Chemical ageing effects on the mechanical behaviour of ethylene-propylene diene monomer. (December 2017) - McDonnell, Darren
Abstract: Ethylene-propylene diene monomer (EPDM) elastomer diaphragm failures due to material degradation pose a major risk in the biopharmaceutical industry, as they can result in long periods of production downtime. It is suspected that a key cause of this EPDM degradation is due to the chemical solutions used in equipment cleaning processes. However this has never been empirically investigated in the public domain. Twenty four virgin samples were utilised for testing, twelve of which were subject to common chemical cleaning solutions used in the biopharmaceutical sector. The chemical solutions under investigation were aqueous solutions of NaOH, NaClO, H3 PO4, and the interaction between 100 °C H2 O and NaClO. The characterisation of the degradation process was conducted by mechanical testing. The results show that degradation of the polymer bulk proceeds predominantly via crosslinking for all exposure types. NaOH and H3 PO4 exposure results in an accelerated rate of crosslinking compared to NaClO in the early stages of exposure. Highlights: Ethylene-propylene diene monomer parts exposed to NaOH, NaClO, and H3 PO4 solutions. Crosslink density of all samples increases up to 168 h exposure time. Further exposure to 504 h results in chain scission reactions in NaOH and H3 PO4 . Conversely, NaClO exposed samples continually form new crosslinks. Hardened surface layers form, impacting bulk mechanical properties.