Fig.(5): Effect of exposure time in months on degradation (pH values evaluation) of fabrics cotton at Alexandria and Helwan Cities (Year2002/2003)

Fig.(6): Effect of exposure time in months on changes of pH values % of fabrics cotton at Alexandria and Helwan Cities (Year2002/2003)

3. Whiteness, Yellowness indices and Brightness:

Table (4) and figs (7-9) shows the spectrophotometer measurements of the indices of brightness, yellowness and whiteness of the examined samples, which were exposed at the urban, and industrial and weather at Alexandria as well as Helwan cities. It is observed that at the start of the exposure of the samples in Helwan and Alexandria the whiteness and brightness decrease with increasing the duration of exposure. While Yellowness index increases with increasing duration of exposure. Also, the degradation of the samples exposed in Helwan is higher than the samples exposed in Alexandria.

This may by attributed to the fact that a lot of cement particles from the surroundings atmosphere and which were emitted from the cement factories - were settled on the fabric surface giving it less white appearance on one hand, On the other hand an oxidation of the cotton fabric had occurred by action of the sunlight and the humidity of the atmosphere.

Table (4)) : Monthly data of Spectrophotometer Properties of fabrics cotton at Alexandria and Helwan Cities(Year2002/2003) :

Fabr. : Fabric G. 70 : Giza 70

Alex. : Alexandria Helw. : Helwan