Tenacious adhesion

Eractice, as the barbed head is next to impossible to pull om wood. The head is attached to the arrow by drilling a hole in the shaft and using a little wax to secure it. The use of wax instead of some other more tenacious adhesive is so that when it is pulled from the wound, the head will remain inside. Play with the design a little. There is much room for variation. 

It is often demanded that the surface of polymeric biomaterials should exhibit permanent tenacious adhesion to soft connective and dermal tissues. However, conventional non-porous, polymeric materials will be encapsulated by a fibrous membrane generated de novo by surrounding fibroblasts, when subcutaneously implanted into the living body in contact with soft connective tissues. This is a typical foreign body reaction of the living system to isolate foreign materials from the host inside the body. On the other hand, it should be noted that the small gap present between a percutaneously-implanted device and the surrounding tissue provides a possible route for bacterial infection because of the lack of microscopic adhesion at the interface. 

When a very thin film (e.g., thicknesses of less than 1 pm) of a polymer is applied to a smooth surface of platinum, most polymers peel off within minutes upon immersion in liquid Lf20. This is also true for most plasma polymers applied to platinum surfaces. However, when an ultrathin film of CH4 LCVD was deposited under the conditions that provide plasma energy density sufficiently high to sputter aluminum from the electrodes, tenacious adhesion that survived over 10 h of boiling in saline solution was obtained, probably due to the incorporation of electrode metal at the interface. 

The same plasma polymer deposited in a closed-system reactor has a graded elemental composition with a carbon-rich top surface, and the oligomer content is much lower [10], both of which increase the level of adhesion. The adhesion of the same water-borne primer is excellent and survives 8 h immersion in boiling water. When this surface is treated with O2 plasma, the adhesion does not survive 1 h of boiling, while the dry tape test still remains at the level of 5. The water-sensitivity of adhesion depends on the chemical nature of the top surface as depicted by XPS data shown in Figure 28.12. Water-insensitive tenacious adhesion, coupled with good transport barrier characteristics, provides excellent corrosion protection, as supported by experimental data [1-4], and constitutes the basic principle for the barrier-adhesion approach. 

Fig 1 33 Tenacious adhesion of superior vena cava along the proximal coil of an implantable cardioverter-defibrillator lead with a free-floating filar coil design. Note coil despiralization in the proximal end as a consequence of lead extraction... 

Fig. 5.99 A glass fiber reinforced LCP composite is shown to have interesting morphology. A polished thin section is shown in polarized light (A) (color section) to exhibit a fine domain texture with some orientation of the polymer on the glass surfaces. SEM fracture views (B-D) show the tenacious adhesion of the LCP to the fibers. Fibrillar structures are oriented parallel to the fiber surface and submicrometer sized domains are observed (D).

High solids epoxy primer 73 75-150 3 h 16 h Tenacious adhesion to steel and concrete as primer for epoxies, urethanes and vinyls, good chemical resistance suitable for food contact... 

The utihty of these adhesives arises from the electron-withdrawing character of the groups adjacent to the polymerizable double bond, which accounts for both the extremely high reactivity or cure rate and thek polar nature, which enables the polymers to adhere tenaciously to many diverse substrates. 

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. 

Presence of Water on Surfaces to be Bonded. Substances in the Earth s atmosphere adsorb water from it, the water in many instances being bound tenaciously to the surface. This provides the basis for curing of the cyanoacrylate adhesives, which takes place on contact with surfaces covered with such a water layer. 

The actual metal surface that takes part in the bonding is illustrated in Fig. 16.1. Adhesives recommended for metal bonding are in reality used for metal-oxide bonding. They must be compatible with the firmly bound layer of water attached to surface metal-oxide crystals. Even materials such as stainless steel and nickel or chromium are coated with transparent metal oxides that tenaciously bind at least one layer of water. 

The operation of EF is very simple. This is another important feature for EF. By varying current, it becomes possible to create any gas bubble concentration in the flotation medium to fit the variation of the water flow rate and the suspended substances concentration from time to time. If necessary, a gas medium with very great surface area can be formed easily during EF, thereby increasing the probabilities of bubble-particle collision and adhesion and the formation of tenacious particle-bubble complexes (Mallikarjunan and Venkatachalam 1984). 

The main aim of SAIE is the complete elimination of heavy metals from the coating systems an approach that primarily relies on tenacious water-insensitive adhesion and good barrier characteristics of a primer has been taken. It should be pointed out that this approach is theoretically incompatible with the approach that utilizes the primers with corrosion inhibitors, e.g., chromated primers. This is because a primer with super barrier characteristics would not allow the migration of inhibitors and would not provide enough water for their electrochemical reaction to form corrosion protection products, as described in Chapter 28. In order to further elucidate the SAIE concept, both chromated and nonchromated spray primers were employed to generate two types of plasma coating-modified systems, and their corrosion protection behaviors were investigated in this study. 

It can be clearly seen that the tenacious and water-insensitive adhesion achieved by plasma T/F are differentiated in the results of the 12-week Prohesion... 

Table 31.1, tenacious and water-insensitive primer adhesion was always achieved with closed system TMS plasma polymers treated with subsequent Ar plasma applications [Tcs/(Ar)]. 

The corrosion protection of plasma interface-engineered coating systems relies on the tenacious water-insensitive adhesion and good barrier characteristics of the coatings [3]. DC cathodic polymerization and plasma treatment have been demonstrated as efficient in improving the primer adhesion to metallic substrates. 

It should be emphasized that the primers in the plasma coating systems applied to the IVD Al-coated A1 alloys could not be removed by the commercial Turco paint stripper solution. This tenacious and water-insensitive adhesion at the primer/IVD interface achieved by TMS cathodic polymerization in a closed reactor system must be responsible for the excellent corrosion protection performance of these plasma coating systems. In other words, excellent corrosion protection of IVD Al-coated A1 alloys can be accomplished with chromate-free primer coatings with the aid of tenacious and water-insensitive interface adhesion. 

Tumor cells that have the ability to attach to some defined substrates with the same apparent efficiency, as measured by the adhesion assays described above, may nonetheless adhere to the different substrates not with the same strength. Therefore, even though each substrate appears to be able to support cell adhesion, the tenaciousness characterizing each interaction may be different, and it may have an influence on the metastatic ability of tumor cells (Leung-Tack et al., 1988). 

Like other liquid detergents, household surface cleaners have been produced in recent years with added benefits beyond their simple cleaning action. These added benefits include disinfection, surface shine, prevention of tenacious soil adhesion, and reduced fogging. 

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