Synthesis of polymer part 2

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Department of Chemical Engineering, MNIT, Jaipur

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1.2.2 Suspension Polymerization-

This polymerization is also known as pearl polymerization/ bead polymerization/ granular

polymerization. It uses mechanical agitation to mix monomer or mixture of monomers in a

liquid phase such as water, due to which monomer droplets polymerize while they aredispersed by continous agitation. The major application of this process is in production of

PVC, a widely used plastic, as well as Sodium polyacrylate, a superabsorbent polymer used

in disposable diapers.

1.2.3 Solution Polymerization-

This method is used majorly in industrial level of polymerization. A monomer is dissolved in

a non reactive solvent that also has catalyst. The heat released by the reaction is absorbed by

the solvent and so the reaction rate is reduced. Major application of this process is in the

production of sodium polyacrylate, a superabsorbent polymer used in disposable nappies. The

benefitspf such type of polymerization, as compared to bulk polymerization is that is reduces

the viscosity and does not allow auto-acceleration at high monomer concentrations.

1.2.4 Emulsion Polymerization-

Its a type of radical polymerization that usually starts with an emulsion in water, surfactant

and monomer. The most common type of emusion is oil-water emulsion, which has droplets

of monomer(the oil) in continous phase of water. There are water soluble polymers such as

certain polyvinyl alcohols or hydroxyethyl cellulose which are used as emulsifiers/stabilizers.

The name emulsion polymerization is a misnomer that arises from a historical misconception.

Instead of occurring in emulsion droplets, polymerization occurs in the latex particles thatform spontaneously in the beginning of the process. These latex particles are generally 100

nm in size and have many individual polymer chains. The particle are stopped from

coagulating with each other because each particle is surrounded by surfactant, as the charge

present on the surfactant repels other particles electro-statically. When water soluble

polymers are used as stabilizers, the repulsion among the particles arises due to formation of

hairy layer of water soluble polymers as pushing away particles togetherwould involve

compressing these chains.


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Emulsion polymerization is used in manufacture of many polymers. Most of those are used as

solid materials and they must be isolated from the aqueous dispersion after polymerization,

while in others the dispersion itself is the end product. The dispersion formed is called latex

or an emulsion. These emulsions are used in adhesives, paints, paper coating and textile

coatings. They are finding increasing acceptance and are preferred over solvent-based

products due their eco-friendly nature as they dont contain VOCs (Volatile Organic

Compunds).

A general recepie for polymerization on laboratory level would require following proportions

of ingredient (Parts by weight):

100 of monomer,

180 of water,

2-5 of fatty acid soap,

0.2-1.5 of initiator.

Now cationic soaps may be used instead of fatty acid soaps (e.g.dodecylamine

hydrochloride). Various initiator may replace the usual persulphateinitiator(e.g. hydrogen

peroxide and ferrous ion/ water soluble organic hydroperoxide).

The mechanisms and kinetics of an emulsion polymerization process is divided into 3intervals-

Interval I: Free radicals are produced in the aqueous phase by initiator decomposition. They

are captured by micelles swollen with monomer. The polemerization begins in these micelles.

This interval corresponds to particle nucleation and stops when all the micelles have

disappeared.

Interval II: While the particles grow in size, monomer diffuse rapidly from monomer droplets

towards the particles which are saturated with monomer as long as monomer droplets exist.

This interval ends when monomer have disappeared.

Interval III: In this final period, the monomer concentration starts depleting.


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1.2.4.1 Advantages of Emulsion Polymerization-

-Due to high molecular weight polymers can be produced at fast rate. While in bulk and

solution polymerization, there is a trade off between molecular weight and rate of

polymerization.

-As the polymer molecules are contined within the particles, viscosity remains close to that of

water and is not dependent on molecular weight.

-The water has continous phase which is a good conductor of heat and so helps in removing

heat from the system, allowing many methods to increase their polymerization rate.

-The final product obtained can be used in its original form or can be altered/ processed

before its application.

1.2.4.2 Disadvantage of Emulsion Polymerization-

-For dry polymers, removal of water is very energy-intensive process.

-surfactants and other polymerization ingredients remain in the polymer and are difficult to

remove.

-This process is usually designed to operate at high conversion rate of monomer to polymer,

which results in significant chain transfer to polymer.

-This process cannot be used for condensation, ionic or Ziegler-Nutta polymerization,

although some exceptions are there.

1.2.4.3 Applications of Emulsion Polymerization-

Polymers produced can be categorized into three applications-

1.2.4.3.1 Synthetic Rubber

-Some grades of styrene-butdiene (SBR)

-Some grades of polybutadiene


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-Polychloroprene (Neoprene)

-Nitrile rubber

-Acrylic rubber

Fluoroelastomer (FKM)

1.2.4.3.2 Dispersions

-Polyvinyl acetate

-Polyvinyl acetate copolymers

-Latex acrylic paint

-Styrene-butadiene

-VAE(vinyl acetate-ethylene copolymers)

-Some grades of polybutyl-acrylate

1.2.4.3.3 Plastics

-Some grades of PVC

-Some grades of polystyrene

-Some grades of PMMA

-Acrylonitrile-butadiene-styrene terpolymer (ABS)

-Polyvinylidene fluoride

-PTFE


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1.3 Poly(butyl-acrylate)-

Poly(butylacrylate0 is a sponge in nature and thermoplastic. It is the synthetic polymer of

butylacrylate.

1.3.1 Synthesis-

Poly(butylacrylate) is produced by emulsion polymerization, solution polymerization.

Generally radical initiation is used but anionic polymerization of butyl-acrylate can also be

used.

1.3.2 Applications-

Poly(butyl-acrylate) has major applications in various industries. Most important applications

out of them are as follows-

Pressure sensitive adhesives-

These are the materials which can provide strong adhesion to solid surface for a short periodof time. The most common application is to use it as a thin layer over a substrate such asPET, PP and PVC. These can also be used in many sophisticated applications. PSAs can beseparated into 2 groups- Solution PSA and emulsion PSA. Although it has outstanding performance, application of PSA has gradually decreased because of the economic andenvironmental reasons. In contrast, emulsion PSA, especially acrylate solution has beenwidely researched due to its environmental safety, lo cost and optical clarity. In general, theglass transition temperature(Tg) of PSAs should be lower than room temperature.

Latex paint formation-

The basic phenomena of film and paint formation by latex is not new. Although a widevariety of synthetic latexes are used for binders for paint and related coating materials.


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CHAPTER 2

Literature Review

The following chapter comprises the literature on mechanisms, kinetics, optimisation and

control related to emulsion polymerization, on which our polymer production is based on.

2.1 Emulsion Polymerization -

Emulsion polymerization is a process that is used to produce waterborne resins with variouscolloidal and physicochemical properties.These processes are frequently applied for the

production of rubbers, coatings and many other products. This heterogeneous free radical

polymerization process involves emulsification of the relatively hydrophobic monomer in the

water by an oil-in-water emulsifier, followed by the initiation reaction with either a water

insoluble initiator(e.g. ammonium persulphate) or an oil soluble initiator(e.g. 2-2-

azobisisobutyronitrile).

M.J.J. Mayer,(1994), worked on emulsion polymerization in various types of reactor and withdifferent recipies with high monomer contents. The effect of the monomer on polymerization

of styrene was analysed in a batch reactor, a continuously operated stirred tank reactor. The

experiment show that no. of particles at complete conversion and the polymerization rate in

interval 2 are well predicted by Smith-Stewart theory for styrene fractions upto 0.4 in the

recepie, the polymerization rate in interval 2 increses with the monomer content and reaction

volume.

The high viscosity and the psuedoplastic rheological behaviour of the latex, leading to

imperfect mixing and poor heat transfer to the reactor wall is reason behind this increased

rate of reaction. In a batch process,when a pulse of emulsifier is addedto the reaction mixture,

a second generation of particles is produced and heat transfer limitation is avoided. This is

caused by the lower viscosity of latex with bimodal particle size distribution as compared to

unimodal particle size distribution and the same polymer content. While experiments in the

CSTR show that both the particle number and the polymerization rate in the steady state is

predicted by the theory of DeGraff and Poehlin for conversion. When steady state conversion


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is higher than 0.5, the polymerization rate appeared to be higher than that predicted by the

above theory. These high reaction rates are caused by a gel effect which occurs particularly in

the largest particles in the reaction mixture.

2.2 Emulsion Polymerization Mechanisms and Kinetics-

Chern C.S., (2006) studied on emulsion polymerisation mechanisms and kinetics. Emulsion

polymerization involves the propagation reaction of free radicals with monomer molecules in

very large number of polymer particles dispersed in the continous aqueous phase. The

nucleation and growth of latex particles control the colloidal and physical properties of latex

products. It includes nucleation and growth of particle nuclei, after that consumption ofresidual monomer in a heterogeneous system. The propagation of free radicals with monomer

occurs in the latex particles and the emulsified monomer droplets serve to supply the growing

particles of monomer.

In non-uniform latex, polymerization is a potential candidate for offering different application

properties. The interfacial tension between polymer pairs and the particle-water interfacial

tension had an important role in the development of particles morphology. Furthermore, this

predicted theory must match with observed experimentally for the interfacial free energy.Such a thermodynamic analysis only gives the ultimate morphology.

2.3 Modelling of Batch Emulsion Polymerization-

Silvia Curteanu, (2003), worked on modelling and simulation of free radical polymerisation

of styrene which was done under semi-batch reactor conditions. The approach was concerned

with the elaboration of a radical polymerisation model of styrene which is based on a kinetic

diagram that comprises thermal and chemical initiation, propagation and termination by

recombination and chain transfer mechanisms. The formalism which describes the modal in

terms of moments is explained. The model was then used to predict change in monomer

conversion and MW after intermediate addition of monomer and initiator. The obtained

results were dependent on conditions of reaction mass, quantity and moment of substance

addition. So, simulations were done at different times with respect to gel effect w.r.t. different

temperatures and initiators. Increasing the concentration of initiator before the gel effect


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causes an earlier appereance of phenomena and finally leads to decrease in moleculer weight.

The ratio Mw/Mn gives polydispersity index smaller for the intermediate addition of initiator.

No significant occur during or after the gel effect. If with the initiator, unreacted monomer

also enter reactor, a decrease in conversion is observed.

MichealWulkow, (1990), experimented on weight distribution for free radical polymerization

systems. The modelling of this mechanism gives large system of ordinary differential

equations which cannot be solved easily. To solve these a new approach was made called

discrete galerkin method. This method is characterised by galerkin approximation based on

the orthogonal polynomials of discrete variable which represents the polymer degree. It uses

enough computations of complete kinetic schemes with time or moment dependent reaction

coefficients by reducing the complexity.

Victor M., (2005), worked on kinetics and modelling of microemulsion copolymerization. A

model for micro emulsion copolymerization was developed and compared with experimental

conversion vs. time data for the vinyl acetate/butyl acrylate system. The main features pf the

model comprise miceller, homogeneous nucleation and thermodynamic equilibrium to

calculate monomer partitioning between phases. Simulation was used with reported values

for kinetic parameters except for propagation rate constant in the water phase and radical

capture by particles and micelles coefficients which are estimated. The results of simulationshowed assent with experimental data.

2.4 Free Radical Polymerization Reactions-

YaacovAlmong, (1982), worked on radical polymerization of styrene and methyl

methacrylate in dispersed systems. Also, the effect of carbon black was studied. Styrene and

methyl methacrylate were polymerized to yield particles in the range of 10m diameter. In

case of styrene, there is interface by emulsion polymerization. This was minimized by using

lauryl peroxide (LP) as initiator and a low concentration of polyvinyl alcohol (PVA) or

submicellar concentration of sodium dodecyl sulphate (SDS) as emulsifier .Bridging of

submicron molecules on large dispersion particles happened when high molecular weight

PVA was used as steric stabilizer. Although when low molecular weight PVA was used , no

bridging happened amd submicron particles were washed away to yield smooth dispersion

particles.


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Gupta S.K.,(2005), worked on free radical polymerization of n-butylacrylate under non-

isothermal conditions and with intermediate addition of initiator. Experiments and modelling

showed that experimental data on monomer conversion (Xm) and the weight average

molecular weight (Mw) were generated under various isothermal and non-isothermal

conditions for the polymerization of n-butyl acrylate. The non-isothermal results can be used

to provide better test of kinetic models than isothermal datas alone.

2.5 Optimisation of Emulsion Polymerization-

Polymerization reactions are affected by operating conditions such as temperature, pressure,

concentration etc.

G. Francois, (2003), discussed on run to run optimisation of batch emulsion polymerization.

The run to run optimization scheme is used in context tp simulation for the minimisation pf

the batch time of an emulsion polymerisation process with terminal constraints on conversion

and number average molecular weight. There were two possible extensions, the gains are

recomputed a few times to speed up the convergence and information regarding the effect

that uncertainity has on the value of the optimal. Uncertainity related update directions can be

found out using input parameters.


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CHAPTER 3

Experimental Works

3.1 Ingredients-

3.1.1 Monomers-

Monomers are the units that undergo radical polymerization. They are liquid or gaseous at

reaction conditions and are poorly soluble in water. Solid monomers are difficult to dispersein water. If monomer solubility is too high, particle formation may not occur and the reaction

kinetics reduces to that of solution polymerization.

3.1.1.1 n-Butyl acrylate monomer is used as main ingredient in batch emulsion

polymerization.

3.1.1.1.1 Structure-

Figure 3.0: Structure of n-butyl acrylate


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3.1.1.1.2 Properties-

Form Liquid

Odour Ester like, strong

Colour Colourless

Melting temperature -64oC

Boiling temperature 148oC

Vapour pressure 4.3 mbar

Vapour density 4.4

Solubility in water 1.4 g/l

Table 3.0: Properties of n-butyl acrylate

3.1.1.1.3Applications-

- Butyl acrylate forms polymer and copolymers. Copolymers of it can also be prepared from

acrylic acid and its salts, amides and esters, methylacrylates, acrylonitrile, vinyl chloride,

styrene, butadiene and drying oils etc.

- Butyl acrylate is a very useful feedstock for chemical synthesis, because it easily undergoes

various addition reactions with many organic and inorganic compounds.

3.1.2 Initiators-

Redox and thermal generation of free radicals have been used in emulsion polymerization. In

general, persulphate ions are used in both type of initation modes. The persulphate ion readily

breaks up into sulphate ions above 50oC, giving a thermal source of initiation.

3.1.2.1 Potassium Persulphate is used as initiator in poly(butyl-acrylate) synthesis.


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Figure: 3.1 Structure of Potassium persulphate


Molecular formula K 2S2O8

Molecular weight 270.322 g/mol

Appearance White crystal powder

Density 2.478 g/cm

Melting point 100oC

Solubility in water 1.75 g/100ml (0oC), 5.29g/100ml (20oC)

Minimum assay 98.1%

Chloride Not more than 0.05%

Table 3.1: Properties of Potassium per sulphate

3.1.2.1.3 Applications-

Potassium per sulphate is used for bleaching and textile designing, as an oxidizing agent and

antiseptic, also in purification of ammonium sulphate and in manufacture of soap and

pharmaceuticals.

It is food additive and used in hair dye substances such as whitening agent with hydrogen peroxide. It also plays an important role as initiator in emulsion polymerization.


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3.1.3 Surfactants-

The surfactants is used to enable a fast rate of polymerization and minimize coagulation or

fouling in the reactor and other process equipment, prevent high viscosity during

polymerization leading to poor heat transfer and to maintain properties in the final productsuch as gloss, water absorption, tensile strength. Anionic, non-anionic, cationic surfactants

have been used, although anionic surfactants are most prevalent. Surfactants who have low

CMC (critical micelle concentration) are favoured, the polymerization rate shows increase

when MC level is higher than CMC and minimisation of surfactant is preferred for economic

reasons and the adverse effect of surfactant on properties of polymer. Mixtures of surfactant

are also used.

3.1.3.1 Sodium oleate (C 18H 33NaO 2)

It is used as surfactant in the poly(butyl-acrylate) synthesis. It occurs as a whit to yellow

powder or as light brown-yellow coarse powder or lumps. As a fatty acid, sodium oleate is

not generally found but occurs as a component of more complex lipids. In its isolated form,

the substance exudes a tallow like scent and is white crystalline solid at room temperature.


Figure3.2 : Structure of Sodium Oleate


Molecular formula C18H33 NaO2

Phase Solid (STP)


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Appearance Whit to yellow powder

Melting point 233.4oC

Density 1.1 g/cm

Minimum assay 99.1%Maximum limit of impurities

Assay of fatty acid

Free alkali

Heavy metal

Chloride

>83%


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3.1.4.1 Ion exchanged double distilled water is used as a solvent in the production of poly

(butyl-acrylate) by batch emulsion polymerization process.


Figure3.3: Structure of Water


Molecular weight 18.015 g/molPhase Liquid (at STP)

Melting point 0oC

Boiling point 100oC

Density 1 g/cm

Vapour pressure 17.5 mmHg (20oC)

Viscosity 8.9*10- Pa S (25oC)

Refractive index 1.33

Table3.3: Properties of Water solvent


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Appearance Clear, colourless liquid

Physical state Liquid

Molecular weight 92.4Chemical formula C7H8

Odour Sweet, pungent

Specific gravity 0.867 at 20oC

Table 3.4: Properties of toluene Solubilizer

3.1.4.3 Methanol (CH 3OH)-

Methanol is used as a terminator in synthesis of poly(butyl-acrylate) by emulsion

polymerization.


Fig3.5: Structure of Methanol


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Molecular weight CH4Molar mass 32.05 gmol-

Appearance Colourless liquidDensity 0.7916 g/cm

Melting point -97oC

Boiling point 64.7oC

Solubility in water Miscible

Acidity 15.4 (pK a)

Viscosity 0.59 mPa.s (20oC)

Dipole moment 1.69 D (gas)Minimum assay 99.1 %

Refractive index 1.328

Table Properties of methanol

3.1.4.3.3 Application-

-The largest use of methanol is in production of other chemicals.

-About 40% of it, is converted into formaldehyde and from there into products as diverse as

plastics, plywood, paints, explosives and permanent press textiles.

-It is used as a solvent and as antifreeze in piplines and windshield washer fluid.


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3.2 Emulsion Polymerization Reactor-

A jacketed batch reactor provided with a high-speed mixer is used for emulsion polymerization.

Proper arrangements are provided for the control of reaction temperature and RPM of the mixer.

Proper arrangements are provided for administration the initiator under inert atmosphere.


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Figure 3.6 A schematic representation of batch emulsion polymerization process.

(B= batch reactor, N= N2 gas cylinder, R= gas regulator, C= gas supply controller, TW=

three way valve, v= initiator vessel, V=vacuum pump, MT=motor, T=thermometer, PM=

pump, W= water tank, M= monomer, I= initiator, P= polymer)


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The experimental setup consists of the following parts:

1. A jacketed stainless-steel reactor with a volume of three litres, the pressure in which

can be varied from vacuum up to 60 bar, and a cover of nine standardized openings

used for temperature sensor, insert, the inlet of the monomer and solvent, the sampleroutlet etc. Its manufacturer is K C Engineers, Ambala Cantt.

2. A 8 spoke stirrer with gas-tight bearing, which can run at high speeds.3. A 15 Litre water tank with built in heater for storing water and maintaining the

reactors temperature.It is manufactured by K C Engineers, Amabala Cantt.

4 A controller employed to control vacuum pump, water pump, heater and motor and

for reading the temperatures.

5 A 0.5 hp motor for the stirrer. Its rpm is 1500. The manufacturer is Eltek Equipments,Bombay.

6 A 0.25 hp vacuum pump for creating inert atmosphere in the reactor. The rpm is 440.

The capacity is 50 L/min. The manufacturer is Promivac Engineers, New Delhi.

7 A water pump. Its rating is 0.25 hp. The maximum head is 2.5 meters. Maximum

capacity is 90 Litres per hour. The operating pressure is 0.25kg/cm2. The

manufacturer is Promivac Engineers, New Delhi.

8

A vacuum pressure gauge attached to the reactor. Its range is 0 to 760 mm Hg.9 A nitrogen cylinder having a volume of 16 Litres. The supplier is Dinesh Gases,

Jaipur.

10 A rotameter for controlling the flow rate of Nitrogen. Its range is 0.51 LPM to 5.1

LPM. The manufacturer is Eureka.

11 A feed inlet to the reactor having a capacity of 20 ml.

12 An initiator inlet having a capacity of 500 ml. Through it we can feed the initiator to

the reactor in an inert atmosphere.

13 9 Temperature sensors.

14 Control Values for controlling water supply, nitrogen supply, vacuum etc.


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3.3 Preparation of Poly (butyl-acrylate) by Emulsion Polymerization-

Following steps are used in poly (butyl-acrylate) synthesis-

1. Fill the hot water tank, select its temperature 50C and set it on the TIC (temperature

indicator controller) fixed at the front panel. Start the heater and wait until desired

temperature is reached.

2. Inhibitor is removed by heating n-butyl acrylate at a temperature of 45C.

3. Prepare the aqueous solution of emulsifier by thoroughly mixing with water,

4. Charge the aqueous solution of emulsifier and monomer into the reactor through the feed

inlet fixed at the top head of the reactor.

5. Prepare the initiator solution in about 20 ml of water and store it in the vessel provided at

top rear of set-up under an atmosphere of N2.

6. Evacuate the reactor up to 50 mmHg with the help of vacuum pump provided at the base of

setup then stop the vacuum pump and flash point with pure N2 for some time.

7. Start the agitation at the rate of 700-750 rpm and simultaneously bubble the N2 at 3 LPM

into the reaction mixture.(Ensure the absence of O2 in the reactor)

8. Raise the temperature of reaction mixture to a constant reaction temperature by circulating

hot water through the jacket of the reactor. Wait until the desired reaction temperature is

reached and remains constant.

9. During the reaction, the stirring rate is to be maintained constant and N2 supply has be

maintained all through.

10. After exactly ones hour mixing, add initiator to initiate the reaction from initiator vessel

under N2 pressure. Close the initiator feed valve after its delivery and also close the N2 supply

to the initiator storage vessel.

11. After the reaction is initiated, collected 20 ml of reaction mixture at regular intervals of

time. Weigh the sample accurately and add 20 ml of methanol as terminator. The polymer

formed will precipitate in each sample.

12. Dry the polymer in the oven at 70-80C.


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3.4 Recipe for Emulsion Polymerization of Poly (butyl-acrylate) in experimental runs-

Typical recipe consist of following ingredients-

Contents Quantity

Ion-exchanged double distilled water 180 gm

n-Butyl acrylate 100 gm

Sodium oleate 2-5 gm

Potassium per sulphate 0.2-1.5gm

N2 gas 3 LPM

Methanol 50 mlTemperature of Reaction 60oC

Stirring Speed N 325 rpm

Mixing time 1 hour

Table 3.6: Typical Recipe for Emulsion Polymerization


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3.5 Experimental Data

3.5.1 Feed Data

Components Volume (ml) Mass (gm)

Double distilled water 500 481.83

n-Butyl acrylate 300 269.4

Sodium oleate 5

Potassium per sulphate 2

Total volume Total mass

800 758.73

Temperature of reaction 45oC

Stirring speed N 325 rpm

Mixing time 1 hour

Table 3.7: Ingredients for Experimental run 1 (I=2.5 gm)




Sodium oleate 5

Potassium per sulphate 4.5

Total volume Total mass850 760.73



Mixing time 1 hour



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Sodium oleate 5Potassium per sulphate 6.5

Total volume Total mass

850 762.73



Mixing time 1 hour



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S. No. Time (min) Sample volume

(ml)

Wet sample

(gm)

Dry Sample

(gm)

1 0 20 87.5 02 10 20 89.37 1.15

3 20 20 91.26 2.13

4 30 20 92.08 4.18

5 40 20 94.49 5.98

6 50 20 94.39 6.89

7 60 20 95.46 7.96

8 70 20 95.92 8.429 80 20 96.03 8.63

10 90 20 96.41 8.91

11 100 20 96.56 9.06

12 110 20 96.58 9.08

13 120 20 96.65 9.15

14 130 20 96.67 9.17

15 140 20 96.65 9.1516 150 20 96.69 9.19

17 160 20 96.71 9.21

18 170 20 96.73 9.23

19 180 20 96.74 9.24

20 190 20 96.74 9.24

21 200 20 96.74 9.24

Table 3.11 Average weight of samples for Experimental run 2 (I=4.5 gm)


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S. No. Time (min) Sample volume

(ml)

Wet sample

(gm)

Dry Sample

(gm)

1 0 20 87.50 0.002 10 20 88.97 1.47

3 20 20 93.43 5.93

4 30 20 95.63 8.13

5 40 20 97.15 9.65

6 50 20 97.48 9.98

7 60 20 98.28 10.78

8 70 20 98.73 11.239 80 20 99.26 11.76

10 90 20 99.34 11.84

11 100 20 99.69 12.19

12 110 20 99.70 12.20

13 120 20 99.73 12.23

14 130 20 99.95 12.45

15 140 20 100.06 12.5616 150 20 100.11 12.61

17 160 20 100.12 12.62

18 170 20 100.13 12.63

19 180 20 100.13 12.63

20 190 20 100.13 12.63

21 200 20 100.12 12.62

Table 3.12 Average weight of samples for Experimental run 3 (I=6.5 gm)


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3.6 Experimental Calculations-

3.6.1 Experimental Calculations method-

Initial weight fraction of monomer in the mixture

Wfo= (weight of monomer taken)/Total weight of mixture

Wfo= WM/WT

Average density of the feed mixture= Total weight of mixture taken(gm)/total volume

taken(ml)

avg =WT/VT

Weight of polymer= weight of sample before drying-weight of sample after drying

W p= Wsample1+Wsample2

At a particular timet degree of conversion X

X=weight of polymer in the sample/(weight of sample*weight of monomer fraction)

X= W p/Wsamp* Wfo

For each timet degree of conversion is calculated and is fitted to a 4th degree polynomial

passing through origin (0,0).

X= a1t+a2t2+a3t3+a4t4

dX/dt = a1+2a2t+3a3t2+4a4t3

Rate of polymerization: R p (gm/min.lit) = (dX/dt)*(Weight of monomer in feed in gm)/ Total

volume of feed mixture (lit)


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3.6.1.1 Calculation of Conversion-

Following results were obtained by calculation of conversion with respect to time-

S. No.

Time conversion (i=2.5) conversion (i=4.5) conversion (i=6.5)1

0 0 0 02

10 0.0144 0.0363 0.04683

20 0.0312 0.0659 0.17984

30 0.0465 0.1282 0.24085

40 0.098 0.1787 0.28146

50 0.12 0.2062 0.297

60 0.145 0.2355 0.31078

70 0.1583 0.2479 0.32229

80 0.1731 0.2538 0.335610

90 0.1816 0.2611 0.337611

100 0.1919 0.265 0.346412110 0.1951 0.2656 0.3466

13120 0.1978 0.2674 0.3474

14130 0.2025 0.2679 0.3529

15140 0.2042 0.2674 0.3556

16150 0.2081 0.2685 0.3568

17

160 0.2111 0.269 0.357118170 0.2122 0.2695 0.3573

19180 0.2125 0.2698 0.3573

20190 0.2139 0.2698 0.3573

21200 0.2142 0.2698 0.3571

Table Conversion calculation


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3.6.1.2 Calculation of Rate of polymerization (R p)-

Following results were obtained for the calculation of rate of polymerization with respect totime-

Time R p (i=2.5) R p(i=4.5) R p(i=6.5)

0 0 - 0

10 0.0005 0.0019 0.0018

20 0.0014 0.0021 0.0052

30 0.0021 0.003 0.0063

40 0.0018 0.0046 0.0079

50 0.0029 0.0057 0.0083

60 0.0033 0.0058 0.0089

70 0.0034 0.0063 0.0097

80 0.0034 0.0071 0.0103

90 0.0036 0.0082 0.0117

100 0.0045 0.0086 0.0125

110 0.0047 0.0091 0.0139

120 0.0049 0.0089 0.0146

130 0.0052 0.0093 0.0147

140 0.0054 0.0103 0.0151

150 0.0053 0.0108 0.0153

160 0.0057 0.011 0.0159

170 0.0057 0.0113 0.0165

180 0.0059 0.0116 0.017

190 0.006 0.0116 0.0171

200 0.0061 0.0117 0.0172

Table Rate of polymerization calculation


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3.6.1.3 Calculation of Kinetic chain length-

Time

Kinetic chain

length(V) (i=2.5gm)

Kinetic chain

length(V) (i=4.5)

Kinetic chain

length(V) (i=6.5)0 119.97 78.23 23.43

10 154.78 80.05 25.26

20 167.46 81.23 25.6

30 174.65 87.49 27.12

40 176.31 91.27 28.75

50 182.68 93.24 30.02

60 197.77 98.99 30.55

70 198.05 102.15 31.63

80 198.21 117.54 32.41

90 205.25 119.57 34.15

100 210.96 132.95 34.94

110 217.76 139.61 35.39

120 218.47 141.24 36.59

130 223.1 146.78 37.15

140 237.35 153.63 37.13

150 242.94 155.47 38.36

160 242.99 158.95 39.22

170 249.32 158.99 41.22

180 255.35 161.32 40.7

190 255.16 163.75 41.92

200 262.78 163.87 42.27

Table Kinetic chain length calculation


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3.6.1.4 Calculation of Number average molecular weight of samples (theoretical)-

Time Mn (theo.) (i=2.5) Mn (theo.) (i=4.5) Mn (theo.) (i=6.5)

0 15412.157 10093.9 3212.56710 19846.164 10325.77 3445.458

20 21461.207 10476.1 3489.162

30 22378.153 11273.63 3682.456

40 22589.012 11755.2 3889.541

50 23401.012 12006.18 4052.125

60 25323.012 12738.73 4119.856

70 25358.97 13141.31 4256.892

80 25379.654 15101.99 4356.625

90 26276.16 15360.62 4578.25

100 27003.524 17065.23 4678.931

110 27871.028 17913.71 4735.562120 27960.19 18121.38 4889.127

130 28549.98 18827.17 4959.664

140 30366.524 19699.86 4957.653

150 31077.326 19934.28 5114.634

160 31083.696 20377.63 5224.662

170 31890.048 20382.73 5578.418

180 32659.454 20679.57 5712.682

190 32635.248 20989.15 6067.955

200 33605.946 21004.44 6312.465

Table Theoretical number average molecular weight calculation


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3.7 Testing and Characterization

3.7.1 Viscosity

The viscosity of a polymer solution is a resistance force the flow of liquid. The solution of

viscosity is empirically related to molecular weight for linear polymers. Therefore, viscositymeasurements constitute a valuable tool for molecular weight characterization of polymers.

Measurement of solution viscosity( ) are usually made by comparing the efflux time trequired for a specific volume of polymer solution to flow through a capillary tube with thecorresponding efflux time to for the solvent (of viscosity o)

Figure 3.7: Ostwald viscometer

Ostwald viscometer

Relative viscosity

rel= / o=t/to

Where =viscosity of polymer solution

o=viscosity of solvent

t=efflux time required for solvent

to =efflux time for solvent


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3.7.2 pH

A pH meter is used to measure the pH (acidity or basicity) of a liquid. A typical pH meterconsists of a special measuring probe (a glass electrode) connected to an electronic meter thatmeasures and displays the pH reading. The pH probe measures pH as the activity of hydrogenions surrounding a thin-walled glass bulb at its tip. The probe produces a small voltage (about0.06 volt per pH unit) that is measured and displayed as pH units by the meter.

Calibration with at least two, but preferably three, buffer solution standards is usually performed every time a pH meter is used. One of the buffers has a pH of 7.01 (almost neutral pH) and the second buffer solution is selected to match the pH range in which themeasurements are to be taken: usually ph 10.01 for basic solutions and ph 4.01 for acidicsolutions at 25OC.

3.7.3 Electrical Conductivity

Electrical conductivity or specific conductance is a measure of a materials ability to conductan electric current. When an electric potential difference is placed across a conductor, itsmovable charges flow, giving rise to an electric current. The conductivity is defined as theratio of current density J to the electric field strength E: J= E. Conductivity of polymersolution is measured by conductivity meter. Conductivity meter is firstly calibrated with 0.1 N KCL solutions.

Conductivity is the reciprocal of electrical resistivity, , and has the SI units of Siemens permeter (S.m-1) and CGS units of inverse second (s-1): =1/.

3.7.3.1 Electrical Conductivity Meter

An electrical conductivity meter (EC meter) measures the electrical conductivity in asolution. Commonly used in hydroponics, aquaculture and freshwater systems to monitor theamounts of nutrients, salts or impurities in the water.

The common laboratory conductivity meters employ a potentiometric method and fourelectrodes. Often, the electrodes are cylindrical and arranged concentrically. The electrodesare usually made of platinum metal. An alternating current is applied to the outer pair of theelectrodes. The potential between the inner pair is measured. Conductivity could in principle be determined using the distance between the electrodes and their surface area using theOhms law but generally, for accuracy, a calibration is employed using electrolytes of well-known conductivity.


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3.7.4 Poly (butyl-acrylate) testing-

3.7.4.1 Viscosity of different concentrations of poly (butyl)-acrylate-

( to = 5.16seconds)

S.No Weight of polymer(gm)

Conc. In 50ml benzene(gm/lit)

Effluix timet for polymersolution

rel=/ o=t/to

in cp

10

8 8.57 1.38 1.389

20.65

18 8.76 1.42 1.423

3

3.80

36 8.93 1.43 1.4514

4.2148 9.17 1.48 1.488

55.58

64 9.43 1.53 1.530

66.46

76 9.68 1.57 1.571

75.89

82 9.84 1.61 1.597

Table 3.13 Viscosity of various concentration of polymer solution in experiment 1

( to = 6.30seconds)

S.No Weight of polymer (gm)

Conc. In 50ml benzene(gm/lit)

Effluix time tfor polymersolution

rel=/ o=t/to

in cp

10.00

0 7.55 1.42 1.426

20.76

54 7.76 1.46 1.466

33.99

80 7.93 1.50 1.498

44.96

100 8.16 1.53 1.541

55.53

114 8.42 1.58 1.590

66.06

124 8.67 1.64 1.637

77.89

130 8.83 1.68 1.667

Table 3.14 Viscosity of various concentration of polymer solution in experiment 2


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S. No. Conductivity (mhos) pH1 2.97 7.30

2 3.13 7.12

3 4.03 7.22

4 4.00 7.00

5 5.32 7.12

6 5.36 7.42

Table3.16 Conductivity and pH of various concentration of polymer solution inexperiment 2

S. No. Conductivity (mhos) pH

1 3.03 7.27

2 3.19 7.14

3 4.09 7.11

4 4.13 7.11

5 5.39 7.13

6 5.45 7.14

Table 3.17 Conductivity and pH of various concentration of polymer solution inexperiment 3


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3.7.5 Melt Flow Index (MFI)-

MFI is a measure of ease of flow as a thermoplastic polymer is melted. It is defined as the

mass of polymer (gm), flowing in ten minutes through a capillary of a specific diameter and

length by a pressure applied via prescribed alternative gravimetric weights for alternative prescribed temperatures.

It is an indirect measurement of molecular weight, with high melt flow rate corresponding to

the ability of materials flow under pressure. It is inversely proportional to the viscosity of the

melt at the conditions of the test, though it should be borne in mind that the viscosity for any

such material depends on the applied pressure. Ratios between 2 values for one material at

different gravimetric weights are used as a measure of the broadness of molecular weight

distribution.

Procedure-

Following steps are considered while calculating MFI-

1. A small amount of the polymer sample (4 gms) is taken in the specially designed MFI

apparatus which is nothing but a miniature model of extruder. The apparatus has a small die

inserted into the extruder, with the diameter of the die generally being 2.09 mm and height 8mm.

2. The material is packed properly inside the extruder barrel to avoid formation of air

pockets.

3. A piston is introduced which acts as the medium that causes extrusion of the molten

polymer.

4. The sample is preheated for around 6 min at 230C.

5. After the preheating, a specified weight is introduced onto the piston of weight 1.2kg.

6. The weight exerts a shear force on the molten polymer and it immediately starts flowing

through the die.

7. A sample of the melt is taken after period of 35sec and is weighed accurately.

8. MFI is expressed as grams of polymer/10 minutes of flow time. MFI= 5.447 gm/10min


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3.7.6 Melting Point-

The sample is heated and analyzed through microscope. The temperature changes gradually

and the point at which we can see the change in the shape of sample put in the slide under

microscope, the temperature reading will be our melting point. The temperature in

microscope is 140.22oC.

3.7.7 Density -

Test Method- ASTM D 792 at CIPET Jaipur

Density of poly (butyl-acrylate) as per test result comes out to be 850.95 kg/m3.

3.7.8 Molecular Weight Distribution -

Molecular weight distribution of the polymer nBA was found out using Gel Permeation

Chromatography technique. In this technique, molecular weights of different samples

collected at different time are calculated and using that an average molecular weight is

calculated.

Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC)

that separates analysts on the basis of size. The technique is often used for the analysis of

polymers. As a technique, SEC was first developed in 1955 by Lathe and Ruthven. It is often

necessary to separate polymers, both to analyze them as well as to purify the desired product.

When characterizing polymers, it is important to consider the polydispersity index (PDI) as

well the molecular weight. Polymers can be characterized by a variety of definitions for

molecular weight including the number average molecular weight (Mn), the weight average

molecular weight (Mw) (see molar mass distribution), the size average molecular weight

(Mz), or the viscosity molecular weight (Mv). GPC allows for the determination of PDI as

well as Mv and based on other data, the Mn, Mw, and Mz can be determined.


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The number average molecular weight and weight average molecular weight of samples were

measured by gel permeation chromatograph (HPLC- high performance liquid

chromatography) using tetrahydrofuran (THF) as the medium. Sample solutions of nBA were

prepared by THF to give different concentrations of nBA. The solution was filtered using

0.10-micron filter and 100 microliters of solution was then injected into THF stream

(5ml/min) of a GPC system operating at 45oC. Polymers were separated on as series of 5

columns of microstyragel 105, 104, 103, 102, 10 . The instrument was calibrated against 16

polystyrene standards in the range of 1.05*10^6 to 520. Following molecular weight

distribution curves were obtained.

3.7.8.1 Procedure-

A GPC/SEC instrument consists of a pump to push the solvent through the instrument, an

injection port to introduce the test sample onto the column, a column to hold the stationary

phase, one or more detectors to detect the components as they leave the column, and software

to control the different parts of the instrument and calculate and display the results.The

polymer sample is first dissolved in a solvent. This is an important step, because although

polymer molecules can be described as long chains of monomers linked together, they dont

exist like that in solution. Once they have been dissolved, the molecules coil up on

themselves to form a coil conformation, which resembles a ball of string. So although theyare chains, when we analyze them by GPC/SEC they behave like tiny spheres, with the size

of the sphere dependent on the molecular weight; higher molecular weight polymers coil up

to form larger spheres.These coiled up polymer molecules are then introduced into the mobile

phase and flow into the GPC/SEC column. The dissolved polymer molecules move past the

beads as the mobile phase carries them down the column. As the polymer coils move past

each bead, several things can happen. If the polymer coils are much larger than the biggest

pores in the beads, they cannot enter the pores and so are carried straight past by the mobile phase. If the polymer coils are a little smaller than the biggest pores they can enter the larger,

but not the smaller pores as they pass by, occupying some, but not all of the available

stationary phase. If the polymer coils are smaller than the smallest pores in the beads, then

they can enter any of the pores and so can potentially occupy all of the stationary phase. As

the molecules enter the column, this partitioning occurs repeatedly, with diffusion acting to

bring the molecules into and back out of any pores they pass as they travel down the column.

As a result, small polymer coils that can enter many pores in the beads take a long time to pass through the column and therefore exit the column slowly. Conversely, large polymer


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Fig 3.8 GPC Process

Fig 3.8 Chromatogram (log(MW) vs. %Wt fraction)


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3.7.8.2 Differential and cumulative weight fraction analysis-

Following results were also obtained from the testing for a sample from the experimental

run1 (i=2.5gm) -

S. No. Log(MW) Wt. fraction % Cumulative wt. fr. %

1 3.8 1.20 1.20

2 3.84 1.01 2.21

3 3.9 3.46 5.67

4 3.95 4.95 10.62

5 4.01 8.15 18.77

6 4.06 11.53 30.3

7 4.11 21.85 52.14

8 4.17 15.43 67.58

9 4.21 11.99 79.57

10 4.29 7.81 87.38

11 4.36 5.23 92.61

12 4.39 4.00 96.61

13 4.42 2.03 98.64

14 4.46 1.15 99.79

15 4.5 0.18 99.97

Table Chromatogram readings


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3.7.8.4 Polydispersity index analysis-

In following table, variation of Polydispersity index with weight fraction of nBA in THF

solvent is shown for I=2.5 gm.

S. No. Temperature

(K)

Wt. fraction

in THF

solvent

Mw Mn PDI=Mw/Mn

1 343 10 12146 9874 1.23

2 343 20 18675 10639 1.76

3 343 40 23987 11767 2.03

4 343 60 28605 13698 2.08

5 343 80 34003 16118 2.1

Table Variation of Polydispersity index with weight fraction of nBA in THF solvent


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CHAPTER 4

Mathematical Modelling

The model is developed to formulate the temperature controlling in the batch emulsion

polymerisation and emulsion of butyl acrylate at the steady state. Conversion of energy

accounts for the heat generated by the propagation reaction and heat removal through the wall

of the reactor and by convective fluid flow. The density of mixture is the function of the

conversion , amount of solvent introduced in the feed and the temperature.

4.1 ASSUMPTIONS

Emulsion polymerisation occurs in batch reactor at steady state. The density of the mixture is a function of the conversion amount of the solvent

introduced in the feed and the temperature.

Heat capacities of the monomer, solvent and the polymer are assumed to be constant,independent of temperature.

On a unit mass basis monomer and polymer are assumed to have same heat capacity. Homogeneous nucleation is assumed. Free radical mechanism is considered for the polymerization of n-butyl acrylate,

which has 3 major steps namely-

1. Initiation

2. Propagation3. Termination

Following classical model is considered as the reference model-


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kd

ki

Classical Model

Initiation

I +

Where I is the Initiator

is the radical formed

K d is the initiator decomposition rate constant

Here,

Where R d is the rate of decomposition of initiator

+M R

Where is the monomer

Where R i is the Rate of initiation

As the free radicals have high reactivity and as soon as they are formed by decomposition ofinitiator, they attack the monomer and start the initiation process. Therefore it can be assumedthe rate of formation of free radicals is equal to the rate of decomposition of the same.Therefore,

R i=R d=2k d[I]

In actual practice, some radicals of the initiator disproportionate are not effective as they areeither lost as side products by way of processes such as recombination or are notdisprortionated at all.

Where f is the fraction of free radicals produced effective in initiating the chain growth (0.5).


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kp

kp

kp

ktc

ktd

Propagation

R + RM

RM + M RMM

RMM +nM PMn+2

Where k p is the propagation rate constant

[] Where R p is the Rate of propagation.

Termination

Coupling

RMn1 + RMn2 RMn1MMMn2R

Where k tc is the termination rate constant by combination

Disproportionation

RMn1 + RMn2 RMn3 + RMn4

Where RMn3 has the saturated chain end and represents the inactive polymer chain to whichan electron has been transferred.

RMn4 represents the inactive chain with an unsaturated chain end.

Here k td is the rate constant for disproportionation step

At steady state i.e. when the number of chain growths initiated equals the number of chaingrowth arrested. The rate of initiation is equal to the rate of termination i.e.

R i = R t

2k df[I] = 2k t[]2


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But

Therefore

Where k t=k tc+k td

Also,

But

Using, k t = k tc + k td


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ktri

kb

kbb

Following model is proposed to be compared with reference model and experimentalmeasurements-

Developed Model

Other than the reactions taking place in the classical mechanism we can also consider thefollowing reactions to take place.

Initiation

The initiator may react with the monomer radical to terminate the monomer chain and form polymer.

R + RMR

Where k tri is termination rate constant by transfer to initiator

Combination reaction of Initiator

2 I

Where k b is the combination reaction rate constant

Therefore, the rate of initiation is give by

Propagation

The occurrence of intramolecular radical transfer, also termed backbiting, thus changing thestructure of the radical

R n R n

Where k bb is the backbiting rate constant


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kp1

ktd

ktc

ktri

ktrm

Reinitiation

R n + M RMn

Where k p1 is the reinitiation rate constant

Assuming quasi steady state for both radicals RMn and R ,

Termination

In termination reaction polymer chain radicals are destroyed. This occurs only when a polymer radical reacts with another polymer radical or with a primary radical. The former iscalled mutual termination and the latter is called primary termination.

Mutual Termination

RMn1 + RMn2 RMn3 + RMn4

RMn1 + RMn2 RMn1MMMn2R

Primary Termination

RMn1 + RMn1MR

Similar Reactions are found to occur quite commonly in radical polymerization withmonomers.

RMn1 + M + RMn1MR

Where k tri is termination rate constant by transfer to initiator

K trm is termination rate constant by transfer to monomer

Therefore,

But


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Using, k t = k tc + k td

Estimation of Kinetic Chain Length-

The simplest estimation of the molecular weight from the kinetics is given by kinetic chain

length, defined as the ratio of the rate of propagation divided by rate of initiation. Kinetic

chain length V of a radical chain polymerization is given as the average number of monomer

molecules consumed per each radical-

Where [M] and [I] are the monomer and initiator concentration, f is the initiator efficiency

and the k values are rate constants.

Estimation of Number Average Molecular Weight-

The number average degree of polymerization is given by

Xn= V+1

The number average molecular weight of a polymer is given by

Where Mo= molecular weight of monomer


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Results & Discussion

The synthesis of poly (butyl-acrylate) was done in batch emulsion polymerization reactor andits characterization was done in CIPET Jaipur. Rate of polymerization and degree of

conversion at particular time is calculated for different runs. When monomer and initiator

started to disappear, rate of monomer and rate of initiator consumption were calculated. For

characterization of the polymers, viscosity, conductivity, density, melting point, melt flow

index (MFI) and pH values of polymers were calculated for different runs. As emulsion

polymerization is exothermic reaction in nature, temperature of reactor fluctuates at the

starting of reaction because of heat of reaction. Temperature can be maintained by externalmedium. Control valve are also used to control the flow rate of cold water. The simulation of

the kinetics of the reaction was modelled assuming homogenous free radical polymerization

using MatLab and the corresponding results were plotted graphically.


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5.1 Degree of conversion profile for batch emulsion polymerization for poly(butylacrylate)-

Degree of conversion X increases with time. From fig 5.1, it is clear that at a particular timet=120 the conversion in experiment is 0.43 and in experiment 2 iso.40. the difference is because of the difference in concentration of monomer.

Figure 5.1(a) Degree of conversion v/s time profile Exp 1

Figure 5.1(b) Degree of conversion v/s time profile Exp 2

y = 5E-10x4 - 2E-07x3 + 1E-05x2 + 0.0023x - 0.0089

R = 0.9905

-0.05

0

0.05

0.1

0.15

0.2

0.25

0 50 100 150 200 250

X ( C o n v e r s i o n

)

Time (min)

conversion (i=2.5)

Poly. (conversion (i=2.5))

y = 6E-11x4 + 8E-08x3 - 4E-05x2 + 0.0062x - 0.0155R = 0.9894

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250

X ( C o n v e r s i o n )

Time (min)

conversion (i=4.5)

Poly. (conversion (i=4.5))


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Fig 5.3(c) Rate of polymerization v/s time profile for Exp 3

Fig 5.3(d) Rate of polymerization v/s time profile

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

0 50 100 150 200 250

R p ( R a t e o f p o

l y m e r i z a t i o n )

g m / l i t

. m i n

Time(min)

Rp

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 50 100 150 200 250

R p ( R a t e

o f p o

l y m e r i z a t i o n )

g m / l i t

. m i n

Time (min)

conversion (i=2.5)

conversion (i=4.5)

conversion (i=6.5)


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5.4 Weight of polymer vs. time profile for Emulsion Polymerization of poly(butyl-acrylate)-

The weight of polymer W p increases with time. From figure 5.4 it is clear that at a particulartime t=120, the weight of polymer in experiment 1 is 5.89gm and in exp 2 it is 7.5gm. Theweight of polymer increases due to monomer conversion increase with time. This differencein weight of polymer is due to difference in concentration of monomer.

Fig 5.4 (a) Weight of polymer v/s time profile for exp 1

Fig 5.4(b) Weight of polymer v/s time profile for exp 2

0

1

2

3

4

5

6

7

8

0 50 100 150 200 250

W e i g h t o f p o

l y m e r

( g m

)

Time (min)

wt of polymer (P)

0

1

2

3

4

5

6

7

8

9

10

0 50 100 150 200 250

W e i g h t o f p o

l y m e r

( g m

)

Time (min)

wt of polymer


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Fig 5.4(c) Weight of polymer v/s time profile for exp 3

Fig 5.4(d) Weight of polymer v/s time profile for exp 3

0

2

4

6

8

10

12

14

0 50 100 150 200 250

W e i g h t o f p o

l y m e r

( g m

)

Time (min)

wt of polymer

0

2

4

6

8

10

12

14

0 50 100 150 200 250

W e i g

h t o f p o

l y m e r

( g m

)

Time (min)

wt of polymer(i=2.5)




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5.5 Kinetic chain length vs. time profile for emulsion polymerization of n-(butylacrylate)-

Kinetic chain length was calculated for every sample drawn at specific time intervals as theratio of rate of propagation to rate of initiation.

Fig Kinetic chain length v/s time profile

0

50

100

150

200

250

300

0 50 100 150 200 250

Kinetic chain length(V) (i=2.5)




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5.6 Number average molecular weight v/s time profile for emulsion polymerization ofpoly (butyl acrylate)-

Number average molecular weight was calculated from kinetic chain length calculation fordifferent initiator concentration and experimental data were obtained from gel permeationchromatography.

Fig Number average molecular weight v/s time

0

5000

10000

15000

20000

25000

30000

35000

40000

0 50 100 150 200 250

N o . a v g . M w

( g m

)

Time (min)

Mn (exp.) (i=2.5)

Mn (exp.) (i=4.5)

Mn (exp.) (i=6.5)

Mn (theo.) (i=2.5)

Mn (theo.) (i=4.5)

Mn (theo.) (i=6.5)


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5.5 Rate of initiator Disappearance v/s time profile for emulsion polymerization ofpoly(butyl acrylate)-

Rate of initiator disappearance decreases with time linearly as shown in figure 5.5(a) and (b),

This may be because initially high concentration of initiator is available which break down tofree radicals and as polymerization starts. As the reaction f proceeds, the concentration ofinitiators decreases linearly and hence the rate of disappearance of initiator also decreases.

Fig Rate of initiator disappearance v/s time

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0 2000 4000 6000 8000 10000 12000 14000

model 1(i=2.5)

model 2 (i=2.5)

model 1(i=4.5)

model 2(i=4.5)

model 1(i=6.5)

model 2(i=6.5)


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5.6 Rate of monomer disappearance v/s time profile for emulsion polymerization ofpoly(butyl acrylate)-

Figure 5.6 shows the relation of rate of disappearance of monomer with time. Rate decreasescontinuously as in beginning high concentration of monomer is present which after initiatorreacts rapidly. As the reaction proceeds, the concentration of monomer decreases and hencethe rate of disappearance of initiator also decreases

Fig Rate of monomer disappearance v/s time

0

0.5

1

1.5

2

2.5

3

0 2000 4000 6000 8000 10000 12000 14000

exp (i=2.5)

exp(i=4.5)

exp(i=6.5)

model 1 (i=2.5)

model 2 (i=2.5)

model 1(i=4.5)

model 2(i=4.5)

model 1(i=6.5)

model 2(i=6.5)


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5.7 rate of polymer formation v/s time profile for emulsion polymerization of poly(butyl acrylate)-

Figure 5.7 shows the relation of rate of formation of polymer with time. Rate decreasescontinuosly as in beginning high concentration of monomer is present which after initiationreacts rapidly. As the reaction proceeds, the concentration of monomer and initiator decreasesand hence the rate of formation of polymer also decreases.

Fig Rate of polymer formation v/s time

0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0.018

0.02

0 2000 4000 6000 8000 10000 12000 14000

exp(i=2.5)

exp(i=4.5)

exp(i=6.5)

model 1(i=2.5)

model 2(i=2.5)

model 1(i=4.5)

model 2(i=4.5)

model 1(i=6.5)

model 2(i=6.5)


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5.8 Comparison of Experimental results with classical model (1) and applied model (2)-

On the basis of monomer concentration obtained from experimental run (for i=2.5gm) resultsobtained from classical model and proposed model and coefficient of correlation and MAPEwere calculated.

time(min) experimental R 2 1 R22 %MAPE1 %MAPE0 2.5631 2.5633 2.5633 7.8E-05 7.8E-05

10 2.387 2.4334 2.3983 0.019439 0.00473420 2.223 2.3122 2.249 0.040126 0.01169630 2.1 2.1999 2.114 0.047571 0.00666740 1.9587 2.0952 1.9915 0.069689 0.01674650 1.8519 1.9983 1.8805 0.079054 0.01544460 1.8389 1.9078 1.7793 0.037468 0.03241170 1.6561 1.8238 1.6868 0.101262 0.01853880 1.5774 1.7453 1.6022 0.106441 0.01572290 1.4789 1.6724 1.5244 0.13084 0.030766

100 1.4523 1.6042 1.4528 0.104593 0.000344110 1.4165 1.5404 1.3867 0.087469 0.021038120 1.3549 1.4808 1.3256 0.092922 0.021625130 1.2487 1.4248 1.2691 0.141027 0.016337140 1.215 1.3723 1.2166 0.129465 0.001317150 1.1533 1.323 1.1679 0.147143 0.012659160 1.0959 1.2766 1.136 0.164887 0.036591170 1.0701 1.2329 1.0804 0.152135 0.009625180 1.0178 1.1918 1.041 0.170957 0.022794

190 1.0089 1.153 1.0042 0.142829 0.004659200 0.9353 1.1164 0.9698 0.193628 0.036887Rsq 0.9958607 0.997151 0.102811 0.016032

MODEL1 MODEL2 MAPE1 MAPE2

Table Calculation of coefficient of correlation and MAPE

Since the value of coefficient of correlation for classical model (model 1) on comparison with

experimental values (R2 1=0.9958 ) and for proposed model (model 2) on comparison with

experimental values (R2

2=0.9971 ) were almost equal, so further MAPE was calculated whichis 10.28 for classical model (Model 1) as compared to proposed model (model 2) 1.60. So

this is clear that proposed model is better fit for the actual process than the classical model.


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Conclusion

Butyl acrylate polymer was successfully prepared by the batch emulsion polymerisation and

characterized. The simulation of the process was carried Range kutta algorithm on

MATLAB. Corresponding graphs were plotted for concentration of initiator, monomer,

butyl acrylate with respect to time hence the complete analysis of batch polymerisation

process was done.

Butyl acrylate is characterised by estimation of properties of butyl acrylate solution like

viscosity, ph and conductivity. For particular time degree of conversion and rate of

polymerization is calculated which shows the Trommsdorff effect. The graphs are plotted

from results and discussed.

From the successful synthesis of butyl acrylate from emulsion polymerisation we got better

experimental yields as compared to other polymerisation techniques and thus it is suggested

that this technique can be extended for the preparation of other polymer as well.


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12. YaacovAlmog& Moshe levy [1982], Free radical polymerization of styrene and butyl

acrylate in dispersed system and the effect of carbon black, Ind. Eng.Chem. Prod.

Res . Dev., Vol.21, No.2 , page. 164-170.

13. AswiniSood, aparnasingh [2013] lumped model for butyl acrylate emulsion

polymerisation, department of chemical engineering, HBTI Kanpur, 208002 india.

Accepted 27 Feb 2013.

14. OdianGeorge , [2004] Principles of polymerization 3rd edition ., John Wiley & Sons ,

New York , page , 335- 352.

15. Fried , Joel R ., Polymer Science and Technology, 2nd edition , Prentice Hall PTR,

1995 , New Jersey , Page, 23-72.

16. William L. Luyben [1996] , Process modelling , simulation , and control for chemical

engineering , second edition , McGraw- Hill Publishing , page , 23-27 and 46- 62.

17. Mohammad Anwar Hosen , MohdAzlanHussain , Farouq S . Mjalli . [2008],

optimum kinetics for polystyrene batch reactor by Neural Network approach

.Computers & chemical Engineering , Volume 21, supplement 1 , pages S463

S468.


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APPENDIX A

Kinetics rate constant for free radical polymerization of Polybutyl acrylate:

Constants Value of ConstantsF 0.58K d 0.001834 min-K p 49876.54 lit/mol-minK tr M 1.40813 lit/mol-minK 1 K p K td K t K tc 0.0K t 1.414*109 lit/mol-minK tri 49876.54 lit/mol-min


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APPENDIX B

Programming Algorithms on MatLab for Poly(butyl)-acrylate

For Classical model

function classicalmodel % Initiator is potassium persulphate having molecular weight of 270.322 % Monomer is n butyl acrylate having molecular weight of 128.17 tspan=[0:60*10:200*60]; % time span is 200 minutes x0=[(2.5/270.322)/.820 (269.4/128.17)/.820 0]; [t x]=ode15s(@poly_unstd,tspan,x0) figure(1),plot(t,x(:,1)) figure(2),plot(t,x(:,2)) figure(3),plot(t,x(:,3))

function [dx] = poly_unstd(t,x) dx=zeros(2,1); R=0.008314; T=343; kd=8.5*10^-5; % where kd is the rate constant of dissociation of initiator % kd=(7.90*10^7)*exp(-78.62/(R*T)) kp=26.0671; % where kp is the rate constant of propagation % kp=(1.7*10^4)*exp(-17.4/(R*T)); kt=41728.43967; % where kt is the rate constant of termination %kt=(1.9*10^5)*exp(-4/(R*T)) f=0.5; % where f is the fraction of free radicals produced effective in initiating % the chain growth dx(1)=(-2*f*kd*x(1)); % Gives concentration of Initiator dx(2)=(-kp*((kd*f)^(0.5))*((kt)^(-0.5))*(x(1)^(0.5))*x(2)); % Gives concentration of Monomer dx(3)=((kt*kd*f*x(1))/kt); % Gives concentration of Polyner

end

end


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For Developed model

function developedmodel % Initiator is potassium persulphate having molecular weight of 270.322 % Monomer is n butyl acrylate having molecular weight of 128.17 tspan=[0:60*10:200*60]; % time span is 200 minutes x0=[(6.5/270.322)/.820 (269.4/128.17)/.820 0]; [t x]=ode15s(@poly_unstd,tspan,x0); figure(1),plot(t,x(:,1)) figure(2),plot(t,x(:,2)) figure(3),plot(t,x(:,3))

function [dx] = poly_unstd(t,x) dx=zeros(2,1); R=0.008314; T=343; kd=(6.90*10^7)*exp(-78.62/(R*T)); % where kd is the rate constant of dissociation of initiator % kd=7.3378*10^-5 kp=(1.7*10^4)*exp(-17.4/(R*T)); % where kp is the rate constant of propagation % kp=38.0671 kt=(1.9*10^5)*exp(-4/(R*T)); % where kt is the rate constant of termination % kt=4.6728*10^4 ktrm=(4*10^-5)*kp; % where ktri is termination rate constant by transfer to monomer ktri=(0.5)*kp; % where ktri is termination rate constant by transfer to initiator kp1=9.78*10^6; % where kp1 is the reinitiation rate constant kbb=3.14*1000; % where kbb is the backbiting rate constant f=0.5; % where f is the fraction of free radicals produced effective in initiating % the chain growth keq=72.44; % where keq is the equilibrium rate constant for the Initiator kback=(kd/keq); % where kb is the combination reaction rate constant dx(1)=(-2*f*kd*x(1))+(0.5*x(1)*kback*f)-((ktri*((kd*f)/kt)^0.5)*(x(1)^1.5)); % Gives concentration of Initiator dx(2)=(-kp*((kd*f)^(0.5))*((kt)^(-0.5))*(x(1)^(0.5))*x(2))*(((kp1*x(2))+((2*f*kt*kd*dx(1))^0.5))/(kbb+(kp1*x(2))+((2*f*kt*kd*dx(1))^0.5))); % Gives concentration of Monomer dx(3)=((kt*kd*f*x(1))/kt)+((ktri*((kd*f)/kt)^0.5)*(x(1)^1.5))+(ktrm*x(2))*(((kd*f*x(1))/kt)^0.5); % Gives concentration of Polymer end

end


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APPENDIX C

Poly(Butyl-acrylate) pictures

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