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

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 (T C =31.1 ℃ ) and a moderate critical pressure ( P C = 7.3 MPa )

Research Topics Synthesis of Electrically Conductive Polypyrrole - Insulating polymer Composites Using Supercritical Carbon Dioxide (SCCO 2 ) – Effect of the Impregnating Conditions – Effects of the Oxidizing Conditions

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

Experimental Procedures: Impregnating of insulating polymer with pyrrole monomer in SCCO 2 : Insulating polymer A: SCCO 2 B: pyrrole monomer

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

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

Result 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 FeCl 3 aqueous solution. (a) (b) Polystyrene (PS) was chosen as insulating host polymer

Table 1. Elemental analysis of the polymer composite

Fig. 2 TGA curves of (a) pure PS substrate (b) undoped PPy/PS composite (c) doped PPy/PS composite with 2.25M FeCl 3. The composites were prepared at 40 ℃ and 10.5MPa

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

Effect of impregnating conditions: Fig.3 Plots of the electrical conductivity against the concentration of FeCl 3. The impregnating conditions in CO 2 are at (a) ▲, 30 ℃ and 7.95MPa, (b) ■, 40 ℃ and 10.5MPa, (c) ●, 50 ℃ and 13.14MPa

Table 2. Maximum electrical conductivity under various impregnating conditions. (Density of carbon dioxide is fixed at kg-mole/m 3 )

Summary2 (impregnating conditions) The electric conductivity of composite will be higher when impregnating in supercritical state than liquid state of CO 2. The electric conductivity of composite will be higher when impregnating in SCCO 2 of 50 o C,13.14MPa than 40 o C, 10.5MPa.

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

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

Fig. 5 The electrical conductivity of the PPy/PS composites at various oxidizing temperatures (FeCl 3 concentration: ■, 2.0 M; ●, 2.25 M; ▲, 3.0M )

Fig. 6 Plots of the electrical conductivity of the composites against the oxidant concentration with various oxidants ( ●, Fe 2 (SO 4 ) 3 ; ◆, Fe(ClO 4 ) 3 )

Fig. 7 Scanning electron micrograph of composites oxidized with (a) FeCl 3 (b) Fe (NO 3 ) 3 (2000X) (a)(b)

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

Summary3 (doping conditions) Water is a better oxidizing solvent than acetonitrile. 25 o C is a suitable temperature for oxidizing in FeCl 3 aqueous solution. The composite shows highest electric conductivity when FeCl 3 was used to be the oxidant in this study