Thermal and Gas Barrier Properties of COC/SiO ₂ Nanocomposites

This study is performed primarily to investigate the effects of chemical modification on silica surface and the silica content on the thermal and gas barrier properties of a cyclo olefin copolymer (COC) matrix. The COC/SiO ₂ nanocomposites were constructed from COC and three species of SiO ₂ nanoparticles (AEROSIL A200, R805 and R974) with different organic groups, prepared by solution blending. The thermal properties of the composites were studied by DSC and TGA. The gas barrier properties of the composites were characterized by use of a gas permeability analyzer. The glass transition temperature (T _g ) and decomposition temperature (T _d ) of these composites increased obviously with the silica content ranging from 0.5 to 10 wt.%. The composite with 10 wt.% R805 exhibited the highest T _g , which was 14.1 °C higher than that of pure COC. The water and oxygen permeability decreased with increasing the content of SiO ₂ . The composites with 10 wt.% R974 had the minimum values of water and oxygen permeability and were 32% and 36% lower than those of pure COC, respectively. The dispersion of these silica particles in the COC matrix was made by SEM and consideration was given to the relationship between the modified silica surface and the COC matrix, and thermal properties and gas barrier properties.