The influence of a non-isocyanate urethane monomer in the film formation and mechanical properties of homogeneous and core-shell latexes

Abstract

A urethane methacrylate monomer, 2-((methylcarbamoyl)oxy)ethyl methacrylate, (MEM), was synthesized via a non-isocyanate pathway and incorporated into latexes using a semi-continuous emulsion polymerization. Homogeneous and core-shell latexes were prepared using MEM, methyl methacrylate (MMA) and butyl acrylate (BA). Narrow particle size distribution and high conversion was achieved for all latexes. Core-shell structure was corroborated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and transmission electron microscopy (TEM). Thermal properties, viscoelastic, mechanical properties and morphology were evaluated and compared as a function of increasing concentration of the urethane methacrylate monomer. Enhanced viscoelastic and mechanical properties were obtained with higher MEM content in both homogeneous and core-shell latexes. Incorporation of MEM into latexes lowered the minimum film formation temperature (MFFT) and also enhanced the extent of film formation. Core-shell latexes displayed higher storage modulus, Young's modulus, tensile strength and hardness compared to homogeneous latexes due to the combination of hard core and the pendent urethane present in the continuous phase (shell).