Direct adhesion

Excessive load, reduced fluid viscosity, and low speed can cause a breakdown of the lubrication layer to the point of a metal-metal contact. Direct adhesive contact can lead to molecular interaction strong enough to tear material out of the surface. This process is also known as cold welding . Metal surfaces under ambient conditions are usually covered with oxide layers that prevent cold welding at moderate loads. 

The presence of EPS in subaerial biofilms (Fig. 11.1) is also an important prerequisite for inter-organismal interactions and communication. The EPS layer enables other microorganisms to join the biofilm by direct adhesion and might also stimulate growth of accompanying bacteria (Fig. 11.4), as well as promote contact with photobionts (Gorbushina et al., 2005). 

Coextrusion is the latest process by which a series of plies can be joined together in the hot state. This may involve direct adhesion between plies or the use of extruded tie or adhesive layers. These bonding layers are frequently only a few micrometres thick and involve relatively low grammage levels. However, coextrusion is only cost-effective as a long-run process since set-up times can be lengthy. 

As an example of how wear behavior with a changing rate can be treated, let us examine a model for the competition of metal removal from a slider by direct adhesive transfer and by combined oxidation and ablation of the oxide. The total rate of phenomenological wear is given by... 

Electron microscopy of cells cultured on plastic substrata reveals that the plasma membrane does not make direct adhesive contact with plastic but rather is separated from the plastic surface by a layer of proteinaceous material of about 100 angstrom thickness (39). Due to the presence in serum of fibronectin, vitronectin, laminin (1-3) and possibly other cell adhesion proteins, cells cultured in serum containing medium adhere to their substrata via one or more cell... 

Elimination of a manufacturing process step It may be more cost effective to use olefinic color coats with their direct adhesion to the non-polar, untreated TPO surface than to use an extra manufacturing step to pre-treat the TPO surface with AP, flame or plasma. 

Minimization of Compounded effects of errors during manufacturing It is estimated that the compounded effects of errors when olefin color coats are used may be lower than in above mentioned pre-treatments and their quality control methods. This notion is based on the capability of the olefinic color coats to achieve direct adhesion to the untreated... 

Feasibility of Automotive Coatings Designed fw Direct Adhesion to TPO Materials 271... 

Chem. Descrip. Methacrylate sol n. polymer in butylacetate/MEK (70 30) Uses Acrylic for heat-sealing lacquers, direct adhesion to aluminum, sealing to PP, PS, PVC... 

Isotropic adhesives conduct current equally in all directions and are the most common and widely used in industry. The anisotropic types, also referred to as z-direction adhesives or anisotropic-conductive adhesives (ACA), although filled with metal particles, are filled at much lower levels (0.5%-5% by volume) than isotropic types (filled 25%-30% by volume). The volume Iraction of filler is well below the percolation threshold at which the adhesive becomes highly conductive in all directions. Because of the low volume Iraction of metal particles, there are no continuous electrically conductive paths in the x-y plane. During the connection process, the anisotropic adhesive, either as a film or paste, is positioned between a flip-chip bumped die or a tape-automated bonded (TAB) die and the corresponding pads of an interconnect substrate. Pressure and heat are... 

The results on crossed polymer fibers obtained by Briscoe and Kremnitzer shown in Fig. 9.16 gave good agreement with Equation (9.16). The friction force increased more rapidly than Coulomb s law predicted at low loads but approached Coulomb s law at high loads. The value of the work of adhesion W from these friction experiments was near 0.1 Jm , close to the value determined in direct adhesion experiments on the same fibers. 

Wilson, N. H. F. Direct adhesive materials current perceptions and evidence - future solutions. J. Dent. 2001, 29, 307-316. 

Flexible acrylic polymers in the form of latexes are used as pigment binders on fiberglass, polyester, and other fabrics that are not readily dyed. They are also used to prepare caulks and adhesives. Very soft, tacky acrylic polymers have direct adhesion to most surfaces and need no adhesion promoters. Hard acrylic polymers are readily modified with simple compatible silanes to obtain good adhesion to mineral surfaces Soft, flexible, non-tacky acrylics have many desirable properties, but do not have good direct adhesion to most solid surfaces and the bonds to mineral surfaces are not water-resistant. 

Most of those who develop adhesive compositions consider the form and ultimate use of an adhesive to be the most useful categories because these guide and direct adhesive development. The ability of the adhesive formulator to satisfy an end use will be very much related to the completeness of the information available concerning performance attributes required or expected. Price is a category of immense interest to the adhesive developer as it helps to define the raw materials from which the formulator may choose. The adhesive development team often must work closely with the customer to learn what is really needed from an adhesive. 

The goal remains to improve the direct adhesion to substrates by the adhesive. However, this is complex. Chemical pretreatments generally provide good wettability due to their low viscosity. The adhesive s higher viscosity reduces the wettability and also the adhesion quality. 

Direct adhesion measurements were performed between a PE film (thickness 20 m) and a CaCOs sheet (a polished section of a piece of calcite from OMYA, France). The films/sheets were treated with the interface modifiers, compressed and then the force of peeling was measured. 

Differences in the value of adhesion between conventional surfactants and RS are expected. The comparison of conventional anionic, cationic and nonionic surfactants with reactive ones was performed with calculations based on wetting experiments and direct adhesion measurements that reflect the real value of adhesion most directly. The well-known Owens-Wendt [7] and Wu [8] methods were used for calculating the work of adhesion. The calculated and the measured peeling force values are given in Table 1. 

The combination of the effect of inertial impaction, diffusion, interception, and electrokinetic attraction on the cell particle capture and retention to a fibre is called direct adhesion, and the most important mechanism of leucocyte depletion filtration... 

The retention of the capmred blood cells in the nonwoven filter mostly depends on the following mechanisms sieving, direct interception, direct adhesion (including inertial impaction, diffusion, interception and electrokinetic attraction), and indirect adhesion (including bridging and particle re-entrainment). 

Direct adhesion of particles to fibres can be explained with Deijaguin—Landau— Verwey—Overbeek (DLVO)" " theory for soft cell particles,and the adhesion of cell particles to the fibres may be quantified by using the attachment rate coefficient, att which is related to the collision efficiency, rj, and the sticking efficiency, , as follows... 

Two-shot injection molding. Two-shot or overmolding refers to a process wherein either different colors or different materials are molded into one part. In this process, the first material or color is injected, then the mold is rotated, and the second shot is injected as depicted in Fig. 1.67. An alternative method is to use a retractable core." In this case, the first material is injected and cooled to solidify, and then the core is retracted to allow injection of the second material as shown in Fig. 1.68. Bonding is accomplished through either strictly mechanical means or by adhesion between the two components through diffusion of the chains. This can result in parts with two combined materials without the need for an additional adhesive bonding step." In the case in which direct adhesion of the materials is desired, proper selection of compatible materials is required. Table... 

It is estimated that resin composite restorations have a service life of 6-7 years, which is far less than half of the service life of dental amalgam. The main reason for replacement of direct adhesive resin composite restorations is secondary caries. Therefore failures at the interface has, to a great extent, inspired development of novel strategies to reduce degradation of the resin-tooth interface. Limitations within the material and intrinsic properties of the dentin have... 

Another application of interfacial phenomena in the coatings is presented in the studies of Malmos (2008) and Jensen (2008). The projects were in collaboration with a Danish wood paint company. Both investigations are about wood stains (wood paints) which were smdied using direct adhesion measurements with the pull-off test method (Figure 6.15) and the methods of surface chemistry presented in this chapter (contact angle measurements and analysis of the results using the van Oss-Good method). Commercial products were tested in aU cases. 

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