Composite degradation mechanisms

In order to evaluate the effect of hygrothermal fatigue on the physical and mechanical properties of composites in actual service, it is crucial to resolve the basic phenomena driving the complex water sorption behaviour and degradation mechanisms in various combinations of moist environment and temperature. 

The changes that occur after the heat processing of food systems are often monitored by different parameters, such as total carotenoid content (and therefore isomerization and oxidation are underestimated), individual carotenoids (overall changes may be missed), and CIELAB color parameters (no information on carotenoid degradation mechanism). The data given in Table 12.3 reflects the influence of matrix composition, food state (liquid or solid), and measured parameter on the carotenoid degradation kinetics. 

Composite materials, such as glass, carbon and aramid reinforced plastics, are principally used for their mechanical rigidity and strength. The most significant degradation mechanisms are therefore also mechanical or have mechanical consequences. Even when... 

Yu, J., Yi, B., Xing, D., Liu, R, Shao, Z. and Fu, Y. 2003. Degradation mechanism of polystyrene sulfonic acid membrane and application of its composite membranes in fuel cells. Physical Chemistry Chemical Physics 5 611-615. 

There is little question that one of the most active research areas in materials science is studying interfaces. In the past, emphasis in materials science has been placed on relating the bulk properties to the structure and composition of the solid. Today, efforts are in progress that relate surface reactivity and stability to the crystallographic orientation and composition, primarily at the S/G interface. Since a fundamental understanding of interfacial behavior and degradation mechanisms at an atomistic level is necessary if short-time test data are to be extrapolated to 30-year lifetimes, careful studies at the S/S, S/G, and S/L interfaces are required (4). 

Perhaps the most promising method for understanding the degradation mechanism for woolen archaeological textiles is the systematic examination of specimens by amino acid analysis. The study of the changes in concentration and composition of the amino acids present in the wool substrate for archaeological and modern specimens is currently under investigation. 

The environment is an important factor affecting the rate and degree of biodegradation of polymer substrates. The other key aspects determining biodegradability are related to the chemical composition of the polymer. The polymer chemistry governs the chemical and physical properties of the material and its interaction with the physical environment, which in turn affects the material s compostability with particular degradation mechanisms. 

Multiple Quantum NMR methods have been used to characterize the results of multiple degradation mechanisms on complex silicone polymer composites. 

One of the most important degradation mechanisms of SLM is an emulsification ofthe membrane phase due to lateral shear forces. Therefore, formation of barrier layers on the membrane surface by physical deposition [98] or by interfacial polymerization could prevent instability [99, 100]. A polysulfone support with N-methylpyiTolidone as a solvent was coated by a poly(ether ketone) layer as the outside layer and gave a specific composite membrane support. Such composite hoUow-fiber membranes showed significant improvement in stabUity in copper ions permeation. 

The dominant degradation mechanism may depend significantly on the details of structure and composition, including the types of end groups terminating the polymer chains, and the presence of structural defects, additives or impurities. In any case, loss of weight can only start... 

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