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MASTER THESIS
Chemical Engineer
Escola Tècnica Superior d’Enginyeria Industrial de Barcelona (ETSEIB) Universitat Politècnica de Catalunya (UPC)
by
Mlle. Ester SÁNCHEZ CASAS
MONITORING CONDUCTIVITY OF
EMULSION POLYMERIZATION
DIRECTED BY: Mme. Nida S. OTHMAN
M. Tim F. McKENNA
CPE Lyon
Laboratoire d’Automatique et de Génie des Procédés (LAGEP) Laboratoire de Chimie et Procédés de Polymérisation (LCPP)
43, Boulevard du 11 Novembre 1918 69616 Villeurbanne, cedex, France
23rd July 2012
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I. Abstract
In a polymerization reaction it is essential to control the physical properties of the particles which have
been obtained. These physical properties: molecular weight distribution, particle size, polymer
composition and morphology are fundamental parameters which determine the properties of the polymer.
In this project we attempt to develop on-line measurements controlling these parameters throughout the
polymerization: we are interested in studying the conductivity of the reaction medium during the
emulsion polymerization of styrene by radical (ascorbic acid, H2O2) and with the presence of surfactant
(SDS).
For this study we will rely on such measures as coupled calorimetry, dry mass and zetasizer (to
determinate the particle size), which will allow us to parameterize the conductivity measurement.
Initially, we will study the conductivity of a solution of surfactant without monomer to determine the
CMC (critical micelle concentration) of SDS at different temperatures (Series 0).
In the second part of the study we will investigate the reaction of styrene polymerization by adjusting
various parameters:
- The concentration of surfactant (Series 1)
- The introduction flow rate of the initiator (Series 2)
- The initial concentration of monomer (Series 3)
To reach a conclusion from these experiences: the conductivity can control precisely the presence of
micelles in the medium. These micelles are responsible for the control of physical parameters of the
resulting polymer. The conductivity should be calibrated according to the medium, the monomer and the
surfactant.
We will do additional tests to delve into the essence of this study, and understand the behavior of the
conductivity. We will also use a video probe to observe how could the particle size change size due to
different variations in the parameters.
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II. Summary
I. Abstract 3
II. Summary 4
III. Nomenclature 5
IV. Introduction 6
V. Theoretical part 7
1) Reaction et Kinetics 7
2) Monitoring the calorimetry polymerization 8
3) Monitoring the polymerization by dry mass 9
4) Emulsion polymerization 9
5) Formation of micelles and Conductivity 10
6) Formation of micelles and particle size 11
7) SDS on the surface of droplets 11
VI. Experimental part 13
1) Equipment 13
2) Experimental process 15
2.1 Series 0 15
2.2 Series 1,2 and 3 16
2.2 Video measurements 21
VII. Results and Discussion 22
1) Effect of temperature on the CMC (Series 0) 22
2) Effect of surfactant concentration (Series 1) 24
3) Effect of initiator’s flow rate introduction (Series 2) 30
4) Effect of monomer concentration (Series 3) 35
5) Experiment using APS as initiator 40
6) Experiments using KPS (Series A) 43
7) Experiments using VA-086 (Series B) 46
8) Video measurements 47
9) Different studies of conductivity 55
10) Miniemulsion (M01) 58
VIII. Conclusion 59
IX. Bibliographic references 60
X. Vocabulary 61
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III. Nomenclature
Symbol Name Units
[ ] Concentration mol.m-3
F Flow rate g/h
rpm Agitation Tour/min
G.P. Feed rate of the initiator %
M Mass kg
Cp Heat capacity J.kg-1.°C-1
U Heat transfer coefficient J.mol-1.°C-1
A Exchange surface m²
Q Amount of heat J
σ Conductivity S.m-1
λ Conductance S.m².mol-1
MW Molar mass g.mol-1
Np Number of particles
Dp Particle diameter nm
H Enthalpy J
T Temperature °C
v Speed mol.s-1
k Rate constant m3.s-1
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IV. Introduction
This study is focused on monitoring conductivity of a polymerization. Nowadays, polymers are very
important in the chemical industry, thus it is important to control the polymerization. One way to control
these reactions by monitoring conductivity coupled with calorimetry.
Actually, during an emulsion polymerization takes place the micelle formation which can be controlled
by conductivity. The essential particularity of these micelles is the particle.
Firstly, we will consider the CMC (critical micelle concentration) of our surfactant and we will try to
establish a relationship between micelle formation and the particle diameter obtained and the amount of
polymer formed.
The parameterization of the conductivity sensor will be using calorimetric measurements.
Calorimetry allows us to obtain Qr (the heat of reaction) and allows us to analyze the rate of
polymerization, the conversion throughout the reaction and the size of the particles.
We will do different measurements in order to study the polymerization, from samples taken at different
times during the reaction.
Additionally, we will do some studies in order to understand the meaning of the anomalies found during
the previous experiments.
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V. Theoretical part
1) Reaction et Kinetics
Reaction scheme:
HO
CH2
OH OH OH
OH
CH2HO
CH2HO CH2CH2HO
+
* Decomposition of the initiator (H2O2 / ASCA) of the polymerization:
H2O2 2 HO° 2 HO-M °
We suppose that ka is higher than kd and we have define the efficacy of initiator f
* Propagation:
HO-M ° + M HO –M-M°
* Termination: - By disproportionation
- Par coupling :
kd vd = = 2 f kd [H2O2]
va= ka [M][HO°]
ka
vp = ‐ = kp × [M] × [M°]
kp
vt = ‐ = 2 kt × [M °]²
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QR is the heat generated by the polymerization reaction
UA(TR-Tj) is the heat exchanged through the jacket
Qloss Qloss is the heat lost during the reaction through the device
• x is the conversion
• M0 is the initial mass of monomer
• MW represents the molecular weight of monomer
• n is the average number of radical particles
• Np is the number of particles per liter
• NA is Avogadro's number
• [M] p the concentration of monomer in the particles
We define the rate of polymerization: Rp = kp × [M]p n × = - =
2) Monitoring the calorimetry polymerization
Our reaction proceeds in a batch reactor (hall mock), the reaction temperature is controlled by a jacket.
We can write the energy balance as follows:
micpi × = Ficpi(Ti-TR) + QR – UA(TR-Tj) – Qloss
We neglect the other terms of energy due to agitation, and other
reactor components.
We can define the progress calorimetry as follows: X calorimetry (t)= , where Qmax is the
maximum heat maximum heat generated by the reaction. It is calculated using the following equation:
Q max = .
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3) Monitoring the polymerization by dry mass
We can define progress by measuring the dry mass from the equation above:
X masse=
Mlatex represents the mass of the solution
Msèche represents the mass remaining after drying
Mmonomère represents the monomer mass
4) Emulsion polymerization
An emulsion polymerization consists in an aqueous solution of water in a double-shell reactor. This water
is heated to a fixed temperature and is stirred at 300 rpm. We add to this water, a sufficient quantity of a
surfactant in order to form micelles. The surfactant is SDS in this study (see Figure 1). Once the mixture
has reached the set temperature the monomer (styrene) and the initiator (H2O2) were added into the
aqueous phase by the distilled water if necessary.
The surfactant stabilizes the monomer, and then there are formed micelles and monomer droplets in the
reaction medium because the monomer is less soluble in water than in the monomer (these droplets are
very big and will become reservoirs for monomer for the polymerization). The initiator is present in the
aqueous phase. Then we should allow the mixture to be homogenized for several minutes. Then we start
by running the reaction rate of ascorbic acid content in a syringe (the speed is also a parameter that we
will study). Ascorbic acid will allow the formation of radicals in the aqueous phase by reacting with the
monomer forming oligoradicals. The radicals or oligoradicals have statistically more probabilities to enter
into the micelles than in the monomer droplets and do not stay in solution. As their size increase, they
have less affinity with water.
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OSO3‐ Na+
Figure 1: Nucleation mechanisms during an emulsion polymerization.
The particle growth is then effected by transfer through the monomer from the aqueous phase drops. The
monomer in the aqueous phase is gradually consumed to increase the size of the micelles in oligoradicaux
precipitates or in solution. This implies the dissolution of monomer droplets which are thus progressively
consumed by displacement of equilibrium. Growth of primary particles can also occur by coagulation of
particles. Is obtained at the end of the reaction a polymer latex, i.e., a stable emulsion of polymer particles
whose size can range from 0.05 to 5 microns typically.
5) Formation of micelles and Conductivity
A surfactant is composed of a hydrophilic part which is soluble in water and a hydrophobic portion
(insoluble in water) soluble in polar solvents:
Figure 2: Schematic of surfactant: SDS
When the surfactant is introduced into the reactor (containing water) to a concentration below the
CMC: Assuming that the SDS is fully ionized, the solution contains a surfactant mixture
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composed of a hydrophilic surfactant. The ionic part is in the form of sodium ions and ion-
dodecyl C12H25SO4 .Cette ionic part is at the origin of the conductivity of the reaction mixture.
The conductivity of the solution then follows a linear law: σ = λNa+ x [Na+] + λSDS- x [SDS-]
(Q: we made several assumptions: There is no HO-ions in our environment because of H2O2 and ascorbic
acid has a negligible conductivity in the reaction medium)
If the surfactant concentration in the reactor is greater than the CMC, micelles are formed in the
reaction. The reason for their formation is because a surfactant molecule can reduce the solvation
energy by assembling the hydrocarbon chains in the form of a droplet. This droplet is excited
about the hydrophilic parts of surfactants, and is then soluble in water. The conductivity
decreases since then the concentration decreases surfactant free.
6) Formation of micelles and particle size
Surfactants are compounds that reduce surface tension between two media. When a medium is
saturated with surfactant molecules there will be formation of micelles. The CMC depends on
the geometry and functionality of the surfactant. And a surfactant with a longer chain form
micelles with a larger diameter and increase the CMC. When the micelle formation in a stirred
medium there is a thermodynamic equilibrium constant this is set up between fragmentation and
coalescence of the drops. This balance depends on various parameters including agitation but
also the surfactant selected. We can then "control" the size of the micelles which allows
controlling the particle diameter.
7) SDS on the surface of droplets
In order to calculate the SDS amount into droplets we have done these calculations:
º /
43
4
Units : σ (S.m‐1), λ (S. m2.mol‐1), [] (mol.m‐3)
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_ where: 40 80
_
_
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VI. Experimental part
1) Equipment
‐ ZETASIZER MALVERN: For measuring diameter particles.
Figure 3: Zetasizer de malvern.
‐ Metler LJ16: To calculate the dry mass.
Figure 4:Metler LJ16.
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‐ Conductivity probes:
Probe 1: Fisher bioblock scientific K10/PT1000/300mm :
Figure 5: Conductivity probe 1.
Probe 2: SKT21T-30
Probe 3: 856 Conductivity Module Metrohm :
Figure 6: Conductivity probe 3.
Ampliation:
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2) Experimental process
2.1 Series 0
1. Prepare the SDS + water and weigh.
2. Weight the water before putting into the reactor.
3. Put inside a syringe the solution of 1, and take out the bubbles inside of the surfactant; then don not
forget to weigh it full of solution.
4. Open the condenser (water entry).
5. Add water.
6. Connect the conductimeter between the PC & reactor.
7. Change Tsp in the computer (Tsp = 20/70/60/50... °C).
8. Cover all the entries of the reactor by caps.
9. Turn on ‘Bain’ and ‘Agitation’ buttons.
Figure 7: PC Supervision. Buttons.
10. Open the programme ‘Conductimeter2’ in ‘stages’ folder and create an empty excel file in our own
folder.
11. In the programme: Open the folder below and open the file already created.
12. When the Treactor is close to the estimated temperature:
- Press Start in the programme.
- Connect the syringe to the machine and turn on while timing by chronometer.
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(it goes slowly at the end, and the flow rate could change. Thus, stop the machine and the
chronometer).
13. Stop the programme.
14. Weigh the empty syringe.
2.2 Series 1,2 and 3
1. Check the aspiration (the hood).
2. Start the program (Reacteur) on the “PC supervision”.
3. Check the connection with the balance.
4. Clean the reactor with water 3 times.
5. Weight the necessary amount of surfactant on the precise balance.
6. Add water using the balance for more weight.
7. Add the conductivity probe and check connections.
Figure 8: Conductimeter.
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8. Open nitrogen valve (1 bar), check the flow rate after few minutes.
Figure 9: Nitrogen cylinder.
9. Insert into the reactor the surfactant + some water.
10. Open 2 valves of water (one for the condenser and another for cooling the bath), check the flow rates.
Stirrer is at 300 rpm.
Figure 10: Valves of water (condenser and bath cooler).
11. Press the green buttons of the bath and agitation.
12. Temperature set-point = 70°C; (Chauf_Inactif) with option auto.
13. Once temperature attains 70°C (30min) Add H2O2 and styrene. Keep it inside for 15 min till you
add the Ascorbic Acid.
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Figure 11: Hood to take the styrene from its bottle.
14. At PC supervision: put on the program (Supervision IFix). Execute (). Modify set-point again to
70°C. Do not close this window!
15. At PC distant:
Figure 12: PC Distant.
- Put on the program (Supervision pc distant). Execute ().
- write 70 in the file c:\donneeslabview\commandeT
- write 0 in the file c:\donneeslabview\commande_pompe
- « Autorisation commande » in « double enveloppe »
- « Autorisation commande » in « pompe manu » for semi-continuous exp.
- « Effacer le fichier de mesure »
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16. Start MATLAB:
- Directory C:\Documents and Settings\calorimetre\Bureau\stages\prog_matlab
- Open folder / Control-T-et-debit
17. Execute Conductimetre2 in stages.
Create an Excel file empty in the folder of conductivity and link it below.
18. Introduce Ascorbic Acid solution into the reactor by a syringe.
19. Put the azote (nitrogen) in the air of the reactor (or close it)
20. At PC distant:
- in Labview program clic on « marche enregistrement ».
- Execute Matlab program « control_T_et_debit”
- Clic on (Début commande temperatire)
21. Write the hour on the « PC distant »
22. Take a sample every 10 min.
Figure 13: Samples.
At the end:
23. PC distant : - Close the program conductimetre2.
- clic on FIN in matlab figure.
- write 20 in the file C:\DonneesLabview\commande_T.
- click on « arrêter l’enregistrement » in labview.
- copy the file « mesures » in c:\donneeslabview.
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24. Empty the reactor if T<40°C, latex goes into empty solvent bottles.
25. Put some water inside the reactor (about 100 g ) and through it into the latex bottle.
26. Clean the reactor with water once (through it into the sink).
27. Clean the reactor with THF (about 30min), put it back into its bottle.
28. Clean the reactor with water several times.
Figure 14: Reactor cleaned.
Data treatment :
29. Matlab / Open / Main-filtration in directory stage. Execute.
30. Excel / Open / stages/ prog_matlab / result filter-reduit / copier / collage / special / valeur adapt
length of all.
31. Copy data from the file of conductivity that we created before adapt length of all.
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2.2 Video measurements
We have assembled the necessary equipment to make a series of experiments with the video probe in
order to study the behaviour of the particles.
Figure 15: Equipment necessary for the studies with the video probe.
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VII. Results and Discussion
1) Effect of temperature on the CMC1 (Series 0)
During this series of measurements were studied the conductivity of distilled water with the continuous
addition of a SDS2 solution with known concentration. Here are all the data of this series:
Agitation 300 rpmWater reactor 800 g Syringe: Water 40 g SDS 5 g
Table 1: Data of series 0.
Figure 16 : Monitoring the conductivity of the mixture depending o the amount of SDS introduced.
We could notice that the experiment at 80 ºC is very different from the others because we have used a different probe.
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As we could see in the figure below, the CMC of SDS at 70 ºC is around 3 g SDS/l of water.
Figure 17: CMC of SDS at 70 ºC.
Table 2: CMC vs. T
Figure 18: Monitoring critical micelle concentration as a function of temperature.
Temperature (°C)
CMC (g/L)
22 2,4
40 2,4
50 2,67
70* 3
80 3,75
It is observed that the CMC increases with temperature. The more temperature, the more solubility of
SDS. In order to form micelles at higher temperatures more surfactant should be added.
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2) Effect of surfactant concentration (Series 1) During this series of measurements has been studied the effect of surfactant concentration. Here are all
the data of this series:
Styrene 6 % Water 800 g
H2O2 3 g/l
Agitation 300 rpm
Temperature 70 º C Solution of ascorbic acid. Seringe:
Asc Acid 0,5 g Water 10 g G.P.3 22 %
Flowrate 0,45 g/h
Table 3: Data of series 1.
- Temperature & Heat:
We note that when we add more surfactant concentration, the heat generated by the reaction is higher.
Actually, it is because adding more surfactant, the number of micelles increases and therefore, the number
of particles.
Figure 19: Medium temperature of the reaction vs. time.
69
69,5
70
70,5
71
71,5
72
72,5
73
0 10 20 30 40 50 60
(°C
)
Time (min)
Temperature[SDS]=3.4g/L[SDS]=3.4g/L*[SDS]=3.6g/L[SDS]=3.8g/L[SDS]=4g/L[SDS]=4.2g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
[SDS] (g/l)
SERIE 1 ES7 3,4 ES8 3,1 ES9 3,8 ES10 4,2 ES11 3,6 ES19 ES9 3,8 ES18 4,2 ES20 5 ES21 6 ES22 ES10 4,2 ES30 ES7 3,4 ES31 4 ES32 5,5
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Figure 20: Heat produced by the reaction vs. time.
- Conversion:
Conversion was plotted versus time in two different ways. The first way, is the thermal conversion from
the heat reaction (Figure 21) and the second way, is from the dry mass of samples which has been taken
experimentally during the reaction (Figure 212).
The turning point (the half of the conversion) corresponds to the maximum peak temperature, which is
due to the maximum heat generated by the reaction. After this phase, the reaction rate decreases because
there is less of monomer present in the reactor. There is no relation between the fact of increasing the
concentration of surfactant and the conversion. The conversion depends on many things but the most
important sources of error are:
a. Variable thermal transmittance coefficient; U (W/m2K), which depends on the heat loss
in the reactor (Qloss).
b. The beginning of the reaction; because sometimes the reaction starts late because of the
presence of bubbles in the syringe.
The technique for measuring the conversion using the dry mass can be distorted by different sources of
error:
a. Take a sample unrepresentative from the mixture in the reactor.
b. Machine error of the dry mass.
c. By not agitating sufficient the sample before the measurement.
0
10
20
30
40
50
60
0 10 20 30 40 50 60
(W)
Time (min)
Heat produced by the reaction[SDS]=3.4g/L[SDS]=3.4g/L*[SDS]=3.6g/L[SDS]=3.8g/L[SDS]=4g/L[SDS]=4.2g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
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Figure 21:Plot of conversion (measured by calorimetry) vs. time.
Figure 22: Plot of conversion (measured by dry mass) vs. time.
- Mean diameter & Particle number: Theoretically, by increasing the amount of SDS in the reactor, the number of miscelles should increase
and also the polymer particles formed into the miscelles sould be smaller. We observe a decrease in the
particle mean diameter and an increase in the number of particles (Figures 23 & 24).
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
(%)
Time (min)
Conversion
[SDS]=3.4g/L[SDS]=3.4g/L*[SDS]=3.6g/L[SDS]=3.8g/L[SDS]=4g/L[SDS]=4.2g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30 35 40 45 50
(%)
Time (min)
Conversion
[SDS]=3.4g/L[SDS]=3.4g/L[SDS]=3.6g/L[SDS]=3.8g/L[SDS]=4g/L[SDS]=4.2g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
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Figure 23: Average particle diameter vs. time.
Figure 24: Number of particles vs. time.
In our experiments we could notice that the heat of the reaction could be related to the number of particles
(See experiences with [SDS] = 6 g/l and 5,5 g/l in figures 20 & 26). The more particles created, the more
heat generated because there are more reactions.
10
15
20
25
30
35
40
45
50
55
0 10 20 30 40 50
(nm
)
Time (min)
Mean diameter
[SDS]=3.4g/L*[SDS]=3.8g/L[SDS]=4g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
0
3E+17
6E+17
9E+17
1,2E+18
1,5E+18
0 10 20 30 40 50Time (min)
Particle number[SDS]=4.2g/L
[SDS]=4g/L
[SDS]=5.5g/L
[SDS]=6g/L
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As we could see in the figures below, the mean diameter decreases as a function of SDS concentration, and the particle number increases. Furthermore, it is observed that along the reaction more particles with a smaller diameter are formed.
Figure 25: Average diameter of particles as a function of conversion.
Figure 26: Number of particles as a function of conversion.
0
10
20
30
40
50
60
0 20 40 60 80 100
(nm
)
Conversion (%)
Mean diameter
[SDS]=3.8g/L
[SDS]=4g/L
[SDS]=5g/L
[SDS]=6g/L
[SDS]=5.5g/L
0
3E+17
6E+17
9E+17
1,2E+18
0 20 40 60 80 100Conversion (%)
Particle number
[SDS]=3.8g/L
[SDS]=4g/L
[SDS]=5.5g/L
[SDS]=6g/L
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- Conductivity :
We could see that the conductivity of the mixture at the beginning of the reaction is lower than expected
conductivity (Series 0, Table 4 & Figure 17). We have introduced a higher SDS concentration than the
CMC. The difference can be explained by the presence of the monomer (non-conductive carbon chain
part), which is present in the reactor in droplets that reduces the conductivity and may also affect the
measurement of the conductivity probe. We had used 2 different probes during the project, and we have
noticed that the probes are affected adversely by the monomer which fixes fast on the surface of the
plaques. The more experiments were performed, more erroneous results were obtained.
Figure 27: Monitoring the conductivity of the reaction function of time.
[SDS] (g/L)
conductivity (µS/cm)
3,4 441 3,6 454 3,8 466 4,2 487 4 476 5 521
Table 4: Conductivity vs. SDS concentration at 70 ºC. Series 0.
0
100
200
300
400
500
600
0 10 20 30 40 50 60
(µs/
cm)
Reaction time (min)
Conductivity[SDS]=3.4g/L[SDS]=3.4g/L*[SDS]=3.6g/L[SDS]=3.8g/L[SDS]=4.2g/L[SDS]=4g/L[SDS]=5g/L[SDS]=5.5g/L[SDS]=6g/L
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3) Effect of initiator’s flow rate introduction (Series 2)
During this series of measurements has been studied the effect of the flow rate of the initiator (ascorbic
acid) has been studied. We have introduced by a syringe, a solution of ascorbic acid, changing the flow
rate of this syringe. You can see below all the data obtained of this series:
Styrene 6 % SDS 3,4 g/l
Water 800 g
H2O2 3 g/l
Agitation 300 rpm
Temperature 70 º C Solution of ascorbic acid. Seringe:
Asc Acid 0,2 g Water 10 g
Table 5: Data of series 2.
- Temperature & Heat:
We can observe that the flow rate of Ascorbic Acid is important. If the flow rate is slower, the reaction
starts later. There is not much difference between the amounts of the heat produced by the reaction as a
function of ascorbic acid’s flow rate, but we can see that the reaction is faster for higher flow rates.
Figure 28: Monitoring of temperature vs. time.
67
68
69
70
71
72
73
0 20 40 60 80 100 120
(°C
)
Time (min)
Temperature
F AscA = 0.076 g/h
F AscA = 0.129 g/h
F AscA = 0.173 g/h
Flowrate Asc Acid (g/h)
SERIE 2 ES12 0,136 ES13 0,143 ES14 0,076 ES25 0,055 ES27 ES12 0,136 ES33 0,129 ES34 0,173 ES35 0,286 ES36 0,284 ES37 0,087
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Figure 29: Monitoring of heat production vs. time.
- Conversion:
We observe the same that in the case of the section of Temperature & Heat; the conversion starts before
with a higher flow rate. However, it does not mean that it should achieve the highest conversion. There is
no relation between these factors.
Figure 30: Monitoring of the conversion (measured by calorimetry) vs. time.
0
5
10
15
20
25
30
35
40
0 20 40 60 80 100 120
(W)
Time (min)
Heat produced by the reactionF AscA = 0.076 g/h
F AscA = 0.129 g/h
F AscA = 0.173 g/h
0
10
20
30
40
50
60
70
80
90
0 20 40 60 80 100 120
(%)
Time (min)
Conversion
F AscA = 0.076 g/h
F AscA = 0.129 g/h
F AscA = 0.173 g/h
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Figure 31: Monitoring of the conversion (measured by dry mass) vs. time.
- Mean diameter & Particle number:
We obtained a mean diameter particle of: 30-55 nm. We could also appreciate that with a lower flow rate,
we are able to obtain particles with a larger diameter. In the experiments of flow rates from 0,129-0,286
g/h it is not possible to appreciate any relation with the initiator’s flow rate.
Figure 32: Average diameter of particles vs. time.
0
10
20
30
40
50
60
70
80
90
100
0 20 40 60 80 100
(%)
Time (min)
Conversion
F AscA = 0.076 g/h
F AscA = 0.129 g/h
F AscA = 0.173 g/h
0
10
20
30
40
50
60
0 20 40 60 80 100
(nm
)
Time (min)
Diameter
F AscA = 0.076 g/h
F AscA= 0.086 g/h
F AscA = 0.129 g/h
F AscA = 0.136 g/h
F AscA = 0.143 g/h
F AscA = 0.173 g/h
F AscA = 0.284 g/h
F AscA = 0.286 g/h
SÁNCHEZ CASAS, Ester
33
We could see that the particle number increases when the initiator’s flow rate is higher:
Figure 33: Number of particles vs. time.
We also plotted the mean diameter and the particle number with the conversion of the reaction.
Unfortunately, we realized that there is not any direct relation.
- Conductivity :
We could only observe that the conductivity decreases before (the reaction starts) when the initiator’s
flow rate is higher. However, we could not notice any relation between the other experiments, and we
have also a lot of problems in this series with the conductivity probe. As decreasing near 0, we had
noticed that the probe was broken.
Besides, the reaction time (decreasing part) is approximately the same in both cases. We cannot
appreciate any difference.
According to the Series 0, both experiments should start at 441 µS/cm (3,4 g/l SDS).
0
2E+17
4E+17
6E+17
8E+17
1E+18
1,2E+18
0 20 40 60 80 100Time (min)
Particle number F AscA= 0.086 g/h
F AscA = 0.129 g/h
F AscA = 0.143 g/h
F AscA = 0.284 g/h
SÁNCHEZ CASAS, Ester
34
Figure 34: Monitoring the conductivity of the medium vs. time.
We also plotted the conductivity with the conversion of the reaction. Unfortunately, we realized that there
is no any direct relation.
0
100
200
300
400
500
600
0 10 20 30 40 50 60 70 80 90 100
(µs/
cm)
Reaction time (min)
Conductivity
F AscA = 0.076 g/h
F AscA = 0.143 g/h
START
SÁNCHEZ CASAS, Ester
35
4) Effect of monomer concentration (Series 3)
During this series of measurements has been studied the effect of monomer concentration. Here are all the
data of this series:
SDS 4,2 g/l Water 800 g
H2O2 3 g/l
Agitation 300 rpm
Temperature 70 º C Solution of ascorbic acid. Seringe:
Asc Acid 0,5 g Water 10 g G.P. 22 %
Flowrate 0,45 g/h Table 6: Data of series 3.
- Temperature & Heat:
The more monomer addition, the reaction reaches a higher temperature, and the heat of reaction is higher
too. We could see that the curve of Styrene at 7% starts very late, the main reason could be that there
probably were bubbles into the syringe and did not work well at the beginning. In fact, we had had a lot of
problems with the flow rate of ascorbic acid, which could not find any logical relation between the
obtained results.
Figure 35: Monitoring of temperature vs. time.
67
68
69
70
71
72
73
74
75
76
0 10 20 30 40 50 60
(°C
)
Time (min)
Temperature
Sty = 6 %Sty = 7 %Sty = 8 %Sty = 11 %
Styrene (%)
SERIE 3 ES10 6 ES15 8 ES16 9,6 ES17 11 ES38 7 ES39 9
SÁNCHEZ CASAS, Ester
36
Figure 36: Monitoring of heat production vs. time.
- Conversion:
We can see that there is no logical relation between the conversion and the concentration of monomer
introduced into the reactor, if we measure by dry mass. Probably, this is because of the number of error
sources already explained in series 1.
Figure 37: Plot of conversion (measured by calorimetry) vs. time.
0
10
20
30
40
50
60
0 10 20 30 40 50 60
(W)
Time (min)
Heat produced by the reaction
Sty = 6 %
Sty = 7 %
Sty = 8 %
Sty = 11 %
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
(%)
Time (min)
Conversion
Sty = 6 %Sty = 7 %Sty = 8 %Sty = 11 %
SÁNCHEZ CASAS, Ester
37
Figure 38: Plot of conversion (measured by dry mass) vs. time.
- Mean diameter & Particle number:
We could notice that the more monomer added the more diameter particles. Nevertheless, we cannot say
the same for the particle number. It seems to be similar in all the experiments, no difference between all
of them.
Figure 39: Average diameter of particles vs. time.
0
20
40
60
80
100
120
0 10 20 30 40 50 60
(%)
Time (min)
ConversionSty = 6 %Sty = 7 %Sty = 8 %Sty = 9.6 %Sty = 11 %Sty = 11 %*
0
10
20
30
40
50
60
0 20 40 60
(nm
)
Time (min)
Diameter
Sty = 6 %
Sty = 7 %
Sty = 11%
SÁNCHEZ CASAS, Ester
38
Figure 40: Number of particles vs. time.
It is observed that the diameter particles increases as a function of conversion, and the particle number
does not change a lot during the reaction.
Figure 41: Average diameter of particles as a function of conversion.
0
5E+17
1E+18
1,5E+18
2E+18
2,5E+18
0 20 40 60
Time (min)
Particle number
Sty = 6 %
Sty = 7 %
Sty = 11%
Sty = 11 %*
0
10
20
30
40
50
60
0 20 40 60 80 100 120
(nm
)
Conversion (%)
Diameter
Sty = 6 %
Sty = 7 %
Sty = 11%
Sty = 11 %*
SÁNCHEZ CASAS, Ester
39
Figure 42: Number of particles as a function of conversion.
- Conductivity :
Theoretically, if the monomer added is higher, the reaction should start before, but according to the
experiments done, we are not able to confirm that. As increasing the quantity of monomer, we increase
the amount of non ionic substances in the reactor, and this affects directly the conductivity which starts at
a lower value. Some of the ionic substances are diluted.
It is very difficult to validate the last two experiments of this series (Sty at 7% and at 11%) because they
have been made with a limited number of samples because the new probe has been broken by the
agitation of the reactor.
Figure 43: Monitoring the conductivity of the medium vs. time.
0
5E+17
1E+18
1,5E+18
2E+18
2,5E+18
0 20 40 60 80 100
Conversion (%)
Particle number
Sty = 6 %
Sty = 7%
Sty = 11%
Sty = 11 %*
0
100
200
300
400
500
600
0 10 20 30 40 50 60
(µs/
cm)
Reaction time (min)
ConductivitySty = 6 %Sty = 7 %Sty = 8 %Sty = 11 %*
SÁNCHEZ CASAS, Ester
40
5) Experiment using APS4 as initiator
At the beginning of the project we realized an experiment using APS in order to get in use with the
equipment and the programs, and take some decisions from the results for future experiments:
Styrene 20 % SDS 1,87 g/l
Water 800 g
APS 3 g/l
Agitation 400 rpm
Temperature 70 º C Table 7: Data of APS experiment.
- Temperature & Heat :
We could observe the gel effect, which is a dangerous reaction behaviour that can occur in free radical
polymerization systems. It is due to the localized increases in viscosity of the polymerizin system that
slow termination reactions. The removal reaction obstacles therefore causes a rapid increase in the overall
rate of reaction, leading to possible reaction runaway and altering the characteristics of the polymers
produced. The gel effect can also occur when the temperature of the reaction is kept constant. (RAVVE,
2000)
Figure 44: Temperature & Heat vs. time.
60
62
64
66
68
70
72
74
0 50 100
(°C
)
Time (min)
Temperature
TréacteurTj inTj outset-point
0
10
20
30
40
50
60
0 20 40 60 80 100
(W)
Time (min)
Heat produced by the reaction
SÁNCHEZ CASAS, Ester
41
- Conversion & Solids content:
We could see the conversion obtained by calorimetry. We also plotted the conversion obtained by dry
mass; however, the results differ greatly from reality.
In order to prevent coagulation for future experiments, we decided that the limit of solid content should
be at 10 %.
Figure 45: Conversion & Solids content vs. time.
- Mean diameter & particle number :
We obtained a diameter particle around 90 nm for all the samples.
The number of particles increases during the reaction.
Figure 46: Mean particle diameter & Number of particles.
0,00
20,00
40,00
60,00
80,00
100,00
0 20 40 60 80 100
(%)
Time (min)
Conversion
0
2
4
6
8
10
12
14
0 20 40 60 80 100
(%)
Time (min)
Solids content
0
20
40
60
80
100
0 20 40 60 80 100
(nm
)
Time (min)
Mean particles diameter
0
5E+16
1E+17
1,5E+17
2E+17
2,5E+17
3E+17
3,5E+17
0 20 40 60 80 100Time (min)
Number of particles
SÁNCHEZ CASAS, Ester
42
- Conductivity :
We notice an important decrease in conductivity when adding monomer.
We could see that the addition of ammonium persulfate (APS) increases significantly the conductivity.
This is because APS decomposes by hemolytic scission due to thermal. The degradation of one mole of
the initial reagent (NH4)2S2O8, provides two moles of free radicals, each carrying one negative charge at
their extremity: SO•4
-, NH4
+. (BOUTTI, 2002)
Figure 47: Conductivity vs. time.
We have observed a lot of coagulation around the stirrer. After this experiment (stirring at 400 rpm), we
decided to use 300 rpm for future experiments, in order to reduce coagulation.
0
200
400
600
800
1000
1200
-30 -20 -10 0 10 20 30
(µs)
Reaction time (min)
Conductivity conductivity
monmer addition
APS addition
SÁNCHEZ CASAS, Ester
43
6) Experiments using KPS5 (Series A)
We have done this simple series in order to realize that the conductivity probe was definitely broken. It is
easy to see it from this series because there were a lot of previous studies with this initiator. In fact, we
took the same conclusions from Series 2 with ascorbic acid as initiator.
Styrene 6 % SDS 3,4 g/l
Water 800 g
Agitation 300 rpm
Temperature 70 º C
‐ Temperature & Heat :
When increasing the KPS concentration, the reaction starts before.
Figure 48: Temperature & Heat produced by the reaction vs. time.
60
62
64
66
68
70
72
74
0 10 20 30 40
(°C
)
Time (min)
Temperature
[KPS]=2g/l
[KPS]=3g/l
0
10
20
30
40
50
0 10 20 30 40
(W)
Time (min)
Heat produced by the reaction
[KPS]=2g/l
[KPS]=3g/l
[KPS] (g/l)
SERIES A ES40 2 ES41 3
Table 8: Data of series A.
SÁNCHEZ CASAS, Ester
44
‐ Conversion & Solids content :
We could see that the conversion works well for this series. As increasing the KPS concentration, the
reaction starts before.
Figure 49: Conversion & Solids content vs. time.
‐ Mean diameter & particle number :
We notice that the more KPS concentration, smaller diameter particles and higher number of particles
generated during the polymerization.
Figure 50: Mean particles diameter & Number of particles vs. time.
0102030405060708090
100
0 10 20 30 40
(%)
Time (min)
Conversion
[KPS]=2g/l[KPS]=2g/l[KPS]=3g/l[KPS]=2g/l 0,0
1,0
2,0
3,0
4,0
5,0
6,0
0 10 20 30 40
(%)
Time (min)
Solids content
[KPS]=2g/l
[KPS]=3g/l
0
10
20
30
40
50
60
0 10 20 30 40
(nm
)
Time (min)
Mean particles diameter
[KPS]=2g/l
[KPS]=3g/l
0
2E+17
4E+17
6E+17
8E+17
1E+18
1,2E+18
0 10 20 30 40Time (min)
Number of particles
[KPS]=2g/l
[KPS]=3g/l
SÁNCHEZ CASAS, Ester
45
Figure 51: Diameter & number of particles vs. conversion.
‐ Conductivity :
Unfortunately, we realized that the conductivity probe 2 was broken after doing this experiment. We had
to stop this study of conductivity because we could not take any real measurement of conductivity.
0
10
20
30
40
50
60
0 20 40 60 80
Dia
met
er (
nm)
Conversion (%)
Diameter vs. Conversion
[KPS]=2g/l
[KPS]=3g/l0
2E+17
4E+17
6E+17
8E+17
1E+18
1,2E+18
0 20 40 60 80
Num
ber
of p
arti
cles
Conversion (%)
Number of particles vs. Conversion
[KPS]=2g/l
[KPS]=3g/l
SÁNCHEZ CASAS, Ester
46
7) Experiments using VA-0866 (Series B)
The advantage of using VA-086 is a nonionic initiator that will not affect the conductivity.
VA-086 3 g/l
SDS 4,5 g/l
Water 800 g
Agitation 300 rpm
Temperature 70 º C
‐ Temperature & conductivity :
At the beginning we see an important decrease of conductivity at nucleation time (as in APS experiment).
We notice that the conductivity of water, SDS and monomer droplets is higher in ES4 than in ES5, this
could be because there are more droplets.
In both experiments we could appreciate that there is not an important effect on conductivity when the
reaction should starts. We did not observe any decrease in conductivity, probably there is no coagulation
since diluted, but the increase of ES4 seems to be similar to APS experiment. This increasing part may be
due to the consumption of monomer droplets or some existing coagulation.
Figure 52: Conductivity vs. time.
0
100
200
300
400
500
600
700
800
900
1000
-20 30 80 130 180 230
(µs/
cm)
Reaction time (min)
Conductivity (µs) Conductivity ES4
Conductivity ES5
Initiator addition
start ES4
start ES5
Styrene (%)
SERIES B ES4 6 ES5 11
Table 9: Data of series B.
SÁNCHEZ CASAS, Ester
47
Figure 53: Conductivity & Treactor vs. time.
After this series of experiments, we made an important decision. According to the results, we concluded
that the VA-086 which was bought in 1999 was probably too old and does not work well for
polymerization. We decided to use another non ionic initiator: hydrogen peroxide, because it was easily at
our disposal.
8) Video measurements
8.1 Effect of stirring rate
We had done two different tests changing the stirring in order to know how could affect the particle size
and the distribution. According to this experiment we will decide at which stirring rate we will work for
future experiments. In the pictures below of two different tests, we could notice that the droplets are
smaller when increasing the stirring rate. We can observe at the highest stirring rate for both tests, that
there are some big particles, but we should not confuse with this, because these are the some bubbles
which had been created because of the high agitation.
Figure 54: Stirring at 200 & 520 rpm (TESTS "S").
69
69,5
70
70,5
71
71,5
0
100
200
300
400
500
600
0 30 60 90 120
T(°
C)
(µs/
cm)
Reaction time (min)
Conductivity ES4Treactor ES4
69,5
70
70,5
71
71,5
0
100
200
300
400
500
0 50 100
(°C
)
(µs/
cm)
Reaction time (min)
Conductivity ES5
Treactor ES5
SÁNCHEZ CASAS, Ester
48
Figure 55: Stirring at 663 & 873 rpm (TESTS "S").
Figure 56: Stirring at 200 & 300 rpm (TESTS TG1).
Figure 57: Stirring at 400 & 500 rpm (TESTS TG1).
SÁNCHEZ CASAS, Ester
49
We could observe that the surface area of droplets is very small (in TG and “S”). According to the results
of [SDS] into water and the conductivity, we can consider that do not change because of the stirring rate.
They are almost constant when changing the agitation rate. This means that we do not need to take into
account droplet size during future conductivity calibrations.
Figure 58: Effect of stirring in diameter, conductivity, [SDS] into water and surface area.
8.2 Effect of monomer concentration
We realized that the monomer composition has a minor effect on the droplet size; however, it has an
important effect on the number of droplets. As increasing the monomer concentration we obtained:
‐ An increasing of Ndroplets.
‐ An increasing of Sdroplets.
‐ A slightly decreasing of [SDS] into water.
0
10
20
30
40
50
60
70
80
0 500 1000
Dia
met
er (
µm
)
Stirring rate (rpm)
Effect of stirring
S
TG1
0
100
200
300
400
500
600
0 500 1000C
ond
uct
ivit
y (µ
S/c
m)
Stirring rate (rpm)
Effect of stirring
0,98
1,00
1,02
1,04
1,06
1,08
1,10
1,12
1,14
0 500 1000
[SD
S]
into
wat
er (
g)
Stirring rate (rpm)
Effect of stirring
0,0
0,2
0,4
0,6
0,8
1,0
1,2
0 500 1000
Rat
io o
f su
rfac
e a
rea
Stirring rate (rpm)
Effect of stirring
SÁNCHEZ CASAS, Ester
50
Besides, we concluded that is not necessary to take into account the monomer concentration (Styrene)
during conductivity calibrations because its effect is almost negligible.
Figure 59: Effect of [monomer] on conductivity, number of droplets, ratio of surface area and diameter particles.
Figure 60: Effect of [monomer] on conductivity vs. diameter
0
100
200
300
400
500
600
0 2 4 6 8 10
Con
du
ctiv
ity
(µS
/cm
)
monomer (%)
Effect of monomer composition
0,0E+00
1,0E+08
2,0E+08
3,0E+08
4,0E+08
0 5 10
Nu
mb
er o
f d
rop
lets
monomer (%)
Effect of monomer composition
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
0 5 10
Rat
io o
f sr
ufa
ce a
rea
monomer (%)
Effect of monomer composition
0
10
20
30
40
50
60
0 2 4 6 8 10
Dia
met
er (
µm
)
monomer (%)
Effect of monomer composition
0
100
200
300
400
500
600
46 48 50 52 54
Con
du
ctiv
ity
(µS
/cm
)
diameter (µm)
Effect of monomer composition
SÁNCHEZ CASAS, Ester
51
Figure 61: Volume droplet size distribution vs. diameter.
Figure 62: Number droplet size distribution vs. diameter.
0
1
2
3
4
5
6
7
8
9
10
0 50 100 150 200
(%)
Diameter (µm)
Volume droplet size distribution
[St]=12.6%
[St]=18.2%
[St]=21.1%
0
1
2
3
4
5
6
0 50 100 150 200
(%)
Diameter (µm)
Number droplet size distribution
[St]=12.6%
[St]=18.2%
[St]=21.1%
SÁNCHEZ CASAS, Ester
52
8.2.1 Styrene into water (ES44)
We tried to study if the concentration of styrene could affect directly to the conductivity. Here there are
the values of this experiment:
Mass syringe full 70,9 g Mass syringe empty 54 g
G.P. 26 %
Agitation 400 rpm
Introduction time 26,50 min Flow rate 38,26 g/h
Temperature Tamb º C Table 10: Data of ES44.
This experiment could explain many things that we have not understand till now for series 1, 2 and 3.
In fact, we could observe that increasing addition of monomer composition makes decrease the
conductivity. Thus, this effect explains why we had always obtained an initial value of conductivity
below the expecting value (from the series 0). To sum up, the addition of monomer in a
polymerization makes decrease the conductivity.
Figure 63: Conductivity vs. time.
y = -0,9614x + 324,69R² = 0,9972
295
300
305
310
315
320
325
330
0,00 5,00 10,00 15,00 20,00 25,00 30,00
(µs)
Time (min)
Conductivity
SÁNCHEZ CASAS, Ester
53
Figure 64: Conductivity vs. diameter & diameter vs. monomer composition.
Figure 65: Conductivity & ratio of surface area vs. monomer composition.
We have calculated the ratio of surface area as we explained before in the theoretical part, section 7.
0
50
100
150
200
250
300
350
0 20 40 60 80
Con
du
ctiv
ity
(µS
/cm
)
diameter (µm)
Monomer + water
0
10
20
30
40
50
60
70
0 2 4 6
Dia
met
er (
µm
)
monomer (%)
Monomer + water
0
50
100
150
200
250
300
350
0 2 4 6
Con
du
ctiv
ity
(µS
/cm
)
monomer (%)
Monomer + water
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0,7
0,8
0 2 4 6
Rat
io o
f sr
ufa
ce a
rea
monomer (%)
Monomer + water
SÁNCHEZ CASAS, Ester
54
8.3 Effect of [SDS]
In the figure of diameter vs. SDS concentration, we could notice that [SDS] has a minor effect on the
droplet size. This means that [SDS] onto droplets is almost constant. In the second figure of conductivity
vs. [SDS], we could see that the measured conductivity is similar to the conductivity into water;
increasing linearly.
Figure 66: Effect of [SDS] on diameter and conductivity.
Figure 67: Effect of [SDS] on conductivity vs. diameter.
0
10
20
30
40
50
60
0 10 20 30
Dia
met
er (
µm
)
[SDS] (g/L)
Effect of [SDS]
0
200
400
600
800
1000
1200
1400
0 10 20 30C
ond
uct
ivit
y (µ
S/c
m)
[SDS] (g/L)
Effect of [SDS]
0
200
400
600
800
1000
1200
1400
44 46 48 50 52
Con
du
ctiv
ity
(µS
/cm
)
diameter (µm)
Effect of [SDS]
SÁNCHEZ CASAS, Ester
55
9) Different studies of conductivity
9.1 Styrene into water + SDS (ES42)
We studied if there styrene composition could affect directly a solution of water and SDS. Here there are
the values of this experiment:
Mass syringe full 56,4 g Mass syringe empty 40,3 g
G.P. 26 %
Agitation 400 rpm
Introduction time 29 min Flow rate 33,31 g/h
Temperature Tamb º C Table 11: Data of ES42.
By adding monomer, we could observe 2 effects:
1. The dillution of ionic species.
2. The capture of SDS on monomer droplets.
At the beginning we observe the same behaviour that in ES44; a decreasing because of the monomer
addition, but after that, we notice that the conductivity is till slightly decreasing. This explains why we
had obtained a low value of conductivity at the beginning of all our series (1, 2 and 3).
Figure 68: Conductivity vs. time.
460
480
500
520
540
560
580
0 10 20 30
(µs)
Time (min)
Conductivity
SÁNCHEZ CASAS, Ester
56
According to the particle size, we execute a program which determines the distribution of the particle size
taking pictures from all the videos that the video probe had created. We could see that firstly, the particles
are bigger, and at the end of the experiments they became a bit smaller.
Figure 69: Distribution of number of particles vs. diameter particle from ES42.
Figure 70: Effect of monomer introduction.
0 50 100 150 200 250 300 350 4000
20
40
60
80
100
120
140
Taille (µm)
Nom
bre
ES42-01
0 50 100 150 200 250 300 350 400 450 5000
500
1000
1500
2000
2500
3000
Taille (µm)N
ombr
e
ES42-07
0
100
200
300
400
500
600
700
0 20 40 60 80
Con
du
ctiv
ity
(µS
/cm
)
diameter (µm)
Effect of monomer intro.
0
10
20
30
40
50
60
70
0 2 4 6
Dia
met
er (
µm
)
monomer (%)
Effect of monomer intro.
0
100
200
300
400
500
600
700
0 2 4 6
Con
du
ctiv
ity
(µS
/cm
)
monomer (%)
Effect of monomer intro.
0,0
0,2
0,4
0,6
0,8
1,0
0 2 4 6
Rat
io o
f sr
ufa
ce a
rea
monomer (%)
Effect of monomer intro.
SÁNCHEZ CASAS, Ester
57
We have already explained how to calculate the ratio of surface area in theoretical part, section 7.
9.2 KPS into water (ES45)
We notice that the addition of initiator KPS, as being an ionic initiator makes increase the conductivity of
the mixture. It is very helpful to understand the series A at the beginning of the experiment.
Unfortunately, we did not obtain real values of conductivity for series A.
Seringe Mass (g) Water 40,08 GP 99% KPS 3,1 T 70 °C
Flowrate 2,8071 g/min Introduction t 14 min Introduced m 39,3 g
Water reactor 807,3 g Table 12: Data of experiment ES45.
Figure 71: Conductivity vs. KPS introduced.
y = 3E+06x + 79,412R² = 0,9976
0
500
1000
1500
2000
2500
3000
0,E+00 2,E-04 4,E-04 6,E-04 8,E-04 1,E-03
Con
duct
ivit
y (µ
S/c
m)
[KPS] (g/L)
SÁNCHEZ CASAS, Ester
58
10) Miniemulsion7 (M01)
We started to understand how a miniemulsion works in order to find the effect of droplet size on
conductivity, as we have already done in video experiments. Here we have the data of this experiment:
Water 800 g SDS 3,4 g/l
Styrene 4 %
n-hexadecane 2 g Table 13: Data of M01.
As we can see, by adding the monomer, the conductivity decreases a little. Besides, when we increase the
stirring rate, the conductivity decreases significativily till the reaction achieves stability.
Figure 72: Conductivity vs. time.
We could not increase more the agitation because the latex was almost overflowing from the container.
500
700
900
1100
1300
1500
0 10 20 30 40 50
Con
duct
ivit
y (µ
S/c
m)
Time (min)
Conductivity Miniemulsion500 rpmmonomer+n-hexadec."1000 rpm2000 rpm
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VIII. Conclusion
The monitoring of emulsion polymerization is complex and depends on many parameters.
The fact of using an anionic surfactant such as SDS, allowed us to determine the CMC of SDS. When the
micelle formation starts, we can control the diameter and particle number. This measurement of
conductivity depends mainly on the amount of monomer added and the convenience to be absorbed into
water reactor.
We have realized the difficulties of using a conductivity probe. The metal plates were very fragile. In fact,
we had two different probes at our disposal; one of them had the plates exposed directly to the solution,
this made them get dirty quickly because of the different phases in the reactor and thus we have obtained
incorrect conductivity measurements. The new conductivity probe seemed better at first glance, because
the plates were covered with glass and fixed between them. However, the glass which was fixed between
them was broken too. Thus, the plates were vibrating because of the agitation of the reactor at each
experiment, and we obtained unreal and distorted conductivity measurements.
In addition to this problem, there is the issue of the necessary calibration of the probe before each
experiment, which is not possible to be made in a continuous process such as in the industry. On an
industrial scale, monitoring conductivity seems to be difficult to implement for monitoring emulsion
polymerization. However, it is conceivable to be used in order to determine exact the end of the reaction.
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IX. Bibliographic references
ASUA, José M. (2007). Polymer reaction engineering. Institute of polymer materials (polymath). The
University of the Basque Country (Spain). Blackwell Publishing Ltd.
BOUTTI, S. (2002). High solid content latexes. Villeurbanne: Ph.D Thesis. Universite Claude Bernard
Lyon I. Laboratoire de chimie et procédés de polymérisation (LCPP).
FARSHCHI TABRIZI, Farshad (2004). On-line monitoring of emulsion polymerization by conductimetry
and calorimetry. Villeurbanne: Ph.D Thesis. Universite Claude Bernard Lyon I. Laboratoire
d'Automatique et de Génie des procédés (LAGEP) et Laboratoire de Chimie et Procédés de
Polymérisation (LCPP).
Mason TG, W. J. (2006). Nanoemulsions: formation, structure, and physical properties. Journal of
Physics: Condensed Matter.
RAVVE, A. (2000). Principles of polymer chemistry. New York: Kluwer Academic / Plenum Publishers.
Second Edition.
SH'EIBAT OTHMAN, Nida. (2000). Advanced strategies for composition control in semi-continuous
emulsion polymerization. Villeurbanne: PhD Thesis. Universite Claude Bernard Lyon I. Laboratoire de
Chimie et procédés de polymérisation CNRS - CPE.
http://www.msc.univ-paris-diderot.fr/~henon/III-micelles.pdf
http://hal.archives-ouvertes.fr/docs/00/13/58/98/PDF/These_Stephane_Arditty.pdf
http://ethesis.inp-toulouse.fr/archive/00000737/01/rondel.pdf
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X. Vocabulary
1 CMC (Critical Micelle Concentration): concentration of surfactants above which micelles form and
almost all additional surfactants added to the system go to micelles. Before reaching the CMC, the surface
tension changes strongly with the concentration of the surfactant. After reaching the CMC, the surface
tension remains relatively constant or changes with a lower slope. The value of the CMC for a given
dispersant in a given medium depends on temperature, pressure, and (sometimes strongly) on the
presence and concentration of other surface active substances and electrolytes. Micelles only form
above critical micelle temperature.
2SDS: Sodium dodecyl sulfate
3 G.P.: Graduation Pump
4 APS: Ammonium Persulfate.
5 KPS: Potassium persulfate.
6 VA-086: Is a trade product name for a non ionic initiator. See the information attached provided from
the supplier:
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7 Miniemulsion: (also known as nanoemulsion) is a special case of emulsion. A miniemulsion is obtained
by shearing a mixture comprising two immiscible liquid phases (for example, oil and water), one or
more surfactants and, possibly, one or more co-surfactants (typical examples are hexadecane or cetyl
alcohol). Stable droplets are then obtained, which have typically a size between 50 and 500 nm.
Miniemulsion-based processes are, therefore, particularly adapted for the generation of nanomaterials.
There is a fundamental difference between traditional emulsion polymerisation and a miniemulsion
polymerization. Particle formation in the former is a mixture of micellar and homogenous nucleation;
particles formed via miniemulsion however are mainly formed by droplet nucleation. (MASON TG,
2006)