For using two component glue. Total thickness of the

 

For the 1st two samples we used poled PVDF films. Using these
films we prepared bi and multilayer films. The aluminium film on one side of
the film has been removed by etching. The films were glued together in the
reverse dipole moment direction using two component glue.

For the 2nd two samples we used P (VDF-TrFE) 56/44 mol% and P
(VDF-TrFE) 70/30 mol% composite granulate. From these composite granulate, we
prepared films by using hot press. These films are unpoled. Films were glued
together using two component glue.

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S1: Sample one consists of two PVDF films, each film thickness is 9µm. These
two films glued together in the reverse dipole moment direction using two
component glue. Total thickness of the films is 21µm

 

S2: Sample two consists of three PVDF films, each film thickness is 9µm.
These three films glued together in the reverse dipole moment direction using
two component glue. Total thickness of the films is 30µm

 

S3: Sample three consists of two P(VDF-TrFE) films with different molar
and weight ratios one side is P(VDF-TrFE) 56/44 mol%, 10µm and the other side
P(VDF-TrFE) 70/30 mol%, 10µm. These two films glued together using two
component glue. Total thickness of the films is 23µm

 

S4: Sample three consists of two P (VDF-TrFE) films with different molar
and weight ratios one side is P (VDF-TrFE) 56/44 mol%, 10µm and the other side
P(VDF-TrFE) 70/30 mol%, 10µm. These two films glued together using two
component glue. Total thickness of the films is 25µm

 

S5: Sample three consists of two P (VDF-TrFE) films with different molar
and weight ratios one side is P (VDF-TrFE) 56/44 mol%, 13µm and the other side
P(VDF-TrFE) 70/30 mol%, 13µm. These two films glued together using two
component glue. Total thickness of the films is 30µm

S6: Sample three consists of two P (VDF-TrFE) films with different molar
and weight ratios one side is P (VDF-TrFE) 56/44 mol%, 15µm and the other side
P (VDF-TrFE) 70/30 mol%, 15µm. These two films glued together using two
component glue. Total thickness of the films is 33µm

3.1 Hot Press:

The film maker and its cooling system are packed in a protective plastic
case. The contents of the case are as follows:-

1 Film Maker, comprising top platen, bottom platen and guiding ring

1 Cooling Chamber

A set of spacer rings as listed below. These are engraved to denote
nominal thickness to be produced:-

Spacer rings                Thickness

A                                  15µm

B                                  25µm

C                                  50µm

D                                  150µm

E                                  250µm

F                                  500µm

 

1 Pack of 200 AI foil discs

1 Stainless steel forceps

20 Specacards

Heated platens with 20° – 300°C temperature Controller 220-240V, 50Hz

 

INSTALLATION AND OPERATION

1. Connect the cooling system to a cold water supply and drain via the
inlet/outlet ports on the rear of the unit.

2. Assemble the Specac Heated Platens on the press according to the
instructions supplied and set to the required pressing temperature 180degree
centigrade.

3. Select the spacer ring for the required thickness and locate the ring
on the bottom platen of the film maker around the central raised polished
surface.

4. Place the guiding ring around the spacer.

5. Place one aluminium foil disc on the bottom platen of the film maker
locating it inside the spacer ring. If a reduction in spectroscopic
interference fringes is sought, this disc should be placed matt surface
uppermost. Conversely if fringes are required, for example to measure
thickness, place the shiny surface uppermost.

6. Place the sample to be pressed on the foil disc and locate the top
platen of the film maker (polished surface facing down) on top of the sample
using the guiding ring for location. The handle of the top platen should be
located between the guiding pins on the bottom platen.

7. Locate the assembled film maker centrally between the heated platens
on the press so that the top platen makes contact with the film maker. Allow
approx 5 minutes for the film maker to reach the required temperature. If
required a thermocouple may be inserted into a drilled hole in either the top
platen or guiding ring. As the sample softens the top bolster of the press may
be screwed down further.

8. Tighten the locking nut on the press and pump until the required load
(4 tons) is reached. Allow the film maker to remain under load for 3-4 minutes
then release.

9. Transfer the film maker to the cooling unit.

10. The film maker may be removed from the cooling unit after 3-5
minutes depending on original temperature and water flow rate. Close the lid of
the cooling unit between Operations to allow self-cooling.

11. Disassemble the film maker by lifting the top platen. This should
come away easily. For emergency use a release lever is provided on the
right-hand side of the bottom platen.

12. The pressed film will be removed with the top platen together with
the foil disc. Use the forceps provided to remove the foil disc and then the
sample.

13. The sample may be mounted in a Specacard (P/N 3800 or 3810) or a
magnetic film holder (P/N 3820) for spectroscopic analysis.

NOTES ON TOLERANCE

The spacer rings have manufacturing tolerances such that the sample
thickness tolerances are +/- 3µm for rings A and B and +/- 10µm for all other
rings. This refers to the absolute thickness produced; once a pressing cycle
has been established reproducibility will be greater than this tolerance.

Spacer rings A and B are engraved with a series of one to four dots. To
achieve the stated tolerance it is essential that the number of dots matches
the number engraved adjacent to the polished surface on the bottom platen. If
replacement rings or bottom platen are required please specify this number of
dots.

Both the bottom and top polished surfaces are removable from the platens
by releasing the three locating screws in each case. Should it be necessary
these surfaces may then be returned to Specac for repolishing. Repolishing of
the bottom surface will obviously affect the thickness produced in subsequent
pressings but reproducibility will be maintained. 3

3.2 Aluminium etching:

Aluminium on PVDF film surfaces should be removed because due to small
amount of aluminium on surface of PVDF can deviate the polarization results

We need three components to remove aluminium

NAOH solution

1 beaker

1 tweezer

Hand gloves

Take NAOH solution and pour it in the
beaker till half of the beaker.
Hold the PVDF film with tweezer and
place it in the solution.
Using tweezer itself stir the
solution continuously until 5 minutes
After 5 minutes aluminium layer on
PVDF film gets removed. Now we can use this films for our experiment

Make sure NAOH solution is pure.

3.3 Electrode deposition:

Electrode deposition was done by thermal evaporation of Aluminium. To
get the desired shape of the bottom electrodes, a mask was aligned on top of
the samples. And To get the desired shape of the top electrodes, a mask was
aligned on bottom of the samples. The mask had initially been designed to
produce single-layer samples. 4

 

3.4 Poling PVDF:

In order for the smart composite structure to generate responses due to
an applied load, the PVDF material must be polarized to align the dipole
moments of its crystalline structure. The crystalline structure of the PVDF
film will determine the polarization properties of the film. There are four
possible crystalline forms of the PVDF polymer: the alpha, beta, gamma, and
delta phases 17. Only the beta, gamma, and delta phases can be polarized.
However, the alpha phase can also be polarized by applying a large electric
field, which will convert the alpha phase to the delta phase 17. The
processing conditions of the PVDF film determine the dominant crystalline
phase. When the PVDF film layers in the composite samples are melted and
solidified, the dominate phase is the alpha crystalline phase 18. Since the
alpha phase is the dominate phase upon solidification, an electric field must
be applied to convert the alpha phase to the delta phase and to align the
dipoles for the proposed smart composite structures. Existing research shows
that an electric field of around 125 MV m?1 is required to fully polarize a
predominately alpha phase PVDF film 19. However, a higher piezoelectric
coefficient can be attained by polarizing a beta phase film since the beta
crystal phase has a greater dipole moment than the delta phase 20. One of the
most common means mentioned in the literature to achieve a predominately beta
phase PVDF film is to stretch the film mechanically to many times its original
length 21. A second method to transition from an alpha phase film to a beta
phase film is to apply a very high electric field on the order of 500 MV m?1
19. A third method mentioned in the literature to achieve a predominately
beta phase PVDF film is to cure the film under high pressure 22. Finally, the
copolymers of PVDF containing trifluoroethylene (TrFE) or tetrafluoroethylene
can be added to the film to encourage the formation of the beta phase 23.

 

3.4.1. Polarization
set up

During hot press pvdf film looses small amount of polarization because
of high temperature. To conduct polarization measurements we need fully polarized
film. So we used one method to increase its polarization.

For that method we need equipment set up. The following figure shows the
set up to increase polarization in pvdf film.

1.  
Function gernerator

2.  
Oscillator

3.  
Sample holder

4.  
Resistance box

5.  
Voltage amplifier

Figure 5:
Polarization set up

 

1.     Connect function
generator input wire to voltage amplifier input

2.     Reistance box input
wire  to sample holder input

3.     Resistance box output
wire to oscillator output

4.     Amplifier output wire
to sample holder output wire

 

Apply voltage is depending on the thickness of the film.

Apply voltage until we get hysteresis curve. After that press sweep
on/off button and then press shift and then press rate and then press trigger.
Sample will get polarized fully.

 

3.5 Annealing:

Annealing involves heating a material to above its recrystallization
temperature, maintaining a suitable temperature, and then cooling. The heat
treatment is necessary to increase the crystallinity of ferroelectric copolymer
layers. Annealing process occurs in three stages. For example, sample has to
annealed at 110°C. First stage the copolymer gets heated from 30°C temperature
to 110°C in one hour. In the second stage the copolymer must stay for 2 hours
at 110°C. In this stage recrystallization occurs. In the third stage the
copolymer gets cooled from 110°C to 30°C in one hour. 5

 

Figure 6: Annealing

1.6  Soldering:

We need: –

 1. Pins

2. silver

3. soldering kit

4. two component glue

Place sample on sample holder using two component glue

Solder pins on sample holder

Draw connections using silver

Check connection using resistance measurement

4. Measurements

4.1
Theoretical calculations

From LIMM method we will get pyroelectric spectrum and reference
spectrum.

Pyroelectric spectrum consists fx, Xf, Yf

Fx= frequency

Xf= real value of sample front side

Yf= imaginary value of sample front side

 

Reference spectrum consists fp, Xp, Yp

Fp= frequency

Xp= real value of photo diode

Yp= imaginary value of photo diode

 

   

 

 

If Xf, Yf positive

 

If Xf negative, Yf positive

 

If Xf negative, Yf negative

 

If Xf positive, Yf negative

 

If Xp, Yp positive

 

If Xp negative, Yp positive

 

If Xf negative, Yf negative

 

If Xf positive, Yf negative

 

 

Now we have Zp, ?p, Zf, ?f

 

 Corrected values   

 

 

From the corrected values we have to find pyroelectric coefficient

Pco= pyroelectric coefficient

 

 

Pco = a – b

To calculate the thickness

x

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