Ultimate bond strength

Figure 4. Effect of press time on ultimate bond strength.

After mating, the surfaces may be positioned for up to two minutes before the reaction starts and the bond forms. Mild contact pressure is maintained for 5-10 minutes 75% of the -ultimate bond strength is reached within one hour. Lap shear strengths of 3500 psi and peel strengths of 20 pli have been achieved in model systems. 

Mechanical fasteners offer ultimate bonding strength immediately. 

In the first paper, Petke reviews the current literature for developments in structure-property relationships of adhesives. He illustrates how chemical and physical structure affect both the adhesive and cohesive properties of polymers. In his review, he shows how the balance of adhesive and cohesive properties determine the ultimate bond strength of an adhesive. Relationships are cited for several types of adhesives. 

Water base contact cements will generally require greater pressures for ultimate bond strengths than can normally be accomplished on the job site. As a result, they are relegated to the cabinet shops and areas where controlled conditions and uniform pressures can be applied. They tend to be absorbed into the substrate, resulting in a starved glue joint. Thus, in the event a water base cement is used, adequate thickness of adhesive is essential. Many times this may require two or even three coats of the contact cement. Of course, both the plastic laminate and the substrate need to be coated. 

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. 

Contact bonding In this method, both surfaces are coated and the adhesive is permitted to become dry to the touch. Within a given time, these surfaces are pressed together and near-ultimate bond strength is immediately achieved. In this method, both surfaces may be nonporous. Neoprene latex adhesives are commonly utilized in contact bonding... 

Fig.4 Ultimate Bond Strength of Reinforcing Bars in SFRC...

Technology Ultimate bond strength Advantages Disadvantages Capitai costs Cost per part Potentiai for future development... 

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