Applications in Polymer Applications in Polymer ProcessingProcessing

Principle Investigator: Yan - Ping ChenResearch Worker: Tsung - Yao Wen Tz - Bang Du

Department of Chemical EngineeringNational Taiwan University

The Usage of Supercritical The Usage of Supercritical Carbon DioxideCarbon DioxideTo replace the highly pollutive organic

solvent in traditional polymer processingIt is readily available, nonflammable,

nontoxic, and inexpensive. It has a relatively low critical temperature

(TC=31.1 ) and a moderate critical ℃pressure ( PC = 7.3 MPa )

Research TopicsResearch Topics

Synthesis of Electrically Conductive Polypyrrole - Insulating polymer Composites Using Supercritical Carbon Dioxide (SCCO2)– Effect of the Impregnating Conditions– Effects of the Oxidizing Conditions

Experimental Apparatus:Experimental Apparatus:

1 CO2 Gas Reservoir 4 Metering Pump 2 Pressure Gauge 5 Reaction Vessel 3 Refrigeration Unit 6 Thermostated Water Bath

Experimental Procedures:Experimental Procedures:

Impregnating of insulating polymer with pyrrole monomer in SCCO2 :

T

4

5

insulatingpolymersubstrate

add 0.05ml pyrrolemonomer with glass syringe

put in

Insulating polymer

A: SCCO2 B: pyrrole monomer

Synthesis and doping of polypyrrole (PPy) - insulating polymer composite :

impregnated insulatingpolymersubstrate

dipping in

oxidant aqueous solution

Characterization of composite :– measurement of conductivity by conductivity

meter– observation of the morphology by SEM– measurement of the composition by EA– Fe of the blend was analyzed by ICP-AES – measurement of thermal decomposition

temperature by TGA

ResultResult

Fig.1 Scanning electron microscope results of the impregnated host polymer (a) without the oxidizing process. (b) with the oxidizing process in a 2.25 M FeCl3 aqueous solution.

(a) (b)

Polystyrene (PS) was chosen as insulating host polymer

Method of preparation C (%) H (%) N (%)

Impregnated host polymer

without oxidizing

91.93 7.78 0.06

Impregnated host polymer with

oxidizing in a 2.25M FeCl3

aqueous solution

88.56 6.61 0.54

Table 1. Elemental analysis of the polymer composite

300 350 400 450 500

Tem pera tu re (oC)

0

20

40

60

80

100

Wei

ght (

%)

ab c

Fig. 2 TGA curves of (a) pure PS substrate (b) undoped PPy/PS composite (c) doped PPy/PS composite with 2.25M FeCl3. The composites were prepared at 40 and 10.5MPa℃

Summary1 (PPy/PS composite)Summary1 (PPy/PS composite)

To blend PS with PPy will not only show electric conductive, but also improve the thermostability.

Effect of impregnating conditions:Effect of impregnating conditions:

0.0 1.0 2.0 3.0 4.0FeC l3 C oncentra tion (M)

0.0

1.0

2.0

3.0

Co

nd

uct

ivity

( 1

0 -

2 S

/ cm

)

Fig.3 Plots of the electrical conductivity against the concentration of FeCl3. The impregnating conditions in CO2 are at (a)▲, 30 and 7.95MPa, ℃ (b) ■, 40 and 10.5MPa, (c)●, 50 and 13.14MPa℃ ℃

State Temperature

(℃)

Pressure

(MPa)

[ FeCl3 ]aq

(M)

Maximum

Conductivity

(S/cm)

HPL CO2 30 7.95 3.0 2.1×10-3

SC CO2 40 10.50 2.25 1.12×10-2

SC CO2 50 13.14 1.5 2.97×10-2

Table 2. Maximum electrical conductivity under various impregnating conditions. (Density of carbon dioxide is fixed at 14.17 kg-mole/m3 )

Summary2 (impregnating conditions)Summary2 (impregnating conditions)

The electric conductivity of composite will be higher when impregnating in supercritical state than liquid state of CO2.

The electric conductivity of composite will be higher when impregnating in SCCO2 of 50oC ,13.14MPa than 40oC, 10.5MPa.

Effect of oxidizing conditions:Effect of oxidizing conditions:

0.0 1 .0 2 .0 3 .0FeCl3 C oncen tra tion (M)

0.0

4 .0

8 .0

12 .0

Con

duct

ivity

( 1

0 -3

S /

cm )

Fig. 4 Plots of the electrical conductivity against the doping concentration with various oxidizing solvents (●, water ; ▲, acetonitrile )

Oxidizing Solvent Concentration of FeCl3

(M)

Maximum Conductivity

(S/cm)

CH3CN 0.25 5×10-3

H2O 2.25 1.12×10-2

Table 3. The electrical conductivity of the PPy/PS composites with different oxidizing solvents

10 20 30 40 50D op ing Tem pera tu re ( 0C)

0.0

4.0

8.0

12.0

16.0

20.0

Con

duct

ivity

( 1

0 -3

S/c

m )

Fig. 5 The electrical conductivity of the PPy/PS composites at various oxidizing temperatures (FeCl3 concentration: ■, 2.0 M; ●, 2.25 M; ▲, 3.0M )

0.0 0 .5 1 .0 1 .5 2 .0 Concentra tion ( M )

0.0

4 .0

8 .0

12 .0

Con

duct

ivity

( 1

0 -3

S /

cm )

Fig. 6 Plots of the electrical conductivity of the composites against the oxidant concentration with various oxidants ( ●, Fe2(SO4)3; , Fe(ClO◆ 4)3 )

Fig. 7 Scanning electron micrograph of composites oxidized with (a) FeCl3 (b) Fe (NO3)3 (2000X)

(a) (b)

Oxidizing

Agents

Oxidant

Concentration

in Aqueous

Solution (M)

Maximum

Conductivity

( S/cm )

C

(%)

H

(%)

N

(%)

Fe

(%)

(undoped) - <1×10-7 91.93 7.78 0.06 -

FeCl3 2.25 1.12×10-2 88.56 6.61 0.54 1.18

Fe2(SO4)3 1.50 1.11×10-2 87.45 7.23 0.31 0.88

Fe(ClO4)3 1.00 3.14×10-3 90.80 6.73 0.30 0.16

Fe(NO3)3 0.50 2.49×10-5 89.05 7.43 0.28 0.14

Table 4. Maximum conductivity and elemental analysis results of the PPy/PS composites with various oxidants

Summary3 (doping conditions)Summary3 (doping conditions)

Water is a better oxidizing solvent than acetonitrile.

25oC is a suitable temperature for oxidizing in FeCl3 aqueous solution.

The composite shows highest electric conductivity when FeCl3 was used to be the oxidant in this study