Tension adhesion tests

Figure 18-4. Direct tension adhesion test A is the rubber-fabric test piece B and B are metal...

Cured coating Solid surface tension Adhesion Test... 

Anodized layer Internal tension Adhesion (Ring-Scher-Test) (always aluminum breaking) Pore-free coating from ca. Coefficient of friction (with lubricant)... 

Figure 2 Tensile adhesion test geometries (a) pi tensile test, ASTM D-897 (b) bar and rod tensile test, ASTM D-2094 (c) sandwich tensile test, ASTM D-257 (d) cross-lap tension test, ASTM D-1344.

Creep Properties of Adhesives in Shear by Tension Loading, Test for (D 2294)... 

Fatigue tests on hybrid joints bonded with the FT-EP adhesive were also carried out, by using a tension-tension fatigue test (Croccolo et al., 2010 Sekercioglu et al., 2005) on a resonant testing machine. 

In the early 1990s, Chaudhury and Whitesides proposed using a standard adhesion test developed in 1971 by Johnson, Kendall, and Roberts (known as the JKR test) to determine interfacial tensions between a solid and a liquid or a solid and a vapor. The procedure consists of bringing a hemispherically shaped solid, of radius typically 1 mm, in contact with a planar surface made of the same material (Figure 2.25). 

In the simple vesicle-vesicle adhesion experiment, two vesicles are aligned and maneuvered into close proximity the pipets are maintained in these fixed positions so that no axial force is exerted during the adhesion test [20,22,24,29]. The extent of adhesion is then controlled via the tension in the left-hand adherent vesicle membrane, which in turn is controlled by pipet suction pressure. 

Lap-shear tests. The lap-shear or tensUe-shear test measures the strength of the adhesive in shear. It is the most common adhesive test because the specimens are inexpensive, easy to fabricate, and simple to test. This method is described in ASTM D 1002, and the standard test specimen is shown in Fig. 7.20a. The specimen is loaded in tension, causing the adhesive to be stressed in shear until failure occurs. Since the test calls for a sample population of five, specimens can be made and cut from large test panels, illustrated in Fig. 1.20b. 

In metal bonding the issue of wetting is easily settled. Clean metal surfaces have extremely high critical wetting tensions, in the order of several hundred dynes/cm. As a consequence, adhesives with a typical surface tension of 35 dynes/cm have little trouble wetting metal surfaces. If wetting problems occur, it is almost always the result of contamination on the substrate surface, a condition that can be quickly checked with the water break test. If water with a surface tension of 73 dynes/cm wets the surface, it is a safe assumption that no problem will be encountered with lower surface tension adhesives. 

In a recent case study (see Svendsen et al, 2007 and also Problem 6.1), in collaboration with a paint company, the adhesion of six different epoxies-silicon systems has been studied. These paints are used in marine coating systems. Some epoxies showed adhesion problems in practice while others did not. The purpose of the study was to understand the origin of these problems and whether adhesion could be described/ correlated to surface characteristics, e.g. surface tensions. An extensive experimental study has been carried out including both surface analysis (contact angle measurements on the six epoxies, surface tension of silicon at various temperatures, atomic force microscopy (AFM) studies of the epoxies), as well as measurements of bulk properties (pull-off adhesion tests and modulus of elasticity). Theoretical analysis included both estimation of Zisman s critical surface tensions and surface characterization using the van Oss-Good theory. 

Adhesion test, stud-pull An adhesion test whereby a protrusion (stud) is bonded to the surface of the film and pulled in tension. 

Rheometric Scientific markets several devices designed for characterizing viscoelastic fluids. These instmments measure the response of a Hquid to sinusoidal oscillatory motion to determine dynamic viscosity as well as storage and loss moduH. The Rheometric Scientific line includes a fluids spectrometer (RFS-II), a dynamic spectrometer (RDS-7700 series II), and a mechanical spectrometer (RMS-800). The fluids spectrometer is designed for fairly low viscosity materials. The dynamic spectrometer can be used to test soHds, melts, and Hquids at frequencies from 10 to 500 rad/s and as a function of strain ampHtude and temperature. It is a stripped down version of the extremely versatile mechanical spectrometer, which is both a dynamic viscometer and a dynamic mechanical testing device. The RMS-800 can carry out measurements under rotational shear, oscillatory shear, torsional motion, and tension compression, as well as normal stress measurements. Step strain, creep, and creep recovery modes are also available. It is used on a wide range of materials, including adhesives, pastes, mbber, and plastics. 

The contact an e or adhesion tension of a binder solution with respecd to a powder can be determined from the slope of the penetration profile. Washburn tests can also be used to investigate the influence of powder preparation on penetration rates. The Bartell cell is related to the Washburn test except that adhesion tension is determined by available gas pressure which opposes penetration. [Bartell Osterhof, Ind. Eng. Chem., 19, 1277 (1927).]... 

Fig. 16. The results of Dyckerhoff and Sell for inlerfacial strengths measured hy butt-tensile tests for various lacquers (adhesives) against various plastics as a function of the surface energy, ys of the plastics. Arrows indicate the surface tensions of the adhesive, y, used in the generation of each curve, showing rough agreement with the requirement that a maximum in adhesion is achieved when yt ys (I kp/cm- 0.1 MPa). Redrawn from ref. [71. ...

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

To check the efficacy of grease removal, the alkali solution is rinsed away or neutralised by dipping in dilute acid. If, after removal from the acid, the draining metal surface remains wetted evenly all over for 30-60 s (or until it dries by evaporation), hydrophobic soils have been removed. Traces of grease cause the surface to de-wet, and surface tension draws the water into separate droplets. This is the water-break test. Traces of grease which remain when the work is plated do not prevent electrodeposition, but are detrimental to adhesion and corrosion resistance. 

The catalyst bed was a coated wall reactor using commercial CuZnAl catalyst. An alumina sol was used to enhance the adhesion of the catalyst to the channel walls. After the shims were washed thoroughly, the alumina adhesion layer was deposited using an alumina sol (NYACOL AL20DW colloidal alumina, PQ Corporation) and then dried at 60 °C. To decrease the surface tension of the wash-coat solvent, small amounts of 2-propanol were added to a catalyst slurry of ICI Synetix 33—5 catalyst, with 20 wt % alumina sol and water. The catalyst was calcined at 350—400 °C for 2 h after air-drying. Before testing, the catalyst was reduced by flowing H2/N2 over it at 280 °C. 

---