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Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer
Author(s) -
Guo Huimin,
Kumar Vipin
Publication year - 2015
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.42226
Subject(s) - nucleation , materials science , glass transition , saturation (graph theory) , solubility , thermal diffusivity , atmospheric temperature range , chemical engineering , composite material , polymer chemistry , thermodynamics , polymer , chemistry , organic chemistry , physics , mathematics , combinatorics , engineering
Effect of glass transition temperature and saturation temperature on the solid‐state microcellular foaming of cyclic olefin copolymer (COC)—including CO 2 solubility, diffusivity, cell nucleation, and foam morphology—were investigated in this article. COCs of low T g (78°C) and high T g (158°C) were studied. Solubilities are 20–50% higher in high T g COC than in the low T g COC across the saturation temperature range. Diffusivities are about 15% higher on average in high T g COC for temperatures up to 50°C. A much faster increase of diffusivity beyond 50°C is observed in low T g COC due to it being in the rubbery state. Under similar gas concentration, high T g COC starts foaming at a higher temperature. And the foam density decreases faster in low T g COC with foaming temperature. Also, high T g COC foams show about two orders of magnitude higher cell nucleation density than the low T g COC foams. The effect of saturation temperature on microcellular foaming can be viewed as the effect of CO 2 concentration. Nucleation density increases and cell size decreases exponentially with increasing CO 2 concentration. Uniform ultramicrocellular structure with an average cell size of 380 nm was created in high‐ T g COC. A novel hierarchical structure composed of microcells (2.5 μm) and nanocells (cell size 80 nm) on the cell wall was discovered in the very low‐density high‐ T g COC foams. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132 , 42226.