Basic Soap and Detergents
From DetailingWiki
Basic Soap and Detergent Chemistry:
I think this illustrates the importance of detailers understanding the ‘science’ of cleaning; and to this end it is helpful to have a basic knowledge of soap and detergent chemistry and what is needed to achieve effective cleaning
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, other water molecules only on the waterside surround those molecules. 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. 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."
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. 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). 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. Soaps are water-soluble sodium or potassium salts of fatty acids. Soaps are made from fats and oils, or their fatty acids, by treating them chemically with a strong alkali. First let's examine the composition of fats, oils and alkalis; then we'll review the soap making process.
Fats and Oils - the fats and oils used in soap making come from animal or plant sources. Each fat or oil is made up of a distinctive mixture of several different triglycerides. In a triglyceride molecule, three fatty acid molecules are attached to one molecule of glycerine. There are many types of triglycerides; each type consists of its own particular combination of fatty acids. Fatty acids are the components of fats and oils that are used in making soap. They are weak acids composed of two parts: A carboxylic acid group consisting of one hydrogen (H) atom, two oxygen (O) atoms, and one carbon (C) atom, plus a hydrocarbon chain attached to the carboxylic acid group. Generally, it is made up of a long straight chain of carbon (C) atoms each carrying two hydrogen (H) atoms.
Alkali - an alkali is a soluble salt of an alkali metal like sodium or potassium. Originally, the alkalis used in soap making were obtained from the ashes of plants, but they are now made commercially. Today, the term alkali describes a substance that chemically is a base (the opposite of an acid) and that reacts with and neutralizes an acid. The common alkalis used in soap making are sodium hydroxide (NaOH), also called caustic soda; and potassium hydroxide (KOH), and also called caustic potash.
How Soaps are made- saponification of fats and oils is the most widely used soap making process. This method involves heating fats and oils and react them with a liquid alkali to produce soap and water (neat soap) plus glycerine. The other major soap making process is the neutralization of fatty acids with an alkali. Fats and oils are hydrolyzed (split) with a high-pressure steam to yield crude fatty acids and glycerine. The fatty acids are then purified by distillation and neutralized with an alkali to produce soap and water (neat soap). When the alkali is sodium hydroxide, sodium soap is formed. Sodium soaps are "hard" soaps. When the alkali is potassium hydroxide, potassium soap is formed. Potassium soaps are softer and are found in some liquid hand soaps and shaving creams. The carboxyl ate end of the soap molecule is attracted to water. It is called the hydrophilic (water-loving) end. The hydrocarbon chain is attracted to oil and grease and repelled by water. It is known as the hydrophobic (water-hating) end.
How Water Hardness Affects Cleaning Action - although soap is a good cleaning agent, its effectiveness is reduced when used in hard water. Hardness in water is caused by the presence of mineral salts - mostly those of calcium (Ca) and magnesium (Mg), but sometimes also iron (Fe) and manganese (Mn). The mineral salts react with soap to form an insoluble precipitate known as soap film or scum. Soap film does not rinse away easily. It tends to remain behind and produces visible deposits on clothing and makes fabrics feel stiff. It also attaches to the insides of bathtubs, sinks and washing machines. Reacting with hard water minerals to form the film uses up some soap. This reduces the amount of soap available for cleaning. Even when clothes are washed in soft water, some hardness minerals are introduced by the soil on clothes. Soap molecules are not very versatile and cannot be adapted to today's variety of fibres, washing temperatures and water conditions.
Surfactants in detergents - a detergent is an effective cleaning product because it contains one or more surfactants. Because of their chemical makeup, the surfactants used in detergents can be engineered to perform well under a variety of conditions. Such surfactants are less sensitive than soap to the hardness minerals in water and most will not form a film. Detergent surfactants were developed in response to a shortage of animal and vegetable fats and oils during World War I and World War II. In addition, a substance that was resistant to hard water was needed to make cleaning more effective. At that time, petroleum was found to be a plentiful source for the manufacture of these surfactants.
Detergent surfactants are made from a variety of petrochemicals (derived from petroleum) and/or oleo chemicals (derived from fats and oils). Petrochemicals and Oleo chemicals like the fatty acids used in soap making, both petroleum and fats and oils contain hydrocarbon chains that are repelled by water but attracted to oil and grease in soils. These hydrocarbon chain sources are used to make the water-hating end of the surfactant molecule. Other Chemicals, such as sulphur trioxide, sulphuric acid and ethylene oxide, are used to produce the water-loving end of the surfactant molecule. All surfactants have the following features: they make the removal of dirt easier by reducing the surface tension between the water and the paint surface, they produce foam, and this foam suspends dirt and stops it from being re-deposited.
How Detergent Surfactants Are Made Anionic Surfactants - the chemical reacts with hydrocarbons derived from petroleum or fats and oils to produce new acids similar to fatty acids. A second reaction adds an alkali to the new acids to produce one type of anionic surfactant molecule. First converting the hydrocarbon to an alcohol and then react with the fatty alcohol with ethylene oxide produce non-ionic surfactants non-ionic surfactant molecules. These non-ionic surfactants can be reacted further with sulphur containing acids to form another type of anionic surfactant.
How Soaps and Detergents work-these types of energy interact and should be in proper balance. Let's look at how they work together. Let's assume we have oily, greasy soil on clothing. Water alone will not remove this soil. One important reason is that oil and grease present in soil repel the water molecules. Now let's add soap or detergent. The surfactant's water-hating end is repelled by water but attracted to the oil in the soil. At the same time, the water-loving end is attracted to the water molecules. These opposing forces loosen the soil and suspend it in the water. Warm or hot water helps dissolve grease and oil in soil. Washing machine agitation or hand rubbing helps pull the soil free.
Foam or Suds - back when laundry was done with soap flakes, suds level was an indicator of cleaning performance. So, many people today think that a good rich level of suds is necessary for clean laundry. However, this is no longer true. Today's detergents are formulated to have any suds level desired without affecting cleaning performance. "They make the removal of dirt easier by reducing the surface tension between the water and the paint surface.
In reality suds (a chemical foaming agent or coconut oil) do absolutely nothing to clean, they are simply a structure that a portion of the solution had taken due to being mixed with air. The amount of foaming produced has nothing to do with its cleaning efficiency (although it does provide a means of encapsulation as well as acting a cushion between the paint surfaces and cleaning tool) They are there simply because we are so engrained with the idea that soap suds do the cleaning that it is impossible to use anything else. In most all detergents the suds are made by a foaming agent, not by the cleaning agents in the detergent. In fact, industrial cleaners usually have no foaming agents and specialized users do not want suds. Think of a hand degreaser, there are no suds yet it sure does the job
Car Wash Concentrates: A good quality car wash (Zaino Z-7™ Show Car Wash or Groit’s Car Wash) provides a slightly alkaline pH-7.5 and balanced blend of active biodegradable ingredients, to provide lubrication to prevent scratching, to lift and encapsulate dirt, road grime and oils.
Water quality (pH value, mineral content, harness, etc) and other characteristics will affect how well a car wash concentrate works. As well as conditioners to maintain the shine without stripping the paint of essential oils (the way detergents do) and dispersing them in the rinsing process, warm water (not hot) will improve the cleaning abilities of wash concentrates.
The amount of foaming produced has nothing to do with its cleaning efficiency (although it does provide a means of encapsulation as well as acting a cushion between the paint surfaces and cleaning tool) when laundry was done with soap flakes; suds level was an indicator of cleaning performance. Many people still equate a good rich level of suds with cleaning; however, this is no longer true. Today's quality car wash concentrates are formulated with anionic surfactants that have a very low suds level without affecting cleaning performance. One of the advantages of this formulation is that road dirt and grime are encapsulated in its structure (micelles), which makes for very easy and efficient rinsing.
Harsh detergents found in some car wash soaps contain sodium silicate or sodium hydroxide may etch the surface of the clear-coat leaving white residue or dulling the entire finish. Car wash concentrates that contain a high foaming (suds) agent can be corrosive, if sodium (salt) is used as an agent to create the foaming. The usual dilution is l oz per two gallons water (using a lesser dilution will leave a film on the paint surface) Avoid products that contain harsh detergents as they will emulsify and leach out any oils or waxes that provide protection and/or flexibility
(See also Alkalinity, pH Values, Hard Water, Water Filtration)
Information resource -
- “Automotive Detailing Inside & Out, A Knowledge Base for the Perfectionist"– by Jon Miller aka TOGWT™ "
