Morphology and mechanical properties of radiation‐polymerized urethane–acrylates. I. Pure oligomers

Abstract

AbstractThe morphology of electron beam cured polyacrylo–urethane films based on polyethylene adipate and toluene diisocyanate was characterized to explain their mechanical properties. The polyacrylo–urethane films have a one‐phase morphology in which the hard urethane segments and the soft polyester segments are homogeneously mixed. The films obtained from 1000‐molecular‐weight oligomer are hard and somewhat brittle due to their one‐phase morphology in which hard glassy segments play a dominant role. The films obtained from 4600‐ and 6000‐molecular‐weight oligomers are soft and tough, once again due to their one‐phase morphology in which soft rubbery segments are more effective. The original crystalline structure of 6000‐molecular‐weight oligomer is retained in the precrystallized γ‐irradiated film, but electron‐beam‐irradiated films showed partial melting of the crystallites due to the heat of polymerization. The solid state polymerized films have a lower eleongation, a higher modulus, and a higher breaking strength due to their crystallinity.