Optimum Bond Strength

What this expression says is that the measured strength of an adhesive bond, Fmeas) is first dependent upon the mechanics of the adhesive bond itself, M. Secondly, it is dependent upon the work of adhesion, Thirdly, it is dependent upon the physical properties of the adhesive such as the complex Young s and shear moduli, E and G, respectively, and the same moduli for the adherend. Fourthly, it is dependent upon the fracture resistance of the material, Fifthly, it is dependent upon the strength of interfacial chemical bonds, and sixthly on the amount of mutual 

Conway, Mechanics of Materials, Prentice-Hall, Englewood Cliffs, New Jersey (1959). 

Hearle, Polymers and Their Properties, Vol. 1, Ellis Horwood, Chichester, UK (1982). 

Viscoelastic Properties of Polymers, John Wiley, New York (1980). 

---

Films. Both structural and nonstructural adhesives are commonly available in film form. Adhesives applied in the form of dry films offer a clean, hazard-free operation with minimum waste and excellent control of film thickness. However, the method is generally limited to parts with flat surfaces or simple curves. Optimum bond strength requires curing under heat and pressure, which may involve considerable equipment and floor space, particularly for large parts. Film material cost is high in comparison to liquids, but waste or material loss is the lowest of any application method. 

Medium- to high-strength bonds, suitable for noncritical applications Optimum bond strength per FPL etch process. Specified in ASTM D 2651 and MIL-A-9067. Solvent degrease may replace alkaline cleaning. 

Hansen, G. P., et al.. Achieving Optimum Bond Strength with Plasma Treatment, presented at the Soc. of Mfg Eng. Adhesives Conf., paper No. AD89-537 (Sep. 12-14,1989)... 

O. S. Kolluri, S. L. Kaplan, and P. W. Rose, SPE Adv. Polymer Composites 88 RETEC, 1988. G. P. Elansen, R. A. Rushing, R. W. Warren, S. L. Kaplan, and O. S. Kolluri, Achieving optimum bond strength with plasma treatment, Technical Paper AD89-537, Society of Manufacturing Engineers, Dearborn, MI, 1989. 

Once the metal surface has been adequately cleaned of oxide contamination, dusted off and once more degreased, it is vital that the application of a bonding agent primer coat be carried out as quickly as possible to ensure that the re-oxidation of the metal surface is kept to a minimum. Ambient temperature, humidity and dust must all be controlled if the optimum bond strength is to be achieved. To consistently ensure optimum bond quality, metal components, whether unprimed or primed, should be kept in enclosed cabinets. At no time should cleaned and degreased metals be handled with bare hands. Human skin, however clean it may appear, always carries a surface layer of oils and fats, which are bond killers. Neither should metals, whether in the just cleaned state, or... 

The optimum viscosity of the adhesive will need to be determined by experimentation to achieve optimum bond strength. 

Irrespective of pretreatment procedure, optimum bond strengths can be attained if the laminates are dried before bonding to remove any moisture absorbed from the atmosphere. This should be carried out, immediately before joint assembly, in an air-circulating oven at a temperature at which no thermal damage will be imparted to the laminate. 

Correct surface preparation is critical to achieving optimum bond strength and joint reliability. Cleaners, such as surfactants and solvents are used to ensure that surfaces to be bonded are clean and free from dust and other loose materials, grease, oils, and other impurities that may affect the adhesion and ultimate bond strength. 

Hansen GP, Rushing RA, Warren RW, et al. Achieving Optimum Bond Strength with Plasma Treatment. Presented at Society of Manufacturing Engineering Adhesives Conference, Paper No. AD89—537. September 12—14, Dearborn, MI, 1989. 

For optimum bond strength, use the procedure described above under Ethylene—Chlorotiifluoro-ethylene Copolymer (Section 1.2.1). ... 

Although thermal welding is ordinarily used for bonding this material to obtain optimum bond strength, adhesives are used under certain conditions. Three types of adhesives are used solvent, structural, and nonstructural. Hexafluoroacetone sesquihydrate is used for solvent cementing. Structural adhesives are generally thermosets. Many of these adhesives can be used continuously at temperatures up to 177°C, which is higher than the recommended continuous-use temperature of 104°C of the copolymer. 

---