Tensile adhesion

Crosslinking has been claimed to improve thermal resistance of the cyanoacrylate adhesive [18]. However, in other reports [6], little or no improvement in thermal resistance of the adhesive was demonstrated by the addition of a difunctional monomer. As seen in Fig. 2, the addition of varying amounts of crosslinker 7 provided no improvement in the tensile adhesive strength of ethyl cyanoacrylate on steel lapshears after thermal exposure at 121 °C for up to 48 h. 

A variety of techniques has been developed to measure the condition of a coating so that some evaluation of its protective ability can be made. Many of these are based on electrochemical measurements [2]. The four techniques used in this study are (1) corrosion potential, (2) AC conductance, (3) tensile adhesion, and (4) weight gain. 

The adhesion was measured by fastening a lead anchor of known area (2,84 cm ) to the coating with a cyanoacrylate adhesive (Loctite 414) and after curing, pulling it off normal to the surface with a Dillon tensile tester. The force to remove the coating was divided by the area of attachment to convert it to a normalized tensile adhesion value. 

The tensile adhesion values show no correlation with the extent of corrosion the bisphenol A epoxy cured with a polyamide amine showed blistering, which represents a complete loss of adhesion. The polyester showed cohesive failure at less than 1000 hours of exposure, so a true adhesion value could not be determined. The other epoxies and the vinyl ester all had values in the 150-200 psi range, with no apparent relationship to the amount of corrosion. 

It should be noted that the electrochemical measurements (corrosion potential and conductivity) for the two novolac epoxies cured with an aromatic amine from different sources showed good agreement, although the tensile adhesion and weight gain values were not as reproducible. 

Only one of the four techniques—the conductivity—showed any correlation with the observed extent of corrosion. The lack of correlation of the tensile adhesion values with corrosion is a result of the fact that the method integrates adhesion loss at the substrate... 

Of the four techniques studied for evaluating coatings on steel for corrosion control (corrosion potential, conductance, adhesion and weight gain), the most useful was conductance. Corrosion potential did not show a consistent relationship, and weight gain and tensile adhesion showed no correlation with corrosion. 

Loss of Adhesion When Wet. Many coatings, particularly those applied to a roughened surface, show excellent tensile adhesion to steel but lose this adhesion after exposure to pure water at room or elevated temperatures. A thin film of water at the interface is apparently responsible for the loss of adhesion. If the coating is allowed to dry without destructively testing the adhesion, the dried coating often exhibits the original tensile adhesion. The phenomenon is... 

A sealant s adhesion is commonly studied by 180 degree peel tests such as ASTM C794 or by tensile/adhesion joints tests such as ASTM C719. The adhesion test protocol should simulate actual field conditions as closely as possible. Sealants often have good adhesion to dry substrates, but this adhesion may be quickly destroyed by water. Because most sealants are exposed to water over their lifetime, adhesion testing should include exposure to water for some length of time. ASTM C719 is one of the better tests to determine a sealant s adhesion durability as it exposes sealants to seven days of water immersion. 

Butt tensile—adhesives. Bolt shaped specimens were bonded and cured as for the surface coating specimens and tested in the same way. 

Anderson, G. P., et al., Effect of Removing Eccentricity from Button Tensile Adhesive Tests, Adhesively Bonded Joints Testing, Analysis, and Design, ASTM STP 981, W. S. Johnson, ed., American Society of Testing and Materials, Conshohocken, PA, 1988. 

Test Method for Adhesion in Peel of Elastomeric Joint Sealants Recommended Practice for Surface Preparation of Concrete for Application of Chemical Resistance Resin Monolithic Surfaces Method of Testing Release Papers Used with Preformed Tape Sealants Test Method for T-Peel Strength of Hot Applied Sealants Test Method for Tensile Adhesive Strength of Preformed Tape Sealants by Disk Method... 

Standard Test Method for Determining Compatibility of Liquid Applied Sealants with Accessories Used in Structural Glazing Systems Determining Tensile Adhesion Properties of Structural Sealants Specification for Structural Silicone Sealants... 

ASTM D 1623 is used for tensUe and tensile adhesion voperties of rigid cellular plastics. The vocedure is essentially similar to that of ASTM D 3574 described above. Three types of specimens are used -Type A, where adequate material is avaUable, type B, where only smaller specimens are avaUable, as in sandwich panels, and Type C, which covers tensile adhesion properties of a cellular plastic to a substrate, as in a sandwich panel, or the bonding strength of a ceUular plastic to a single substrate. 

ASTM D 1623-78 Standard Test Method for Tensile and Tensile Adhesion Properties of Rigid Cellular Plastics, 9 pp (DOD Adopted) (FSC 9330) (YD) (Comm D-20)... 

The adhesion tests were conducted with flat, well-mated substrate specimens to minimize the effect of mechanical interlocking of the adhesive to the substrate. However, with bone containing surface pits, greater tensile adhesion values were obtained. Bone etched with 37% phosphoric acid prior to applying the adhesive did not improve joint strength. 

This bond strength is considerably higher than any value for the adhesion to smooth dentin surfaces which has been previously reported. The bond strength is slightly decreased when more dilute citric acid solutions are used. Other pretreatments yielding tensile adhesion values above 10 MPa include solutions of 1% alcoholic (1 2) citraconic anhydride, 1% alcoholic tetrahydrofuran -2,3,4,5-tetracarboxylic acid, and 1% aqueous ethylenediamine-tetraacetic acid tetrasodium salt. 

Increasing the length of storage of the joined (citric acid pretreated) specimens in the thermocycled water bath considerably decreases the tensile adhesion. Seven-day bond strength values of... 

Jellenlk ( ) has considered the case of tensile adhesion, for which the tensile stress due to a llquid-llke layer between the two adhering phases separated by distance Is just AP =... 

Table 5.4 Tensile adhesion strength (ASTM C633-13) of LPPS (VPS) hydroxyapatite coatings Cl (deposited from as-received powder) and C2 (deposited from powder sintered for 1 h at 1300°C) as a function of immersion time in HBSS (n = 5) (Heimann and Vu, 1997).

The three types of coating were deposited onto Ti6Al4V substrates. The coating thickness varied between 160 and 270 pm. The parameter space used in the statistical design matrix is shown in Table 6.2. Table 6.3 shows the coded relevant parameters (in bold) for optimum values of surface roughness (Kj, porosity (P) and tensile adhesion strength (a). 

The coating properties varied as follows porosity 3-9%, surface roughness 9-22 pm and tensile adhesion strength 30-58 MPa (Table 6.4). 

Figure 6.2 shows cross-sectional SEM images of coating type I with maximum surface roughness (a), type II with maximum porosity (b) and type III with maximum tensile adhesion strength (c). The (crystalline) phase contents of the as-sprayed coatings are shown in Table 6.5. Coating type I has a maximum hydroxyapatite content of 66 3 mass%, followed by type III with 61 3 mass%. The... 

The coating tensile adhesion strength determined by ASTM C633-13 designation (see Chapter 7.5.1.1) can be expressed by the polynomial equation... 

Figure 7.40 Development of all-through cracks in a plasma-sprayed hydroxyapatite coating of about 200 pm thickness, 10 0.5 pm average surface roughness (fta), 5 1% porosity and 50 9 MPa tensile adhesion strength (Heimann et at., 2001).

DIN EN 582-01 (1994) Thermal spraying determination of tensile adhesive strength 2014 Beuth-Verlag GmbH, Berlin, Germany. 

The sample is preferably prepared using a lathe and the conically shaped ends fit into specially shaped holders that make the fracture within the gauge marks more probable. The standard speed of test machine jaw separation should be between 3 to 6 minutes to rupture with a suggested rate of cross-head movement set at 1.3 mm minute for each 25.4 mm of test section gauge length. This test method also can be used to determine the tensile adhesion properties. 

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