Melt Processing of Metastable Acrylic Copolymer Carbon Precursors
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A second approach was evaluated using carbon dioxide (CO2) to plasticize AN copolymers to an extent that facilitates processing at reduced temperatures, below where thermal degradation is significant. A batch saturation method to absorb CO2 in AN copolymers was developed. Differential scanning calorimetry and thermogravimetric analyses were used to measure the glass transition temperature (Tg) reduction and amount of absorbed CO2 (respectively). A pressurized rheometer and measurement procedure was designed to obtain viscosity measurements of saturated AN copolymers. Up to 6.7 wt. % CO2 was found to absorb into a 65 mole % AN copolymer with the saturation method used, resulting in a 31oC glass transition temperature (Tg) reduction, 60% viscosity reduction, and 30oC potential processing temperature reduction. It was found that CO2 can absorb into copolymers containing up to 90 mole % AN (with the absorption methods used) with the following results (for a 90/10 mole % AN/MA copolymer): 3.0 wt. % uptake, 27oC Tg reduction, 56% viscosity reduction, and potential processing temperature reduction of 9oC. Via estimates of the required pressure, sealing fluid flow rate, and length of a pressure chamber to prevent foaming of the saturated polymer melt during extrusion, melt spinning of saturated AN copolymers appears feasible.
- Doctoral Dissertations