Degradation kinetics of polymers in solution: Dynamics of molecular weight distributions

Journal Article · Sat Mar 01 04:00:00 EST 1997 · AIChE Journal

DOI:https://doi.org/10.1002/aic.690430325· OSTI ID:460566

McCoy, B J; Madras, G ^[1]

---

1. Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

Polymer degradation occurs when macromolecular 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 the authors 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 MWDs. The governing integrodifferential 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 describe 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 macromolecular degradation processes, particularly how bimodal MWDs can evolve during degradation.

• Sponsoring Organization: USDOE Pittsburgh Energy Technology Center, PA (United States); Environmental Protection Agency, Washington, DC (United States)
• DOE Contract Number: FG22-94PC94204
• OSTI ID: 460566
• Journal Information: AIChE Journal, Journal Name: AIChE Journal Journal Issue: 3 Vol. 43; ISSN AICEAC; ISSN 0001-1541
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DECOMPOSITION
EROSION
MATHEMATICAL MODELS
MOLECULAR WEIGHT
POLYMERS
THEORETICAL DATA
THERMAL DEGRADATION