TITLE:
A process for producing epoxy composite material with enhanced mechanical
properties.
FIELD OF THE INVENTION:
The present invention relates to a process for producing epoxy composite material with
enhanced mechanical properties.
BACKGROUND OF THE INVENTION:
The use of fillers in both thermoplastic and thermosetting polymers has been
common. The primary motivation for using various fillers in to polymers is to
obtain enhanced physical properties of the composite body besides achieving the
cost reduction. Conventionally, fillers are commercial grade material with particle
diameter of several microns. In recent years, usage of nano fillers have been
reported for achieving composite materials (both in thermoplastic and
thermosetting polymers) with enhanced electrical, mechanical, thermal and
environmental properties.
Fillers could be chemically active or inert in the composite matrix. When the fillers
are chemically inert, they are primarily extendersin the composites. However,
with the addition of an active filler material or in the form of active coating, fillers
can be utilized as reinforcements in the composites.

Calcium carbonate is the widely used extender type of filler for plastics. Calcium
carbonate is also been coated with stearic acid and calcium stearate to improve
rheological properties. Other organic materials, like, salts of alkylolamines and
long chain polyaminoamides (high molecular weight acids) have also been used
as extender type coating materials.
Alumino-silicate materials like, kaolin clay is another common material that is
used as extender in plastics, which is often treated with silane, polyester, and
metal hydroxide for surface modifications is also well known in this area.
Other aluminosilicate materials like, glass, asbestos group of materials, and
wollastoniteetc have been reported to be used as reinforcements with and
without combinations of various surface modifying agents and have been
used in various industrial applications.
Patent number DE 4037972 Al dated Jun 27. 1991 by Thomas et al
describes that a component with high electric field load capacity and long
term stability, used as an insulator in high voltage equipment is based on
an organic dielectric matrix in which fine inorganic additive particles are
finely dispersed. The novelty is that the particles consist of at least 80 wt.
% inorganic oxides (pref. A1203 or Ti02) make up 1-40 wt% of the total

component material and have a particle size of max. 1 micron. Pref. the
dielectric consists of plastics (e.g. polyethylene or epoxy resin). The
component has a high electric field strength peak value (e.g. up to 12
MV/cm) before breakdown and has long term stability.
Patent number US 8440121 B2, dated May 14, 2013 by Dunleavy et al describes
that a bulk dielectric material can include a solid composite material having a
solid matrix material and a plurality of filler elements distributed within the matrix
material. The bulk dielectric material can have, at a frequency of greater than
1MHz (i) a permittivity with a real part of magnitude greater than 10 and an
imaginary part of magnitude less than 3, and (ii) an electrical breakdown strength
greater than 5 kV/mm and can have a minimum dimension greater than 2 mm.
W02001089827 A1 dated 29 Nov 2001 by Ching Ping Wong et al describes that
the present invention is directed to polymer-ceramic composites having high
dielectric constants formed using polymers containing a metal acetylacetonate
(acacs) curing catalyst. In particular, it has been discovered that 5 weight percent
Co(lll) acac can increase the dielectric constant of DER661 epoxy by about 60 %.
The high dielectric polymers are combined with fillers, preferably ceramic fillers,
to form two phase composites having high dielectric constants. Composites

having about 30 to about 90 % volume ceramic loading and a high dielectric base
polymer, preferably epoxy, have been discovered to have a dielectric constants
greater than about 74 to about 150. Methods to increase the dielectric constant
of the two phase composites having high dielectric constants are also provided.
EP2228406 Al dated Sep 15, 2010 by Helmut Meyer etal (Bayer Material
Science AG) describes improved mechanical properties of epoxy filled with
functionalized carbon nanotubes. The invention deals with a methodology of
incorporating carbon nanotubes (CNTs) into an epoxy matrix and thereby
producing epoxy-based CNT nanocomposites. Both the pristine and ozonized
CNTs are almost homogeneously dispersed into the resin by this approach.
Compared with the pristine CNTs (p- MWCNTs), the ozonized ones (f-MWCNTs)
offer considerable improvements on mechanical properties within the epoxy
resin.
US20100130646 A1 dated 27 May 2010 by Soo.Jin Park, Jae-Rock Lee,
Etal, (Korea Institue of Chemical Technology) describes manufacturing
epoxy nanocomposite material containing vapor-grown carbonnanofibers
and its products thereby improving mechanical properties. The method

comprises physically mixing 0.1-5.0 parts by weight of vapor-grown carbon
nanofibers as reinforcing materials with 100 parts by weight of an epoxy
matrix resin to disperse the carbon nanofibers in the epoxy matrix resin,
adding a curing agent to the mixture, and curing the mixture, the vapor-
grown carbon nanofibers are sufficiently dispersed in the epoxy matrix
resin compared to the case of using a solvent. Therefore, it is possible to
produce an epoxy nanocomposite material having excellent mechanical
strength and low friction/wear properties at room temperature and
excellent thermal properties even at high temperature.
US8129463 B2 dated 6 Mar 2012 by Dongsheng Mao and ZviYaniv (Applied
NanoTech Holdings Inc.) describes Carbon nanotube-reinforced
nanocomposites for improving mechanical properties. It is found that
combination of MWNTs (herein, MWNTs have more than 2 walls) and DWNTs
significantly improves the mechanical properties of polymer nanocomposites. A
small amount of DWNTs reinforcement (<1 wt. %) significantly improves the
flexural strength of epoxy matrix nanocomposites. A same or similar amount of
MWNTs reinforcement significantly improves the flexural modulus (stiffness) of
epoxy matrix nanocomposites. Both flexural strength and flexural modulus of the

MWNTs and DWNTs-coreinforced epoxy nanocomposites are further improved
compared with same amount of either DWNTs or MWNTs-reinforced epoxy
nanocomposites. In this epoxy/DWNTs/MWNTs nanocomposite system,
SWNTs may also work instead of DWNTs. Besides epoxy, other thermoset
polymers may also work.
Science Direct Particuology 9 (2011) 80-85 described the shape and size
effects of ceria nanoparticles on the impact strength of ceria/epoxy resin
composites. By introducing ceria nanoparticles with controlled shapes and sizes
into epoxy resin, the enhancement in impact strength of the composites was
achieved. The ceria nanorods/EP composite shows the highest impact strength,
up to 17.27 kJ/m2 which is about four times that of the neat epoxy resin, due to
their special one-dimensional nanostructure. These composite materials
possess good mechanical performance and might be potentially applied in
various fields.
Science Direct Surface & Coatings Technology 201 (2007) 5269-5272 explains
the modified CTBN (carboxyl-terminated acrylonitrile-butadiene), ATBN (amine-

terminated butadiene acrylonitrile), BMI (1,3-bis (maleimido) benzene),
functionally terminated acrylates, poly (phenylene oxide) and alkylene oxides to
improve their mechanical properties nano-Si02 dispersed in epoxy resin. Impact
strength and thermal properties of epoxy resin have been improved by forming
inter cross-linked networks in epoxy resin with nano-Si02.
International Journal of Application or Innovation in Engineerings Management
(IJAIEM) Volume 2, Issue 11, November 2013 describes Epoxy matrix
reinforced by particles of silica and alumina with different weight fractions
for mechanical properties such as stress-strain and bending. The filler
particles content was varied from 2%, 4%, 6% and 8% by weight of total
matrix in the composites.
Material in technologize / Materials and technology 47 (2013) 3, 285-293
explains modification of a polymer matrix with silica fillers to increases in the
modulus and strength contributions of the matrix to the overall composite
properties.
Nano-science and Nano-engineering 1(2): 89-93, 2013 describes the mechanical
properties of epoxy polymer reinforced with nano-SiC particles, where the matrix

reinforced with silicon carbide nanoparticles with different weight percentage (5,
10,15 and 20) were studied for mechanical properties at room temperature. It is
observed that there is an increase in mechanical strength up to 10 to 20 wt. % of
filler loading and there is decrease the strength and strength decreases with
further increase in the weight percentage of the reinforcement
International Journal of Engineering Research and General Science Volume 2,
Issue 5, August-September, 2014 explains mechanical properties of epoxy
based hybrid composites reinforced with Sisal/SlC/Glass Fibres. In this study,
sisal/glass/Sic fibre reinforced epoxy composites are prepared and their
mechanical properties such as tensile strength, flexural strength and impact
strength are evaluated. Composites of silicon carbide filler (without filler, 3, 6 &
9wt %) sisal fibre and glass fibre are investigated. The results indicate that the
ultimate tensile strength for the composite without silicon carbide is higher than
the composite with silicon carbide filler, flexural strength for the composite with
silicon carbide of 3% filer is higher than the other composite.

Mat Res. vol.17 no.4 Sao Carlos July/Aug. 2014 Epub July 04, 2014 describes a
study on mechanical properties including traction, flexion, compression, and
hardness characteristics of a composite made from the combination of epoxy
resin and granitic stone powder. Two Granite types, named 53-A and 12-A, were
incorporated with different mass percentages of 0%, 30% and 50%, in the
polymeric matrix, DGEBA, formed by the Araldite polymer GY 279 and the curing
agent Aradur 2963. The test results with 50% show a compression of 79 MPa
with a maximum increase of 121% compared with the pure epoxy resin.
S. Mohamed Ghouse, S. Venkatesh, R.Rajesh. and S. Natarajan.
International Journal on Electrical Engineering and Informatics - Volume 5,
Number 4, December 2013] describes the electrical insulation system with
improved electrical break down strength using epoxy dielectric by
employing nano- fillers such as Titania and Silica. The research envisages
the use of epoxy resin mixed with nano-fillers for ascertaining the ability of
the nano-composite to be utilized as a dielectric/ insulator in power apparatus.
The epoxy resin is mixed with appropriate proportion of Si02 and TiO2 by-
high speed shear mixer. Classical breakdown voltage withstand tests such

as AC power frequency. DC voltage, lightning impulse and switching
impulse test is carried out on epoxy dielectrics (with and without nano-
fillers). The composites are shown to have improved breakdown strength
compared to unfilled epoxy.
Q. Wang and G. Chen, Advances in Materials Research, Vol. 1, No. 1
(2012) 93-107 describes that addition of 20 nm and 80 nm nano Si02 fillers
in different weight percentage to the epoxy by vacuum degassing and high
speed mixing process. The composites are shown to have decreased
electrical breakdown strength. Compared with both pure and micro filled
epoxy resin, for all epoxy resin nanocomposites, there is a reduction in
breakdown strength.
The present invention differs from the practices disclosed in the prior art. This
application does not use any conventional materials, like calcium carbonate, clay
or glass. Instead, this application use nano-sized fumed silica powder
incorporated into the commercial grade epoxy resin and hardener system
targeting enhancement of mechanical properties in the derived epoxy composite
material. This approach produces epoxy composite materials with enhanced
BDV by merely incorporating up to 4 wt% of the said filler material to that of the
blank epoxy system.

nRJECTS OF THE INVENTION:
An object of the present invention is to describe a process for producing epoxy
composite material with enhanced mechanical properties
Another object of the present invention is to modify the certain commercial grade of
epoxy resin material by incorporating appropriate filler material thereby fabricating the
modified epoxy composite that would have enhanced mechanical strength, which would
a superior insulation material as compare to the conventional epoxy resin cast body for
high voltage insulation and specifically to switchgear applications.
Still another object of the present invention is to specify the filler material, which
is nanostructured silicapowder with a tapdensity of about 0.054 g/cc, which is
available commercially from one or more sources.
Further object of the present invention is also to specify the level/s of loading of
nanostructured silicapowder filler material into the experimented epoxy system
so as to maximize the mechanical strength in the modified epoxy resin composite
body.

Still further object of the present invention is to define the processing conditions
and its process parameters etc for incorporation of the filler material and thereby
the fabrication of the modified epoxy composites with better mechanical strength.
BRIEF DESCRIPTION OF THE INVENTION:
According to this invention there is provided a process for producing epoxy
composite material with enhanced mechanical properties comprising: mixing the
filler material with one or more commercial epoxy resin material, flexibilizer,
accelerator and dispersing agent in pre-defined ratio to form a filler-mixed epoxy
resin, mixing a hardener material to the filler mixed epoxy resin; subjecting the
said filler-mixed epoxy mix to the step of casting heating the casted material in an
oven at a temperature range of 80 to 90°C; subjecting heated casted material
again to the step of heating in an oven at the temperature range of 140-150°c.
nPTAILED DESCRIPTION OF THE INVENTION
The invention describes the enhancement of mechanical strength of filler-
modified epoxy resin cast body using nanostructured silica powder as a
representative filler material, which is superior a candidate for various switchgear
applications. Nanostructured fumed silica powder that has a tap density in the
range 0.04 - 0.06 g/cc, preferably 0.054 g/cc, specific surface area of about 184

m2/g and average particle size (agglomerated) of about 472nm is mixed with
conventional epoxy resin, accelerator, flexibilizer, dispersing agent system in a
pre-defined ratio and then mixed with a hardener followed curing for fabricating
composite body. The said composite body shows enhancement of tensile
strength in the range of 25 - 55%, compressive strength 10 - 25% and flexural
strength 30 - 55% by loading the silica filler in the range of 1 - 4 wt% in a
commercial grade of epoxy resin material. The modified resin composite body
could be used in the area of high voltage insulation switchgear applications.
According to this invention, there is provided a process along with its parameters
for fabricating an epoxy resin composite body, which is modified by an identified
filler material, i.e., nanostructured silica having tap density of 0.054 g/cc for
achieving enhanced mechanical strength in the filler-modified composite body as
compare to its conventional epoxy resin body.
The incorporation and fabrication of the nano-structured silica filler modified
composites, comprise the following steps:

Mixing the filler material with one or more commercial epoxy resin (bisphenol-A)
flexibilizer (polyglycol based liquid) and accelerator (tertiary amine based liquid)
and dispersing agent (y-butyrolactone) in pre-defined ratio in order to obtain a
"filler-mixed epoxy resin"
Mixing the "filler-mixed epoxy resin" with one hardener material (carboxylic acid
based anhydride) under vacuum of about 20-30 mbar
Casting the thus-derived material into moulds as per the dimension/shape of the
components/specimens by maintaining vacuum level in the range of 1-5 mbar
Heat treatment of the casted body in air in an oven in the temperature range of
80- 90°C preferably at 80°C for a period of 6 - 8 hours, which results pre-cured
filler modified epoxy resin composite body
Heat treatment of the procured filler modified epoxy resin composite body in air in
an oven in the temperature range of 140° - 150°C preferably at 140°C for a
period of 6-8 hours, which results fully cured "nanostructured crystalline silica
modified epoxy resin

composite bodyTesting of thus-derived ' nanostructured silica modified epoxy resin
composite body" for mechanical properties as per IEC standard
The present invention refers to fabrication of nanostructured silica filler modified
epoxy body with enhanced mechanical strength, which is a better insulating
material for various switchgear applications.
According to the present invention, there is provided a process for incorporating
nanostructured silica filler material for fabricating epoxy composite body with
enhanced mechanical strength, which is disclosed in this invention.
In a more particular embodiment of the present invention, the properties are
defined in the Table 1 (below). As described, the filler material, i.e.,
nanostructured silica has properties, as given in the below.


As per the invention, the said nano structured silica filler material is mixed with
the epoxy resin ( bisphenol A) along with flexibilizer (polyglycol based liquid),
accelerator (tertiary amine based liquid) and dispersing agent in predetermined
weight ratio using a mixing machine for a period of about 20 hrs.
The resultant material is then mixed with hardener liquid for a period of another
about 2 hrs, which is then vacuum mixed for a period of about 45 min.
The resultant material is then casted as per the shape/ size of component, which
is then to be heat treated at a temperature of about 80°C for a period of 6 hrs,
which results in pre- cured body.
The pre-cured body is to be post cured in air at a set temperature range of about
140°C for a period of about 6 hrs in order to get the silica filler modified epoxy
composite body.
The filler -modified epoxy composites are then tested for mechanical
properties (tensile, compression and flexural) using standard dimensions of
the test samples as per IEC norms.

Table 1 represents mechanical properties of the silica filler-modified epoxy
composites as compared to blank conventional epoxy system, all of which have
been processed under identical conditions

EP: Commercial Epoxy (without any filler material- blank)
EFI: Commercial Epoxy + 1% Silica
filler EF2: Commercial Epoxy + 2%
Silica filler
EF3: Commercial Epoxy + 3% Silica
filler
EF4: Commercial Epoxy + 4% Silica
filler

WE CLAIM:
1. A process for producing epoxy composite material with enhanced mechanical
properties comprising:
mixing the filler material with one or more commercial epoxy resin material,
flexibilizer, accelerator and dispersing agent in pre-defined ratio to form a
filler-mixed epoxy resin,
mixing a hardener material to the filler mixed epoxy resin;
subjecting the said filler-mixed epoxy mix to the step of casting heating the
casted material in an oven at a temperature range of 80 to 90°C;
subjecting heated casted material again to the step of heating in an oven at
the temperature range of 140-150°c.
2. The process as claimed in claim 1 wherein the epoxy resin material is bis-
phenol-A epoxy resin, flexibilizer is polyglycol based liquid, accelerator is
tertiary amine based liquid and dispersing agent is (y-butyrolactone).
3. The process as claimed in claim 1, wherein the said hardener material is
carboxylic acid based anhydride.

4. The process as claimed in claim 1 wherein the said hardener material is
mixed with epoxy resin under vacuum of about 20-30 mbar.
5. The process as claimed in claim 1 wherein the said step of casting is
preferred by maintaining vacuum level in the range of 1 to 5 mbar.
6. The process as claimed in claim 1 wherein the step of heating is preferred
preferably at 80°C for a period of 6 - 8 hours.
7. The process as claimed in claim 1 wherein the step of heating the casted
material is preferred at preferably at 140°C for a period of 6 to 8 hours.