Auto-adhesion

A 2D soft-sphere approach was first applied to gas-fluidized beds by Tsuji et al. (1993), where the linear spring-dashpot model—similar to the one presented by Cundall and Strack (1979) was employed. Xu and Yu (1997) independently developed a 2D model of a gas-fluidized bed. However in their simulations, a collision detection algorithm that is normally found in hard-sphere simulations was used to determine the first instant of contact precisely. Based on the model developed by Tsuji et al. (1993), Iwadate and Horio (1998) incorporated van der Waals forces to simulate fluidization of cohesive particles. Kafui et al. (2002) developed a DPM based on the theory of contact mechanics, thereby enabling the collision of the particles to be directly specified in terms of material properties such as friction, elasticity, elasto-plasticity, and auto-adhesion. 

Felby, C., Pedersen, L.S. and Nielsen, B.R. (1997a). Enhanced auto adhesion of wood fibers using phenol oxidases. Holzforschung, 51(3), 281-286. 

Additional drawbacks to the use of polyimide insulators for the fabrication of multilevel structures include self- or auto-adhesion. It has been demonstrated that the interfacial strength of polyimide layers sequentially cast and cured depends on the interdiffusion between layers, which in turn depends on the cure time and temperature for both the first layer (Tj) and the combined first and second layers (T2) [3]. In this work, it was shown that unusually high diffusion distances ( 200 nm) were required to achieve bulk strength [3]. For T2 > Tj, the adhesion decreased with increasing T. However, for T2 < Tj and Tj 400 °C, the adhesion between the layers was poor irrespective of T2. Consequently, it is of interest to combine the desirable characteristics of polyimide with other materials in such a way as to produce a low stress, low dielectric constant, self-adhering material with the desirable processabiHty and mechanical properties of polyimide. 

It is important to point out that the improvement in adhesion did not result from an increase in the solubihty of the imidized polymer containing the flexible coblock after the Tj cure cycle. In fact, the block copolymers demonstrated less than 2 % swelling (72 h) in the casting solvent, whereas PMDA/ODA polyimide homopolymer swells approximately 20-30 % (72 h). Clearly these data suggest that the improved auto-adhesion results from melt flow at 400 °C [44]. 

Tack is best thought of as the ability of two pieces of rubber to stick when pressed together and is sometimes called auto adhesion. Therefore, it is not quite the same as stickiness or adhesion, which generally involves sticking or adhering to a second material. High tack can be a nuisance when handling sheets of rubber but is very important in the manufacture of articles built up from separate pieces of uncured compound. 

The second theory—winter-diffusion—would seem applicable to the particular case of the adhesion of like surfaces (known also as auto-adhesion ). Certainly it occurs in the welding of plastics, and in instances such as tyre manufacture when unvulcanized rubbers adhere spontaneously. On the other hand, it is unlikely that much inter-diffusion takes place when materials dissimilar chemically are brought together. It is well-known that many plastics are incompatible and if mixed will, over a period of time, tend to separate— forming eventually discrete layers. Behaviour of this kind is precisely the reverse of inter-diffusion. 

Trees, B., Auto Adhesive Extrusion Systems, Adhesives and Sealants Industry, May 2002. 

We should mention that in the A region the aluminum film is continuous. This property is no more verified in the B region. Evidence of the discontinuity of the metallic film has been found in plane and cross section TEM micrographs. So the increase of the adhesion in region B in respect to tne A region may come from the auto adhesion of the PET with the EAA which is used for the peel test. We also see that when we decrease the thickness of the film (from 10 to 3 nm), we decrease the coverage of the... 

Part 3 1975. Two Types of Laminated Board (Roofboards) with Auto-Adhesively Boruled Reinforcing Facings for Use as Roofboard Thermal Insulation for Built- Up Roofs, 17... 

The modified layer on iPP surface consisting from macromolecules with many oxidizing groups contributes to the self-adhesive properties of iPP. The weak cohesion of this, only several micrometers thick layer, causes the adhesive joints to be less mechanically resistant. The stability of hydroperoxides at the surface was investigated by measuring the strength of auto adhesive joints (Fig. 8). At the contact of two surfaces of modified iPP foils new bonding may arise between these surfaces because of hydroperoxide decomposition. The data in Fig. 8 indicate that the work of auto adhesion increases with temperature of the formation of auto adhesive joints. This fact corresponds well with the decrease of the concentration of hydroperoxides determined after destruction of auto-adhesive joints. The concentration of hydroperoxides is almost zero at 423 K. 

Fig. 8. Variation of auto-adhesion work and hydroperoxide concentration of iPP modified by corona discharge with the time of auto-adhesive joint formation...

The higher efficiency of the modification for extruded iPP when compared to biaxially oriented iPP was explained by different susceptibility to oxidation due to different crystallinity. Linear dependence of either PC of the surface energy or hydroperoxide concentration of modified iPP on current density was observed. A decrease in the exposition time of iPP foil resulted in lower modification effect. The sensitivity on exposition time was more pronounced for extruded iPP. Aging of modified PP foil leads to a significant drop in surface energy during first 24 hours for extruded iPP, while for biaxially oriented iPP the decrease was small. An increase of the mechanical work of adhesion was observed if temperature of auto-adhesive joints rised. The observed decrease of hydroperoxide concentration after a destruction of the auto-adhesive joints is in accordance with the previous data. 

Let us now return to the apparently simpler problem of the way in which interfacial strength develops with time when two identical glassy polymers are brought together and annealed above their glass transition temperature - the case of auto-adhesion. Several authors have studied the time dependence of this... 

Contact adhesive A contact adhesive has the property of auto adhesion. ... 

Neoprene, or polychloroprene, was the first synthetic elastomer used by the adhesives industry, and is one of the most versatile materials ever developed as a backbone for elastomeric adhesives. Neoprene combines rapid bond strength development with good tack or auto-adhesion, and resistance to degradation by oils, chemicals, water, heat, sunlight, and ozone. It is popular in numerous areas such as shoe sole attachment, furniture construction, automobile assembly, and a variety of construction applications. 

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