polymer chemistry united 2

Presented by

Polymer Chemistry 1I Nazarbayev University

Click to enter name

Polymer Syntheses Eugene F Douglass, MS, PhD Polymer

Science - Professor

Chapter 1

Polymerization of Hydrocarbons

Introduction

Free Radical Polymerization

Cationic Polymerization

Anionic Polymerization

Coordination Catalysts

Miscellaneous Methods

Introduction Polymerization of ethylene with substituent groups

1 benzyl ethylene Styrene

Vinyl Chloride

Isoprene

Acrylic and Methacrylic acid

Methyl and Ethyl Acrylates

Most common method Free radical polymerization

Addition polymerization

Free radical polymerization Initiation

Initiators Peroxides, AIBN, Oxidation/Reduction, Halogens

Propagation

Termination

Radical coupling

Disproportionation

Chain transfer

Techniques Bulk

Solution

Suspension

Emulsion

Precipitation

Experimental Techniques Bulk Polymerization Thermal polymerization of Styrene

Recipe

Dry and inhibitor free styrene 50 g in test tube

1.0 g Benzoyl Peroxide

1-2 Hours at 80C in water bath, until it become syrupy

Add toluene to dissolve and remove, ppt in Methanol to give

solid polystyrene

Calculate % yield.

Get IR for analysis

Emulsion Polymerization Polystyrene Concept

Monomer dispersed in water containing a soap forming an emulsion

Water soluble initiator is used

Start

Relatively large droplets of monomer are present (about 1 m in diameter), stabilized by soap molecules

Micelles of 50-100 soap molecules swollen with monomer of about 10

nm in diameter are present

Aqueous phase consisting of a few monomer molecules and the

initiator which form free radicals

Propagation

Emulsion Polymerization Polystyrene Propagation

Monomer droplets and micelles compete for the free radicals, most

enter micelles

Polymerization occurs within micelles, new monomer dragged by

equilibrium forces from monomer droplets through aqueous phase

until monomer supply is exhausted.

Termination

Polymerization terminates upon entry of another free radical into

micelles unless replenished by more free radical and monomer.

Final product is a stable dispersion (latex)

Emulsion Polymerization Polystyrene Used for coatings grade polystyrene

Large quantities of soap residue that impair clarity and

electrical properties.

Experimental Techniques Emulsion Polymerization Styrene

Recipe

Dry and inhibitor free styrene 71.2 g

128.2 g of distilled water

31.4 ml of 0.680% Potassium Persulfate

100 ml of a 3.56% soap solution

Purge system with Nitrogen gas to remove dissolved air

(oxygen).

Raise temp to 80C using mantle, stir well for 2-3 hours

Describe results, put material to dry in evaporating dish

Emulsion Polymerization

Explain thoroughly mechanism based on recipe.

Discussion of reaction conditions

Pilot plant and plant scale up, what features can be

used, techniques??

Read pages 57-66 Polymer Synthesis T & P

Acrylate Polymerization - Emulsion Please read these informative pages from The Macrogalleria

Polystyrene

Poly(methylmethacrylate)

Free Radical Vinyl Polymerization

Emulsion Polymerization

Goal

The goal is to for you, the enthusiastic lab student, to synthesize a polymer by free-radical emulsion

polymerization. Procedure

Obtain a 10 or 20 mL Erlenmeyer flask

Place the following into the flask:

4 mL of deionized water

potassium persulfate free-radical initiator

sodium lauryl sulfate surfactant

2 mL of monomer

Purge with nitrogen gas for about 1 minute

Shake flask vigorously to form emulsion

Place in an 80oC oil bath for one hour, shaking periodically

Add DI water and NaCl to the flask to break emulsion

Remove polymer from flask and wash repeatedly with DI water

Dry polymer in oven

Different Acrylate monomers Styrene

Methyl Methacrylate

Ethyl Acrylate

Butyl Acrylate

Hydroxyethyl Acrylate

Acrylic Acid

Methacrylic acid

Different comonomer blends make different copolymers

Some added all together at once, others added one at a time.

Some articles to read and look at, go to moodle

Acrylic Polymers Saunders Chapter 6 All based on Acrylic acid

Three routes to acrylic acid Propylene

Acetylene

Ethylene

Methacrylic Acid

Esters of Acrylic acid Various esters of acrylic acid are commercially available, but,

methyl, ethyl and butyl acrylates are most widely used.

Various esters are commercially available but Methyl

Methacrylate is most important.

Propylene route

Esters of Methacrylic acid

Acrylonitrile 3 routes, only one used most often.

Acrylamide

Cyanoacrylates

Polyacrylic Acid and Polymethacrylic acid

Next Weeks lab Polymerization of Ethyl Acrylate

Poly(Methyl Methacrylate) Bulk Polymerization

Prepolymer formation, using benzoyl peroxide at 0.5%, then placed in a

casting cell and cured for 15 hours at 40C. 95C for 1 hour.

Suspension Polymerization batch amounts

Stirred reactor, for heating and pressure.

Heated to 80C to start, exotherm causes it to rise to 120C and

pressure to go up. Polymerization occurs in about an hour

Hard, rigid material results

Acrylic Copolymers Thermoplastic acrylics

Methyl Methacrylate and an Alkyl Acrylate for flexibility

Acrylic Solutions

Aromatic hydrocarbon or ketone, such as MEK

Benzoyl Peroxide 0.2-1%

90-110C under slight pressure in a jacketed kettle

Acrylic latices - latex

Acrylic Copolymers Thermosetting acrylics

Crosslinked films on heating

Acrylic Solutions

Acrylic Copolymers Thermosetting acrylics

Thursdays lab http://matse1.matse.illinois.edu/polymers/a.html

300 ml of 0.6 M (5%) ethyl acrylate, CH2 = CHCOOCH3 (To

prepare: mix 16 ml of ethyl acrylate with 284 ml of water.)

5 ml of 0.1 M potassium bromate, KBrO3, (To prepare:

dissolve 0.4 g KBrO3 in water and dilute to 25 ml. This will

be enough for 5 demonstrations.)

5 ml of 0.45 M sodium hydrogen sulfite, NaHSO3 (freshly

prepared) (To prepare: dissolve 0.47 g NaHSO3 in water and

dilute to 10 ml. This will be enough for 2 demonstrations.)

Thursdays lab - procedure http://matse1.matse.illinois.edu/polymers/a.html

Procedure:

Perform this demonstration in a hood and wear gloves.

Place 300 ml of 5% methyl acrylate in a 1-Liter Erlenmeyer flask.

Add 5 ml of 0.1 M potassium bromate solution and 5 ml of 0.45 M

sodium hydrogen sulfite solution.

Swirl the flask to mix the contents thoroughly and allow the reaction to

proceed for about 15 minutes, shaking the flask occasionally during this

time. As the particles grow, the mixture quickly takes on a milky

appearance.

Pour the emulsion into 300 ml of 5 M sodium chloride solution to

coagulate the polymer.

Polyacrylonitrile - PAN Textile Fibers end use

Solution Polymerization and Suspension Polymerization

primary methods, solution method is most convenient, as

when a solvent for the polymer is used, the fiber can be then

directly spun.

Polyacrylonitrile Copolymers about 10% to make fibers easier to dye.

Examples include MMA, VA, 2-vinylpyridine

Heating of fibers leads to decomposition at higher

temperatures, heating at 1500-3000C results in a carbon fiber

with graphitic crystalline structure. The most important

source now for carbon fibers.

Nitrile resins

70:30 Acrylonitrile and MA formed in presence of butadiene-

acrylonitrile rubber (10-15%).

Polyacrylamide Polyacrylamide is water soluble, so has only limited

commercial applications

Prepared by free radical polymerization

Different type of polymer results when initiated by a strong

base, a polyamide Nylon 3 is formed.

Polyacrylamide

Poly(2-cyanoacrylate)s Methyl and ethyl 2-cyanoacrylate form the basis of the so-

called super glues

Anionic polymerization easily occurs due to two electron

withdrawing groups on double bond. Weak bases such as

water bring about rapid polymerization

UV Curable polymers/coatings

Based primarily on acrylate monomers

Prepolymers made first with retention of crosslinking

functionality.

Very low VOC (volatile organic compounds)

Monomer often used as solvent

Prepolymer used as thickener

Combination of solution/bulk polymerization

UV Cured polyMMA bulk polymer

UV Cured coatings presentation

http://www.intermediates.basf.com/chemicals/coatings/uv-coatings

Suspension polymerization Saunders pages 26, 79, 84, 94, 108,118,139, 144,152,155,

163,209,438

Recipe:

150 ml of a 1% solution of sodium poly(methacrylate) in water

50 ml of a 5% solution of sodium poly(methacrylate) in water (see

Note 1)

A buffer solution of 0.85 g of disodium phosphate and 0.05 g of

monosodium phosphate in 5 ml of water

0.5 g of dibenzoyl peroxide paste in water

50.0 g of methyl methacrylate (inhibitor free)

Deionized water (several liters)

Suspension polymerization Procedure

1. In a laboratory hood, equip a 500-ml three-necked flask with a sealed stirrer and motor,

condenser, thermometer, and an addition funnel.

2. Add 150 ml of a 1% solution of sodium poly (methacrylate) in water and a buffer solution of

0.85 g of disodium phosphate and 0.05 g of monosodium phosphate in 5 ml of water

3. Add a dispersion of 0.5 g of dibenzoyl peroxide in 50 g of inhibitor-free methyl methacrylate to

the reaction flask.

4. Measure 25 ml of the 5% aqueous solution of sodium poly(methacrylate) into the addition

funnel.

5. Place the assembled reaction flask in the water bath, attach the stirring motor, and begin

stirring.

6. Adjust the stirrer speed so that droplets of monomer form that are 2-3 mm in diameter.

7. Heat the flask with the water bath at 80-82C for 45 to 60 min (see Notes 3 and 4).

8. Collect the solid particles on a funnel fitted with cheesecloth.

9. Bundle the particles in the cheesecloth, and place the bundle in 1 liter of boiling deionized

water. Remove the bundle and wash two more times in fresh boiling deionized water.

10. Open the bundle. Dry the product under reduced pressure at 60-70C.

Polyamides Nylon 6-10 Interfacial technique

A. Sebacoyl chloride (reagent grade or freshly distilled)

B. Tetrachloroethylene (reagent grade or freshly distilled)

C. Hexamethylenediamine (reagent grade or freshly distilled)

D. 50% aqueous ethanol

Procedure 1. Add a solution of 3.0 ml (0.014 mol) of sebacoyl chloride dissolved in 100 ml of

anhydrous tetrachloroethylene as received (see Note 1) to a tall-form beaker.

2. Carefully pour a solution of 4.4 g (0.038 mol) of hexamethylenediamine (see Note 2)

dissolved in 50 ml of water over this acid chloride solution.

3. Grasp the poly amide film that begins to form at the interface of these two solutions

with tweezers or a glass rod and slowly pull it out of the beaker in a continuous

fashion. Stop the process when one of the reactants becomes depleted.

4. Wash the resulting "rope"-like polymer with 50% aqueous ethanol or acetone, dry, and

weigh to afford 3.16-3.56 g (80-90%) yields of polyamide.

Polyamides Linear aliphatic polyamides capable of fiber formation,

commonly called nylons. Fibers and engineered composites.

Fatty polyamides, derived from fatty acids.

Aromatic polyamides - aramids

Proteins

Polyimides

Linear Aliphatic Polyamides

Nylon 6,6 based on 6 carbon diamine and 6 carbon

dicarboxylic acid or di-acid chloride.

Nylon 6 based on ring opening of caprolactam

Condensation polymer

Raw Materials Adipic acid

Hexamethylenediamine

Raw Materials Azelaic acid

Sebacic acid

Dodecanedioic acid

-Aminoundecanoic acid

Caprolactam

Preparation Neutralization of an aqueous solution of adipic acid by the

addition of hexamethylene diamine; exact end point

determined electrometrically. You must have exact

equivalence of the reactants. Why??

On heating, nylon salt dissociates and then polymerization

occurs

Preparation Nylon 6,9; 6,10; & 6,12

All prepared by same methods above, except different diacids or diacid

chlorides

Nylon 11 is produced continuously by the heating of -aminoundecanoic acid at 200-220C with the continuous removal of

water. Why continuous removal of water?

Nylon 6 is produced by the ring opening polymerization of

caprolactam. 5-10% water by weight, and 0.1% acetic acid is fed

into a reactor containing caprolactam (purged with nitrogen).

Mixture heated at about 250C for 12 Hours, at 15 atm pressure.

Low molecular weight material removed by leaching with water or

heating in a vacuum.

Nylon 12 heating dodecyl lactam at 300C in the prescence of

aqueous phosphoric acid

Polymerization mechanism

Polymerization mechanism - anionic

Physical Properties

Polyesters Unsaturated polyesters

Alkyds

Poly(allyl ester)s

Poly(ethylene terephthalate)

Poly(butylene terephthalate)

Cyclohexylenedimethylene terephthalate polymers

Polyester thermoplastic elastomers

Polyarylates

Poly(p-hydroxybenzoate)s

Polyester plasticizer

Unsaturated Polyesters Linear polyesters containing aliphatic unsaturation to crosslink

1946 Diethylene Glycol and Maleic Anhydride, cross linked

with styrene.

Glass fiber reinforced polyester laminates 1940s

Bulk Molding Compounds 1950s

Sheet Molding Compounds 1960s

Essentially mixtures of unsaturated polyesters, glass fiber and

filler, which are processed using standard techniques for

thermosetting materials

Raw Materials Diols

Propylene glycol is the diol most widely used for the manufacture of

linear unsaturated polyesters. Preferred because it forms polyesters

that are compatible with styrene.

Diethylene glycol greater flexibility

Neopentylene glycol (2,2-dimethyl-1,3-propanediol) resistance to

thermal degradation

Diether of propylene glycol and bisphenol A

Ethylene Glycol helps crystallization and added with other diols.

Raw Materials Unsaturated Acids and Anhydrides

Maleic Anhydride

Fumaric Acid and Chloromaleic acid

Phthalic Anhydride

Raw Materials Unsaturated Acids and Anhydrides

Adipic Acid, Sebacic Acid, for flexibility, or Isophthalic acid toughness

with high heat distortion temperatures.

Flame resistance can be imparted with chlorinated acids and

anhydrides.

Crosslinking Monomers

Styrene, by far the most common

MMA

Diallyl Phthalate and Triallyl cyanurate

Preparation Typical formulation

Propylene glycol 100 parts by weight

Maleic anhydride 72

Phthalic anhydride 54

The molar ratio of the ingredients shown above is 1.2: 0.67 : 0.33

Excess of glycol is to allow for loss during the reaction and limit the

molecular weight of the polymer.

150-200C for 6 -16 hours and water is continually distilled from the reactor.

Sometimes xylene is added o help remove water by azeotropic distillation,

and p-TSA added as a catalyst to lower reaction time.

It is then moved to a blending tank with about half the weight of polymer of

monomer is added, along with hydroquinone as inhibitor.

This blend is called the Polyester or Unsaturated Resin, which is then allowed

to cool to room temperature and then shipped to the customer

Preparation

Crosslinking Use Styrene, or MMA most commonly

Types of initiators

Benzoyl Peroxide, 2,4 dichlorobenzoyl peroxide, di-tert-butyl

peroxide, and lauryl peroxide. Stable at RT, rapidly crosslink from 70

150C.

Cold curing use accelerators, and peroxides like methyl ethyl ketone

peroxide, and cyclohexanone peroxide.

Crosslinking Cold curing use accelerators, and peroxides like methyl ethyl ketone

peroxide, and cyclohexanone peroxide. Metal salts of fatty acids used

as accelerators.

Alkyds Natural polyesters Network polymers used in surface coatings

Many derived from phthalic anhydride and glycerol, then

modified with drying oils and fatty acids.

Raw materials

Polyhydric alcohols

Glycerol 3 OH groups on propane 1,2,3 propanetriol

Pentaerythritol, trimethylolpropane &n sorbitol

Sometimes ethylene and propylene glycols are added to

reduce crosslink intensity.

Dibasic acids and anhydrides

Phthalic anhydride, maleic anhydride, isophthalic acid, adipic

and sebacic acids.

Raw materials

Modifying oils and fatty acids

Oils and fatty acids derived from them are essentially

naturally occuring triglycerides, esters of glycerol and mixed

fatty acids (long carbon chains, zero to two or three double

bonds on chain)

Alkyd Resins

Short, medium and long oil resins

Drying oil resins most used in coatings

and alkyd paints

Semi-drying - some use in coatings and

alkyd paints for special purposes, like

high gloss finishes

Nondrying plasticizers

Preparation of Alkyd Polyesters Fatty Acid process

Fusion method

Oil hydrolyzed to give free fatty acids

Heat to 240C with a mixture of polyol and dibasic acid.

Simultaneous transesterification of polyol, dibasic acid and fatty acids

occur, with all becoming part of the polymer structure.

Solvent or solution method

Xylene (5% by weight) added to the reaction, mixture heated with a

condenser/separation funnel apparatus, which collects an azeotrope

of xylene and water, which then separates, enabling return of the

xylene to the reaction flask.

Provides good temperature control

Preparation of Alkyd Polyesters

Alcoholysis process

Oil heated with the polyol to 240C with a

basic catalyst (Ca(OH)2)

molar ratio, resulting in principal

product of monoglyceride

Add dibasic acid, and then treated the

same as in the fatty acid process, fusion or

solvent method.

Structure of Alkyd Polyesters

Fatty acid residues incorporated into the structure enable usefulness of material in surface coatings.

Alkyd Film Formation Mechanism by which an alkyd resin is converted from a liquid

to a dry film is largely determined by the nature of the fatty

acid residues present (Saunders, page 245)

Drying process involves attack by oxygen in the unsaturated regions of

the unsaturated fatty acid residues.

Crosslinking initiated by the decomposition of the oxidation process.

Usually too slow under ambient conditions so resin requires driers,

which are usually naphthenate, linoleates or octoates of metals, like

Cobalt, Lead and Manganese

Modified alkyd resins Blends with alkyd resins

Cellulose nitrate

Chlorinated rubber

Silicone resins

Incorporated during manufacture

Phenolic resins

Amino resins

Post manufacture

Styrene and other vinyl monomers, heated with initiators under reflux

until required viscosity is reached.

Epoxies Bisphenol A and Epichlorohydrin

Bisphenol A

Epoxies Bisphenol A and Epichlorohydrin

Epichlorohydrin

Liquid Resin Preparation

Bisphenol A and epichlorohydrin 1:4 molar ratio heated to 60C with

stirring. Add solid NaOH (2 moles / mole BPA) slowly so reaction

remains neutral.

Reaction is exothermic, cooling applied to keep at 60C.

Epoxies Solid Resin Preparation

Bisphenol A and epichlorohydrin 1:4 molar ratio heated to 100C with

stirring. Add aqueous NaOH with vigorous stirring.

Results in 30% water in resin emulsion, coagulated washed with hot

water, water is then removed by heating to 150C under reduced

pressure.

Reactant Ratios yield different products

Crosslinking agents Cannot be crosslinked at a reasonable rate by heat alone, so

we need a curing agent, so all systems are two part systems.

Resin

Curing agent

Curing agents

Tertiary amines

Crosslinking agents Curing agents

Tertiary amines


Polyfunctional amines

Crosslinking agents Mechanism of amine link reaction with epoxy resin

Crosslinking agents

Mechanism of amine link reaction with epoxy resin


Acid Anhydrides

Modified BPA Epichlorohydrin epoxy

Resin Modified epoxies Phenol Formaldehyde resins

Resin Modified epoxies Amino resins

Lab Thursday Bring things to glue together, perhaps use IR.

Reagents and Materials

Test glue curing time with a variety of materials

Tongue depressors, wood, paper, metal, etc.

IR of material between two glass slides.

Polyvinyl acetate - PVAc Raw Materials

Ethylene route

Mixture of ethylene and acetic acid are oxidized over a palladium

catalyst at 5-10 atm, and 150-200C. Exit gases are quenched and vinyl

acetate is separated by distillation. 95% yield is typical

Acetylene route

Mixture of acetylene (in excess) and acetic acid vapor is passed

through a reaction tube at 190-220C. Tube contains a Zinc catalyst, and

about 50% of the acetic acid is converted per pass with other materials

recycled.

Polyvinyl acetate Production - first commercial production of PVAc began in

Germany in 1920.

Readily polymerized by bulk, solution, suspension, and emulsion

techniques. Emulsion is the primary method. Resulting latexes used

mainly for water based paints and adhesives.

Emulsion polymerization

Polyvinyl acetate Structure head to tail mostly

Properties

Too brittle, too much cold flow to be useful in bulk form for rigid

applications. PVAc mostly finds applications in film form in surface

coatings and adhesives. Tg is often lowered by using a plasticizer or

copolymers.

Polyvinyl acetate Soluble in many solvents, swells in water and softens on

prolonged immersion in water. Readily hydrolyzed to

polyvinyl alcohol by acids and bases.

Decomposition occurs above 70C, accompanied by

elimination of acetic acid giving polyacetylene.

Copolymers

To help film formation and flexibility comonomers are often used in

emulsion polymerization, they include butyl acrylate, 2 ethyl-

hexylacrylate, diethyl fumarate, diethyl maleate and vinyl esters of fatty

acids. Typically 15-20% comonomer

Polyvinyl alcohol very important hydrolysis product

Polyvinyl alcohol (PVA) cannot be prepared from its

monomer, as its monomer rapidly converts to acetaldehyde.

For commercial purposes all is obtained from polyvinyl

acetate by hydrolysis.

Acid and base hydrolysis often results in contamination, so most

common is alcoholysis using a small amount of base as catalyst:


Preferred method to manufacture is solution polymerization

of vinyl acetate in methanol, followed by alcoholysis with base

catalyst.

A continuous process is mentioned in the book:


Many grades of PVA are so-called partially hydrolyzed grades

in which 87-89% of the acetate groups have been replaced,

and completely hydrolyzed grades with 99-100% of the

acetate groups removed.

Water soluble for 87-89% hydrolyzed material, 99-100% no

Physical properties are somewhat dependent on the degree

of alcoholysis.

Glue Video wood glues, PVA etc

https://youtu.be/B9BHxscvE9g

Lab on Thursday Seeded Emulsion Terpolymerization of Vinyl Acetate, Butyl

Acrylate, and Vinyl Neodecanoate with Gradual Monomer

and Initiator Additions

Lab on Thursday

Lab on Thursday Making Polyvinyl alcohol from Polyvinyl acetate

Polyvinyl Chloride Developed in 1872, but only a lab curiosity for over 50 years,

then in 1928 and years following Union Carbide, DuPont and

Farben (in Germany) started working with copolymers of

vinyl chloride with vinyl acetate. Then in 1930 BF Goodrich

developed an alternative approach that made the polymer

PVC usable in plasticized form, using high boiling organic

liquids to plasticize it.

First use mainly for electrical cable insulation, again all uses

were in the plasticized form.

One of the top four polymers in use today for all sorts of

applications. New car smell is plasticizer for the PVC

dashboard and other parts.

Polyvinyl Chloride Raw materials from acetylene and ethylene

Polyvinyl Chloride Preparation Mainly prepared by suspension polymerization,

bulk and emulsion lesser degrees

Bulk Polymerization, uses monomer as dispersent, done at high

pressure and 75C

Suspension polymerization

Polyvinyl Chloride Preparation Mainly prepared by suspension polymerization,

bulk and emulsion lesser degrees

Emulsion polymerization high pressure, similar process to suspension

Polyvinyl Chloride Structure primarily head to tail.

Polyvinyl Chloride Structure primarily head to tail.

Some evidence that commercial PVC is branched

Polyvinyl Chloride Physical properties colorless rigid material, relatively high

density and low softening point, high dielectric constant &

power factor, and flame retardant due to high chlorine content.

Very limited solubility, soluble at RT in oxygen containing, and

chlorinated solvents.

Most used with plasticizers: phthalates, aryl phosphates, aliphatic

acid estyers, epoxidized oils. 40-60 parts plasticizer to 100 parts

of polymer is typical for most common applications.

Degradation easy due to high temperatures and/or ultraviolet

light, so problem with some formulations in plastic car parts, like

dashboards.

Dehydrochlorination, elimination until almost all chlorine is gone,

unzipping.

Polyvinyl Chloride

Polyvinyl Chloride Oxidation degrades more rapidly when heated in air.

Polyvinyl Chloride Photodegradation - dehydrochlorination

Polyvinyl Chloride - modifications Chlorinated PVC

Commercial 63-68% chlorine, copolymer of vinyl chloride and s-dichloroethylene

Vinyl Chloride Vinyl acetate copolymers

Made with suspension and solution polymerization (page 108)

Vinylidene chloride copolymers suspension and emulsion

processes. Page 110-11.

Polyurethanes Types Flexible foams, rigid foams, integral foams,

elastomers, surface coatings, and adhesives

Development commercial development dates from 1937 when

Bayer (IG Farben, later Farbenfabriken Bayer, Germany) found

that the reactions of diisocyanates and glycols gave

polyurethanes with interesting physical properties as plastics and

fibers.

Raw materials urethane group results from the reaction

between an isocyanate and a hydroxyl compound

Polyurethanes Raw materials diisocyanates, diols and polyols are the

principle raw materials

Diisocyanates

Made primarily by the reaction of phosgene and primary amines

Toluene diisocyanate (TDI) made from nitration and hydrogenation

then reaction with phosgene of toluene to get different types of TDI:

65:35 TDI

80:20 TDI

100% 2,4-TDI



Diisocyanates


Diphenylmethane diisocyanate (MDI) derived from aniline



Diisocyanates


Naphthylene diisocyanate (NDI) derived from naphthalene



Diisocyanates


Hexamethylene diisocyanate (HDI) derived from

hexamethylene diamine:

Isophorone diisocyanate



90% Polyethers flexible and rigid foams, coatings,

elastomers Mw from 500 to 3000 is typical

10% Polyesters Mw from1000-2000 is typical, hydroxyl

terminated polyesters primarily. Polyesteramides originally

developed for elastomers, but now for leather adhesives and

flexible coatings for rubber goods.

Isocyanate reactions

Polyurethane products Foams

Flexible foams

Diisocyanate, polyol and water two reactions proceed

simultaneously:

TDI is preferred diisocyanate

Polyether foams flexible foams produced by a one-shot process

Diisocyanate, polyol, water and catalysts and surfactant mixed

simultaneously

80% slab stock, 20% molded into parts

Polyurethane products Polyether foam furniture applications, cushions

Polyester foam textile laminates, coat shoulder pads


Rigid foams

Polymeric MDI is preferred diisocyanate

Polyether and polyester foams, also one shot process, different

blowing agents are used, typically low boiling halogenated alkanes are

used. Trichlorofloromethane is most common.

Typical formulation:


Rigid are closed cell structures used for thermal insulation

products 97% of the volume of a typical foam is occupied by

gas.

Flexible foams furniture applications

Integral foams cellular core and a solid skin, molding

applications like automobile parts.

Elastomers

Cast elastomers


Rigid are closed cell structures used for thermal insulation

products 97% of the volume of a typical foam is occupied by

gas.

Flexible foams furniture applications

Integral foams cellular core and a solid skin, molding

applications like automobile parts.

Elastomers

Cast elastomers poured into a heated mold

Typical use printing rollers

Cast elastomers

Millable elastomers Can be compounded in mills, and vulcanization is possible

Thermoplastic Elastomers Typically prepared as fibers spandex

Use linear polyethers/polyesters and linear polyisocyanate

Typically prepolymer is prepared terminated with isocyanate,

then aliphatic diamine is added to effect chain extension.

Then material is spun into a coagulating bath or hot air to

produce a fiber.

Surface coatings One component systems

Air curing systems

Urethane oils, drying due to atmospheric oxygen

Moisture curing

Cure with atmospheric water

Heat curing systems

Blocked isocyanates and polyester/polyether prepolymers mixed and

then cured using heat in an oven.

Two component systems

Isocyanate polyol mixed immediately prior to use

Prepolymer polyol systems

Adhesives same types, just between two substrates

Silicones Fluids, Resins and Elastomers History early 20th century, polymer was considered a

problematic by-product.

Commercial interest developed in the 1930s by Corning

Glassworks and General Electric company, working on

electrically insulating materials

Nomenclature Silicone analogues to similar carbon compounds

are called silanes, or polyorganosiloxanes

Substituted silanes named after parent compound

Hydroxyl derivatives are silanols

Silanes with ether linkages are called siloxanes

Nomenclature

Raw materials Silane production starts with chlorosilanes, which are

manufactured from silicon, or silicon dioxide and chlorine gas.

Production Grignard process

Production Direct process

Production Olefin addition process

Polymerization Hydrolysis of chlorosilanes to silanols, which then condense

spontaneously to siloxanes:

Polymerization Hydrolysis of chlorosilanes to silanols, which then condense

spontaneously to siloxanes:

Mechanism

Silicone Products Fluids Mw from 4000 to 25000

Silicone Products Elastomers Mw from 300k 700k

Silicone Products Other elastomers (pgs 400-405):

Vinyl silicone elastomers

Phenyl silicone elastomers

Nitrile Silicone elastomers

Fluorosilicone elastomers

Room temperature vulcanizing elastomers

Liquid silicone elastomers

Borosilicones

Resins consist of branched polymers based on the

hydrolysis of trichlorosilanes and dichlorosilanes blended

together to avoid an unusable cross link density.

Silicone Products Resins often have a mixture of methyl and phenyl groups as part of the

backbone.

Silicone Products Types of resins:

Modified resins blending or copolymerization. Silicone alkyd resins

are one common example.

Physical properties

Thermal stability

Water repellant

Fluids

Silicone Products Vulcanized Elastomers

Silicone Products Vulcanized Elastomers

Crosslinked resins surface coatings and glass fiber laminates

Surface coatings heat resistance, water repellency, nonstick surfaces,

such as cake, candy, confection boxes often have silicone coatings.

Since they are crosslinked/cured, they serve well as nontoxic/nonstick

surface treatments for food handling equipment.

Glass fiber laminates best for electrical insulation quality

under high heat conditions (250C).

Fluoropolymers History early 20th century, polymer

polychlorotrifluoroethylene was considered of limited value.

Commercial interest developed in 1938 when Plunkett

discovered polytetrafluoroethylene at the DuPont company

by accident

Important Homopolymers

Polytetrafluoroethylene

Polychlorotrifluoroethylene

Polyvinyl Fluoride

Polyvinylidene Fluoride

Development 80% of current output is PTFE (Teflon)

Pilot plant production started in 1943, and large scale

production in 1950 by DuPont (USA)

Many other polymers on this base have been investigated with

a few having commercial value.

Physical Properties

Outstanding Chemical Resistance

Outstanding Thermal Resistance extremes of temperature

Anti-stick characteristics, non-stick surfaces

Raw Materials Tetrafluoroethylene

Chlorotrifluoroethylene

Vinyl Fluoride -

Raw Materials Vinylidene Fluoride

Polytetrafluoroethylene Suspension polymerization

Conventional techniques to produce granular product for molding

and extrusion

Specialized process to give finer particle size and lower molecular

weight, stabilized for latex form product suitable for film casting,

coatings and fiber treatment.

Coagulated from latex form for powder production used for extrusion

of thin sections

Physical Properties

White solid

Waxy appearance and feel

Tough flexible material with moderate tensile strength

Tendency to creep under certain conditions.

Physical properties

Polychlorotrifluoroethylene Suspension polymerization

Conventional techniques to produce granular product for molding

and extrusion, temperature kept low

Physical Properties

White solid

Waxy appearance and feel

Greater tensile strength, hardness and resistance to creep

than PTFE

Lower softening point, less crystalline, can make thin

transparent films by quenching.

Others discussed in book pages 156-166.

Videos Check You Tube and Google for any of interest to you.

https://youtu.be/vns5TVZ5xzw

https://youtu.be/rtPhlWi8t3I

Presented by (click to enter name)

The End

Presented by

Polymer Chemistry 1 Nazarbayev University

Click to enter name

Principles of Polymerization Eugene F Douglass, MS, PhD Polymer

Science - Professor

Chapter 4- Emulsion Polymerization Topics to Cover

Process

Quantitative aspects

Other characteristics

Initiation

Surfactants

Chain Transfer

Other components

Energy Concerns

Molecular Weight

Particle size distribution

Surfactant free

Other Emulsion Polymerization systems

Living Radical Polymerization

Emulsion Polymerization - Process Utility

First used during WW II for producing synthetic rubbers from 1,3

butadiene and styrene.

SBR and copolymers today

Vinyl acetate, chloroprene, acrylate copolymers.

Methacrylates, vinyl chloride, acrylamide, some fluorinated

ethylenes.

Qualitative picture

Components - recipe

Dispersing medium (mostly water)

Emulsifier and water-soluble initiator

Recipe

Grams lab scale lbs/kg plant scale

Site of Polymerization Monomer droplet polymer monomer mix droplet

Site of polymerization Polymer particle swollen with monomer

Initiation occurs in aqueous phase with micelles forming

around growing polymer and dissolved monomer

Monomer droplet aqueous phase growing polymer particle swollen with monomer

Two mechanisms for particle nucleation

Micellar particle nucleation

Homogeneous particle nucleation precipitated species

are stabilized with surfactant and absorb more monomer

and grow

Progress of Polymerization Three intervals, separate monomer phase in intervals I and II.

Quantitative aspects Rate of polymerization

rp = kp[M] like before

Other characteristics Initiators

Water soluble K or NH4+ persulfate, hydrogen peroxide, 2,2-

azobis(2-amidinopropane)dihydrochloride

Partially soluble ones have also been used

Redox systems advantages include temps below 50C, persulfate with

ferrous, cumyl hydroperoxide or hydrogen peroxide with ferrous,

sulfite or bisulfite.

Surfactant

Anionic surfactants mostly used fatty acid soaps (sodium or

potassium stearate, laurate or palmitate), sulfates and sulfonates.

Nonionic surfactants often used to stabilize final polymer emulsion or

paint.

Other components antifreeze additives, inorganic electrolytes, buffers

Other emulsion polymerization systems Surfactant free uses initiator that imparts surface active

properties to the polymer particles i.e. persulfate with

latexes

Inverse emulsion polymerization, water in oil emulsions.

Use nonionic surfactant to stabilize final emulsions

Mini and Micro-emulsion polymerization

Problems 4-1 to 4.3 assignment

Presented by

Polymer Chemistry 1 Nazarbayev University

Click to enter name

Principles of Polymerization Eugene F Douglass, MS, PhD Polymer

Science - Professor

Chapter 3 Topics to Cover

Nature of Radical Chain Polymerization

Structural Arrangement

Rate of Radical Chain Polymerization

Initiation

Molecular Weight

Chain Transfer

Inhibition and Retardation

Energy Concerns

Auto-acceleration

Molecular Weight Distribution

Pressure effects

Process Conditions

Specific Commercial Polymers

Living Radical Polymerization

Nature of Radical Chain Polymerization Comparison of Chain and Step Polymerization

High Molecular Weight material is formed immediately

Radical, Anionic or Cationic reactive center adds many monomer

units very quickly in a chain reaction

Monomer concentration decreases quickly as polymer grows

Mixture consists of solvent, monomer, high polymer and growing

chains

Step very different

Any two molecular species can combine

Monomer disappears much faster as dimers, trimers etc form

Long reaction times necessary for both high conversion and high

molecular weights

Radical vs Ionic Chain Polymerizations General Considerations

Thermodynamic

Polymerization will be impossible if reaction is not

thermodynamically feasible, G between monomer and polymer must be negative

Kinetic feasibility will process proceed at a reasonable rate under a

proposed set of reaction conditions??

Radical, cationic, and anionic used under different conditions, as not all

processes can be used for all monomers or in proposed set of reaction

conditions,

Most monomers will react with free radical polymerization

Some monomers will not react with either cationic or anionic

parameters

Polymer Considerations Carbon Carbon Double bond in monomers

Carbon Oxygen Bonds in Aldehydes and Ketones

Effect of Substituents Free radical and Ionic

Electron donating vs Electron withdrawling groups affect each

type of initiating and propogating species.

Resonance Stabilization with free radicals

Structural Arrangement of Monomer units

Possible Modes of Propagation:

Carbon #1

Carbon #2

Structural Arrangement of Monomer units

Possible Modes of Propagation:

Head to Tail

Head to Head, tail to tail or random

Experimental Evidence

Head to Head:

The synthetic approach involves an appropriate choice of monomer for the particular HH

polymer. For example, HH poly(vinyl chloride) is obtained by chlorination of 1,4-poly-1,3-

butadiene,

Rate of Radical Chain Polymerization Sequence of events

Initiation

Propagation

Rate of Radical Chain Polymerization Sequence of events

Termination

Combination or disproportionation:

Addition of Cap or terminator

Resulting in dead polymer, one that no longer grows

Rate of Radical Chain Polymerization Rate of monomer disappearance or rate of polymerization is

given by the term:

[]

= + ,

=

Steady State approximation leads to:

= = 2 2 Resulting in the rate of Polymerization being equal to:

= [](

2)1/2

Initiation Types of Initiators:

Thermal homolytic dissociation

Redox intiators

Photochemical

Ionizing Radiation Electron beam

Pure thermal

Electrolysis of monomer solutions

Thermal homolytic dissociation:

Acyl peroxides acetyl and benzoyl peroxides

Alkyl peroxides cumyl and t-butyl peroxides

Hydroperoxides t-butyl and cumyl hydroperoxies

Peresters

Acyl alkylsufonyl peroxides, dialkylperoxydicarbonates

, diperoxyketals, and ketone peroxides

Azo compounds AIBN

Thermolytic Initiators

Azo Compounds

Driving force production of highly stable Nitrogen molecule ????

Other types: Disulfides,

Redox Initiators 1. Peroxides and Reducing agents

Hydrogen peroxide with Fe+2

H2O2 + Fe+2 HO-1 + HO + Fe+3

Other peroxides and Fe+2

ROOR RO-1 + RO

ROOH OH-1 + RO

ROOCOR RCOO-1+ RO

Other reducing agents can also be used including Cr+2 , V+2 ,

Ti+3, Co+2, & Cu+1

You can also use amines as the reductant.

Redox Initiators 2. Inorganic reductants and inorganic oxidants

3. Organic inorganic redox pairs

4. Monomer itself, and thiosulfate or N,N-dimethylaniline

Photochemical Initiation Photochemical or Photoinitiated polymerization

Reaction conditions UV, Visible, IR

Often uses a photosensitizer

1. Some compound in the system undergoes excitation by

energy absorption and subsequent decomposition into

radicals.

2. Some compound undergoes excitation and the excited

species interacts with a second compound (by either energy

transfer or redox reaction) to form radicals derived from the

latter and/or former compound(s).

UV Curable Coatings

Self-catalysis:

Bulk Monomer Some monomers

M + h M*

M* R + R

Polymerization then continues as before. Conjugated double

bonds work the best.

Irradiation of Thermal and Redox initiators

Ionizing Radiation C + C+1 A + B+1 B+1 + e-1 B The radiolysis of olenic monomers results in the formation of cations, anions, and

free radicals as described above. It is then possible for these species to initiate

chain polymerizations. Whether a polymerization is initiated by the radicals,

cations, or anions depends on the monomer and reaction conditions. Most

radiation polymerizations are radical polymerizations, especially at higher

temperatures where ionic species are not stable and dissociate to yield radicals.

Radiolytic initiation can also be achieved using initiators, like those used in

thermally initiated and photoinitiated polymerizations, which undergo

decomposition on irradiation.

Thermal homolysis of impurities primarily

Some monomers are easier than others. And Styrene is the one monomer that

undergoes polymerization purely driven by heat.

Pure Thermal Initiation

Other methods Electrolysis of monomer solutions

Plasma Polymerization placed in electrical discharge under

low pressure

Sonication

Chain transfer to initiator

Side reactions of initiator species

Initiator efficiency

Cage effect f (efficiency) < 1

Brackets indicate presence of solvent cage which traps the free radicals for a short time until they defuse apart.

Termination Disproportionation

Coupling

Molecular Weight ideally stop at desired molecular weight

Kinetic Chain length v - as the average number of monomer

molecules consumed (polymerized) per each radical, which

initiates a polymer chain. This quantity will obviously be given

by the ratio of the polymerization rate to the initiation rate

or to the termination rate, since the latter two rates are

equal.

Mode of Termination Number average degree of polymerization Xn, average

number of monomer molecules contained in a polymer

molecule

For termination by coupling Xn = 2v

For termination by disproportionation Xn = v

Mn = M0Xn where M0 is the molecular weight of the

monomer.

Most polymer radicals appear to terminate by coupling,

except where chain transfer predominates.

Higher temperature gives more disproportionation.

Styrene, methyl acrylate and acrylonitrile mostly coupling

Methyl methacrylate both types are evident

Chain transfer

Mn + XA Mn-X + A

XA can be monomer, initiator, solvent or

other material Purpose of chain transfer is to modify the molecular weight

by decreasing the size of the propagating chain.

Dependent on rate of reinitiation comparable to initial

propagating radical

It is a chain breaking reaction.

Molecular Weight Effects by chain transfer

Chain transfer to monomer and initiator

Monomer Chain Transfer constants Monomer chain transfer constants are generally small for

most monomers (Table 3-4).

Cm generally low

because the reaction

involves the breaking of

the strong vinyl C-H

bond.

Note Vinyl chloride is High!

Initiator Transfer Constants Either monomer or initiator chain transfer constants

Agent Chain Transfer Constants Some cases transfer to agent is likely, designed that way!

Chain transfer to polymer Results branching of polymer chain

Sometimes crosslink, sometimes intramolecular - backbiting

Inhibition and Retardation Inhibitors stop every radical

Retarders stop only a portion of the radicals

Use Stabilize monomers for storage, control specialty

polymerizations.

Energetic Characteristics Activation energy and frequency factor

Particularly important for thermally initiated polymerization

Thermodynamics of Polymerization Significance of G, H and S

Effects of Monomer structure 1. Differences in the resonance stabilization of monomer and

polymer due to differences in conjugation or hyperconjugation.

2. Steric strain differences in the monomer and polymer arising

from bond angle deformation, bond stretching, or interactions

between nonbonded atoms.

3. Differences in hydrogen bonding or dipole interactions in the

monomer and polymer.

Polymerization De-polymerization Equilibria Ceiling Temperature

A temperature at which the propagation step becomes a reversible one.

The net rate of polymer production is zero

Floor temperature

A temperature that occurs in some cases where below this temperature

polymerization is impossible

Auto-acceleration reaction rate increases with conversion

Diffusion controlled termination

Translational diffusion of two propagating radicals

Rearrangement of two chains which brings ends close

Chemical reaction of two radical ends.

Course of Polymerization

Auto-acceleration of pMMA

Process conditions Bulk Polymerization Monomer is used as solvent for growing polymer chains, until

you get precipitation or gel formation. Products: Polyethylene, Polystyrene, and

pMMA.

Problems highly exothermic nature of polymerization can lead to unzipping or

even charring/discoloration. Thermal control.

Broad distribution of molecular weight due to chain transfer to polymer

Run away effects

Necessary to react to low conversion and finish reaction later

Strong and elaborate stirring apparatus required

Solution polymerization Polymerization of monomer occurs in solution, solvent

effectively dissolves even completed polymer. Products: pVinyl Acetate, PAN, and

esters of Polyacrylic acids

Solvent as diluent aids in heat transfer away from exothermic reaction of

polymerization

Solvent aids in stirring, because viscosity is decreased.

Must design proper system to avoid solvent as chain transfer agent

Heterogeneous polymerization Precipitation Polymerization begins as homogeneous polymerization (bulk or

solution) and then polymer falls out of solution, because the polymer is insoluble in the

reaction medium

Powdered or granular products often result

Initiators are soluble in reaction medium

Polymerization occurs upon absorption of monomer and initiator into growing

polymer particles.

Suspension polymerization Suspending monomer as droplets in water. The droplets

contain the reacting monomer and initiator, which are prevented from coalescing by

agitation and additives which stablize the suspension

Water acts as diluent aids in heat transfer away from exothermic reaction of

polymerization

Water aids in stirring, because viscosity is decreased, reaction is occurring inside

droplets. Each droplet is a bulk polymer system.

Must design proper system to avoid solvent as chain transfer agent

Emulsion or Dispersion Polymerization chapter 4

Specific Commercial Polymers Polyethylene low density polyethylene is produced

Specific Commercial Polymers Polystyrene continuous solution polymerization important

for industrial production, suspension and emulsion

polymerization is also used.

Specific Commercial Polymers Polyvinyl chloride mostly suspension polymerization, some

bulk and emulsion polymerization also done.

Specific Commercial Polymers Polyvinyl acetate, and polyvinylidene chloride, copolymers and

polymers derived from them are most often made with

suspension or emulsion polymerization processes

Acrylic Family

Acrylate and Methacrylate products, many of these are copolymers

with different esters of acrylic or methacrylic acid using as co-

monomers in the emulsion or suspension polymerization process.

pMMA made by solution, emulsion and suspension types. You want to

avoid overheating to avoid bubble formation as the bp of MMA is

100.5C

Polyacrylonitrile PAN mostly produced by solution and suspension

processes

Specific Commercial Polymers Fluoropolymers polymers made from alkenes substituted

with one or more fluorine atoms

Primarily suspension polymerization, with some emulsion

polymerization

Polymerization of Dienes

Isoprene industrially produced

Butadiene, ABS rubber

Others brief discussion

Living Radical Polymerization Free radical has to be stabilized somehow.

Monomers added mixed together in desired ratios

Monomers added one at a time to react.

First polymerization done to 90% conversion, then other

monomer(s) are added.

A-B, AAAA-BBBB etc

ABA

ABC

ABCB, CABAC many combinations

Block copolymer production

Functional Polymers Usually copolymers with a small amount of functional group

added as a copolymer

Acrylic acid, Acrylonitrile, Alcohol end group

Acetylenic polymers

Reactions of acetylenes or diacetylenes to form conjugated polymers

of various kinds, even to add functionality.

Polymers are macromolecules built from smaller molecular subunits, called monomers. Synthetic polymers can be classified into two

main types according to the mechanism by which they synthetically grow from monomer to polymer: chain-growth polymers and step-

growth polymers. In this lab, chain-growth polymerization of styrene monomer using benzoyl peroxide initiator will be performed. The

characteristics of chain-growth polymerizations are (A.,Ravve, 1995):

The repeating units are added one at a time to the chain,

Monomer concentration decreases steadily throughout the reaction,

High molecular weight polymers are formed quickly and the molecular weight of the polymers changes gradually throughout the

reaction,

Long reaction time produces high yields, but affects the molecular weight only slightly. While there are many types of specific chain-

growth polymerization mechanisms, four frequently used types are: free radical, anionic, cationic and coordination.

In our case we use free radical polymerization, which consists of three steps: Initiation, Propagation and Termination. At the

initiation stage of chain-growth free radical polymerization of styrene monomers, the initiator, I, forms free radicals species: , which

then couples with one electron of the carbon-carbon double bonds of the styrene monomer to form another radical. These bonds are

particularly susceptible to radical attack because of their relatively low stability and resonance stabilization of the resulting radical

throughout the phenyl group. In the next stage, propagation, the newly formed radical reacts with another monomer to form another

radical, resulting in a polymer that is one unit longer (Fred W, 1984). The process is then repeated to form a chain of monomers (a

polymer). The propagation step is terminated when two radicals combine together to form a neutral species, known as coupling or

combination or disproportionation, in which hydrogen transfer results in the formation of two molecules: one saturated and one

unsaturated end group (Hart H., 1999).

In this experiment free radical polymerization technique was used. In order to undergo initiation step, styrene was used with NaOH to

remove inhibitor and make it reactive, because styrene is stored with inhibitor to make it more stable for storing. Then, we placed

styrene inside a tube and flushed with nitrogen, this was done to avoid formation of explosive mixture of styrene and air. This is not

enough to make free radicals in initiation step; we need to add some benzoyl peroxide, which is used as initiator. Since, benzoyl

peroxide decomposes with hemolytic cleavage of oxygen-oxygen bond. We need to heat our sample to 80-90 degrees for 90 min. in

order to break down oxygen-oxygen bond and start initiation process. In case of low temperature, this reaction could take weeks. In

case of too high temperature, our product will be not syrupy, but solid like.

Initiation Step

Then during the reaction process we undergo propagation step, when new formed radical reacts with another monomer to form

another radical.

Propagation Step

Then this chain can be terminated by combining two radicals, known as coupling, so our polymer is growing and its chain continues.

Termination Step

Combination or Coupling

After 90 minutes of heating inside the water bath, we added toluene to dissolve the content in a tube. Actually, we might use any

non-polar solvent (like acetone), according to rule like dissolves like. Then all staff was placed inside the methanol (which is polar)

and it stops the reaction and finally solid polystyrene is precipitated.

Reaction conditions were discussed previously. Then what is important is a Pilot plant approach.

Pilot plant:

The technique seems quite similar to which we do in lab; instead amounts are much greater. What is interesting is that by pilot plant

approach they could produce super high molecular weight compounds (over MW: 320,000).

I 2R

2R + CH2 CH

X

RCH2C

X

H

R CH2CH CH2C

X

CH2 CH

X

H

X

+ R CH2CH2 CH2C

H

X

n n+1

CH2C

H

X

CCH2

H

X

CH2C

H

X

CCH2

H

X

+

Initiation Step

Then during the reaction process we undergo propagation step, when new formed radical reacts with another monomer to form another radical.

Propagation Step

Then this chain can be terminated by combining two radicals, known as coupling, so our polymer is growing and its chain continues.

Termination Step Combination or Coupling

Initiation Step Then during the reaction process we undergo propagation step, when new formed radical reacts with another monomer to form another radical. Propagation Step Then this chain can be terminated by combining two radicals, known as coupling, so our polymer is growing and its chain continues. Termination Step Combination or Coupling

If we want to understand experiment more deeply, we need to know the history of Polystyrene. First of Polystyrene is described as a strong plastic,

which is created from the monomer called styrene. Molecular formula is (C8H8)n and it has relatively low melting point ( 240 degree Celsius). Also,

it is one of the most used polymers in the world. According to article in Finanz Nachrichten, the worldwide market worth in 2012 accounted for

11.9 billion US dollars (Finanz Nachrichten, 2013). Moreover, it is predicted that in 2018 the data will be 19.1 billion dollars. For instance, it has

applications in production of cups, packaging peanuts, building materials and many household items.

Polystyrene has a long history of evolution behind it. In 1839, a German apothecary called Eduard Simon discovered polystyrene. Eduard Simon

isolated the substance from natural resin. However, he did not know what he had discovered. It took another German, organic chemist, Hermann

Staudinger, to realize that Simon's discovery comprised of long chains of styrene molecules, was a plastic polymer.

In 1922, Hermann Staudinger published his theories on polymers, stating that natural rubbers were made up of long repetitive chains of

monomers that gave rubber its elasticity. He went on to write that the materials manufactured by the thermal processing of styrene were similar to

rubber. They were the high polymers including polystyrene. In 1953, Hermann Staudinger won the Nobel Prize for Chemistry for his research (Bellis

M., 2015).

Thus, we understand how Polystyrene was invented and what is actual use is. Now, we will shift to the process by which it synthesized in our lab

experiment. The technique is Emulsion polymerization it refers to a unique process employed for some radical chain polymerizations. It involves the

polymerization of monomers in the form of emulsions (i.e., colloidal dispersions) (Sandler, 1998). Below is the simplified representation of Emulsion

Polymerization system.

From this (Fig. 4-1) we might clearly understand that polymer particle swollen with monomer. Then, initiation processes is held in aqueous phase

and at that time micelles forming around growing polymer and dissolved monomer. Also, there are two possibilities for particle nucleation. The first

one is Micellar particle nucleation and the second is Homogeneous particle nucleation. Where in second mechanism precipitated species are

stabilized with surfactant and absorb more monomer (Douglass E., 2015).

From the graph above (Fig. 4-2), we see three different intervals. Those intervals are different rate behaviors, which are observed during the

emulsion polymerization process. In interval I, the nucleation of the particle takes place. At this stage, the monomer convention is about 5-10%

(10171018 particles per liter are formed). Usually during the rest of the batch process, the number of particles is constant, only in case coagulation it

changes significantly.

In Interval II, the system is composed of monomer droplets and polymer particles. We might observe that monomer diffuses from the monomer

droplets through the aqueous phase. The transition occurs at about 7080% conversion. This step ends when the monomer droplets disappear.

The transition from Intervals II to III occurs at about 40% conversion for styrene. This represents that most of the monomer polymerizes during

Interval III. In this interval, the monomer concentration in the polymer particles decreases continuously (JKU, 2015).

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