Effect of norbornene content on deformation properties and hot embossing of cyclic olefin copolymers

Abstract

The dynamic mechanical behaviour of a series of cyclic olefin copolymers (COCs) with varying norbornene content has been examined in the vicinity of the glass transition temperature, T _g. Using dynamic mechanical thermal analysis (DMTA), the temperature of the glass transition in COC increased linearly with increase in % norbornene. Above T _g, the magnitude of the elastic storage modulus, E′, decreased exponentially with rise in temperature for all of the copolymers. The loss modulus, E″, has also sharply decreased at temperatures above the transition with a levelling-off in E″ at ≥20 °C above T _g for all grades. The results of DMTA have been used in the identification of the optimum conditions for hot embossing experiments. Hot embossing of COC at ≥20 °C above the transition temperature in a region of viscous liquid flow has resulted in a full replication of channel depth without cracking or distortion.