Adhesion measurements

Fig. 18. Yield strengths in three-point bend tests of highly filled composites of polyfvinyl butyral) and silica particles treated with methylsilane and octylsilane coupling agents to varying degrees of surface coverage vs. work of adhesion measured independently using IGC. Redrawn from ref. [90].

The finite size effects in the contact between a spherical lens of polyurethane and a soft flat sheet of crosslinked polyfdimethyl siloxane) (PDMS) has been addressed by Falsafi et al. [37]. They showed that for deformations corresponding to contact diameters larger than the sheet thickness, the compliance of the system was affected by the glass substrate supporting the soft sheet. In order to minimize the finite size effects in the adhesion measurement of small elastomeric lenses, Falsafi et al. [38] and Deruelle et al. [39] used relatively thick elastic sheets to support their samples. 

Fig. 7. Schematic of the apparatus used for JKR type adhesion measurements. For a constant applied displacement S, the contact radius a and the load P are measured.

JKR-type mea.surements on soft elastomers. In their original paper, Johnson and coworkers [6] reported on adhesion measurements between soft materials. 

Numerous AFM imaging techniques have been developed and commercialized to monitor topography, friction, mechanical response, capacitance, magnetic properties, etc. However, adhesion measurements require the tip to come into, and out of, contact to measure attractive and adhesion forces. Therefore, other than to select an analysis region, most imaging techniques are not useful for adhesion studies. Instead, measurements are necessarily based on force-displacement curve approaches. 

Adhesion of copper films to PMDA/ODA polyimide was determined by peel tests conducted on samples that were prepared by vapor-depositing a thin layer of copper onto the polyimide and then building the thickness of the metal layer to about 18 p,m by electrodeposition of copper. Results of the adhesion measurements correlated well with substrate pretreatment. When the substrate... 

It has been observed by Koleske et al. [76] that factors other than specific chemical interaction can influence adhesion measurements. They studied a film of mixed-chain-length fatty acid and found that the adhesion of the tip over the shorter chain was 20% larger than over the longer chain, despite the fact that both had the same CH3 terminating... 

Forster AM, Zhang WH, Crosby AJ, Stafford CM (2005) A multilens measurement platform for high-throughput adhesion measurements. Meas Sci Technol 16 81-89... 

Nolle AJ, Chung JY, Walker ML, Stafford CM (2009) In-situ adhesion measurements utilizing layer-by-layer functionalized surfaces. ACS Appl Mater Interfaces 1 373-380... 

The work of adhesion measures the degree of attraction between the two phases. For the specific case where A is a solid (S) and B is a liquid (L), ya becomes the solid surface energy, ys, Yb become the liquid surface tension, yl, and Young s equation, Eq. (2.72),... 

K. C. Mittal, ed., Adhesion Measurements of Thin Films, Thick Films and Bulk Coatings, ASTM STP, Philadelphia, Pa., 1978, p. 640. 

Good, R. J. In Adhesion measurement of thin films, thick films and bulk coatings. K. L. Mittal, (ed.) ASTMSTP 640, ASTM, Philadelphia, PA., 1978, p. 41... 

Figure 12. Si-29 NMR spectrum of a very highly oligomerized 50 vol % APS in heavy water solution which was subsequently diluted to 0.1 vol %. Adhesion measurements confirmed that little loss of adhesion with oligomerization seemed to have occurred. The symbols NO, Nl, Ol and 02 designate Si-29 NMR absorption bands which are believed to correspond to various degrees of APS oligomerization.

Both fiber-matrix interphase-sensitive mechanical tests (interlaminar shear strength, 90° flexure) and interphase-insensitive tests (0° flexure) were conducted on high volume composite samples fabricated from the same materials and in the same manner as discussed above to see if the interphase and its properties altered the composite mechanical properties and in what manner. A summary of the data is plotted as a bar graph in Fig. 7. The first set of bars represents the difference in fiber-matrix adhesion measured between the bare fibers and the sized fibers by the ITS. The composite properties plotted on the figure also show increased values for the epoxy-sized material over the bare fiber composite. 

Remarks on Adhesion Tension—It is clear that adhesion tension (or the work of adhesion) measures the degree of wetting of a solid by a liquid. A high interfacial tension in a solid-liquid system indicates a low adhesion tension and conversely a low interfacial tension is associated with a high adhesion tension. 

Another test for determining the viscosity of liquid adhesives measures the time it takes the test liquid to flow by gravity completely out of a cup with a certain size hole in the bottom. These consistency cups are designed to expel 50 mL of sample in 30 to 100 s under controlled temperature and relative humidity conditions. The number of seconds for complete flow-out of the sample is determined. There are different cup volumes and hole sizes... 

TABLE 11 The Acid-base Character of Carbon Fiber Surfaces and The Degree of Adhesion Measured by IFSS System on Monofilaments and ILSS on Composites... 

Adhesion Measurement. The solution of polyamic acid was spin-coated onto a chromium-coated Si wafer and cured at 400 °C for 40 min. Thickness of the polyimide layer is approximately 6 um. A thin layer (200 A) of gold was... 

Samples for adhesion measurements were prepared in a separate chamber with a base pressure of 1 x 10 ° Torr under identical conditions. Typically, -1000 A silver coverages were used for adhesion measurements. Adhesion strength of the deposited Ag films was determined using a polyester adhesive tape and standard peel test procedures on an Instron tester. 

The metallic layers were examined either by conventional or cross-section TEM in a Jeol 200 Cx microscope. For the cross section preparation a sandwich of two laminates is made, glued face to face with an epoxy, cut in small pieces, mechanically polished, and then ion milled to a final TEM observation thickness. The plane section TEM sample are prepared by dissolving the PET in trifluoroacetic acid for 5 to 10 mn. The area observed, on plane section TEM, for the grain size calculation is close to 0.2 urn. For the adhesion measurements, test pieces consist of aluminum support (1 mm thick) double sided tape (Permacel P-94) PET (12pm) / evaporated aluminum/ ethylene acrylic acid (EAA) copolymer film. These laminates are prepared for the peel test by compression under 1.3 105 N.m2 at 120°C for 10 seconds. The peel test is performed by peeling the EAA copolymer sheet from the laminate in an INSTRON tensile tester at 180° peel angle and 5 cm min peel rate. 

Figure 4 a) Variation of the thickness of the aluminum thin film with the adhesion measure by peel testing, b) Variation of the average grain size of the aluminum thin film with the adhesion measure t>y peel testing. 

However, this method has several advantages compared to other quantitative and semiquantitative adhesion measurement techniques. 

An attempt is made to evaluate the accuracy of data obtained by these techniques, to determine the main causes of scattering and the optimal conditions for contact angle and work of adhesion measurements. 

Closely related to cleavage experiments are adhesion measurements. Adhesion measurements have been done with mica in the so-called surface force apparatus (SFA) [62-64], In the surface force apparatus two crossed mica cylinders of... 

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