1. Chapter 5:Polymerization Techniques
Bulk polymerization
Solution polymerization
Suspension polymerization
Emulsion polymerization
Interfacial condensation polymerization
Etc.
Polymer Technology (A. Cattaleeya)

2. 1. Bulk Polymerization : In the reactor:- Liquid monomer Initiator
Inhibitors
Chain transfer agents
Homogeneous : polymer remains dissolved in monomers.
Ex. PMMA
Heterogeneous : aka. Precipitation polymerization
polymer is insoluble in its monomers.
Ex. Polyacrylonitrile, PVC
Problem : heat transfer not good
Make objects with a desirable shape by polymerization in a mold.
Polymer Technology (A. Cattaleeya)

3. Model of Batch Polymerization
Monomer

4. Pros & Cons of Bulk Polymerization
Advantage
Disadvantage
Obtain purest possible polymer
Conveniently cast to shape
Obtain highest polymer yield per
reactor volume
Difficult to control
Reaction has to be run slowly
Cannot get high rate and high
MW at the same time
Difficult to remove last traces
of unreacted monomer

6. Ex. 1 The maximum possible temperature rise in a polymerizing batch may be calculated by assuming that no heat is transferred from the system. Estimate the adiabatic temperature rise for the bulk polymerization of styrene, Hp = kcal/mol, molecular weight = 104
Solution Hp for polymerization of styrene = 16,400 cal/mol (assuming complete conversion)  meaning that polymerization of 1 mol styrene release heat in the amount of 16,400 calories.
In the absense of heat transfer, all this energy heats up the reaction mass.
To a reasonable approximation, the heat capacity of most liquid organic systems may be taken as 0.5 cal/g-oC
From Q = mc T
(Note that- Boiling point of styrene = 146 oC)

7. 2. Solution Polymerization
Solution Polymerization : Monomer dissolved into inert solvent / inhibitor
Monomer
Initiator
CTA
Inert solvent
Solvent helps controlling heat transfer from reaction.
Use for :
Thermosetting condensation polymer (stop before gel point)
Ionic polymerization
Ziegler-Natta solution process

8. Model of Solution Polymerization
Monomer I I
Initiator I I I
Solvent

9. The effect of solvent solubility on the molecular weight of polyurethane produced by solution method
Viscosity of polymer solution
Precipitation of polymer out of the solution
Xylene
Chlorobenzene
Nitrobenzene
Dimethyl sulfoxide
0.06
0.17
0.36
0.69
Precipitate immediately
Precipitate within 0.5 hr.
Polymer remain dissolved in solution
Viscosity of polymer  MWpolymer
 High viscosity = high molecular weight !

10. Pros & Cons of Solution Polymerization
Advantage
Disadvantage
solvent
Rate [M]  reduce rate,
chain length xn
Solvent waste
Need solvent separation &
recovery
Have traces of solvent, monomer
Lower yield
Solvent may not be really inert
(May interfere w/ rxn.-act as CTA)
Reduces the tendency toward
autoacceleration
Increases heat capacity/heat-
transfer
Reduces viscosity
Minimize runaway reaction

11. Ref: S.L. Rosen, John Wiley & Sons 1993

12. Ex. 2 Estimate the adiabatic temperature rise for the polymerization of a 20% (by weight) solution of styrene in an inert organic solvent
Solution In 100 g of the reaction mass, there are 20 g of styrene, so the energy liberated on its complete conversion to polymer is
Temperature rise is calculated from Q = mc T
Therefore, the adiabatic temperature rise is then

13. Ref: S.L. Rosen, John Wiley & Sons 1993

14. Ref: S.L. Rosen, John Wiley & Sons 1993

15. 3. Suspension Polymerization :
Monomer into water,
suspending agents (Ex.Ionic detergent, barium sulfate)
Model of suspension polymerization
Water
monomer
(Hydrophilic)
Initiator +
(Hydrophobic)
Suspending agent
- Ex. Polyvinyl alcohol
- Beads of polymer ( m)

16. Monomer (hydrophobic) Initiator (dissolved in monomer) Monomer phase
Typical Composition:
Monomer (hydrophobic)
Initiator (dissolved in monomer) Monomer phase
Chain-transfer agent (dissolved in monomer)
Water – suspending medium
Protective Colloid
Suspending agent
Insoluble inorganic salt

17. Pros & Cons of Suspension Polymerization
Advantage
1. Easy heat removal
and control
2. Obtain polymer in a
directly useful from
Disadvantage
Low yield / reactor volume
Traces of suspending agent on particle surfaces
Cannot run continuously
Cannot be used for
-condensation polymers
-ionic or Ziegler-Natta polymerization

18. Ref: S.L. Rosen, John Wiley & Sons 1993

19. 4. Emulsion Polymerization
Emulsion Polymerization : Use emulsifier / soap
monomer
Water
Soap
Initiator
(Hydrophilic)
Reaction occurs in water phase until polymer gets very
hydrophobic and then dissolve back in the monomer region.
Ex. Latex - very very small particle stable in solution
- particle size << 1 m
- can generate very high MW. polymer

20. Emulsion Polymerization (cont.):
Typical ingredient
100 part (by wt.) monomer (water insoluble)
180 part water
2-5 parts acid soap
part water-soluble initiator
0-1 part CTA (monomer soluble)

21. Steps in Emulsion Polymeriztion
Water-soluble initiator
Polymer born in water
Monomer swollen micelle
Polymer moves to micelle
growing polymer particle
Monomers inside the micelle decrease
Unreacted monomers in other
micelles and in droplets diffuse
through water to the growing particles
Reaction terminates when 2nd radical gets in
reaction starts again for the 2nd chain when 3rd particle gets in.

22. Ref: S.L. Rosen, John Wiley & Sons 1993

23. Ref: S.L. Rosen, John Wiley & Sons 1993

24. 5. Interfacial Polycondensation
water
CCl4
Advantage : =
Monomer1 : Hexamethlyene diamine
Monomer2 : Sebacoyl chloride
Polymer formed at interface
Commercial scale  easier to stir the phases together
Reaction  rapid at room temperature
(no need for high T., vacuum P.)
Interfacial Polycondensation of Nylon 6/11

25. Interfacial Polycondensation of Nylon 6/11
Experiment on
Interfacial Polycondensation of Nylon 6/11
การดึงเส้นใยไนลอนจากผิวสัมผัสของสารละลาย

26. Pros & Cons of some polymerization techniques
Bulk
- easy
- No contamination
- Difficult to control temp. and heat transfer
- High viscosity
Solution
-good heat transfer
-easy to control reaction temp.
-low viscosity
-polymer produced may be used directly in the solution form
- Need to use solvent –adding cost
Difficult to eliminate solvent entirely
Solvents sometimes act as chain transfer agent  leading to lower MW polymer
Suspension
- Good heat transfer
- easy to control reaction temp.
- low viscosity
- polymer produced may be used directly as polymeric suspension
-Need extra process in washing out suspending agent/contaminants and drying the polymer beads
-Polymer beads may stick together and maybe contaminated with suspending agent
-Good only for addition polymerization using hydrophobic free radical initiator.
Emulsion
-- Good heat transfer
- polymer produced may be used directly as polymer latex
-Need extra process in washing out emulsifier/ contaminants and drying
-Good only for addition polymerization using hydrophilic initiator.
Interfacial
Reaction is fast at room temp. and pressure.  No need for high temp. like in normal polycondensation.
Can produce polymer in fiber form
Limited to polycondensation where the two reactants are insoluble in each other ex. Acid chloride (quite expensive)
Need extra process in recovering solvent and excess reactants

27. Comparing different techniques for Polycondensation conditions บัลค์
(bulk)
สารละลาย
(solution)
ระหว่างผิว (interfacial)
Temp
สูง
จำกัดอยู่ที่จุดหลอมเหลวและจุดเดือดของตัวทำละลายโดยทั่วไปทำที่อุณหภูมิห้อง
Heat stabilization
จำเป็น
ไม่จำเป็น
Kinetic of Reaction
สมดุล เป็นขั้น
บ่อยครั้งไม่สมดุล คล้ายปฏิกิริยาลูกโซ๋
Reaction time
1 ชั่วโมงถึงหลายวัน
หลายนาทีถึง 1ชั่วโมง
Productivity
ต่ำถึงสูง
Equality of reactants
ไม่ค่อยจำเป็น
Purity of reactants
Equipment
พิเศษ ระบบปิด
ง่ายๆ ระบบเปิด
Pressure
สูง, ต่ำ
บรรยากาศ

28. 6. Gas-Phase Olefin Polymerization :
Use Zieler-Natta catalyst
Moderate P (7-20 atm)
Low temperature ( < 100 oC)
Use fluidized bed reactor
Good Point :
No solvent
Monomer separation is easy
Low capital + operating cost

29. Ref: S.L. Rosen, John Wiley & Sons 1993

30. Ref: S.L. Rosen, John Wiley & Sons 1993