Title:
Basalt Mat Fabric-epoxy resin composite with better dielectric property of dissipation
factor.
FIELD OF INVENTION:
This invention relates to basalt mat fabric-epoxy resin composite with better dielectric
property of dissipation factor.
BACKGROUND OF THE INVENTION:
The use of glass fabric-epoxy resin laminates as electrical insulating material is an
established prior art for years together and is very common. Conventionally, glass
fabrics are commercial grade material with fabrics of various thickness as well as
densities. In recent years, different fabrics such as carbon fabrics, S-glass fabrics
have been reported to be introduced in order to achieve composite laminates with
enhanced mechanical, thermal and environmental properties. While targeting the
enhancement of electrical properties, particularly for high voltage electrical insulation
applications, the dissipation factor of these laminates are of significant interest.
European Patent Number EP137715 B1 is an invention relating to a flexible product
comprising a basalt fabric provided with a coating layer. The flexible product of the
invention, as per the claim, consist of at least a polyester polyurethane coating layer
coating at least partly a face of the fabric.

Ths Patent Number WO 2009/109216 A1 describes an electrical article like an
electrical hollow core insulator wherein the wall of said electrical insulator is made
from a fibre reinforced organic polymer composite system comprising a hardened or
cured electrically insulating matrix resin composition and a reinforcing fibre
comprising an outer layer and an inner layer, wherein the outer layer of the wall is
reinforced with a corrosion sensitive fibre having the inner layer of the wall
reinforced with a corrosion resistant fibre selected fibre preferably being poly-
ethyleneterephthalate (PET) or alumina.
The patent Number WO2004/101872 A1 describes a thin polyester polyurethane
coating on at least one face of a basalt fabric and a metallic reinforcing element for a
fire resistant product having specified abrasion resistance.
The patent US7740925B2 describes an invention of a laminate consisting of a
substrate layer, a knitted porous layer disposed in a thermoplastic material and an
epoxy resin to form a bagging hopper or vibratory panel.
The patent Number US4913955 describes an invention of an epoxy resin laminate of
glass fibre woven cloth with the outer layers made of organic fibre.
The patent number WO2012/078058 A1 describes an invention of flame retardant
epoxy resins and epoxy glass reinforced laminates.
The patent number EP0040848 A1 describes the electrical laminate comprising a
plurality of fibrous cellulosic substrate layers and alternately interposed layers of

cured epoxy or unsaturated polyester resin between the adjacent substrate layers,
wherein each of the substrate layers is embedded in a matrix of said cured resin
which is substantially integral with said layers of cured resin.
The present invention differs from the practices disclosed in the prior art. This
invention does not use any conventional fabrics like glass fabric. Instead, this
invention utilizes the Basalt Mat and Fabric for the preparation of the laminate. This
material is arranged one layer over the other in a suitable die and vacuum moulded
under heat with an epoxy resin system consisting of a bisphenol A epoxy, a suitable
carboxylic acid anhydride based liquid hardener and the tertiary amine accelerator to
obtain a laminate. This approach produces Basalt mat fabric-epoxy resin composite
laminate with better dielectric properties of improved dissipation factor and better
thermal conductivity.
OBJECTS OF THE INVENTION:
An object of the invention is to prepare a Basalt mat fabric-epoxy resin composite
laminate suitable for application as an electrical insulating material.
Another object is to prepare the Basalt mat fabric-epoxy resin composite laminate
using commercially available epoxy resin system consisting of a bisphenol A epoxy,
a suitable carboxylic acid anhydride based liquid hardener and the tertiary amine
accelerator to obtain composite laminate suitable for application as an electrically
insulating material.

Yet another object is to prepare the Basalt mat fabric-epoxy resin composite
laminate using an impregnating process under vacuum and heating to obtain
composite laminate suitable for application as an electrical insulating material.
A further object is to prepare the Basalt mat fabric-epoxy resin composite laminate
with better dielectric properties of improved dissipation factor and better thermal
conductivity.
BRIEF DESCRIPTION OF THE INVENTION:
This invention relates to a process for preparing basalt mat fabric-epoxy resin
composite with better dielectric property of dissipation factor comprising: preparing
epoxy resin system consisting of bisphenol A epoxy, carboxylic acid anhydride
based liquid hardener and tertiary amine accelerator, arranging the suitably cut
basalt mat in a die and closing the die to ensure it is leak proof, casting the resin
mixture into moulds, subjecting the said casted moulds to the step of heat treatment
in an oven at 80-90°C to produce pre-cured basalt fabric-resin body, heating the said
pre-cured basalt mat fabric in an oven at 140°C - 150°C to produce fully cured basalt
fabric-epoxy resin composite laminate.

DETAILED DESCRIPTION OF THE INVENTION:
The present invention refers to the preparation of the Basalt mat fabric-epoxy resin
composite laminate following pre-defined procedure and process parameters, which
has better dielectric properties of improved dissipation factor and better thermal
conductivity, which would serve as an electrical insulation in high voltage
applications.
In a more particular embodiment of the present invention, the Basalt mat and fabric
of 200 grams per square meter density and a thickness of 0.15 to 0.20 millimetres
each is chosen in this invention. The material is to be dried in the temperature range
of 90-100 degree Celsius for a period of 30 -60 minutes to make it dry and free of
moisture before using.
As per the invention, 15 to 18 pieces of Basalt mat fabric of 200 grams per square
meter density and a thickness of 0.15 to 0.20 millimetre each are dried in the
temperature range of 90 - 100 degree Celsius for a period of 20-40 minutes to make
it dry and free of moisture. The dried basalt mat fabric pieces are stacked one over
the other inside the cavity of the pre-fabricated die and then the cavity is closed with
the cover securely using the required nuts and bolts.
As per the invention, a commercially available liquid epoxy resin system of bisphenol
A epoxy resin is mixed with the carboxylic acid anhydride based liquid hardener and
the tertiary amine accelerator in pre-determined proportions using an anchor shaped
laboratory mixer with de-gassing attachment for a period of 30 - 60 minutes,
maintaining a vacuum level of 3 - 5 mbar.

The mixed epoxy resin system is admitted into the cavity of the die containing the
basalt fabrics and de-gassed under heat of set temperature of 80 - 90 degree
Celsius preferably at 80 Celsius for a period of 1 - 2 hours. The temperature is then
increased 140-150 Celsius preferably at 140 Celsius for a period of 4 - 6 hours and
then is cooled down to ambient temperature.
The die is then opened to obtain the Basalt mat fabric-epoxy resin composite
laminate.
The Basalt mat fabric-epoxy resin composite laminate are then tested for the
dielectric property of dissipation factor.
According to this invention, there is provided a process along with its parameters for
the preparation of Basalt mat fabric-epoxy resin composite laminate using an
impregnating process under vacuum and heating obtain composite laminate for
achieving better dielectric properties of improved dissipation factor and better
thermal conductivity.
The process of preparation of the Basalt mat fabric-epoxy resin composite laminate
comprises the following steps:
a) Cutting the.Basalt Mat and Fabric to a suitable size
b) Preparing the commercially available epoxy resin system consisting of a
bisphenol A epoxy, carboxylic acid anhydride based liquid hardener and
the tertiary amine accelerator and degassing the mixture under vacuum to
remove the entrapped gases inside the resin mixture

c) Arranging the required number of suitably cut Basalt mat and fabric in a
cavity of a suitable die and closing the die with suitable nuts and bolts to
obtain a leak proof cavity containing the basalt fabric
d) Casting the resin mixture into moulds as per the dimension/shape of the
components/specimens and ensuring thereby de-gassing as well during
casting in order to remove the air bubble in the composite body
e) 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 basalt fabric - resin body
f) Heat treatment of the pre-cured Basalt mat fabric - resin 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 basalt fabric - epoxy resin
composite laminate
g) Opening the nuts and bolts of the die to obtain the fully cured Basalt mat
fabric-epoxy resin composite laminate
h) Testing of the Basalt mat fabric-epoxy resin composite laminate for the
better dielectric property of improved dissipation factor.

The invention would be more understood in terms of taking various examples, which
are explained in the following:
EXAMPLE .1:
2 pieces of Basalt fabric of 200 grams per square meter density and a thickness of
0.20 millimetres and 13 pieces of Basalt mat of 200 grams per square meter density
and a thickness of 0.20 millimetres are dried at the temperature of 90 degree Celsius
for a period of 40 minutes to make it dry and free of moisture. The dried Basalt mat
and fabric pieces are stacked one over the other inside the cavity of the pre-
fabricated die having an inside cavity of 140-150 millimetre x 140-150 millimetre x
2.5-3 millimetre in such a manner that the top and bottom layers are Basalt fabric
and the Basalt mat is sandwiched between the top and bottom layers of Basalt fabric
and then the cavity is closed with the cover securely using the required nuts and
bolts. A commercially available liquid epoxy resin system of bisphenol A epoxy resin
(30-40 grams) is mixed with the carboxylic acid anhydride based liquid hardener
(30-40 grams) and the tertiary amine accelerator (6-10 grams) using an anchor
shaped laboratory mixer with de-gassing attachment for a period of 40 minutes,
maintaining a vacuum level of 3 - 5 mbar.
The mixed epoxy resin system is admitted into the cavity of the die containing the
basalt fabrics and de-gassed under heat of set temperature of 80 degree Celsius for
a period of 1 hour. The temperature is then increased 140 for a period of 4 - 6 hours
and then is cooled down to ambient temperature.

The die is then opened to obtain the basalt fabric - epoxy resin composite laminate.
The basalt fabric - epoxy composite laminates are then tested for the better
dielectric properties of improved dissipation factor.
For comparison, specimens with conventional cast samples of commercially
available liquid epoxy resin system of bisphenol A epoxy resin mixed with the
carboxylic acid anhydride based liquid hardener and the tertiary amine accelerator
as well as conventional composite laminate specimen of glass fabric and
commercially available liquid epoxy resin system of bisphenol A epoxy resin mixed
with the carboxylic acid anhydride based liquid, hardener and the tertiary amine
accelerator in the same proportions and the process were also prepared and the
dielectric property of dissipation factor compared under identical conditions.
The derived Basalt mat fabric - epoxy composite laminate showed an improved
dissipation factor and better thermal conductivity, which are much better than that of
the cast epoxy samples and glass fabric - epoxy resin composite laminate (Table 1
&2).
Example 2 :
In this example, the procedure arid all the experimental parameters and conditions
thereof remained the same as that of as described in the Example 1, except that the
pieces of Basalt mat was 16 pieces instead of 15 pieces, sandwiched between the
top and bottom layers of Basalt fabric.

The derived Basalt mat fabric - epoxy composite laminate showed an improved
dissipation factor and better thermal conductivity, which are much better than that of
the cast epoxy samples and glass fabric - epoxy resin composite laminate (Table 1).
Example 3 :
In this example, the procedure and all the experimental parameters and conditions
thereof remained the same as that of as described in the Example 1, except that the
pieces of Basalt mat was 18 pieces instead of 15 pieces, sandwiched between the
top and bottom layers of Basalt fabric.
The derived Basalt mat fabric - epoxy composite laminate showed an improved
dissipation factor and better thermal conductivity, which are much better than that of
the cast epoxy samples and glass fabric - epoxy resin composite laminate (Table 1).
The Table 1 represents the Dissipation factor of the Basalt mat fabric - epoxy
composite laminate in comparison with pure epoxy casting and glass fabric - epoxy'
composite laminate.

WE CLAIM:
1. A process for preparing basalt mat fabric-epoxy resin composite with better
dielectric property of dissipation factor comprising: preparing epoxy resin system
consisting of bisphenol A epoxy, carboxylic acid anhydride based liquid hardener
and tertiary amine accelerator, arranging the suitably cut basalt mat in a die and
closing the die to ensure it is leak proof, casting the resin mixture into moulds,
subjecting the said casted moulds to the step of heat treatment in an oven at 80-
90°C to produce pre-cured basalt fabric-resin body, heating the said pre-cured basalt
mat fabric in an oven at 140°C - 150°C to produce fully cured basalt fabric-epoxy
resin composite laminate.
2. The process as claimed in claim 1, wherein the said epoxy resin system is
required to be degassed under vacuum to remove the entrapped gases inside the
resin mixture.
3. The process as claimed in claim 1, wherein the said resin mixture is also
degassed during casting to remove air bubble.

4. The process as claimed in claim 1, wherein the preferred temperature to produce
pre-cured basalt fabric-resin body is 80-90°C and the required time period is 6 to
8hrs.
5. The process as claimed in claim 1, wherein the preferred temperature required to
produced fully-cured basalt fabric-epoxy resin composite laminate is 140-150°C and
the time period is 6 to 8 hours.
6. The fully cured basalt fabric-epoxy resin composite laminate as claimed in claim 5
was tested for the desired dielectric dissipation factor values which are given in
Table 1.