Transparent Barrier Urethanes Based on Polyethylene Soft Segments

摘要

A series of polyurethane elastomers has been synthesized through co- polymerization of polyethylene soft segments and methylene bis(4- phenylisocyanate) (MDI) and hydrogenated MDI (H(12)MDI). Polyethylene soft segments were prepared by the hydrogenation of polybutadiene polyols, either before or after copolymer synthesis. Polyols from three different suppliers were used as precursors and ranged in branch content from 15% to (caret)90%. Flexible, transparent materials were produced. The mechanical and barrier properties of these urethanes were evaluated for comparison with the performance of traditional flexible barrier materials (e.g., butyl rubber). Solvent uptake and swelling measurements were used to evaluate barrier performance. Branch content in the soft segment was found to affect both mechanical properties and solvent resistance, with low branch content leading to superior performance. Solvent diffusion coefficients for the materials were in the 10(exp -8)sq cm/s range, comparable to those exhibited by flexible high barrier materials.