Ideal adhesion

It has a thermally activated bonding adhesive ideal for polymer substrate applications. 

The difference between a sol (hquid dispersion) and a gel is therefore adhesion. Ideal sol particles have zero adhesion, are in constant thermal motion, and are pushing ontwards to escape from their containing flnid. By contrast, gel particles adhere strongly, are fixed by adhesive contacts, and are i essing inwards as a result of molecular attractions to collapse the gel and form more contact spots. 

A rapid cure, repair adhesive, ideal for low temperature maintenance conditions, offering handling strength in 10 minutes, a. 1.2 e. 6/23 i. 80 C... 

What surface feature of glass and metals makes urethane adhesive ideal for these materials ... 

The maximum values of adhesive strengths are attained when the surface free energies of the adherends and adhesives are approximately equal. There is some debate on the choice of the surface free energy for adhesive, i.e. whether it should be for the liquid adhesive or for the hardened adhesive. Ideally, Tgi is not minimum at TgY = Tiv (see condition for minimum 7g], equation (25)) but this equality denotes 7gi values close to minimum. So it is quite reasonable to conclude that the adhesive strength is maximum when 7gi is minimum. Furthermore, the conditions for minimum 7sl the... 

One very important property of PUR is its resistance to water. It will not break down in wet conditions even after much flexing. This feature, therefore, makes PUR adhesives ideal materials for footwear that needs to he water resistant. It has been demonstrated that specially developed PUR adhesives can be used to create a waterproof bond between waterproof lining and waterproof insole materials. PUR adhesive has been used successfully to seal the stitched seam on strobel lasted shoes. 

Ideal adhesion simply means the adhesion expected under one or another model situation of uniform materials having intimate contact over a well-defined area. In these cases, the important quantity is the work of adhesion wab between two phases, which is given by... 

A second ideal model for adhesion is that of a liquid wetting two plates, forming a circular meniscus, as illustrated in Fig. XII-13. Here a Laplace pressure P = 2yz.A (h ws the plates together and, for a given volume of liquid. 

Denture Adhesives. Fast hydration and gel-forming properties are ideally mated to produce a thick, cushioning fluid between the dentures and gums (100). The biologically inert nature of poly(ethylene oxide) helps reduce unpleasant odors and taste in this type of personal-care product (see... 

In some cases it is possible to form bridges of metal using air as the dielectric (150). However, if more than two levels of wiring are required then dielectric spacing is necessary. The ideal dielectric film has excellent adhesion and alow dielectric constant to minimize parasitic capacitances. The most common films include siUcon oxide, siUcon nitride, and a number of spin-on dielectrics (216). 

Patterns of ordered molecular islands surrounded by disordered molecules are common in Langmuir layers, where even in zero surface pressure molecules self-organize at the air—water interface. The difference between the two systems is that in SAMs of trichlorosilanes the island is comprised of polymerized surfactants, and therefore the mobihty of individual molecules is restricted. This lack of mobihty is probably the principal reason why SAMs of alkyltrichlorosilanes are less ordered than, for example, fatty acids on AgO, or thiols on gold. The coupling of polymerization and surface anchoring is a primary source of the reproducibihty problems. Small differences in water content and in surface Si—OH group concentration may result in a significant difference in monolayer quahty. Alkyl silanes remain, however, ideal materials for surface modification and functionalization apphcations, eg, as adhesion promoters (166—168) and boundary lubricants (169—171). 

Access for adhesive application and/or process heat nessure is an important consideratiorL Awkward positions should be avoided and ideally processing should bepi ormed from above. 

Another distinction to be made is illustrated with the peel test shown in Fig. 1. Application of stress may cause the joint to fail either adhesively or cohesively . Adhesive failure, shown in Fig. la, is thought ideally to correspond to a perfect... 

The SFA, originally developed by Tabor and Winterton [56], and later modified by Israelachvili and coworkers [57,58], is ideally suited for measuring molecular level adhesion and deformations. The SFA, shown schematically in Fig. 8i,ii, has been used extensively to measure forces between a variety of surfaces. The SFA combines a Hookian mechanism for measuring force with an interferometer to measure the distance between surfaces. The experimental surfaces are in the form of thin transparent films, and are mounted on cylindrical glass lenses in the SFA using an appropriate adhesive. SFA has been traditionally employed to measure forces between modified mica surfaces. (For a summary of these measurements, see refs. [59,60].) In recent years, several researchers have developed techniques to measure forces between glassy and semicrystalline polymer films, [61-63] silica [64], and silver surfaees [65,66]. The details on the SFA experimental procedure, and the summary of the SFA measurements may be obtained elsewhere (see refs. [57,58], for example.). 

Thus far, the discussion of particle adhesion has been mainly limited to ideal spherical particles. This idealization has been employed to simplify the analysis and allow one to better understand the underlying science governing this topic. However, it is clear that most particles normally encountered are highly irregular. 

The above measurements all rely on force and displacement data to evaluate adhesion and mechanical properties. As mentioned in the introduction, a very useful piece of information to have about a nanoscale contact would be its area (or radius). Since the scale of the contacts is below the optical limit, the techniques available are somewhat limited. Electrical resistance has been used in early contact studies on clean metal surfaces [62], but is limited to conducting interfaces. Recently, Enachescu et al. [63] used conductance measurements to examine adhesion in an ideally hard contact (diamond vs. tungsten carbide). In the limit of contact size below the electronic mean free path, but above that of quantized conductance, the contact area scales linearly with contact conductance. They used these measurements to demonstrate that friction was proportional to contact area, and the area vs. load data were best-fit to a DMT model. 

Because most plastic bottles are recycled, it is necessary to separate the label and adhesive from the bottle. The label is contaminated with ink and not recyclable. The adhesive is also not recycled. Ideally the adhesive will stick tenaciously to the film, but release cleanly from the bottle during the recycling operation. Adhesives designed to aid in recycling have been developed for this market. They incorporate conventional surfactants in place of some or all of the oil in PSA compositions [69] or use ingredients such as rosin which when neutralized by base can function as surfactants. A goal of the recycling industry is to eliminate the need to use base in the process. 

Fig. 33. Ni-Cr-Zn pla.sma spray coating on D6AC steel showing complex morphology ideal for adhesive bonding [155].

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