Adhesion group

The disbonding rate decreases with time [35], which can be attributed to the consumption of OH" ions by reaction with adhesive groups. This consumption is obviously partly compensated for by the formation of OH" ions through oxygen reduction these permeate inward from the outer surface of the coating. If this permeation is hindered by an aluminum foil gas seal, the disbonding rate falls off... 

The copy itself can now bond to the surface via the adhesive group and function as a matrix (provided that enough fragments are present). 

Technical Bulletin, Kevlar Applications, Sealants and Adhesive Group, DuPont Company, Wilmington, DE, 2001. 

Q.M. (2010) Ultra-low fouling and functionalizable zwitterionic coatings grafted onto SiO2 via a biomimetic adhesive group for sensing and detection in complex media. Biosensors cf Bioelectronics, 25 (10), 2276-2282. 

Here, is a dimensionless number termed the adhesion group. Clearly the larger the value of the adhesion group the more dominant is the London attractive force for a fixed gap width and particle location. On the other hand, for smaller values of hydrodynamic interactions dominate. 

In the limit of large values of the adhesion group, and h> a, the effect of London attraction on the classical interception efficiency (Eq. 8.3.25) can be calculated relatively easily. The particle capture in this case is pictured schematically in Fig. 8.4.2, where it can be seen that the limiting... 

The limiting trajectory dp = tt) is seen to lie in the range of large h/Up for large values of the adhesion group N j-... 

This result was first derived by G.L. Natanson (see Spielman 1977). We emphasize again that it is valid only for aplarge values of the adhesion group, but not so large that particles are attracted from the area of uniform velocity. It is seen to predict a weaker dependence on particle size than the classical solution A (ap/a) in which London attraction and hydro-dynamic interactions are not considered. Note that the spherical collection efficiency has a similar behavior, given by (Spielman Goren 1970)... 

In Fig. 8.4.3, taken from Spielman FitzPatrick (1973), is shown the approximate analytic expression of Eq. (8.4.25) for the cylindrical collector compared with an exact numerical solution in which London attraction and the complete range of hydrodynamic interactions are included. The agreement of the exact solution with the approximate one is seen to be surprisingly good at relatively low values of the adhesion group, indicating that h does not have to be very large compared with before the hydrodynamic interactions become weak. 

Figure 8.4.3 Collection efficiency versus adhesion group for cylindrical collector. [After Spielman, L.A. c FitzPatrick, J.A. 1973. Theory for particle collection under London and gravity forces. J. Colloid Interface Set. 42, 607-623. With permission.]...

With surface forces present the velocity U appearing in the adhesion group, which in the porous media case represents the superficial velocity, must also be multiplied by A p,. The adhesion group would thus be modified to... 

Hot melt adhesives are the fastest growing adhesive group for packaging applications. They are 100% solids and do not require any type of soivent. 

FUms on these materials can be formed if adhesion promoters are used. With adhesion promoters it is possible to deposit films of conducting polymers on insulators, semiconductors with highly polished surfaces, and corrosive metals. An adhesion promoter consists of an adhesion group, e.g., chloro- or hydroxy silane groups, phosphonic acid groups, which can bond to the surface of the soUd, spacer group, and a monomer molecule as a head group. 

Melt adhesives and plastisols do not contain solvents. The solution adhesives group includes products made from the following polymer-solvent systems nitrocellulose (typical solvents include solvent combinations usually of a ketone or an ester, an alcohol and a hydrocarbon selected from isopropanol, 2-butylhexanol, amyl acetate, acetone, methyl ethyl ketone), nitrile rubber (main solvent - methyl ethyl ketone), polychloroprene (which is usually dissolved in a mixture of solvents including a ketone or an ester, an aromatic and aliphatic hydrocarbon selected from naphtha, hexane, acetone, methyl ethyl ketone, benzene, toluene), and polyvinyl acetate (water). 

Plastics and Rubber Institute, Adhesives Group, Symposium on Adhesives and Sealants in Building and Construction, London, 22 February 1988. 

Another way to distinguish between adhesive groups is the manner by which they flow or solidify. As shown in Table 4.6, some adhesives solidify simply by evaporation of solvent, while others harden as a result of heat activation or chemical reaction. Pressure-sensitive systems flow under pressure and are stable when pressure is removed. 

This adhesive group has been promoted for use as a sealant. The adhesives used are acrylate acid diesters (polyester-acrylic). They are essentially monomeric thin liquids that polymerize to form a tough plastic bond when confined between closely fitting metal joints. Contact with air before use keeps the monomeric adhesive liquid. Metal surfaces accelerate the polymerization in the absence of air (anaerobic conditions). These materials will bond all common metals, glass, ceramics, and thermosetting plastics to each other. Phenolic plastics and some plated metals, such as cadmium and zinc, require a primer such as ferric chloride. Polymerization is essentially a free-radical-type addition polymerization. " ... 

Li, G. Chenga, G. Xue, H. Chena, S. Zhang, F Jiang, S. Ultra low fouling zwitterionic polymers with a biomimetic adhesive group. Biomaterials 2008, 29, 4592-4597. 

Frihart, C. R. (2009). Adhesive groups and how they relate to the durability of bonded wood. Journal of Adhesion Science and Technology, 23, 601-617. 

Li, G., Xue, H., Gao, C., Zhang, R, Jiang, S. (2010). Nonfouling polyampholytes from an ion-pair comonomer with biomimetic adhesive groups. Macromolecules, 43, 14-16. 

In using these approaches, it is important that the base material be resistant to physisorption, or the selectivity of the adhesive groups may be significantly reduced in vivo. A successful approach to prevent adhesion to the base material is via covalent attachment of anti-adhesive factors on the remaining functional groups. 

D.J. Doyle in the Proceedings of the Structural Adhesives in Engineering III, PRI Adhesives Group, Bristol, UK, 1992. 

For both adhesive groups, the nature of the formulation reflects the concern that the products should be adapted as much as possible to the various applications for which they will be used. Across the different adhesive compositions, therefore, one can identify concerns relating to the setting process, to the mechanical behavior of the assemblies and to their durability. These concerns lead manufacturers to combine, with the raw polymer materials (or polymer precursors), various additives (products that mix at the molecular level) and types of filler (non-mixable materials dispersed in various-sized particles, from tens of nanometer to tens of micrometer). 

Due to the existence of different adhesive systems and the potential hazards associated with each system, there are different types of pack ing as well as stor e conditions and shelf fives. Adhesives can be differentiated based on specific criterion and properties. In the literature, one can find various classifications based on the assembly process, delivery form, adhesion mechanism, or application. Within the same adhesive group, the adhesives can be further differentiated based on their physical states or characteristics liquid, paste, or solid (throi viscosity measurements and rheological characterization), and solvent based, water based, or those without volatile content (through solid content measurements). Another classification can be made based on the adhesion mechanism physically dried adhesives from solution, solidified hot-melt adhesive, or chemically cross-linked single- and two-component reactive adhesives. 

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