Degradation kinetics of polymers in solution: Time-dependence of molecular weight distributions. [Quarterly report, January--March 1996]
Polymer degradation occurs when polymer chains are broken under the influence of thermal, mechanical, or chemical energy. Chain-end depolymerization and random- and midpoint-chain scission are mechanisms that have been observed in liquid-phase polymer degradation. Here we develop mathematical models, unified by continuous-mixture kinetics, to show how these different mechanisms affect polymer degradation in solution. Rate expressions for the fragmentation of molecular-weight distributions (MWDs) govern the evolution of the MWDs. The governing integro-differential equations can be solved analytically for realistic conditions. Moment analysis for first-order continuous kinetics shows the temporal behavior of MWDs. Chain-end depolymerization yields monomer product and polymer molecular-weight moments that vary linearly with time. In contrast, random- and midpoint-chain scission models display exponential time behavior. The mathematical results reasonably portray experimental observations for polymer degradation. This approach, based on the time evolution of continuous distributions of chain length or molecular weight, provides a framework for interpreting several types of polymer degradation processes.
- Research Organization:
- California Univ., Davis, CA (United States). Dept. of Chemical Engineering and Materials Science
- Sponsoring Organization:
- USDOE, Washington, DC (United States); Environmental Protection Agency, Washington, DC (United States)
- DOE Contract Number:
- FG22-94PC94204
- OSTI ID:
- 382447
- Report Number(s):
- DOE/PC/94204-T8; ON: DE96050320; CNN: Grant CR 822990-01-0
- Resource Relation:
- Other Information: PBD: 27 Feb 1996
- Country of Publication:
- United States
- Language:
- English
Similar Records
Time evolution to similarity solutions for polymer degradation
Molecular weight effect on the dynamics of polystyrene degradation