Conditioning surface treatment agents

It is not recommended to withdraw large amounts of liquid from the ozone reactor during the treatment, since the hydrodynamic conditions as well as the ratio of mass of ozone per mass of pollutant remaining may change and thus influence the gas-liquid mass transfer or the oxidation rates. The mass transfer might also be influenced by the oxidation, e. g. when surface active agents are oxidized. 

However, in humid conditions y is higher (as with pure All), the friction coefficient remains, however, lower than for the All without treatment, particularly at low speed. The surface active agents which promote the homeotropic orientation and lower the friction coefficient of the LC mixture, did not prevent the increase in y due to moisture. 

After surface treatment, all substrates were stored less than 2 hours in an air-conditioned room (20 2°C and 50 5%r.h.), before polymer application. The epoxy prepolymer used was diglycidyl ether of bisphenol A (MW=348 g mol , DGEBA DER 332 from Dow Chemical). The curing agents were either IPDA from Fluka or DETA from Aldrich. Assuming a functionality of 4 for IPDA, 5 for DETA, and 2 for the epoxy monomer, the stoichiometric ratio aje used was equal to 1 (exceptions are mentioned). 

Neither for the concrete deck in Structure 2 it was possible to detect any penetration depth of the hydrophobic agent after surface treatment. The observation of a thin surface layer of the hydrophobic agent also here demonstrates the importance of the moisture conditions in the concrete at the time of surface treatment. If the moisture content in the concrete substrate is so high that only a thin surface layer of the hydrophobic agent forms, the long-term efficiency of such a protective measure may be reduced. Also other types of surface coatings may then be considered. 

Conditions significant in the design of treatment facilities include high chlorine demand, the presence of surface-active agents, high solids concentrations, and nutrient deficiency. TTie process diversity and complexity, as well as the proprietary nature of many of the process chemicals, require that the pretreatment be established on a case-by-case basis after thorough investigation. 

In cases in which surface treatment produces a smooth oxide (intentionally or unintentionally) bond performance is controlled by chemical bonds across the oxide-epoxy interface. This situation can arise, for example, when an FPL adherend is rinsed in fluorine-contaminated water or is exposed to fluorine vapor. ( 8) The oxide-epoxy bonds are relatively weak and are readily disrupted by moisture.(, 50) As a result, bond failure is rapid upon exposure to humid conditions, and the crack propagates along the adhesive-oxide interface. In cases in which a smooth oxide is formed intentionally, coupling agents such as silanes can be used to improve durability. This is discussed in detail in Chapter 9 by E. Pleuddemann in the accompanying volume, Fundamentals of Adhesion. 

---