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1 Chapter 5:Polymerization Techniques 1.Bulk polymerization 2.Solution polymerization 3.Suspension polymerization 4.Emulsion polymerization 5.Interfacial.

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Presentation on theme: "1 Chapter 5:Polymerization Techniques 1.Bulk polymerization 2.Solution polymerization 3.Suspension polymerization 4.Emulsion polymerization 5.Interfacial."— Presentation transcript:

1 1 Chapter 5:Polymerization Techniques 1.Bulk polymerization 2.Solution polymerization 3.Suspension polymerization 4.Emulsion polymerization 5.Interfacial condensation polymerization 6.Etc.

2 2 1. Bulk Polymerization : - 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. In the reactor:-

3 3 Monomer Model of Batch Polymerization

4 4 Pros & Cons of Bulk Polymerization AdvantageDisadvantage - 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

5 5

6 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- o C From Q = mc  T (Note that- Boiling point of styrene = 146 o C)

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

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

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

10 10 - Rate  [M]  reduce rate, chain length x n - 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) Advantage Disadvantage solvent - Reduces the tendency toward autoacceleration - Increases heat capacity/heat- transfer - Reduces viscosity - Minimize runaway reaction Pros & Cons of Solution Polymerization

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

12 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 13 Ref: S.L. Rosen, John Wiley & Sons 1993

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

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

16 16 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 17 Pros & Cons of Suspension Polymerization Advantage 1. Easy heat removal and control 2. Obtain polymer in a directly useful from Disadvantage 1.Low yield / reactor volume 2.Traces of suspending agent on particle surfaces 3.Cannot run continuously 4.Cannot be used for -condensation polymers -ionic or Ziegler-Natta polymerization

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

19 19 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 4. Emulsion Polymerization

20 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 21 -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 2 nd radical gets in reaction starts again for the 2 nd chain when 3 rd particle gets in. Steps in Emulsion Polymeriztion Water-soluble initiator Polymer born in water Monomer swollen micelle Polymer moves to micelle

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

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

24 24 Interfacial Polycondensation of Nylon 6/11 water CCl 4 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.) 5. Interfacial Polycondensation

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

26 26 ProsCons 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 - easy to control reaction temp. - low viscosity - 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 - Good heat transfer - low viscosity -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 Pros & Cons of some polymerization techniques

27 27 conditions บัลค์ (bulk) สารละลาย (solution) ระหว่างผิว (interfacial) Temp สูงจำกัดอยู่ที่จุดหลอมเหลวและจุดเดือด ของตัวทำละลายโดยทั่วไปทำที่ อุณหภูมิห้อง Heat stabilization จำเป็นไม่จำเป็น Kinetic of Reaction สมดุล เป็นขั้น บ่อยครั้งไม่สมดุล คล้ายปฏิกิริยาลูก โซ๋ Reaction time 1 ชั่วโมงถึงหลาย วัน หลายนาทีถึง 1 ชั่วโมง Productivity สูงต่ำถึงสูง Equality of reactants จำเป็นไม่ค่อยจำเป็นไม่จำเป็น Purity of reactants จำเป็นไม่จำเป็น Equipment พิเศษ ระบบปิดง่ายๆ ระบบเปิด Pressure สูง, ต่ำบรรยากาศ Comparing different techniques for Polycondensation

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

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

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


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