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oai:dora.dmu.ac.uk:2086/255402025-10-29T03:02:37Zcom_2086_2388col_2086_2389

THE EFFECT OF WATER ON THE PHYSICAL PROPERTIES OF EPOXIDES SHALASH, RIADTH JASIM ABBAS The effect of water absorption in epoxide adhesives, both in bulk and joint forms, was examined. Boiling-water immersion was found to be a suitable technique to accelerate water diffusion in bulk epoxides. The boiling-water diffusion was found to be Fickian in epoxides except for the DOM system’, water-vapour diffusion at 25°C was found to be Fickian. To study accurately the effect of water absorption (liquid and vapour) on the mechanical properties of bulk epoxides, a new method of specimen preparation was developed. Water absorption in epoxides was found to involve two processes, namely plasticization and cross linking; the predominant effect depends on the particular system. Water absorption in epoxides was found to seriously depress the glass transition temperature (Tg), which explains the reason for the deterioration in the mechanical properties. A manual torsional pendulum was used to measure the Tg values. In a later stage, an automatic torsional pendulum was constructed to obtain accurate and reproducible results. The effect of water on the mechanical and thermal properties was found to be reversible, suggesting plasticisation was involved and not hydrolysis of chemical bonds. Exposing epoxide-clad aluminium joints to high humidity (100% R.H. at 50°C), caused degradation in joint strengths. From theoretical analysis of fractional water concentration in joints and the observed failure modes of joints, the mechanism of strength loss is believed to be related to the water plasticization of the adhesive. However, above a critical water concentration, interfacial degradation due to water accumulation induces further strength loss. De Montfort University 1979-12 Thesis or dissertation Doctoral PhD en https://hdl.handle.net/2086/25540 https://dora.dmu.ac.uk/bitstreams/afec63ac-75c6-479f-9ff6-01313255eb46/download bd41181d9a4c38b5ebacc69a027024d9 https://dora.dmu.ac.uk/bitstreams/916fde5a-968c-4c54-ab24-f10d6f4b830f/download 21ee35b80fe809d952237ce597eccc7b https://dora.dmu.ac.uk/bitstreams/38a050e0-13a1-44cf-a56f-4d4d86e1891c/download a744401d2a8f757134161ca6e5d15336 Faculty of Health and Life Sciences