Advances in Chemical Engi neering and Science , 2011, 1, 133-139
doi:10.4236/aces.2011.13020 Published Online July 2011 (
Copyright © 2011 SciRes. ACES
Development of Siliconized Epoxy Resins and Their
Application as Anticorrosive Coatings
Prashant Gupta, Madhu Bajpai
Department of Oil & Paint Technology, H. B. Technological Institute, Kanpur, India
Received March 31, 201 1; revised May 17, 2011; accepted July 3, 2011
The present work involves the development of siliconized epoxy resin to overcome the drawback of epoxy
resin like poor impact strength, high rigidity and moisture absorbing nature because of which they are not
applied as corrosion resistant coating. By embedding silicone into the back bone of polymeric resin the
above drawback can be reduced to substantial level. For achieving this, siliconised epoxy resins were pre-
pared by reacting amine terminated silicone resin with novolac epoxy resin and meta-phenylenediamine was
used as curing agent. The applied films of coating were baked at 150˚C. Cured films were evaluated for their
thermal, mechanical, chemical and corrosion resistance properties to ascertain the commercial utility of these
eco-friendly resins for use in anti corrosive formulations. The siliconized epoxy resins system was found to
exhibit good thermal and anticorrosive properties.
Keywords: Epoxy Resin, Silicone Resin, Anticorrosive Coatings
1. Introduction
A novel coating of high performance polymeric m at erial is
a need of today. These polymeric materials have superior
mechanical, thermal and anticorrosive characteristics ide-
ally suitable for adverse environmental conditions [1].
Inorganic-organic hybrid resins have become a creative
polymer with unique combination of distinctive properties
of both constituents for applications in various industries.
Epoxy resins are widely used in protective coatings,
adhesives, sealant, fiber reinforced composites and elec-
tronic industry due to their outstanding surface pro perties
like low shrinkage, ease of cure and possessing good
moisture, solvent and chemical resistance, and excellent
adhesion performances [2,3]. They lack fracture resis-
tance, impact strength, low thermal stability, low pigmen t
holding ability, flexibility and poor hydrophobicity,
which restrict their wide application in the field of coat-
ings and paints [4,5]. To improve these properties the
component like rubber, polyurethane silicone are added
as modifier to the epoxy resins [6-8].
Silicones are used in coating materials because of the
following properties:
improved water repellency
improved thermal stability; resistance to oxidation
they retain physical properties over a wide range of
low toxicity
they impart unique flexibility to the backbone chain
and intrinsic surface active property.
Silicone is suitable modifier for epoxy resins. The
modified resin has superior thermal and thermo-oxida-
tive stability, fracture energy, excellent moisture resis-
tance, partial ionic nature, low surface energy and good
hydrophobicity [9 ].
Aliphatic epoxy modified polysiloxane coatings can
be prepared by the combination of aliphatic epoxy resins,
polysiloxane, organo oxysilane and difunctional ami-
nosilanes hardners which provide highly improved resis-
tance to ultraviolet and weathering in sunlight and im-
proved chemical and corrosion resistance.
In practical applications, amine-based hardeners hold
the largest share in epoxy hardener markets. Aromatic
amine cured epoxy resin systems have excellent resistance
to water, solvents an d alkaline solu tions as well as a range
of good to excellent dilut e acid resistance [10,11] .
Generally, the incorporation of siloxane into polymer
has been carried out through physical blending methods
[12,13]. The blending of siloxane and epoxy causes an
increase in viscosity, phase separation and bleeding of
siloxane component of the blended system.
In the present work an attempt has been made to im-
Copyright © 2011 SciRes. ACES
prove the shortcomings of siloxane epoxy blended coat-
ing. The properties of novolac epoxy resin are enhanced
by embedding the amine terminated silicone into the
backbone of polymeric resin. As silicone is chemically
bonded to epoxy resin, the resulting materials have de-
sired properties and with more consistent results.
2. Experimental
2.1. Materials
Phenol novolac epoxy resin, Synthesized in laboratory,
Epichlorohydrin, EMerck, Diethoxydimethyl silane, Al-
-aminopropyl diethoxy methyl silane, Lancaster.
2.2. Methods
2.2.1. Synthesis of No vol ac R e si n
Novolac Resin was prepared by condensation reaction
between phenol and formaldehyde in acidic medium. Ini-
tially, phenol (1 mole) with some quantity of water was
taken in three neck flask. The pH was adjusted to 0 .5 with
sulphuric acid (used as catalyst) and the contents were
heated to 90˚C with constant stirring. The required amount
(0.5 mole) of formaldehyde (37% formaline solution) was
added over a period of 3 hours through a dropping funnel,
and stirring was continued for an additional 30 minutes,
water was then removed under vacuum.
2.2.2. Synthesis of Ep o xy N o vol ac Resi n
Laboratory prepared Novolac Novolac Resin (1 mole)
was reacted with Epichlorohydrin (10 mole) at 110˚C
and 40% Sodium hydroxide solution was added gradu-
ally to the reactants over a period of 3 hours through a
dropping funnel. After completion of reaction, salt (NaCl)
was removed by washing with hot water and then water
was removed through vacuum distillation.
2.2.3. Determ ina tion of Epoxide Equivalent Weight
Epoxide equivalent weight was determined by standard
BIS method.
2.2.4. Cohydrolysis of Diethox ydi methyl Silane and
-Aminopropyldiethoxy Methyl Silane
Calculated amount of Diethoxydimethyl silane and
aminopropyldiethoxy methyl silane in 97:3 ratio were
taken in three-necked flask, 50 ml aq. alchohol (50:50)
was added dropwise. The reaction was continued at 0˚C
with constant stirring. After complete addition of aque-
ous alcohol, the reaction was further continued for half
an hour. The mix ture was sep arated and d istilled to make
it solvent free. The resin was dried.
2.3. Characterization of Resins
The characterization of synthesized resins like epoxide
equivalent and texture appearance are shown in Table 1.
2.4. Coating Composition and Film Preparation
The coating compositions were prepared by incorpora-
tion of amino terminated silicone resin in the ratio of 1.5
to 7.5 with curing agent (conventional amine).
Simultaneously a standard was also prepared by re-
acting epoxy resin with conventional amine.
The samples EA, EAS1, EAS2, EAS3, EAS4 and EAS5
of different molar ratio (as shown in Table 2) were ap-
plied on steel and glass panels with the help of 100a film
applicator. All efforts were made to maintain a uniform
film thickness of 100
for the general mechanical and
chemical resistance properties. The films were cured at
150˚C till becomes tack free.
2.5. Curing of Epoxy Resin
The curing of the above prepared resin was carried out
by using different curing ag ent under varying cond itions:
a) Curing of epoxy resin with aromatic amine: The ep-
oxy resin was melted and mixed with stoichiometric
amount of curing agent, i.e. m-phenylenediamine ( M PDA)
at a temperature 80˚C.
b) Curing of epoxy resin with mpda and amino termi-
nated silicone resin in different ratios at 150˚C.
3. Results and Discussion
3.1. Spectral Analysis
Figure 1 shows the I.R. spectra of novolac epoxy resin.
A prominent band is observed at 940 cm–1, which shows
Synthesis of Novolac Resin
H 0.5, 90˚C
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Synthesis of Novolac Epoxy Resin
00C / H2OSi
silane -am ino propyl
- H 2O
Cohydrolysis of diet hoxydimethylsilane and -aminopropyldiethoxy methyl silane
Figure 1. I.R. spectra of novolac epoxy resin.
the presence of oxirane ring in epoxy resin.
The formation of amino silicone resin was also con-
Table 1. Characteristics of epoxy and silicone resins.
S.No. Sample Texture appearance
1. Novolac based epoxy resin
(epoxide equivalent= 190) Highly viscous,
water white in colour.
2. Amino silicone resin Viscous, pale yellow
Table 2. Formulation of coating samples.
SampleEpoxy resinMPDA Amino terminated sili-
cone resin (w/w)
EA 100 15. 0 --
EAS1 100 13. 5 1. 5
EAS2 100 12. 0 3. 0
EAS3 100 10. 5 4. 5
EAS4 100 9. 0 6. 0
EAS5 100 7. 5 7. 5
+ Cl – H2C – CH – CH2
Epoxy Novolac Resin
Copyright © 2011 SciRes. ACES
firmed by the I.R. spectral analysis. A peak was observed
at 1021 cm–1 referred as Si-O-Si linkage and a peak near
3369 cm–1 showed the presence of –NH2 group. The
spectrum is presented in Figure 2.
3.2. Evaluation of Film Properties
The cured films were evaluated for their optical, me-
chanical, chemical resistance and anticorrosive properties
as per the standard test methods viz. gloss at 60˚ (ASTM:
D523-99), scratch hardness (ASTM: D 5178), pencil hard-
ness (ASTM: D 3363-00), chemical resistance (ASTM:D
1308-87) and solvent resistance (ASTM:D 5402).
3.3. Mechanical Properties
The results of evaluation of various mechanical proper-
ties have been shown in Table 3.
a) Scratch hardness:
It was determined by using an automatic scratch hard-
ness tester (Sheen U.K.). The scratch hardness varies
from 1700 - 2000 g. It is clear from the data that as we
increase the silicone percentage the scratch hardness of
the film goes on increasing.
b) Pencil hardness:
It was measured by using pencil hardness tester (Sheen
U.K.). The coating films showed that it varies from 3H-
5H. Higher pencil hardness is due to higher silicone con-
c) Cross-hatch adhesion:
It was measured by using crosscut adhesion tester
(Sheen U.K.). All the coating films demonstrated good
cross-hatch adhesion.
d) Flexibility:
Flexibility was determined by using ¼ inch Mandrel
Bend tester (Sheen U.K.). Films of all the coating com-
positions passed ¼ in ch mandrel bend test. Based on th is
qualitative measurement, it can be said that all the films
had reasonably good flexibility.
e) Gloss:
It was measured by using triglossometer (Sheen U.K.).
On watching the films at 60˚ angle, it was observed that
all coating films had good gloss.
3.4. Chemical Resistance
The cured films of coating samples were tested for their
chemical resistance. The codified results of the chemical
resistance have bee n presented in Table 4.
a) Acid resistance:
To examine the acid resistance, coated films were
immersed in 1.0 N aqueous solution of sulfuric acid.
Results showed that all th e samples exhibit from good to
very good resistance against acid.
b) Alkali resistance:
To examine the alkali resistance, coated films were
immersed in 1.0 N aqueous solution of sodium hydroxide.
These films showed good to excellent resistance against
alkali. It was observed that sample with higher ratio of
silicone were found to be excellent.
c) Water resistance:
All the coated films exhibited very good to excellent
resistance against distilled water when they were ex-
posed to it.
d) Solvents resistance:
All the coated films exhibited very good to excellent
solvent resistance when they were exposed to non polar
solvents like xylene and mineral turpentine oil. Resis-
tance against MEK was fair to good because MEK is
very polar solvent. Samples with high silicone content
showed better performance than those having low con-
tent of silicone.
3.5. Salt-Spray Test Results
No visible corrosion products were seen on the surface of
the unscratched area of the coated panels at the end of
the salt-spray test. Corrosion products were seen mainly
on scratched area of the coated panels. Corrosion is
lower in the case of silicon ized epoxy coated pan els than
in epoxy. Siliconized epoxy coated panels show excel-
lent corrosion resistance in salt-spray test. The superior
corrosion resistance showed by coating systems may be
due to the inherent water repelling nature of silicone.
3.6. TGA Analysis
Figure 3 shows the TGA graph of the samples. Activa-
tion energy (E) for the thermal decomposition of sili-
conized epoxy has been evaluated from the dynamic
thermograms. The fractional decomposition for the re-
spective temperature has been evaluated from TGA
graph. Higher value of activation energy (see Table 5)
may be due to the presence of silicon in the resin. High
activation energy for the decomposition of system leads
to better thermal stability o f the compound [14,15].
4. Conclusions
Amino containing siliconised epoxy resin was synthe
sized. The spectral analysis, thermal stability, mechanical
and chemical resistance properties of siliconised epoxy
resins were studied using FTIR, TGA and standard
methods respectively. It was found that on increasing the
ratio of silicone resin, the thermal stability was increased
and the effect of amino silicone resin on epoxy resin im-
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Figure 2. I.R. spectra of aminosilicone resin.
Table 3. Mechanical properties of cured films.
S.No. Property EA EAS1 EAS2 EAS3 EAS4 EAS5
1. Scratch hardness (g) 1700 1750 1800 1850 1900 2000
2. Pencil hardness 3H 3H 4H 4H 4H 5H
3. Cross-hatch adhesion (%) 100 100 100 100 100 100
4. Flexibility (1/4” Mandrel) pass pass pass pass pass Pass
5. Gloss at 60˚ (%) 85 90 92 - 95 92 - 97 92 - 97 95 - 99
Table 4. Chemical resistance of cured films.
S.No. Property EA EAS1 EAS2 EAS3 EAS4 EAS5
1. 1.0 N H2SO4 G G G VG VG VG
2. 1.0 N NaOH G G VG VG VG E
3. Distilled water VG VG E E E E
4. Mineral turpentine oil VG VG VG E E E
5. Methyl ethyl ketone F F F F G G
6. Xylene VG VG VG E E E
P: poor; F: fair; G: good; VG: very good; E: excellent.
Copyright © 2011 SciRes. ACES
Figure 3. TGA graph.
Table 5. Activation energy of samples.
S.No. Sample Activation energy (j/mole)
1 EA 18.2
2 EAS1 20.1
3 EAS2 22.3
4 EAS3 22.5
5 EAS4 23.1
6 EAS5 24.2
proved anticorrosive properties.
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