NEW THERMOGRAVIMETRIC RELATIONSHIPS FOR STUDYING THE PYROLYSIS OF POLYMERS
NAVAL ORDNANCE LAB WHITE OAK MD
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Two thermogravimetric methods were developed to show whether rate of weight loss varies with extent of pyrolysis of a polymer. The first of these, a kinetic technique, involves obtaining at various degrees of degradation the activation energy, the order of decomposition, and the Arrhenius pre-exponential factor by solving three simultaneous equations. The data for these equations are obtained by performing three thermogravimetric experiments at three constant heating rates. The second method, which involves cycling the polymer between 25 deg C and a fixed higher temperature, is based on the compound interest law. If the rate of weight loss changes with extent of decomposition, the experimental points deviate from the theoretical curve if the rate does not vary, the experimental points coincide with the curve. Both techniques show that rate of weight loss does not change appreciably with degree of pyrolysis of Teflon. For a copolymer of tetrafluoroethylene and hexafluoropropylene, these methods show that rate of weight loss does vary with degree of pyrolysis.
- Physical Chemistry
- Polymer Chemistry