Sorption of high pressure fluid mixtures into semi-crystalline polymers: investigation of the system carbon dioxide/vinylidenefluoride/poly(vinylidenefluoride)

• Published in: Journal of physics. Conference series 2008-07, Vol.121 (2), p.022020
• Main Authors: Cipollina, A, Galia, A, Scialdone, O, Filardo, G
• Format: Article
• Language: English
• Subjects: Absorption; Argon; Carbon dioxide; Crystal structure; Crystallinity; Gas absorption; Gas chromatography; Gases; Mass balance; Mathematical analysis; Measuring instruments; Partial pressure; Physics; Polymers; Solubility; Sorption
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/121/2/022020

A novel experimental apparatus for measuring gas absorption has been adopted to study sorption of carbon dioxide CO2 and vinylidenefluoride (VDF) in a semi crystalline polymer, namely poly(vinylidenefluoride) (PVDF). The experimental technique allows to calculate simultaneous absorption of different components in the polymer phase, through a gas chromatographic determination of the composition of the fluid phase. To take into account indirectly the polymer swelling, a suitable not-absorbable probe, namely argon, has been added to the fluid phase. Concentrations of molecules absorbed in the polymer phase were simply calculated through mass balance equations written for each component in the two phases. Several different operating conditions were investigated. Temperature was kept constant at 50°C, while pressure varied between 8 and 35 MPa. Sorption was measured for pure CO2 and VDF and for mixtures containing around 0.20 w/w and 0.40 w/w of VDF in CO2, to analyse how the presence of a different component could affect the sorption of the other. Results show that pure CO2 presents a solubility more than three fold higher than pure VDF at the same pressure conditions. On the other side, when both gases were present in the mixtures, the sorption of CO2 seems to be strongly inhibited by VDF, whereas this latter presents a solubility quite similar to the pure gas if operating at the same partial pressure.