Detergency and Surface Chemistry Essential Principles

Detergent industry is a very large and important area where surface and colloid chemistry principles have been applied extensively (Rosen, 2004). In fact, some detergent manufacturers are involved in 

Water should be able to wet fibers as completely as possible that is, 0 should be less than 10. This is achieved by lowering the snrface tension, y, of the washing water, which thns lowers the contact angle. The low value of surface tension also makes the washing liquid to be able to penetrate the pores (if present), since from the Laplace equation, the pressure needed would be much low. 

For example, if the pore size of fabric (such as, any modem microcotton, Gortex) is 0.3 pm, then it will require a certain pressure (= AP = 2y/R) in order for water to penetrate the fibers. In the case of water (y = 72 mN/m) and using a contact angle of 105°, we obtain 

The detergent then interacts with the dirty soil to start the process of removal from the fibers and dispersion into the washing water. In order to be able to inhibit the soil once removed to readsorb on the clean fiber, one uses polyphosphates or similar suitable inorganic salts. These salts also increase the pH (around 10) of the washing water. 

In some cases, one also uses suitable polymeric anti-redeposition substances (such as carboxymethyl cellulose). 

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