Soaps and Detergents - Phiên bản có thể in
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Soaps and Detergents - 08HH - 05-11-2010
[FONT="]Chemistry[/FONT][FONT="][/FONT]
[FONT="]To understand what is needed to achieve effective cleaning, it's helpful to have a basic knowledge of soap and detergent chemistry. [/FONT][FONT="][/FONT]
[FONT="]Water, the liquid commonly used for cleaning, has a property called surface tension. In the body of the water, each molecule is surrounded and attracted by other water molecules. However, at the surface, those molecules are surrounded by other water molecules only on the water side. A tension is created as the water molecules at the surface are pulled into the body of the water. This tension causes water to bead up on surfaces (glass, fabric), which slows wetting of the surface and inhibits the cleaning process. You can see surface tension at work by placing a drop of water onto a counter top. The drop will hold its shape and will not spread. [/FONT][FONT="][/FONT]
[FONT="]In the cleaning process, surface tension must be reduced so water can spread and wet surfaces. Chemicals that are able to do this effectively are called surface active agents, or surfactants. They are said to make water "wetter." [/FONT][FONT="][/FONT]
[FONT="]Surfactants perform other important functions in cleaning, such as loosening, emulsifying (dispersing in water) and holding soil in suspension until it can be rinsed away. Surfactants can also provide alkalinity, which is useful in removing acidic soils. [/FONT][FONT="][/FONT]
[FONT="]Surfactants are classified by their ionic (electrical charge) properties in water: anionic (negative charge), non-ionic (no charge), cationic (positive charge) and amphoteric (either positive or negative charge). [/FONT][FONT="][/FONT]
[FONT="]Soap is an anionic surfactant. Other anionic as well as non-ionic surfactants are the main ingredients in today's detergents. Now let's look closer at the chemistry of surfactants. [/FONT][FONT="][/FONT]