
silicone rubber joint bonded with the unmodi®ed epoxy
resin showed a contact failure and thus a very low bonding
strength even during the ®nal stage of curing. This result
means that the silicone rubber is not suitable for adhering to
an epoxy resin. However, in the hybrid systems, the joints
bonded with the hybrid containing 4 wt% silica showed an
adherend failure of the silicone rubber substrate during the
®nal stage of curing. Thus, it is clear that the hybrization of
the silica network into epoxy matrix was effective for
improving the adhesion between the epoxy resin and the
M. Ochi et al. / Polymer 42 (2001) 5151±5158 5155
Fig. 4. Dynamic mechanical properties of epoxy/silica hybrid systems. (X)
Unmodi®ed; (O) GPTMS-4; (W) GPTMS-6; (K) GPTMS-10; (V) GPTMS-
14.
silicone rubber substrate. In general, the improvement in the
bonding strength of the silicone rubber was achieved by the
surface treatment or modi®cation with gas plasma, etc. [16±
21]. The addition of GPTMS to the epoxy resin may have
made it possible to adhesively bond silicone rubber without
any surface treatment.
The effect of the GPTMS contents on the bonding
strength of the silicone rubber joints was investigated. The
unmodi®ed epoxy resin and DGEBA/GPTMS hybrids with
different silica contents from 1 to 19.8 wt% were used for
the 908 peel test as adhesives. The results of the peel tests are
shown in Fig. 6. In this ®gure, the dotted line shows the peel
strength of the samples bonded with unmodi®ed epoxy
resin. The peel strength increased with an increase in the
silica contents. The maximum value of the peel strength was
observed at 14 wt% of the silica content and then the peel
strength suddenly decreased. This may result from the
increase in the brittleness with the addition of an excess
amount of GPTMS because the cohesive failure was
observed in the adhesive joint with the hybrid containing
more than 14 wt% silica. This result means that the bonding
strength of the epoxy resin for silicone rubber was signi®-
cantly improved with the hybrization of GPTMS. However,
the addition of the excess amount (more than 14 wt%) of the
silica networks made the adhesion layer brittle and led to a
decrease in the bonding strength.
The temperature dependence of the lap shear strength
with unmodi®ed and modi®ed epoxy resins were measured
in the 25±1808C region as shown in Fig. 7. In all the specimens,
a large decrease in the bonding strength was observed
in the 100±1208C region. For the DMA results of the
DGEBA/GPTMS hybrids (Fig. 4), the storage modulus of
the hybrid systems with over 10 wt% added silica showed
no decrease in the high temperature region over 2008C.
Therefore, it is considered that the large decrease in the
bonding strength observed in the 100±1208C region was
not caused by the glass±rubber transition of the DGEBA/
GPTMS hybrids used as adhesives. The bonding strength of
the specimens with the hybrid containing 14 wt% silica
measured at 1208C was lower than that of the specimens
with a hybrid containing 4 wt% silica at 258C, though adherend
and cohesive failure were observed in the former and
latter specimens, respectively. This result showed that
though a good interfacial adhesion was maintained in the
specimens with the hybrid containing 14 wt% silica even at
1208C, the mechanical properties of the silicone rubber
substrate itself decreased in this temperature region. Thus
the large decrease in the bonding strength observed in the
5156 M. Ochi et al. / Polymer 42 (2001) 5151±5158
Fig. 6. Peel strength of epoxy/silica hybrids with GPTMS. (′ ′ ′) Unmodi®ed
epoxy resin; (1) contact failure; (#) cohesive failure; ( p ) adherend failure.
Fig. 7. Temperature dependence of lap shear strength of epoxy/silica
hybrids with GPTMS. Symbols as in Fig.4; (1) contact failure; (#) cohesive
failure; ( p ) adherend failure.
Fig. 5. Lap shear strength of epoxy/silica hybrids with the progress of
curing (GPTMS). Symbols as in Fig.4; (1) contact failure; (#) cohesive
failure; ( p ) adherend failure.
100±1208C region should result from the heat degradation
of the silicone rubber substrate. In other words, this result
shows that these hybrid materials have a high bonding
strength for silicone rubber even in the high temperature
region, and the bonding strength of the joints heavily
depends on the thermal stability of the silicone substrate
in the region over 1208C.
The lap shear strengths of the silicone rubber joints
bonded with the hybrids containing 6 wt% silica prepared
by changing the fractions of GPTMS and TMOS are shown
in Fig. 8. In this ®gure, the dotted line shows the lap shear
strength of the joints bonded with an unmodi®ed epoxy
resin. The contact failure was observed in the specimens
bonded with an unmodi®ed epoxy resin and some hybrids
containing more than 50 mol% TMOS, and the lap shear
strength decreased with an increase in the addition of
TMOS. In addition, the value of the bonding strength in
the specimen bonded with the hybrid prepared from the
mixture of GPTMS and TMOS in the ratio of 25:75 was
almost the same as that with the unmodi®ed epoxy resin. It
is clear that the improvement in bonding strength of the
silicone rubber joints was not achieved in the hybrids
prepared with TMOS. Thus, it is important for improving
the bonding strength between the epoxy resin and silicone
rubber that the silane alkoxides containing the functional
(epoxy) group that react with the organic component are
used as the inorganic component to form the interaction
between the organic and inorganic phases.
To reveal the bonding mechanism between the silicone
rubber substrate and the hybrids with GPTMS as the inorganic
component, the Si concentration of adhesive layer was
measured by XMA as shown in Fig. 9. The Si concentration
was analyzed along the solid line, and the result is the wavy
line. This result shows that in the adhesive joint of the
silicone rubber, the silica network was concentrated in the
interfacial area. However, a relatively uniform morphology
was observed in the hybrid materials as shown in Fig. 3.
Thus, in the DGEBA/GPTMS hybrids prepared with an
aluminium mold, the heterogeneity of the Si concentration
was not observed as shown in the XMA result (Fig. 9).
These results show that the silica component migrated
from the inside of the adhesive layer to the interfacial area
during the formation of the adhesive bonding between the
DGEBA/GPTMS hybrids and the silicone rubber substrate.
From this result, it is easily expected that the GPTMS and its
network have a good af®nity to silicone rubber and the
migration of GPTMS to the interfacial area may result
from their good af®nity. Thus the af®nity of DGEBA itself,
and the mixture of DGEBA and GPTMS to the silicone
rubber substrate, was evaluated by measuring the swelling
ratio of the silicone rubber. A piece of silicone rubber
(20 ￡ 10 ￡5 mm3) was immersed in DGEBA or a mixture
of DGEBA and GPTMS which contain a different silica
content from 6 to 19.8 wt% at 608C for 3 days. In these
swelling tests, a curing agent was not added to all the
mixtures. The degree of silicone rubber swelling is shown
M. Ochi et al. / Polymer 42 (2001) 5151±5158 5157
Fig. 9. Distribution of Si-concentration in the epoxy/silica hybrid adhesive layer observed by the XMA line pro®le. Total silica content: 6 wt%.
Fig. 8. Lap shear strength of epoxy/silica hybrids prepared from the mixture
of TMOS and GPTMS. (W) Unmodi®ed epoxy resin; (1) contact failure;
(#) cohesive failure; ( p ) adherend failure. Total silica content: 6 wt%.
in Fig. 10. The silicone rubber was not swollen by the
unmodi®ed epoxy resin at all, and the degree of swelling
increased with the increasing GPTMS content in the
mixture. It is clear that the addition of GPTMS plays a
major role in the swelling of the silicone rubber with the
mixture of DGEBA and GPTMS. From these results, it is
considered that the GPTMS molecules in the hybrid materials
should penetrate into the silicone rubber substrate at the
interface due to the good af®nity between the silicone rubber
and GPTMS. The GPTMS molecules should react with each
other in the inner surface of the substrate to form the silica
networks. As the GPTMS has a functional (epoxy) group,
the silica networks formed on the surface of the substrate
could be bonded with the epoxy networks at the interface
between the adhesives and substrates. This is shown by the
dramatic improvement in the bonding strength in the silicone
rubber joints with the addition of GPTMS to the epoxy
adhesives is due to the formation of interfacial bonding
between the silica networks constructed on the surface of
the silicone rubber substrate and the epoxy network formed
in the adhesive layer.
4. Conclusion
Epoxy/silica hybrids containing from 4 to 19.8 wt% of
silica were synthesized from DGEBA and GPTMS or
TMOS by utilizing a sol±gel process. In the DGEBA/
GPTMS hybrids, the storage modulus in the rubbery region
increased and the peak area of the tan d curves in the glass
transition region decreased with the hybridization of small
amounts of silica. This may result from the suppression of
the epoxy network moiety with the incorporation of a silica
network containing a functional (epoxy) group which can
react with the organic component. TEM observations
revealed that silica networks were uniformly dispersed in
the hybrids.
The hybrids containing GPTMS showed a very high
bonding strength for the silicone rubber compared with
that of the unmodi®ed epoxy resin, but this improvement
in the bonding strength was not observed in the hybrids with
TMOS. It is concluded from the XMA analysis results of the
silicone rubber joints and the swelling test of the silicone
rubber with the mixture of DGEBA and GPTMS that the
high bonding strength observed in the DGEBA/GPTMS
hybrids was due to the formation of the interfacial bonding
between the silica networks formed on the surface of the
substrate and the epoxy networks in the adhesive layer.
References
[1] Landry CJT, Coltrain BK, Landry MR, Long VK. Macromolecules
1993;26:3702.
[2] Wang Z, Lan T, Pinnavain TJ. Chem Mater 1996;8:2200.
[3] Zhang C, Lain RM. J Organomet Chem 1996;521:199.
[4] Sellinger A, Lain RM. Chem Mater 1996;8:1592.
[5] Brinker CJ, Scherer GW. Sol±gel science. London: Academic Press,
1990.
[6] Saegusa T, Chujo Y. J Macromol Sci Chem 1990;A27:1603.
[7] Chujo Y, Ihara E, Kure S, Saegusa T. Macromolecules 1993;26:5681.
[8] Huang ZH, Qiu KY. Polymer 1996;38:521.
[9] Huang ZH, Qiu KY, Wei Y. J Polym Sci, Part A: Polym Chem
1997;35:2403.
[10] Yano S, Furukawa K, Kodomari M, Kurita K. Kobunshi Ronbunshu
1996;53:218.
[11] Matejka L, Duesk K, Plestil J, Kriz J, Lednicky F. Polymer
1998;40:171.
[12] Sakka S, Sol±gel hou no kagaku, Agunesyouhysya, Tokyo. 1998.
[13] Matejka L, Plestil J. Macromol Symp 1997;122:191.
[14] Hu Q, Marand E. Polymer 1999;40:4833.
[15] Ahmad Z, Sarwar MI, Wang S, Mark JE. Polymer 1997;38:4523.
[16] Tsai M, Lee Y, Ling Y. J Appl Polym Sci 1998;70:1669.
[17] Swanson MJ, Opperman GW. J Adhesion Sci 1995;9(3):385.
[18] Lai JY, Lin YY, Denq YL, Shyu SS, Chen JK. J Adhes Sci Technol
1996;10(3):231.
[19] Husein IF, Zhou Y, Qin S, Chan C, Kleiman JI, Marchev K. Mater
Res Soc 1997;438:511.
[20] Inagaki N, Tasaka S, Kawai H. J Adhesion Sci Technol
1992;6(2):279.
[21] Inagaki N, Tasaka S, Kawai H. J Appl Polym Sci 1995;56:677.
5158 M. Ochi et al. / Polymer 42 (2001) 5151±5158
Fig. 10. Swelling ratio of silicone rubber substrate with GPTMS at 608C/.

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