Environment-friendly synthesis and performance of a novel hyperbranched epoxy resin with a silicone skeleton

Article abstract of DOI:10.1039/c2ra22969b

Hyperbranched epoxy resins have attracted increasing attention for their excellent comprehensive performance in toughening and reinforcing the diglycidyl ether of bisphenol-A (DGEBA). However, the tedious synthetic procedure, high cost, and the use of large amounts of organic solvents have hampered their industrial application. This paper presents an environment-friendly method to synthesize a novel hyperbranched epoxy resin with a silicone skeleton (HERSS) through a hydrosilylation reaction catalyzed by a heterogeneous halloysite-supported platinum catalyst. The reaction involves only one solvent and affords a high yield (>90%). The chemical structure, molecular weight, and degree of branching of the HERSS were characterized by FT-IR, GPC and NMR. The resulting HERSS was used to modify a DGEBA based epoxy resin and showed excellent performance. With the incorporation of 9 wt% HERSS, the impact, flexural and tensile strength of DGEBA are increased by about 92.5%, 36.0% and 88.6%, respectively. The toughening and reinforcing mechanism was attributed to the sea-island structure of the cure composite, as shown by the SEM micrographs of the fractured surfaces. An initial thermal decomposition temperature of about 380.0 °C of the cured HERSS/methyl nadic anhydride resin also indicates promising applications with regard to high-temperature- resistance.

Full text of DOI:10.1039/c2ra22969b

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PAPER
Environment-friendly synthesis and performance of a
novel hyperbranched epoxy resin with a silicone
skeleton3
Cite this: RSC Advances, 2013, 3,
3095
Daohong Zhang,*a Enbin Liang,a Tingcheng Li,a Sufang Chen,b Junheng Zhang,a
Xinjian Cheng,a Jiliang Zhoua and Aiqing Zhanga
Hyperbranched epoxy resins have attracted increasing attention for their excellent comprehensive
performance in toughening and reinforcing the diglycidyl ether of bisphenol-A (DGEBA). However, the
tedious synthetic procedure, high cost, and the use of large amounts of organic solvents have hampered
their industrial application. This paper presents an environment-friendly method to synthesize a novel
hyperbranched epoxy resin with a silicone skeleton (HERSS) through a hydrosilylation reaction catalyzed by
a heterogeneous halloysite-supported platinum catalyst. The reaction involves only one solvent and
affords a high yield (.90%). The chemical structure, molecular weight, and degree of branching of the
HERSS were characterized by FT-IR, GPC and NMR. The resulting HERSS was used to modify a DGEBA based
epoxy resin and showed excellent performance. With the incorporation of 9 wt% HERSS, the impact,
flexural and tensile strength of DGEBA are increased by about 92.5%, 36.0% and 88.6%, respectively. The
toughening and reinforcing mechanism was attributed to the ‘‘sea-island’’ structure of the cure
composite, as shown by the SEM micrographs of the fractured surfaces. An initial thermal decomposition
temperature of about 380.0 uC of the cured HERSS/methyl nadic anhydride resin also indicates promising
applications with regard to high-temperature-resistance.
Received 20th November 2012,
Accepted 20th December 2012
DOI: 10.1039/c2ra22969b
www.rsc.org/advances
esters,9 thermoplastic polyetherimide,4 and core–shell parti-
cles,4 HBPs2–4,10–15 demonstrated better overall performance.
1. Introduction
Hydroxyl-functionalized HBPs,4,14 epoxy-functionalized HBPs
(Boltorn E1, Boltorn E2),13,15–17 hydroxyl and epoxy-functiona-
lized hyperbranched block copolyethers with core/shell struc-
tures,18 and amine-terminated HBP19 can increase several fold
the fracture toughness of commercial diglycidyl ether of
bisphenol-A (DGEBA), with the use of only 5–20 wt% of HBP.
However, the tensile strength, flexural strength and glass
transition temperature are usually impaired to some extent.
These HBPs/epoxy resin composites are also difficult to
process since the HBPs are either solid or of high viscosity.
In 2006, we synthesized several novel hyperbranched epoxy
resins with low viscosities of 350–5000 cp and a low epoxy
equivalent weight.20 An interesting result was that these
hyperbranched epoxy resins could toughen and reinforce
DGEBA at the same time.3,21 An in situ reinforcing and
toughening mechanism was suggested first3 and further
confirmed through research of unsaturated HBP/linear unsa-
turated polyester resins composites22 and hyperbranched
polyphosphate ester/DGEBA composites.23 The toughening
effect was attributed to the intramolecular cavity from the non-
crosslinking structure of HBPs which may absorb a significant
amount of energy upon impact. The reinforcing function was
Hyperbranched polymers (HBPs) are of interest in many
applications because they are easier to synthesize than
dendrimers and yet possess similar properties.1 Moreover,
HBPs generally have better solubility and lower viscosity than
linear polymers with similar molar mass and chemical repeat
units. It is interesting to note that HBPs are also important
tougheners2–4 for epoxy resins. Epoxy resins are a vital class of
thermosetting polymers and have a broad range of applica-
tions,5 including coatings, paintings, adhesives, laminates,
encapsulants, and electrical insulating materials. However,
their poor toughness or inherent brittleness, high viscosity
and low thermal decomposition temperature have limited
their applications.6
Toughening modification of epoxy resins has been a
subject of intense investigation throughout the world.
Compared with rubbers,7 graphene oxide,8 epoxidized oleic
aKey Laboratory of Catalysis and Materials Science of the State Ethnic Affairs
Commission & Ministry of Education, South-central University for Nationalities,
Wuhan, Hubei Province, 430074, China. E-mail: zhangdh27@163.com;
Fax: +86-27-67842752; Tel: +86-27-67842752
bKey Laboratory for Green Chemical Process of Ministry of Education, Wuhan
Institute of Technology, Wuhan, Hubei 430073, China
Electronic supplementary information (ESI) available. See DOI: 10.1039/
3
regarded as
a
result of the rigid phenyl structure of
c2ra22969b
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hyperbranched epoxy resin.3 The toughening effect was further
substantiated by a novel low-viscosity hyperbranched epoxy
resin2 containing similar chemical structures as Boltorn E1.
Other functional HBPs, including hyperbranched polyglycerol
containing carbonate groups,24 hydroxyl-functionalized
HBPs,25 and hyperbranched poly(ester-amide)26 could also
increase the strength of DGEBA by about 5–20% as a results of
the toughening effect.
Different approaches to synthesize hyperbranched epoxy
resins have been researched for their production and applica-
tion on an industrial scale. Aliphatic and aromatic hyper-
branched epoxy resins were prepared by proton transfer
polymerization27–29 and ATRP.30 Polyester hyperbranched
epoxy resins could be obtained by grafting epoxy groups to
HBPs2,6,20,31–38 with epichlorohydrin. Liquid crystalline hyper-
branched epoxy could be synthesized by a reaction between
benzylidene cyclopentanone biepoxy monomers and trimesic
acid.39 Hydrosilylation has also been adopted to prepare
organic silicone hyperbranched epoxy resin40 and epoxy-
terminated carbosiloxane.41
and removal of the byproduct NaCl.2,6,20,31–38 Another dis-
advantage of these hyperbranched epoxy resins is their low
glass transition and thermal decomposition temperature.
Hyperbranched silicone resins42,43 have good heat-resistance,
whereas the synthetic processes are not only expensive, based
on organic silane coupling agents42 and unrecyclable homo-
geneous platinum catalysts, but also harmful to the environ-
ment due to the release of a great deal of HCl during the
hydrolysis of chlorosilanes.43 Many of the other hyper-
branched epoxy resins reported need to be diluted with a
thinner or solvent during application since they are either a
solid41 or a high viscosity liquid,27–29 and can not be applied in
solvent-free conditions.
In this paper, we present an environment-friendly method
for preparing a novel hyperbranched epoxy resin with a
silicone skeleton (Fig. 1). Firstly, phenyltriallylsilane (PTAS)
was prepared by a reaction between allylmagnesium chloride
(AMC) and phenyltrichlorosilane (PTCS). Secondly, an allyl-
ended hyperbranched resin with a silicone skeleton (AHRSS)
was obtained by a hydrosilylation between the PTAS and
1,1,3,3-tetramethyl-disiloxane (TMDS) using halloysite-sup-
ported platinum as a catalyst. Then, the hyperbranched epoxy
resin with a silicone skeleton (HERSS) was synthesized by a
similar hydrosilylation between AHRSS and 1,1,3,3-tetra-
methyl-disiloxane-propylglycidyl ether (TDPGE) that resulted
from an addition of equal molar TMDS and allylglycidyl ether
(AGE). In all the synthetic processes, the catalyst, excess
materials and THF can be recycled, and the yield of every
Although these techniques were successful in preparing
hyperbranched epoxy resins, many of them were obtained only
in labs, with the exceptions of Boltorn E1 and E2 (Perstorp
Corp., Sweden) and our HyperT E1, E2, E3 and E4 series
(HyperT Resins, China). A great deal of organic solvents, such
as DMF,39 and tedious processes involving synthetic epoxy
monomers27–29 are involved in some methods. In other
methods, a large amount of water is wasted in the washing
Fig. 1 Synthetic schemes of AHRSS and HERSS.
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Differential scanning calorimetry (DSC) measurements were
performed with a differential scanning calorimeter (NETZSCH
DSC204 F1) using a 1.8–3.0 mg sample in standard aluminum
pans at a heating rate of 10 K min21. Thermogravimetric
analysis (TGA) was performed using a thermogravimetric
analyzer (NETZSCH TG209) at a heating rate of 20 K min21
reaction involved was more than 90%. This method is not only
suitable for large-scale production but also for solvent-free
applications. The resulting HERSS was used to modify DGEBA
and showed an excellent toughening and reinforcing ability.
HERSS also showed good heat-resistance and may be used as a
vacuum pressure impregnation insulation resin in high-power
(over 2.5 MW) wind driven generators.
and a nitrogen flow of 20 mL min21
.
2.2 Synthesis of silicone skeleton hyperbranched epoxy
(HERSS) resin
2. Experimental
Preparation of TDPGE. A mixture of AGE (5.71 g, 0.05 mol)
and TMDS (6.70 g, 0.05 mol) was added dropwise to a three-
necked flask containing TMDS (13.43 g, 0.10 mol) and Pt-
Halloysite (6.0 g). The flask was equipped with a stirrer, cooler
and thermometer, and the reaction was allowed to proceed for
10 h at about 60 uC. Then the catalyst was filtered and the
excess TMDS was removed under a pressure of 5 mmHg at 60
uC to yield 12.30 g (98.95%) of a yellowish transparent liquid
1,1,3,3-tetramethyl-disiloxane-propylglycidyl ether (TDPGE).
Preparation of AHRSS. A mixture of PTAS (11.42 g, 0.05 mol)
and THF (20 mL) was added dropwise to a three-necked flask
containing TMDS (6.04 g, 0.045 mol), THF (15 mL) and Pt-
Halloysite (10.0 g) as a catalyst. The flask was equipped with a
stirrer, cooler and thermometer, and the reaction continued
for 12 h at about 65–70 uC. Then the catalyst was filtered and
the solvent was removed under a pressure of 5 mmHg at 65–70
uC to yield 17.06 g (97.7%) of a yellowish transparent liquid
(AHRSS, Mn = 1637 Da, Mw = 3315 Da, Mz = 6795 Da, PDI = Mw/
Mn = 2.03) with a viscosity of 252.5 mPa s (25 uC).
2.1 Materials and measurements
Allylglycidyl ether (AGE), styrene (St), methyl nadic anhydride
(MNA) and other materials were purchased from commercial
sources and used without further purification unless noted
otherwise. Tetrahydrofuran (THF), 1,1,3,3-tetramethyl-disilox-
ane (TMDS), allyl chloride (AC) and phenyltrichlorosilane
(PTCS) were purified by distillation. AC, TMDS, AGE and PTCS
were dried over 24 h with 4 Å molecular sieves before using. A
heterogeneous halloysite supported platinum catalyst (Pt-
Halloysite) with 0.4 wt% of platinum was prepared as
described in our previous paper.44 DETA-AN as curing agent,
was prepared by an addition reaction between acrylonitrile
(AN) and diethylene triamine (DETA)3 at equal molar ratio.
Infrared spectra were taken using a NEXUS 470 Fourier
transform infrared spectrometer. 1H and 13C NMR measure-
ments were conducted using an AVANCE III-400 (Bruker)
nuclear magnetic resonance spectrometer. The molecular
weights and distributions (PDI) were determined with a gel
permeation chromatograph (PL GPC-50) using a PL-RTLS 15/
90 dual-angle LSD as a detector and THF as the eluent. The
Preparation of HERSS. AHRSS (5.24 g), THF (15 mL), TDPGE
(8.05 g) and Pt-Halloysite (5.0 g) was added to a three-necked
flask, and the reaction continued for 10 h at temperature
between 65 uC and 70 uC. A yellowish transparent liquid
(HERSS, Mn = 2163 Da, Mw = 4525 Da, Mz = 10 464 Da, PDI =
Mw/Mn = 2.09) of 9.70 g (99.5%) was afforded after the catalyst
was filtered and the solvent THF was removed. The viscosity of
the product is 1102 mPa s (25 uC) and the epoxy equivalent
viscosity of AHRSS and HERSS was measured using
a
Brookfield DV-III+ viscometer with an RV-S06 spindle at 25
uC and 20 rpm. A transmission/reflection polarizing optical
microscope (TRPOM, XPV-203E, China) equipped with a
thermal platform was used to study micro-phase separation
of the sample during curing.
weight is 550 g mol21
.
The no-notch impact strength of the cured samples (80 mm
6 10 mm 6 4 mm) was determined using a XJJ-5 simple-
supported-beam impact testing machine (ChengDe Precision
Testing Machine Co., Ltd, China) at room temperature (25 uC)
according to ASTM D256-81. The tensile strength of the
dumbbell samples (75 mm 6 5 mm 6 5 mm) was measured
2.3 Preparation of HERSS/DGEBA composites
The HERSS/DGEBA blends containing 0–15 wt% of HERSS
were prepared by mixing HERSS with DGEBA in a glass cup
which was stirred with a glass stick at about 25 uC. A
stoichiometric amount of DETA-AN was added with contin-
uous stirring for 5 min. After the bubbles in the HERSS/DGEBA
blend was removed under vacuum for 10 min, the blend was
put into a silicone rubber mold and cured at 25 uC for 12 h, at
80 uC for 3 h and then post-cured at 180 uC for 6 h. After that,
the samples were cooled gradually to room temperature and
stored for about 12 h. The mechanical performances were then
measured by corresponding standard methods.
by
a WSM-20KN computer-controlled universal testing
machine (ChengDe Precision Testing Machine Co., Ltd,
China) according to ASTM D368-91a with a loading rate of
10 mm min21. The flexural strength of the samples (80 mm 6
10 mm 6 4 mm) was determined according to ASTM D790M-
92 by a WSM-20KN testing machine using a three-point
bending mode.
A scanning electron microscope (SEM) (XL-30FEG, Philip)
was used to examine the morphology of the fractured surface.
A thin section of the fractured surface was cut and mounted on
an aluminum stub using conductive (silver) paint and was
sputter-coated with gold prior to fractographic examination.
SEM micrographs were obtained under conventional second-
ary electron imaging conditions, with an accelerating voltage
of 20 kV.
3. Results and discussion
3.1 Recycle times of the halloysite-supported platinum catalyst
The halloysite-supported platinum catalyst (0.7 g) was used to
catalyze the hydrosilylation between St (0.06 mol, 6.24 g) and
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TMDS (0.025 mol, 3.36 g) at 323–328 K for 2 h with mechanical
stirring. Then the catalyst was recycled by filtration and
reused. The conversion of the Si–H bond of TMDS was
measured by FT-IR after the reaction. The effect of the number
of times the halloysite-supported platinum catalyst has been
recycled on the FT-IR spectra of the product is shown in Fig.
S1, ESI. According to a relative ratio of peak area at 2123 cm21
3
(Si–H) to that at 1494 cm21, a relationship between the
conversion of the Si–H bond of TMDS and number of times
the halloysite-supported platinum catalyst is recycled can be
obtained and is shown in Fig. S2, ESI. When using the same
3
sample of catalyst for the seventh time the conversion of the
Si–H bond of TMDS remains 98.4%, demonstrating the
excellent recyclability of the halloysite-supported platinum
catalyst.
Fig. 3 1H NMR spectra of TDPGE, PTAS, AHRSS and HERSS.
3.2 Characterization of TDPGE, AHRSS and HERSS
FT-IR spectra of AGE, TMDS, TDPGE, PTAS, AHRSS and HERSS
are shown in Fig. 2. Characteristic bonds of TMDS in FT-IR
According to the chemical structure of the AHRSS and its
reaction mechanism, the chemical chains of AHRSS should be
composed of three different structure units, including (1)
branched units (Nb), (2) linear units (Nl) and (3) terminal units
(Nt) (Fig. 5).
(KCl, cm21) are supplied in ESI (S1).
3
The disappearance of the absorption peak of the LC–H
group at 3059 cm21 and 1646 cm21 in Fig. 2c indicates that
there is a complete reaction between AGE and TMDS, and the
diminishment of the peak at 3060 cm21 and the disappear-
ance of the peak at 1629 cm21 (Fig. 2f) also suggests complete
conversion of the double bonds of AHRSS.
Since the difference in structural variation among the three
units is very small, it is very difficult to designate directly the
attributions of these hydrogen atoms in the range of 0.5–1.8
ppm (Fig. 6). The 1H NMR-minus spectrum of model
compound with a similar chemical structure is a convenient
strategy used to analyze effectively these attributions for
simplifying the calculation process and obtaining the DB.32
Herein, we designed and synthesized a model compound tri-
(1,1,3,3-tetramethyl-disiloxane)-phenylpropylsilane (A3) by a
reaction between the TMDS and the PTAS through a similar
synthetic process as for TDPGE. Chemical shifts at d 1.37–1.57
(a, 2H), d 0.91–1.09 (b, 2H) and d 0.60–0.80 (c, 2H) are observed
clearly in the 1H NMR (Fig. 6) of A3. Comparing the
corresponding chemical shifts of A3 to the chemical shifts of
the hydrogen atoms in AHRSS, the three kinds of units (Fig. 5)
can be assigned as following: d 1.37–1.57 (T2–H, 2H and B2–H,
1
The H NMR spectra and 13C NMR spectra of the resulting
compounds are shown in Fig. 3 and 4, respectively. The
chemical shift data are summarized in ESI S2 and S3,
3
respectively.
NMR spectroscopy is a common tool45,46 for measuring the
degree of branching (DB) of hyperbranched polymers accord-
ing to eqn (1). The DB refers to the ratio of branched and
terminal units to total units, i.e.
DB = (Nb + Nt)/(Nb + Nt + Nl)
(1)
Fig. 4 13C NMR spectra of TDPGE, PTAS, AHRSS and HERSS.
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Fig. 2 FT-IR spectra of TMDS, AGE, TDPGE, PTAS, AHRSS and HERSS.
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Fig. 5 Chemical structures of terminal, linear and branched units.
skeleton structure (HERSS) was applied to modify DGEBA
using DETA-AN as a curing agent. The mechanical perfor-
mance of HERSS/DGEBA composites first increases and then
decreases with an increase of the HERSS content (Table 2), and
when the modified DGBEA contains 9 wt% HERSS, the HERSS
can increase the impact, flexural and tensile strength by about
92.5%, 36.0% and 88.6%, respectively.
However, compared with the homogeneous microstructure
of HTDE/DGEBA composites,3 it is interesting to note that a
micro-phase separation ‘‘sea–island’’ structure appears clearly
in the morphology of the fractured surface (Fig. 7). An increase
in HERSS content results in an increase in the number and
volume content of ‘‘islands’’ on the surface (Fig. 7). The
volume contents of the islands observed in SEM micrographs
are close to the theoretical values (Table 3) calculated from
their formula, indicating that the composition of the islands
should be cured HERSS. The difference in solubility para-
meters of DGEBA (d 17.91 (J cm
)
23 0.5) and HERSS (d 15.19 (J
cm
)
23 0.5) changes their compatibility during curing and
Fig. 6 1H NMR spectra of A3 and AHRSS between d 0.5–1.8 ppm.
inducts micro-phase separation. A real-time transmission/
reflection polarizing optical microscope (TRPOM) equipped
with a thermal platform was used to study the micro-phase
6H), d 1.34 (L2–H, 4H), d 0.81–1.09 (T3–H, 2H, B3–H, 6H and
L3–H, 4H), d 0.67–0.78 (B1–H, 6H), and d 0.54–0.67 (T1–H, 2H
and L1–H, 4H) (Fig. 6). The relative areas of all these peaks are
obtained and summarized in Table 1 according to their
relationships among chemical structures. The precise DB
(0.72) of the AHRSS can be calculated by eqn (2). The DB of
HERSS is also 0.72 because it has same silicone skeleton as
AHRSS.
separation (Fig. S3, ESI ) of 9 wt% HERSS/91 wt% DGEBA
3
blend during curing on the surface of a glass slide at 80 uC,
and the result indicates that the micro-phase separation size of
‘‘sea–island’’ structure increases with the curing time.
The clear smooth morphology in Fig. 7a is substantial
evidence of the brittle nature of DGEBA. The appearance of
many ‘‘islands’’ (Fig. 7b–f) in the matrix indicates excellent
toughness of the HERSS/DGEBA composites because the non-
crosslinkable hyperbranched structure in the islands may
absorb energy upon impacting.3 At the same time, improve-
ment in tensile strength and flexural strength is attributable to
the increase in crosslinking density of the composites due to a
large number of epoxy groups in HERSS and strong surface
interactions between ‘‘islands’’ and ‘‘sea’’ (Fig. 7g–h).
However, the crosslinking density and non-crosslinkable
hyperbranched structure have opposite effects on the strength
and toughness of the composites. A balance was found with
the incorporation of 9 wt% HERSS, which demonstrated not
only increased toughness but also excellent tensile and flexural
strength.
(T1zT2zT3) (B1zB2zB3)
z
2
(T1zT2zT3) (B1zB2zB3) (L1zL2zL3)
6
DB~
(2)
z
z
2
6
4
3.3 Application and performance of HERSS
One of the major applications of hyperbranched epoxy resins
is to toughen and reinforce the commercial DGEBA,3,4,15,36,47
however, their glass temperature usually decreases by over
20%. The novel hyperbranched epoxy resin with a silicone
Table 1 Peak areas and DB calculations of the AHRSS
d/ppm
0.54–0.67
0.67–0.78
0.81–1.09
1.34
1.37–1.57
DB
Hydrogen atoms
Areas
T1
0.81
L1
1.11
B1
1.89
T3
0.81
L3
1.11
B3
1.89
L2
1.11
T2
0.81
B2
1.89
0.72
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Table 2 Effects of the HERSS content on the mechanical performances of HERSS/DGEBA composites
Performance
Tensile strength/MPa
Flexural strength/MPa
Impact strength/kJ m22
Glass temperature/uC
DGEBA
31.98
41.79
57.16
60.31
56.18
53.38
31.14
35.35
37.38
42.34
41.64
39.54
1.99
2.99
3.50
3.83
3.60
3.51
126.0
118.0
112.3
108.3
107.5
105.5
3 wt% HERSS
6 wt% HERSS
9 wt% HERSS
12 wt% HERSS
15 wt% HERSS
Fig. 7 SEM micrographs of the fractured surface of HERSS/DGEBA composites and DGEBA: (a) DGEBA, (b) 3 wt% HERSS, (c) 6 wt% HERSS, (d) 9 wt% HERSS, (e) 12
wt% HERSS, (f) 15 wt% HERSS, (g–h) local magnified images.
Table 3 Volume contents of the islands in all composites
HERSS content
Volume content calculated from SEM micrographs/%
Volume content calculated from theoretical formula/%
3 wt% HERSS
6 wt% HERSS
9 wt% HERSS
12 wt% HERSS
15 wt% HERSS
2.86
5.67
8.52
10.28
14.00
2.82
5.64
8.45
11.27
13.06
The glass transition temperature (Tg) of the HERSS/DGEBA
composites decreases slowly with an increase in HERSS
content as shown in Fig. S4, ESI and Table 2. The T (108.3
3
g
uC) of 9 wt% HERSS/DGEBA composites only decreases by
about 14.0% compared with that of DGEBA (126.0 uC),
suggesting a better heat-resistance than other hyperbranched
epoxy resins reported.3,36 For example, the Tg of 9 wt% HTDE-
2/DGEBA composites decreased by about 30.3%.3 Thermal
decomposition temperature, TI (initial thermal decomposition
temperature or temperature at 5% weight loss), of the HERSS/
DGEBA composites increases slightly (Fig. S5 and Table S1,
ESI ) with increase in HERSS content. All the composites have
3
higher thermal decomposition temperatures of about 340 uC
than previous results.3,36 Methyl nadic anhydride (MNA) is the
primary curing agent in preparing solvent-free insulation
materials with high-temperature resistance. The TI of about
380.0 uC (Fig. 8 and Table S1, ESI ) of the cured HERSS-MNA
3
materials is not only much higher than that of DGEBA-MNA
Fig. 8 TGA curves of cured HERSS and DGEBA with MNA.
3100 | RSC Adv., 2013, 3, 3095–3102
(99.1 uC), but also approaches that of cured pure silicone,42
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´
11 X. Fernandez-Francos, J. M. Salla, A. Cadenato, J.
indicating the excellent high-temperature-resistance of
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´
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4. Conclusions
An allyl-ended hyperbranched resin with a silicone skeleton
(AHRSS) was synthesized by a hydrosilylation between phenyl-
triallylsilane
(PTAS)
and
1,1,3,3-tetramethyl-disiloxane
(TMDS), and a novel hyperbranched epoxy resin with a
silicone skeleton (HERSS) was then prepared from 1,1,3,3-
tetramethyl-disiloxane-propylglycidyl ether (TDPGE) and
AHRSS using a recyclable heterogeneous halloysite supported
platinum catalyst. The chemical structure, molecular weight
and distribution and degree of branching of the HERSS were
characterized by FT-IR, GPC and NMR. The impact, flexural
and tensile strength of DGEBA can be increased by about
92.5%, 36.0% and 88.6% respectively with the incorporation of
9 wt% HERSS. A micro-phase separated ‘‘sea–island’’ structure
was observed and attributed to the weak compatibility between
HERSS and DGEBA. Moreover, the high initial thermal
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