Polystyrene Micro Beads

7/27/2019 Polystyrene Micro Beads

1/23

Extraction of Polystyrene micro

beads from EPS with OptimumSolvent Recovery


2/23

Purpose Of the Project

EPS- Expanded Polystyrene popularly known as

Thermocol

It consists mostly of voids filled with gas and are

considered as Use-Throw materials

Polystyrene micro beads are of more economic value

This project is to obtain a more economic valued

beads from Thermocol waste with an optimumsolvent recovery


3/23

Stages Of Project

1) Extraction Of Micro beads

Dissolution of EPS in a solvent Phase

Preparation Of Emulsion

Separation Of Micro beads from Solvent Phase

2)Solvent Recovery Process

Need for most economical way with optimum recovery


4/23

Solvent Selection

D-Limonene is preferred as it is obtained from a renewable

source (citrus oil) and is environment friendly solvent

Initial stage of experiments are carried with toluene as solvent

as it is cheaper than D-limonene and it readily dissolves poly

styrene

These results can be extended to d-limonene as solvent

Solubility parameter values should be studied to select a

suitable solvent for a dissolving polymer


5/23

Solubility Parameter

Dissolution of an amorphous polymer in a solvent is governedby the free energy of mixing

Gm = Hm - TSmwhere Gm is the Gibbs free energy change on mixing, Hm is the

enthalpy change on mixing, T is the absolute temperature, and Smis the entropy change on mixing.

The heat of mixing must be smaller than the entropic term forpolymersolvent miscibility

Gm < 0 The cohesive energy, CED; of a material is the increase in the

internal energy per mole of the material if all of theintermolecular forces are eliminated

Cohesive energy density = CED = (Hvap - RT)/V


6/23

Hildebrand Solubility parameters

Solubility Parameter is given by square root of CED

d = (CED)1/2= ((Hvap - RT)/V)1/2

Hmix = Vmix[(E1/V1)1/2-(E2/V2)

1/2]*(12)

Hmix = Vmix[d1 - d2 ]*(12)12 are mole fractions of solute and solvent

Vmix is Volume of mixture

E1 is energy of vaporization of specie 1

V1 is molar volume of specie 1

Therefore, [d1 - d2] should be small for dissolution.


7/23

Solubility Parameter Values

Solubility parameters for some common

polymers

Solubility parameters for some common

Solvents


8/23

Experiment


9/23

Prepared samples of different wt% of EPS in toluene (1%,

2% and 4% of EPS in toluene). Solvents used are water, methanol, 1:1mixture of water and

methanol.

Take EPS- Toluene sample of known concentration in a test

tube which forms the oil phase. To this sample (oil phase) add the solvent, drop by drop until

the inversion phase occurs.

Now shake the test tube to ensure proper and uniform

dispersion and observe the formation of beads and observetheir behaviour (i.e. stability, coagulation etc.).


10/23

Observations

For water as solvent, no beads are formed (irrespective of

concentration of EPS-toluene sample), but the mixture sample

is retained at the top surface of water. Shaking resulted in

dispersion of EPS sample into polystyrene beads which

immediately settled at the surface of water.

For EPS-Toluene in methanol we got thread like structured

fibers after immediate drying

For EPS-toluene in 1:1 methanol/water emulsion, milky

solution is formed, and slowly beads coalesce to form threadlike structures.


11/23

Effect Of Concentration

These results are similar for 1%,2%,5% EPS in toluene

So as far as concentration change is concerned no significant

change is observed

Also for all these concentrations, there was immediateseparation of phases (oil phase at the top and water at the

bottom)

So in all the cases of experiments above, we stirred rigorously

& within no time poured onto flat plate and dried it

So we need to obtain stability of emulsion to prevent the

separation of phases


12/23

Density effects

When tested with increased concentration of EPS in

toluene(20%), the results ( Polystyrene Spheres Formation)

were better with water than the remaining two solvents.

This could be because of difference of densities of oil phasewith that of solvent phase

Increasing to 20% w/w of EPS (in toluene) will make the

density of oil phase approximate to that of water

Hence the possible dispersion occurs instead of immediatephase separation


13/23


14/23

Take away

Hence concentration of EPS in Toluene should

be optimal considering the density and

viscosity effects

If possible a third component should be added

to oil phase which doesnt increase viscosity

but increases density

Also for stability of emulsion, addition of

emulsifier is must


15/23

What are Emulsifiers

When there is a problem of making an

emulsion, emulsifying agent can be used to

stabilize the emulsion


16/23

Selection Of Emulsifier- The HLB System

There are hundreds of emulsifiers which are available in

industry

But only the appropriate emulsifiers can serve the

purpose efficiently The selection of emulsifier can be done on the basis of

HLB system

HLB stands for Hydrophile-Lipophile Balance

All emulsifiers consist of a molecule that combines both

hydrophilic and lipophilic groups


17/23

HLB System

Hydrophile-Lipophile Balance is the balance ofthe size and strength of the hydrophilic (water-loving or polar) and the lipophilic (oil loving ornon-polar) groups of the emulsifier.

The HLB System enables you to assign a number

to the ingredient or combination of ingredientsyou want to emulsify, and then to choose anemulsifier or blend of emulsifiers having thissame number

An emulsifier that is lipophilic in character is

assigned a low HLB number (below 9.0), and onethat is hydrophilic is assigned a high HLB number(above 11.0). Those in the range of 9-11 areintermediate.


18/23

Available emulsifiers in lab:

SLS

Tween 80 (HLB Value = 15)

Span 80 (HLB Value = 4.3)

The emulsifier we

selected is Tween 80

Because the HLB

number matches with

that of ingredient

Toluene


19/23


20/23

Taken Ingredients:

Solvent: Water and Methanol

Oil phase: Eps in Toluene of different concentrations

Emulsifier: 4:1 blend of Tween 80 and Span 80

HLB Value of Blend of two emulsifiers:

HLB Value of E1 = HLB1

HLB Value of E2 = HLB2 Volume fraction of E1 = x1 Volume fraction of E2 = x2 HLB Value of Blend = x1 * HLB1 + x2 * HLB2

For Tween 80 : Span 80 = 4:1

HLB Value of Blend = 0.8*15 + 0.2*4.3 = 12.86

Result

No convincing change


21/23

Contd..

Emulsifier: Sodium Lauryl Sulphate

Result:

Addition of SLS to water phase:

Mixed SLS in water and then added the oil phase drop by drop.

After stirring and drying, we got fibrous structured polystyrene

Addition of SLS to Oil phase:

Taken SLS in oil phase and added water drop by drop to the oilphase

We were able to get relatively good results in this case

But after the stirring is done, in about 5-10 min and when theemulsion is poured in a flat plate we obtain small beads separatedbut after some time they coalesce


22/23


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Polystyrene Micro Beads

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