Fabric Softeners and Disinfectants

Uses of Surfactants: Fabric Softeners and Disinfectants

Fabric softeners and disinfectants sometimes contain cationic surfactants in which the surfactant part of the molecule is a positive ion. The quarternary ammonium salts are cationic surfactants which contain 4 groups attached to a nitrogen atom, which carries a positive charge. Cationic surfactants and anionic surfactants cannot be used together because the oppositely charged ions would react and cancel each other out.

Some cationic surfactants are used as disinfectants because of their germicidal action. Others, such as dioctadecyldimethylammonium chloride, are fabric softeners. Such compounds form a film on the fabric's surface and lubricate the fibres, making a softer, more flexible fabric.

Toothpaste

Fluoride Additives in Toothpaste

Fluoride ions also help maintain the strength of the enamel. Fluorides are present in toothpastes largely in the form of stannous fluoride (SnF2, Fluoristan), sodium monofluorophosphate (Na2PO3F), and sodium fluoride (NaF).

* replacing some of the hydroxyl groups in the enamel's hydroxyapatite, converting it to a harder mineral, fluoroapatite, which is more resistant to erosion by acids, and

* suppressing the bacteria's ability to generate acids.

Although not our principal protection against tooth decay, the surfactants of toothpaste formulations do not effectively remove loose debris from the mouth and also gives us the sense of cleanliness. Almost all dentifrices contain a bit of saccharin and some flavoring or fragrance to leave us with a sense of sweetness and freshness after brushing.

Bleaches

Bleaches make white things even whiter. There are chlorine bleaches and all-fabric bleaches. Chlorine bleaches contain 4.25% sodium hypochloride solution (NaOCl). In some bleaches the chlorine hits the fabric all at once and can damange some fabrics if direct contact is made. The active ingredient in chlorine bleaches is the hypochloride ion (ClO2-). These bleaches work because they remove loosely-bound electrons which color fabrics. These loosely-bound electrons can color or dull fabrics because they have the ability to absorb visible light as they move to higher energy levels. The absorption of visible light causes the dulling effect. By immobilizing or removing these electrons, the chlorine bleach makes whites look whiter. Chlorine bleach works well on cotton and linen fabrics.

Another type of bleaching agent is composed of the hydantoin and cyanurate bleaches. These bleaches release chlorine slowly in water. A lower concentration of chlorine is less damaging to the fabric.

A third type of bleaching agent is the oxygen-releasing bleach. Sodium perborate, a builder releases hyrdogen peroxide, which acts as a bleach. Oxygen bleaches aren't active chlorine bleaches but they are better for bleaching synthetic fibres. You need to use more bleach, hotter water and a more alkaline solution with these than with chlorine bleach, but they do work well when used properly.

Borax, also known as sodium pyroborate, Na2B4O7, is often added to oxygen-releasing bleaches because of its ability to clean. Its pH is about 9.5, so it produces an alkaline solution which make the all-fabric bleaches work better.

Corrosion Inhibitors

Corrosion Inhibitors

Other ingredients include corrosion inhibitors to protect the machinery that does the washing; suspension agents that help keep the grease, dirt and grime that are in suspension from redepositing on the fabrics; enzymes that help containing bleaches to help remove stains. All of these help the surfactant do its job of producing a clean wash.

Other Ingredients

Some of the remaining ingredients may add more to the appearance of a clean wash than to its reality. Optical whiteners, or brighteners, are organic compounds that are deposited on fabrics and that translate the invisible ultraviolet component of sunlight into an almost impreceptible blue tint. The effect of this blue tint, is to add a bit of brilliance to white fabrics and give them the appearance of extra cleanliness.

Brighteners are very interesting compounds. Many of them contain optical brighteners, which are colourless dyes. They absorb radiation which comes from sunlight and is invisible to us. Then these dyes re-emit this radiation to us as visible light. The re-emitted light is at the blue end of the spectrum, so the clothes take on a bluish tint, which masks any yellowing and make the fabric look brighter. Blancophores are the chemical names of these compounds. The safety of these chemicals is not yet known with certainty. They don't appear to harm human beings, but they have caused minor mutations in microorganisms. However, they are known to cause skin rashes on some people.

Finally, added perfumes and fragrances produce what many regard as a pleasant odour in the finished wash.

How Soap Cleans

Step 1
Decreases the water's surface tension, making it a better wetting agent

Soap first lowers suface tension so that the water carrying the micelles can get to the dirt. When the soap micelles reach the embedded dirt, the soap molecules that form these micelles once again find themselves at a surface.



Step 2
Converts greasy and oily dirt into micelles that become dispersed in the soapy water

Now, as the hydrophilic heads of the soap molecules remain surrounded by water molecules, the soap micelles break up and the hydrophobic hydrocarbon tails, which had remained in the interior of the spherical micelles, become embedded in the grease. With this greasy dirt providing as compatible a chemical environment for the hydrophobic tails as the water provides for the hydrophilic heads, the tails are just as much at home in the grease as the heads are in the water.

Step 3
Keeps the grease micelles in suspension, thereby preventing them from coalescing back to large globules of grease that could be redeposited on a clean surface.

Agitation now breaks the grease into micelles whose surfaces are covered by the negatively charged carboxylate groups, the hydrophilic -CO2- groups of the embedded soap molecules. The grease droplets repel each other and remain suspended in the wash water instead of coalescing and redepositing on the material being cleaned. In the end, the suspended droplets go down the drain with the wash water. (While all this is going on the sodium ions move about freely and independently in the wash water.)