Abstract
dc:description.abstractThe main aim of thia programme was to study the superior durability claimed for phenolic-based adhesives, in hot humid conditions. The systems under study were the nitrile-phenolics AF-10 and AF-30 (3M), the vinyl-phenolic Redux 775 and the modified epoxide Redux 312 (Ciba-Geigy). The AF-30 structural adhesive was used with and without the primer EC-1660 (5% solids). The approach to this problem was to expose unstressed joints to conditions of 50% RH and 100% RH at 50®C, and to determine the residual joint strengths. Exposure periods of up to 10000 h were used. Strengths of all joints declined over a period of about 2000 h at 100% RH and 50oC and then remained relatively static. All joints, however. showed some recovery in strength on reconditioning at 50% RH. For the systems studied, phenolic adhesives showed no advantages in durability over the epoxide. The use of primer did improve durability. Studies on the cured adhesive films, following their uptake of water. revealed that diffusion was Fickian In behaviour and that their water transport properties were similar. A linear correlation was observed for AF-30, AF-30/P and Redux 312 when strength retention of lap joints was plotted against the functional water content. A curved relationship was given for AF-10 and Redux 715, although the reasons for this were unclear. To examine the surfaces of broken joints, in order to gain information on the true locus of failure in the joints, the technique of Electron Spectroscopy for Chemical Analysis (ESCA) was employed. Examination by ESCA revealed that, in many instances, the mode of failure was complicated and also. In some cases, contrary to the visual evidence. To complete the surface study, the phenolic adhesive aluminium inter-face was examined by Inelastic Electron Tunnelling Spectroscopy (lETS). While no direct evidence, in the form of an Al-0 covalent bond, was found. there was support for the formation of complexes consisting of either (i) one acidic and one coordinating group, or (ii) two acidic groups. A literature survey on "Co-ordination to Aluminium" was carried out to see what knowledge existed that might lead to a better understanding of. or even improvement in, adhesive bonding between phenolics and aluminium. Further information on chelate formation and stability was subsequently found.
Degree
thesis:*- Name dc:type.qualificationname
- PhD
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- De Montfort University
- Year dc:date.issued
- 1986
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Tredwell, Stephen