Dynamical mechanical analysis of photocrosslinked hyperbranched urethane acrylates

Abstract

A series of acrylate functionalized samples based on hyperbranched hydroxy-terminated polyesters with different molecular weights and different degrees of acrylation were synthesized. The obtained urethane acrylates were slightly yellow viscose liquids. Their composition was characterized by FTIR and 1H-NMR spectroscopy and their molecular weights were measured by GPC. All the synthesized samples were diluted with 25 wt.% 1,4-butanediol dimethacrylate (BDDM). The rheological properties of the uncured samples and the dynamic mechanical properties of the UV cured samples were examined. All the samples exhibit Newtonian behavior, which indicates the absence of physical entanglements in these polymers. The viscosity increases with increasing number of acrylic groups permolecule. The glass transition temperature of the UV cured samples increases with increasing the number of acrylic groups permolecule. The value of the storage modulus in the rubber-elastic plateau and the cross-link density increase with increasing number of acrylic groups permolecule. The formed networks are inhomogeneous and the residual unsaturation is the highest in the samples with the largest number of acrylic groups per molecule.

Keywords

• urethane acrylate
• hyperbranched hydroxy-terminated polyester
• ftir
• 1h-nmr
• gpc
• rheology
• uv curing
• dynamic mechanical properties