Adhesion apparent

The cause of this electrical adhesion has not been explained completely but appears to be related to the electrical conductivity of the powder. Only for particles with resistivities between 10 and 10, ohm-metre is the adhesion apparent. Below this, the particles discharge on contact with the electrode, acquiring a charge of opposite sign and jumping off the electrode, the so-called pith-ball effect. For larger resistivities, locahzed electric breakdown occurs and no adhesion develops. 

Dynamic mechanical spectra of polyurethane adhesives (apparent rigidity). 

Adhesion, apparent The adhesion observed by applying an external force. If the internal stress is high, the apparent adhesion may be low even if there is strong bonding at the interface, because the internal stress adds to the applied external stress to cause failure. Also called Practical adhesion. 

A variety of trichloroethylene copolymers have been reported, none with apparent commercial significance. The alternating copolymer with vinyl acetate has been patented as an adhesive (11) and as a flame retardant (12,13). Copolymerization with 1,3-butadiene and its homologues has been reported (14—16). Other comonomers include acrylonitrile (17), isobutyl vinyl ether (18), maleic anhydride (19), and styrene (20). 

An apparently universal truth is that intimate contact between adhesive and adherend is a necessary (but not sufficient) requirement for good adhesion. 

Upon comparison of Eqs. 29 and 36, it is readily apparent that both theories predict the same power law dependence of the contact radius on particle radius and elastic moduli. However, the actual value of the contact radius predicted by the JKR theory is that predicted by the DMT model. This implies that, for a given contact radius, the work of adhesion would have to be six times as great in the DMT theory than in the JKR model. It should be apparent that it is both necessary and important to establish which theory correctly describes a system. 

Visually, the failed specimens appeared as shown in Fig. 34. Failure was mostly cohesive within the adhesive. However, there was a small region of apparent interfacial failure at one end of each substrate that was referred to as the metal... 

Visually, failure was mostly eohesive within the adhesive (see Figs. 34 and 46). However, there was a small area of apparent interfacial failure ( initiation zone ) located at one end of each substrate. Line scans were eondueted aeross the initiation zone, from the edge of the substrate to the area of cohesive failure within the adhesive. From the line scans, it was apparent that there were patehes of polymer present in the initiation zone, even when failure appeared to be interfaeial (see Fig. 46). SIMS images of the initiation zone were constructed for various mass numbers (see Figs. 47-49). The images showed well-defined cation-rieh... 

As should be apparent from the variety of applications, there are many test methods for hot melts, most of which are application specific. Many such tests were developed by adhesive suppliers and are proprietary to them. The use of standardized testing is most common for PSA tapes and labels. These tests are discussed elsewhere in this volume. 

Shot or grit blasting Blasting is used to remove rust and to increase the surface area and hence increase apparent adhesion. A variety of abrasives is available, including chilled iron grit and aluminium oxide. The selected abrasive is fired under pressure at the metalwork to create the desired result. 

Linear novolac resins prepared by reacting para-alkylphenols with paraformaldehyde are of interest for adhesive tackifiers. As expected for step-growth polymerization, the molecular weights and viscosities of such oligomers prepared in one exemplary study increased as the ratio of formaldehyde to para-nonylphenol was increased from 0.32 to 1.00.21 As is usually the case, however, these reactions were not carried out to full conversion, and the measured Mn of an oligomer prepared with an equimolar phenol-to-formaldehyde ratio was 1400 g/mol. Plots of apparent shear viscosity versus shear rate of these p-nonylphenol novolac resins showed non-Newtonian rheological behavior. 

On the dusted track the diminished adhesion friction component is clearly apparent for all three rabbers when comparing them with the master curves on the clean track The friction plateau observed for the rubbers filled with 50 pphr black which is typical for tire tread compounds is observed for most rubbers, as shown in Figure 26.5. 

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