Interfacial degradation

The above analysis applies to degradation processes that relate to the bulk adhesive. Interfacial degradation processes such as corrosion can be similarly determined. Thermal and oxidative stability, as well as corrosion and water resistance, depends on the adherend surface as well as on the adhesive itself. Epoxy-based adhesives degrade less rapidly at elevated temperatures when in contact with glass or aluminum than when in contact with copper, nickel, magnesium, or zinc. The divalent metals have a more basic oxide surface than the higher-valence metal oxides and hence serve to promote dehydrogenation reactions, which lead to anion formation and chain scission.7... 

Certain adhesive systems are more resistant to interfacial degradation by moist environments than are other adhesives. Table 15.16 illustrates that a nitrile-phenolic adhesive does not succumb to failure through the mechanism of preferential displacement at the interface. Failures occurred cohesively within the adhesive even when tested after 24 months of immersion in water. A nylon-epoxy adhesive bond, however, degraded rapidly under the same conditioning owing to its permeability and preferential displacement by moisture. 

Molecular aggregation of recombinant human growth hormone (rhGH) due to air-liquid interfacial degradation can be prevented by adding polysorbate-20... 

Other possible interfacial degradative mechanisms include the build up of osmotic pressure at the oxide/adhesive interface(6) (akin to the phenomenon of paint blistering by osmotic gradients), disbonding by alkali produced by the cathodic reaction in metallic corrosion(107), and the imposition of stress leading to bond stress-corrosion cracking( 108-110). 

Pt catalyst ripening, electrocatalyst loss or re-distribution, carbon corrosion, electrolyte and interfacial degradation... 

Figure 2.10. Interfacial degradation mechanisms ofLi(Nii-xCo 02 electrodes in contact with a standard LiPFfcarbonates electrolyte during cycling. Structural modifications of the active material s surface and the formation of a passivation layer. (Reprintedfrom [SEG 99] with permission. Copyright 2005 Elsevier). For a color version of the figure, see WWW. iste. CO. uk/dedryvere/electrodes.zip...

Another problem can arise when some of these thermosetting resins are used as the matrix in fiber-reinforced composites. In such materials there is a high area of fiber-matrix interface and hydrolysis in the interfacial zones is a common source of failure. Interfacial degradation is a common problem in the use of glass-reinforced polyester in marine applications. 

Chateauminois, A., Vincent, L, Chabert, B., Soulier, J.P. (1994). Study of the interfacial degradation of a glass-epoxy composite during hygrothermal ageing using water diffusion measurements and dynamic mechanical thermal analysis. Polymer, 35, 4766 774. doi 10.1016/0032-3861(94)90730-7 Colin, X., Verdu, J. (2003). Plastics rubber and composites, Macromolecular Engineering, 32(8/9), 349-356. 

Kawagoe M, Hashimoto S, Nomiya M, Morita M, Qiu J, Mizuno W, Kitano H (1999) Effect of water absorption and desorption on the interfacial degradation in a model composite of an aramid fibre and unsaturated polyester evaluated by Raman and FT infra-red microspectroscopy. J Raman Spectrosc 30(10) 913-918... 

Lavrentyev, A.l. and Rokhlin, S.I., Models for ultrasonic characterization of environmental interfacial degradation in adhesive joints. Rev. Prog. Quant. Nondestruct. Evai, 13B, 1531-1538 (1994). 

If the interfacial degradation time Tj exceeds the jet break-up time Tib significantly, two-phase mixing occurs since a liquid phase boundary still exists after jet breakup. If this relation is reversed, meaning that Tjb>Ti, single-phase mixing... 

TTF)2l3/Pt structures suggests that no interfacial degradation occurs during the preparation or analysis of these hybrid systems. 

Interfacial degradation is especially common in DMFC systems operating with membranes that are alternatives to Nafion . The main reason for the enhanced probability of an interfacial failure in such systems is poor compatibility between the non-Nafion polymer in the membrane and Nafion -bonded electrodes (Kim et al. 2004). 

A comparison of the long-term DMFC performance between MFAs with good and poor interfaces between the membrane and the electrode(s) is shown in Fig. 7. The cell with a good membrane-electrode interface shows lower unrecoverable performance loss than the cell with a poor interface, 42 versus 70 mA cm after 700h of operation. A greater performance loss of the cell with the poor interface is accompanied by an increase in the high-frequency resistance of the cell (Fig. 7). However, the increased cell resistance is only in part responsible for the total performance loss caused by interfacial degradation. /R-corrected H -air polarization... 

Mechanical properties of WPCs also undergo changes after weathering, which can be attributed to composite surface oxidation, matrix crystallinity changes, and interfacial degradation. 

Post-deposition processing and reactions - e.g. reaction of the film surface with the ambient, thermal or mechanical cycling, corrosion, interfacial degradation, deformation (e.g. burnishing, shot peening) of soft surfaces, overcoating ( topcoat ). 

ESCA Studies of Interfacial Degradation Between Ethylene-Acrylic Acid Copolymers and Lead/Tln Alloys... 

INTERFACIAL CATALYSIS plays a very important part in surface (interfacial) degradation. Oxidation can be catalyzed by various metals. Catalysis can start at metal/polymer interfaces and metal ions can diffuse into the polymer. The catalytic action by copper or its oxides, for instance, during oxidative degradation of polyethylene and isotactic polypropylene, respectively, has been studied in detail. Some relevant results will be briefly discussed here. 

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