Study of poly‐ϵ‐caprolactone bulk degradation

The thermal stability of poly‐ϵ‐caprolactone samples obtained by ring‐opening polymerization in the presence of different metal alkoxides has been investigated. A significant degradation of the polyesters is observed under isothermal conditions at 120°C. The degradation is related to the nature of the endgroup, the presence of catalyst residues, and the presence of molecular oxygen. The hydroxyl endgroups play a determinant role in the process. They probably give rise, under the influence of catalyst residues, to hydroperoxides which are responsible for the polymer degradation by a radical reaction. It is shown that this is clearly different from the change in molecular weights distribution due to the well‐known ester interchange reaction (transesterification equilibrium). Resulting methods for the polymers stabilization are indicated. Copyright © 1976 John Wiley & Sons, Inc.