Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/198654

Title

Surface characterisation of ethylene-propylene-diene rubber upon exposure to aqueous acidic solution

Author(s)

Mitra, Susanta;  Ghanbari-Siahkali, Afshin;  Kingshott, Peter;  Hvilsted, Søren;  Almdal, Kristoffer

Abstract

Two types of pure ethylene propylene diene rubbers were exposed to two different acids for varying period of time. Surface characterisation was carried out using X-ray photoelectron spectroscopy (XPS). Two EPDM rubbers selected for this study were comparable in co-monomer compositions but significantly different with respect to molar mass and the presence of long chain branching. Both rubbers contained 5-ethylidene-2-norbornene (ENB) as diene. Solution cast films of pure EPDM samples were exposed in two different acidic solutions, viz. chromosulphuric (Cr (VI)/H2SO4) and sulphuric acid (H2SO4) (20%, v/v) at ambient temperature from 1 to 12 weeks. XPS analysis indicated that several oxygenated species were formed on the surface of both rubbers after exposure. It was postulated from the XPS analyses that both aqueous acidic solutions attacked the olefinic double bonds (C{double bond, long}C) of ENB. Furthermore, 20% Cr (VI)/H2SO4 also attacked the allylic carbon-hydrogen (C{single bond}H) bonds of ENB resulting in more oxygenated species on the surface compared to 20% H2SO4 under identical conditions. Cr (VI) in the 20% Cr (VI)/H2SO4 was found to play an important role in alteration of surface chemistry. Studies using a model system consisting of EPDM mixed with Cr (VI) and Cr (III) salts revealed that the change of oxidation state from Cr (VI) to Cr (III) as a consequence of direct involvement of Cr (VI) in the chemical alteration of EPDM surfaces. Interestingly, the presence of long chain branching and molar mass did not significantly influence the chemical processes owing to the acid treatment.

Publication type

Journal article

Source

Applied Surface Science, Vol. 252, no. 18 (Jul 2006), pp. 6280-6288

Publication year

2006

FOR Code(s)

0204 Condensed Matter Physics;  0912 Materials Engineering

Keyword(s)

Elastomer;  EPDM;  Ethylene;  Long chain branching;  Monomers;  Oxidation;  Propylene;  Solution cast films;  Solutions;  Surface characterisation;  Synthetic rubber;  X ray photoelectron spectroscopy

Publisher

Elsevier

ISSN

0169-4332

Publisher URL

http://dx.doi.org/10.1016/j.apsusc.2005.08.031

Copyright

Copyright © 2005 Elsevier B.V. All rights reserved.

Peer reviewed