Tensile shear strength

The routine compositional and functional testing done on the adhesives includes gas chromatographic testing for purity, potentiometric titrations for acid stabilizer concentrations, accelerated thermal stabiUty tests for shelf life, fixture time cure speed tests, and assorted ASTM tests for tensile shear strengths, peel and impact strengths, and hot strengths. 

Fig. 8. Steel lapshear tensile shear strengths for ECA, ECA/PMMA, and ECA/Vamac B-124 with and without thermal exposure at l2l°C.

The lapshear tensile shear strength of formulation A without any rubber, declines to ca. 50% of its original strength after 24 h at 12I C. In contrast, the lapshear ten.sile shear strength of formulation C exhibits no loss of adhesion under the same conditions. 

Fig. 10. Tensile shear strength of ECA homopolymer after heat aging at IITC with and without cyclic sulfate, 9, on steel lapshears.

The isophthaloyl based polymer in Table 12 gave unoriented thin film tensile strength, modulus and elongation at room temperature of 114.4 MPa, 3.55 GPa and 4.4%, respectively [35], The relatively high modulus for the amorphous film was unexpected. Titanium-to-titanium tensile shear strengths of the isophthaloyl based polymer after 1000 hours of exposure at 200 °C in air were 34.1 MPa at 23 °C, 22.2 MPa at 150 °C and 7.6 MPa at 177 °C [35]. The strength at 177 °C was surprising since the Tg was only 182 °C. DSC and WAXS analyses revealed that the adhesive was amorphous. 

FIGURE 3.9 Plot of tensile shear strength of an aluminum joint bonded with an elevated-temperature curing epoxy adhesive as a function of test temperature. 

Hybrid adhesive Tensile shear strength, psi T-peel strength, lb/in... 

FIGURE 7.1 The effect of temperature on the tensile shear strength of modified epoxy-phenolic compared to other hybrid adhesives (substrate is aluminum).4... 

Not only is low tensile shear strength noticed on moisture aging, but also the mode of failure changes from one of cohesion to adhesion. Table 7.6 shows the effect of humidity and water immersion on an epoxy-nylon adhesive compared to a nitrile-phenolic adhesive. Substrate primers have been used with epoxy-nylon adhesives to provide improved moisture... 

Tensile shear strength, psi, Peel strength, MIL-A-25463, Adhesive composition at temperature lb/in, at temperature... 

TABLE 7.6 Effect of Humidity and Water Immersion on the Tensile Shear Strength of Epoxy-Nylon and Nitrile-Phenolic Adhesives 10... 

Polysulfide resins combine with epoxy resins to provide adhesives and sealants with excellent flexibility and chemical resistance. These adhesives bond well to many different substrates. Tensile shear strength and elevated-temperature properties are low. However, resistance to peel forces and low temperatures is very good. Epoxy polysulfides have good adhesive properties down to -100°C, and they stay flexible to -65°C. The maximum service temperature is about 50 to 85°C depending on the epoxy concentration in the formulation. Temperature resistance increases with the epoxy content of the system. Resistance to solvents, oil and grease, and exterior weathering and aging is superior to that of most thermoplastic elastomers. 

TABLE 7.9 Cured Tensile Shear Strength of Uncleaned Substrates Bonded with Epoxy-Urethane Hybrid System16... 

Substrate Substrate thickness, mils Tensile shear strength, psi... 

FIGURE 9.9 The effect of mineral extenders on the tensile shear strength of epoxy adhesive (the substrate is aluminum).29... 

Although the addition of fillers often results in an improvement in tensile shear strength, as noted above, it also often results in a decrease in peel or impact strength. This is due to... 

TABLE 10.4 Tensile Shear Strengths of Several Structural Adhesives Incorporating Silane... 

Elongation at break, % Cold-rolled steel tensile shear strength, psi, at... 

With most room temperature curing epoxy adhesives, a significant drop in tensile shear strength occurs between 80 and 120°C. The exact temperature where the drop in strength occurs will depend very much on the specific curing agent used, the fillers or modifiers... 

TABLE 11.6 Effect of Filler on Tensile Shear Strength of Polyamide Cured Epoxy Adhesives5... 

This formulation with aluminum filler will provide tensile shear strengths as follows on various substrates Aluminum 3200 psi... 

As with amidoamine and polyamide cured adhesives, epoxy resins cured with aliphatic amines exhibit tensile shear strength that is dependent on the type of filler and concentration. Table 11.10 shows the effect of filler loading on strength of a simple general-purpose, room temperature curing epoxy adhesive composed of liquid DGEBA epoxy mixed with 10 pph of a tertiary amine. 

TABLE 11.10 Effect of Filler Loading on Tensile Shear Strength of DGEBA Adhesive Formulation Cured with 10 pph Tertiary Amine11... 

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