Challenges in prediction of significant structural changes during photochemical “degelation” of acrylic-urethane network

Abstract

Structural changes induced by photo-aging have significant influence on material properties. The prediction of the period prior to the onset of significant morphological changes is useful in determining material service lifetime. We assume “degelation” to be the starting point of significant morphological change during photo-aging. Herein, we demonstrated the relationship between such time and the “degelation” phenomenon for an acrylic-urethane network polymer. We also derived a “degelation” theory considering network imperfections, e.g. dangling chains and looping chains. This provides a more accurate representation of reactive curing polymers widely used in industries. Lastly, we estimated the “imperfection degree” by comparing the number of elastically active chains obtained from a swelling experiment with the theoretically derived number. In this system, samples may originally possess approximately 10% network imperfection and it influences on the degelation period in aging process. Our study may potentially contribute to a more accurate prediction of the onset of significant structural change.