Applications in Polymer Processing

1. Applications in Polymer Processing • Principle Investigator: Yan - Ping Chen • Research Worker: Tsung - Yao Wen • Tz - Bang Du Department of Chemical Engineering National Taiwan University

2. The Usage of Supercritical Carbon Dioxide • To replace the highly pollutive organic solvent in traditional polymer processing • It 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 )

3. Research Topics • Synthesis of Electrically Conductive Polypyrrole - Insulating polymer Composites Using Supercritical Carbon Dioxide (SCCO2) • Effect of the Impregnating Conditions • Effects of the Oxidizing Conditions

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

5. Experimental Procedures: • Impregnating of insulating polymer with pyrrole monomer in SCCO2 : A: SCCO2 B: pyrrole monomer Insulating polymer

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

7. 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

8. Result Polystyrene (PS) was chosen as insulating host polymer (a) (b) 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.

9. Table 1. Elemental analysis of the polymer composite

10. 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

11. Summary1 (PPy/PS composite) • To blend PS with PPy will not only show electric conductive, but also improve the thermostability.

12. Effect of impregnating conditions: 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

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

14. 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.

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

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

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

18. Fig. 6 Plots of the electrical conductivity of the composites against the oxidant concentration with various oxidants ( ●, Fe2(SO4)3; ◆, Fe(ClO4)3 )

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

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

21. 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