Bulk Polymerization The simplest technique It gives the highest-purity polymer  Ingredients : monomer, monomer-soluble initiator, perhaps a chain transfer agent AdvantagesDisadvantages High yield per reactor volumeDifficult of removing the lost traces of monomer Easy polymer recoveryDissipating heat produced during the polimerization Final product form

Solution Polymerization  Ingredients : monomer initiator solvent Heat can be removed by conducting the polymerization in an organic solvent or water Initiator or monomer must be soluble in solvent Solvents have acceptable chain-transfer characteristics Solvents have suitable melting or boiling points for the conditions of polymerization AdvantagesDisadvantages Temperature control is easySmall yield per reactor volume Easy removedSolvent recovery

Suspention Polymerization Coalescense of sticky droplets is prevented by PVA Near the end of polymerization, the particles harder and they can be removed by filtration, then washing  Ingredients : water-insoluble monomer, water-insoluble initiator, sometimes chain transfer agent suspention medium (water-usually) Advantages (according to bulk polymerization) Disadvantages Forming process not usingPolymer purity is low Stirring is easyReactor capital costs are higher than for solution polymerization Separation process is easy

SUSPENSION POLYMERIZATION In this the monomer is dispersed in a dispersing medium and polymerization occurs in the monomer droplets suspended in the dispersing medium, water soluble monomer cannot be used unless a salting out procedure is used. This method is used with free radical polymerization where the initiator is dissolved in the monomer, which is then dispersed in water using an emulsifying agent. Polymerization is initiated in the monomer droplets dispersed in the aqueous medium. 4

Emulsion Polymerization Particles are formed monosize with emulsion polymerization Polymerization is initiated when the water-soluble radical enters a monomer-containing micelles.  Ingredients : water-insoluble monomer, water-soluble initiator, chain transfer agent, dispersing medium (water), fatty acid, surfactant such as sodium salt of a long chain

EMULSION POLYMERIZATION Polymer particles are 0.1µm in diameter When a water insoluble monomer is dispersed in water that also contains a water soluble initiator & an emulsifier agent, the whole component is present in polymerization system. A small portion of the emulsifier molecule are dissolved in water form colloidal cluster also known as “micelles”, emulsifier molecule arrange their hydro carbon portion towards the interior & the hydrophilic ends towards the outside. 6

Thermal Properties of Polymers  Tg = glass transition temperature – glass to rubber transition  Tm = crystalline melting point –  Factors affecting Tm,Tg  Crystalinity.  Molecular weight.  Chain flexability.  Structure of polymer.  Co-Polymerization.  Geometry.

Copolymerization Effect: where V1 and V2 are the volume fractions of components 1 and 2, respectively For this system, if the glass transitions (Tg1 and Tg2) of the individual homopolymers (1 and 2) are known, it is possible to estimate the Tg of the copolymer using the relation: If you Know the Weight fraction of the two polymers :

Number average Molecular weight (M n )

The relation between Tm and Tg

14 Processing Temperature

T m calculation: Where : Tm= melting point of the copolymer. T 0 m= melting point of the homopolymer.  Hm=heat of fusion of the polymer. X=mole fraction of the homopolymer

Solve the following problems: 1-The Tg of polystyrene is 100°C. What is its melting temperature, Tm? 2-The heat of fusion of the repeating unit for a homopolymer that melts at 250°C is 2500 cal/mol. Predict the melting point of a random copolymer of this polymer with 25 mol% of a comonomer.