Wetting models composite interface

Figure 1.27. (a) Formation of a composite interface in the case of a non-wetting system, (b) Model triangular groove used in the calculation of the critical angle ft. ... 

Exposure to 70 °C gives similar results for the surface treated fiber (Fig. 24). That is, a complete reversibility in noted. The finished fiber (i.e. the fiber with the interphase consisting of the amine deficient brittle interlayer) experiences a nonrecovery of interfacial shear strength after moisture exposure and dehydration. Parallel surface spectroscopic investigation of the fiber surfaces show that under these conditions the fiber surface chemistry is not permanently altered by this exposure. Model studies of epoxies with the amine deficient composition of the interphase show that, the wet Tb of this material is about 70 °C. Therefore, the interphase is at or above its wet Tg and therefore because of the compliant nature of this material, stresses cannot be transfered efficiently and the interface is permanently distorted. 

To improve adhesion of binders to fibres, including carbon fibers, methods of surface treatment by cold plasma were developed. In the course of such treatment, the removal of a weak border layer of the fiber proceeds and the contact between the surface and a binder is improved. At the same time, the number of active centers capable of chemical interaction with a binder increases and the wetting becomes better. It may be expected that pol5mierization under plasma action may also serve as a tool adhesion improvement at the phase border. In spite of the existence of many ways of surface treatment of the reinforcement surface, no model of interaction was proposed which is effective in predicting the t5T)e of reinforcement by surface treatment of a given filler-matrix combination. According to Drzal, the major reason for this lack of theoretical developments is in the over-simplification of the composition and nature of the filler-matrix interface. 

Therefore the three "criteria" for simulation are identical values of kL, kg and a/e in the industrial and the laboratory absorber. "Simulation" means that, if the bulk ccm x)sitions of gas and liquid in the laboratory absorber are the same as in a volume element of the industrial absorber, the absorption rate per unit interfacial area in this elanent will be the same as in the laboratory model determined experimentally as a function of Cgo> or p, and the above balance equations can be integrated numerically step by step between the limit compositions at the entrance and the exit of the industrial absorber to find the length h of the absorber. The third criterion (a/e) is required whenever the reaction between dissolved gas and a reactant in solution is slow. Indeed reactions will proceed in the bulk liquid, and the rate of absorption in industrial or laboratory absorber will depend iqx>n the volume of bulk liquid available per unit area of interface. Comparison of Tables (I) and (II) leads to the choice of the laboratory equipment (62, 110) for a specified gas-liquid contactor. For example it mayoe seen that any wetted wall or stirred vessel can simulate a packed column (with respect to kL and kg) for reactions occuring in the liquid film. 

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