Durability of adhesive bonds

Finally, reports are available on the durability of adhesively bonded aluminium joints... 

Adhesives and sealers can be an important part of a total corrosion protection system. Structural bonding procedures and adhesives for aluminum, polymer composites, and titanium are well established in the aerospace industry. Structural bonding of steel is gaining increasing prominence in the appliance and automotive industries. The durability of adhesive bonds has been discussed by a number of authors (see, e.g., 85). The effects of aggressive environments on adhesive bonds are of particular concern. Minford ( ) has presented a comparative evaluation of aluminum joints in salt water exposure Smith ( ) has discussed steel-epoxy bond endurance under hydrothermal stress Drain et al. (8 ) and Dodiuk et al. (8 ) have presented results on the effects of water on performance of various adhesive/substrate combinations. In this volume, the durability of adhesive bonds in the presence of water and in corrosive environments is discussed by Matienzo et al., Gosselin, and Holubka et al. The effects of aggressive environments on adhesively bonded steel structures have a number of features in common with their effects on coated steel, but the mechanical requirements placed on adhesive bonds add an additional level of complication. 

Kinloch, A. J., Ed. "Durability of Adhesive Bonds", Applied Science Publishers London, 1983. 

Although numerous studies (1-3) have described work aimed at establishing criteria for the durability of adhesive joints, a thorough understanding of effects of the chemical and mechanical properties, on the durability of adhesive bonds is lacking. More specifically, the effects of surface preparation and dynamic loading, especially under environmental service conditions, has not been explored in detail for automotive structures. In this paper, a description of the effects of environment on the durability of adhesive bonds is presented. Particular attention is given to... 

Corrosion Testing. Salt spray testing (ASTM-B-117-52,54) was used to determine durability of adhesive bond in corrosive environment. Lap shear samples were exposed to salt spray for 14 days and then immediately tested for lap shear strength. 

The environmental durability of adhesively-bonded aluminum structures is of prime importance in the aircraft industry. 

Minford, in Durability of Adhesive Bonded Aluminum Joints, Treatise on Adhesion and Adhesives, vol. 3, p. 79. 

The direct way to increase the number of radicals on a substrate surface is to treat it with stable radical solutions. Nitroxyl radicals of the 2,2,6,6-tetramethylpiperidine series have been found to considerably improve durability of adhesive bonds (62,63). For instance, when sticking together high pressure polyethylene, fluoro-plastic F-4 and polyvinylchloride, pretreatment of their surfaces with nitroxyl radical solutions improved the durability of adhesive bonds by 160-170%. This result is considerably better than that obtained by treatment of the aforesaid polymer surfaces with the most active adhesion modifiers known (64). 

Nitroxyl radicals can be used not only to increase durability of adhesive bonds but also to decrease it. This effect can be achieved by thermal treatment of radical-modified surfaces at 100-160°C. This is probably due to the fact that at elevated temperatures nitroxyl radicals react with substrate active groups of surfaces thereby sharply decreasing surface adhesion. 

H Hamada, Z Maekawa, T Morii, A Gotoh and T Tanimoto, Durability of adhesive bonded FRP joints immersed in hot water . Durability of Polymer-based Composite Systems for Structural Applications, eds A H Cardon and G Verchery, London, Elsevier Applied Science, 1991, p 418. 

Bascom, W.D., Cottington, R.L. and Timmons, C.O. Durability of Adhesive Bonded Structures (Ed. Bodnar, M.J.), Journal of Applied Polymer Science, Applied Polymer Symposia 32, J. Wiley and Sons, New York, 1977, p. 165. 

The method used for testing durability of adhesive bonds was developed at 3M by W.D. Sell (16) and is called "sustained load stress durability". The metal substrates were 2024T-3 clad or bare aluminum alloy, 5052T-4 bare aluminum alloy or 1010 cold rolled steel. The surface preparation for the aluminum alloys was either the "optimized" FPL-etch" or the H PO -anodization process (12). The steel was solvent wiped. If a primer was used, it was cured before application of the adhesive. Film... 

Murray, B.D., Anaerobic Adhesive Technology, Preprint Booklet, Symposium on Durability of Adhesive Bonded Stractures, sponsored by U.S. Army Research and Development Command, pp. 599-610, Picatinny Arsenal, Dover, NY, October 27-29, 1976. [Also published in J. Appl. Polym. Set, Appl. Polym. Symposia (M.J. Bodnar, ed.), 32 411 20,1977.]... 

De Lollis, N.J., Durability of adhesive bonds (a review). Proceedings of the 22nd National SAMPE Symposium, Vol. 22, Diversity-Technology Explosion, San Diego, CA, pp. 673-698, April 26-28,1977. 

Because of the large number of factors that influence the durability of adhesive-bonded joints, a durability test should be conducted on all systems before they are selected for any particular application. This test should include the adherends, surface preparation, adhesive, and cure parameters needed for each application. ... 

One of the earlier methods used by the Army for evaluating the durability of adhesive-bonded joints is the stressed temperature/humidity test described in ASTM D2919-01. Army ARDC workers at Picatiimy Arsenal... 

Figure 10.3 Effect of temperature on the durability of adhesive-bonded anodized aluminum at 95%...

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