Durability, of adhesion

The role played by the various ingredients in the composition of sealant, and in particular on the durability of adhesion has been discussed recently [77]. Inert plasticizers, such as trimethylsilyl-endblocked-PDMS, are typically added to silicone sealant compositions in order to adjust the rheology of the uncured sealant. They result in a reduction of the modulus and hardness of the cured sealant. Differences in the durability of silicone sealants are found to be due to differences in their cure chemistry, and more specifically to the nature and... 

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

Developments in glued laminated structures and panel products such as plywood and chipboard raises the question of the durability of adhesives as well as wood. Urea-formaldehyde adhesives are most commonly used for indoor components. For exterior use, resorcinol adhesives are used for assembly work, whilst phenolic, tannin and melamine/urea adhesives are used for manufactured wood products. Urea and casein adhesives can give good outdoor service if protected with well-maintained surface finishes. Assembly failures of adhesives caused by exudates from some timber species can be avoided by freshly sanding the surfaces before glue application. 

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. 

MATIENZO ET AL. Durability of Adhesion Between Aluminum and Coatings 235... 

This work discusses the structure of films formed by a multicomponent silane primer as applied to an aluminum oxide surface as well as the interactions of this primer with the adhesive and oxide to form an interphase region with a distinct composition and properties. The mecanical properties and durability of adhesive joints prepared using this primer system have yet to be evaluated. 

Extensive information on durability of adhesive joints is more available on aluminum than on other substrates. Figure 15.17 illustrates typical results showing the effect of adhesive variations on joint durability during marine exposure. Vinyl-phenolics and nitrile-phenolics have... 

Carter, G. F., Outdoor Durability of Adhesive Joints under Stress, Adhesives Age, October 1967. 

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

Landrock, A. H., Effect of Environment on Durability of Adhesive Joints, Chapter 9 of Adhesives Technology Handbook, Noyes Publications, Park Ridge, NJ, 1985. 

D 2918 Practice for Determining Durability of Adhesive Joints Stressed in Peel... 

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. 

Horioka, K. and Gamoh, M., The Mechanism and Durability of Adhesion in Wood-Glue... 

On that basis, the book intends to bridge current issues, aspects and interests from fundamental research to technical apphcations. In seven chapters, the reader will find an arrangement of latest results on fundamental aspects of adhesion, on adhesion in biology, on chemistry for adhesive formulation, on surface chemistry and pretreatment of adherends, on mechanical issues, non-destructive testing and durability of adhesive joints, and on advanced technical applications of adhesive joints. Prominent scientists review the current state of knowledge about the role of chemical bonds in adhesion, about new resins and nanocomposites for adhesives, and about the role of macromolecular architecture for the properties of hot melt and pressure sensitive adhesives. Thus, insight into detailed results and broader overviews as well can be gained from the book. 

---