Field of Invention
[0001] The present invention relates to test protocol introduced for examining
leaching property of end winding sealing tape in Vacuum Pressure Impregnation
(VPI) resin hardener mixture. More specifically, the present invention relates to
the protocol for examining leaching property of end winding sealing tape in epoxy
resin hardener mixture.
Background of Invention
[0002] Leaching is the process of the pollutant becoming detached or extracted
from carrier into the solvent. It is not desirable for the particular application
where the end winding sealing tape is applied. Understanding leaching
characteristics is important in understanding the leaching process and giving
feedback for making necessary improvements in the manufacturing process/
raw materials of end winding sealing tape. The process of leaching however is
specific to the type of test materials used and testing parameters employed and
often different methodologies will produce different results.
[0003] The end winding sealing tape to BP-25795 is used on the overhang
portion of VPI design stator coils for compacting the end winding portion after
impregnation and curing and stopping resin from flowing out during curing as
the tape shrinks at elevated temperature. The tape contains polyester glass
mixed fabric and polyester film bound together by varnish. The varnish contains
mowital / epoxy resin and Red coloured dye/ pigment.
[0004] The leaching test is carried out to ascertain that during the VPI process,
this red coloured dye/ pigment, does not leach into the VPI resin hardener mix
and deteriorate it. So this test methodology is mandatorily required for
assessment of new vendors during the development stage of end winding sealing
tape.

Objects of the Invention
[0005] The principal object of the present invention is to provide a suitable
protocol for conducting test and observing the leaching from the tape in epoxy
resin mixture at elevated temperature.
[0006] Another object of the present invention is to provide a simple and unique
method for examining the leaching property of end winding sealing tape in epoxy
resin hardener mixture.
[0007] Another object of the present invention is to provide a well-established
method for the evaluation of new materials and vendors and giving feedback to
vendors for improvement.
[0008] Another object of the present invention is to provide a suitable protocol
for conducting test that greatly helped in proper testing of tape samples for
alternate material/ source development.
Summary of the Invention
[0009] The present invention discloses a method for examining leaching property
of end winding sealing tape wherein resin and hardener mix solution is prepared
and heated in well calibrated temperature controlled oven at around 65°C for
about half an hour. There after it is allowed to settle for some time and samples
of end winding sealing tape are added. The resin hardener mixture containing
the tapes is heated for 04 to 06 hours at 65°C±5°C. Allow the tape to remain
dipped in resin and hardener mix during this process and then cool and analyse
the leaching property of the tape samples. The resin and hardener are to be
mixed in the ratio of 45: 55 respectively by weight. The resin is Bisphenol, A
epoxy resin and the hardener used is acid anhydride hardener. The quantity of
resin and hardener mix to be taken is 250 ml to 300ml. Further the samples of
tape used is 1 meter long samples of BP25795 tapes.

Brief description of the drawings
[0010] The nature and scope of the present will be better understood from
accompanying pictures which are by way of illustration of a preferred
embodiment and not by way of any sort of limitation.
[0011] Figure 1 shows the beakers containing resin and hardener mix.
[0012] Figure 2 shows the beakers containing resin and hardener mix solution
and tape dipped therein.
[0013] Figure 3 shows the sample after heating and cooling.
[0014] Figure 4 shows the analysis of the sample.
[0015] The figures depict embodiments of the disclosure for purposes of
illustration only.
[0016] One skilled in the art will readily recognize from the following description
that alternative embodiments of the structures and process illustrated herein
may be employed without departing from the principles of the disclosure
described herein.
[0017] Various objects, features, aspects, and advantages of the inventive
subject matter will become more apparent from the following detailed description
of preferred embodiments, along with the accompanying pictures.
Detailed Description of the Invention
[0018] While the embodiments of the disclosure are subject to various
modifications and alternative forms, specific embodiment thereof have been
shown by way of example in the figures and will be described below. It should be
understood, however, that it is not intended to limit the disclosure to the
particular forms disclosed, but on the contrary, the disclosure is to cover all
modifications, equivalents, and alternative falling within the scope of the
disclosure.

Materials required
[0019] For conducting the leaching test, the materials required are resin and
hardener mix from the VPI Plant, under development sample/ in process sample
tape roll, reference tape roll of already approved vendor, beakers and oven.
[0020] The observations to be made after conducting the leaching test are as
follows:
a. Dye from the tape should not leach in resin and hardener mix solution.
b. The colour and viscosity of the resin and hardener mix solution should not
change remarkably before and after carrying out the test.
c. The polyester film of end seal tape should easily separate from the glass
polyester mix fabric.
d. There is no/minimal transfer of colour on the polyester film after separation.
The test procedure for examining leaching property of the tape is described as
here under.
[0021] The resin and the hardener solution mix taken for the test must be clear,
free from air bubbles, moisture and contamination and should be colorless. If
the resin and hardener are taken separately and are to be mixed, they should be
taken in the ratio of 45 : 55 respectively by weight. The material to be taken for
testing is 1-meter long samples of BP25795 tapes. One sample of approved
vendor’s tape is to be kept for reference and comparative evaluation.
[0022] Approximately 250 to 300 ml of resin and hardener mix is taken in clean
and uncontaminated beakers so that the tape samples must completely sink in
the mix fully. As many beakers are taken as there are number of tapes to be
tested. The identification tag must be pasted on each beaker for each tape
properly with complete details.
[0023] Beakers containing Resin and Hardener mix are heated in well calibrated
temperature controlled oven at around 65°C for about half an hour so that no

traces of air bubble/moisture should be present in the resin mix. This is nearly
the impregnation temperature. Thereafter, the beakers containing resin and
hardener mix are removed from the oven gently and allowed to settle down for a
while.
[0024] Each 1 m long, sample tape is dipped in respective resin and hardener
mix solution so that it is fully submerged in the beakers. After putting tapes in
beakers, the same are kept in oven and heated for 04 to 06 hours (05 hours as
a standard practice in ISE Lab) at 65°C±5°C. The temperature of the oven must
be closely monitored so that no significant variation in temperature takes place.
4 to 6 Hours is approximately the impregnation and pressurization time in which
tape remains dipped in resin and hardener mix during VPI process. After
approximately 5 hours of continuous heating, the oven is switched off and after
some cooling, the beakers having BP25795 tape samples are taken out for proper
analysis. No or minimal leaching should occur. Also the film and cloth should
separated easily and there should be no or minimal transfer of dye on the
polyester film.
[0025] The test may be repeated in case of any doubt and interruption. Complete
comparative analysis must be done with the standard reference tape. After
proper analysis, observations are recorded for further course of action and
follow-up.
Example
[0026] 250 to 300 ml of resin and hardener mixture (in the ratio of 45: 55 by
weight) was taken in a clean and uncontaminated beaker. The resin hardener
mix should be clear, colourless, and free from air bubbles, moisture &
contamination. The beaker containing Resin and Hardener mix is heated in a
temperature controlled oven at 65 ± 5° C for half an hour to remove traces of air
bubble/moisture present in the resin and hardener mix. The beaker containing
resin and hardener mix was removed from the oven gently and allowed to settle
down for a while. One meter long, BP 25795 tape sample was dipped in resin

and hardener mix in the beaker so that it is fully submerged. The beaker along
with the submerged tape sample was kept in oven and heated for 4 to 6 hours
at 65 ± 5° C. The oven was switched off and allowed to cool to room temperature.
The BP25795 tape sample was taken out from the beaker for checking the
leaching property. The colour of the residual resin hardener mix after removal of
tape was as earlier i.e. colourless and clear. There was no transfer of red colour
(leaching) from the tape to the resin hardener mix. In addition, the film and cloth
from the tape separated easily and there was no / minimal transfer of dye on the
polyester film.
[0027] The advantages of the process are as follows:
The present invention is a simple methodology for examining leaching property
of end winding sealing tape in epoxy resin hardener mixture. It ensures the
proper treatment of tape as per the process requirement. In addition, it ensures
the visual assessment for technical suitability of the material. It has the
possibility of testing several samples at a time. Further, it is a simple and user-
friendly process for conducting the test and does not require any major or special
test set-up.
[0028] It will be appreciated by those skilled in the art that the present invention
can be embodied in other specific forms without departing from the essential
characteristics thereof. The presently disclosed embodiments are therefore
considered in all respects to be illustrative and not restricted. The scope of the
invention is indicated by the appended claims rather than the foregoing
description and all changes that come within the meaning and range and
equivalence thereof are intended to be embraced therein.

We Claim
1. A method for examining leaching property of end winding sealing tape
characterised in that
take resin and hardener mix solution;
heated in well calibrated temperature controlled oven at around 65 ⁰C for
about half an hour;
allow to settle;
add samples of tapes;
heated for 04 to 06 hours at 65°C±5°C;
allow the tape to remain dipped in resin and hardener mix during heating
process;
allow to cool and
analyse the leaching property of the tape samples.
2. The method as claimed in claim 1 wherein the resin and hardener to be
mixed are in the ratio of 45: 55 respectively by weight.
3. The method as claimed in claim 1 wherein the resin used is Bisphenol A
epoxy resin and hardener used is acid anhydride hardener.
4. The method as claimed in claim 1 wherein the quantity of resin and
hardener mix is 250 ml to 300ml.
5. The method as claimed in claim 1 wherein the samples of tape used is 1
meter long samples of BP25795 tapes.