Enhancement of tensile strength of low Young's modulus UV curable urethane acrylates

Mechanical properties of UV curable urethane acrylates having low Young's modulus were studied A remarkable enhancement in tensile strength and elongation at break of the cured film was achieved by the introduction of a small amount of di-functional monomer and appropriate amount of urethane acrylate oligomer. The dynamic mechanical analyses of the cured films with various amounts of urethane acrylate oligomers and di-functional monomer indicated that the films showing bimodal loss tangent (tan delta) curve exhibited high tensile strength and elongation. It suggests that the phase separation enhanced the toughness of the cured film. The phase separation could be achieved when two requirements are met, one is an appropriate amount of urethane acrylate oligomer, another is less compatible polyacrylate matrix made by the addition of a small amount of di-functional monomer.