Foaming Cyclo-Olefin Copolymers with Carbon Dioxide

Cyclo-olefin copolymers (COC) based on ethylene-norbornene (E-NB) structures have been investigated with respect to their foamability. COC present interesting characteristics, such as extremely low water absorption, excellent water vapor barrier properties, high strength and very good electrical insulating properties. Varying the ratio of E versus NB monomers enables to tune the glass transition temperature (T _g ) over a wide range. Due to the rigid ring structure of NB, the resin remains amorphous. This study presents basic information related to the foam processing of different grades of COC resins with T _g varying between 80 and 130 °C, adding a special emphasis on process-relevant material characteristics: rheology, solubility and plasticization. CO ₂ -laden COC sheets, where the gas sorption was obtained using high pressure autoclave, were foamed using a biaxial stretcher. The impact of selected processing parameters (temperature, time of pre-heating, speed of deformation, magnitude of stretching) on the microcellular foam morphology and density will be reported throughout this paper.