Journal
POLYMER
Volume 90, Issue -, Pages 331-341Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2016.03.035
Keywords
Open-cell structure; Polypropylene; Copolymer of ethylene-propylene-diene monomer
Categories
Funding
- National Natural Science Foundation of China [21306090]
- Scientific Research Foundation for the Returned Overseas Chinese Scholars (State Education Ministry)
- Scientific Research Fund of Zhejiang Provincial Education Department [Y201327472]
- High-Toughness hydrogels based on dynamic hydrogen-bonding Science Foundation of Ningbo University [XKL141033]
- K. C. Wong Magna Fund in Ningbo University
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This paper reports on a novel process for preparing open-cell polymer foams which consists in (1) blending a desired polymer with one which is much more CO2-philic and which is the dispersed phase, (2) tuning the sea-island type of morphology of the polymer blend to a co-continuous type by selectively swelling the CO2-philic polymer with CO2 saturation, and (3) selectively foaming the CO2-philic polymer by CO2 depressurization. More specifically, a blend composed of 70% of isotactic polypropylene (PP) and 30% of a copolymer of ethylene-propylene-diene monomer (EPDM) is chosen to show the working principle and potential of the above process. PP is a desired polymer and EPDM a CO2-philic one. During the CO2 saturation, the initially sea-island type of morphology of the PP/EPDM (70/30) blend evolves into a more or less co-continuous one due to the much more CO2-philic nature of the EPDM. Upon CO2 depressurization, foaming takes place primarily in the EPDM phase, leading to open cells. To achieve open-cells for the PP/EPDM (70/30) blend, it is necessary to search for an optimum CO2 saturation pressure and temperature window. Within this window, the cell size and the expansion ratio are in the range of 1.5-17.5 mu m and 1.5-6.6, respectively. Tensile results show that the elongation at break of the CO2 saturated and foamed PP/EPDM blends is higher than that of the un-treated one, indicating that the co-continuous morphology of the PP/EPDM blend improves its toughness. Moreover, compression results indicate that the open-cell foams exhibit good flexibility and elasticity. (C) 2016 Elsevier Ltd. All rights reserved.
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