Abstract
In many of the typical thermosetting acrylic polymers, functional groups are incorporated as comonomers so that crosslinking can occur. In this study N-butoxymethyl amide was used as comonomer to introduce functional groups and melamine resin was added so that crosslinking can occur through self-condensation of the base acrylic polymer as well as through reaction with melamine.
Chemical stress relaxation of swollen films in boiling water was determined. In continuous relaxation, a rapid decay of stress occurred at the early stage which probably is due to the loss of unreacted melamine. Subsequent decay of stress was found to follow the following function consisting of three exponential terms:
f(t)/f(0)=Aexp(-k1t)+Bexp(-k2t)+Cexp(-k3t)
With intermittent relaxation, when the degree of crosslinking is low, relative stress f(t)/f(0) was found to decrease at first and then to increase sharply at around 60∼100min. This increase indicates the crosslinking caused either by the unreacted melamine resin or the recombination of the scissions that had occurred earlier.
