Moisture diffusing, inhibited

In summary, there are at least four ways in which residual moisture in the amorphous state can impact on chemical reactivity. First, as a direct interaction with the drug, for example, in various hydrolytic reactions. Second, water can influence reactivity as a by-product of the reaction, by inhibiting the rate of the forward reaction, for example, in various condensation reactions, such as the Maillard reaction. Third, water acting locally as a solvent or medium facilitating a reaction, without direct participation. Finally, by virtue of its high free volume and low Tg, water can act as a plasticiser, reducing viscosity and enhancing diffusivity [28]. 

It appeared to us that if we could add aluminium corrosion inhibitors to the encapsulating resin it was possible that diffusing moisture would transport the inhibitor to the chip surface so that the aluminium conductors would experience an inhibited electrolyte rather than an agressive electrolyte and corrosion would thereby be reduced. It should be noted that this mechanism does not operate in the absence of diffusing moisture but that it is not needed in those circumstances because corrosion would not normally occur. For this approach to be successful the following conditions must be met ... 

This non-equilibrium chemical and physical (mechanical) state of inhibited plastics is caused by incorporated Cl and their carriers (PI) in concentrations exceeding the thermodynamic compatibility threshold with the polymer. The thermodynamic non-equilibrium is a useful property of inhibited plastics since it expands their anticorrosion functional features. The greater the deviation from the non-equilibrium state of such systems, the quicker the relaxation processes in them accompanied by the release of excess Cl into the ambient medium and to the object being protected. The structure and properties of the components of inhibited plastics Cl depend on their composition and can be carried to the mated part by either diffusion in the gaseous (thanks to Cl volatility) or liquid phase via its exudation, its mixture with a PI, or washing of water-soluble Cl and diffusion through the material moisture. These processes bring about mechanical relaxation of the polymer matrix. The point at which the inhibited anticorrosion material moves into a state of thermodynamic equilibrium is usually correlated with its protective ability. 

Thermal studies (DSC) indicate a very high moisture absorption rate for pure PAI-1. The amide linkage m PAI, as in case of polyamides, is known to be very moisture sensitive and undergoes hydrolysis and chain scission when in the melt state in the presence of moisture. PAI-2 does not indicate the same moisture absorption properties observed in PAI-1. Addition of only 10% LCP decreases the moisture absorption of the blend dramatically. The T of the pure components and the blends increases on heat treatment. The presence of LCP is seen to inhibit the imidization of PAI. The major fiictors affecting imidization are temperature, time and diffusion of the water of imidization through the molded part. The presence of LCP which has good barrier properties, inhibits the diffusion of the NMP solvent and water of imidization which in turn inhibits the reaction. The T transition for PAI in DSC... 

Brass plated steel cord that contains low levels of copper is not so sensitive to decohesion caused by moisture. Initial adhesion may be lower because of fewer copper inclusions, but a more coherent ZnO is formed which reduces the amount of Zn ions diffusing through the Cu S layer and so less ZnO/Zn(OH)2 is formed at the interface. Compounding with high levels of ZnO also helps to inhibit the dezincification process by reducing the diffusion rate of Zn ions to the cord surface. 

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