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INTRODUCTION
The increased crosslink density attained when using divinyl
ether reactive diluents in UV curable unsaturated polyester based.
coatings can provide improvements in hardness, mar resistance and
other properties. (ref. 1) Simply replacing styrene with
triethylene glycol divinyl ether (TEGDVE) in these formulations
however can lead to problems such as cracking and loss of adhesion.'.
This set of experiments was undertaken to determine whether there
was evidence for post—UV, cure. crosslinking reactions and If these
could be responsible for crack formation through the development of
excessive internal stress.
• Twelve formulation variations were used for the basic
experiments which constitute this study. They consist of a simple
• polyester with andwithout ally]. ether end groups. Each of these
• was diluted separately with styrene. and TEGDVE. Each of these
variations were then compared with and without cobalt octoate
catalyst. A few experiments utilized MEK peroxide as the thermal
initiator.
Differential Photo Calorimetry (DPC) was used to observe the
energetics of the initial UVcure°process. Subsequent temperature
ramps provided information about thermally induced post cure
reactions. In addition, film specimens were occasionally measured
for internal stress and'glass transition temperature at intervals
of a few days during heat aging.
