1. WHAT MAKES A DETERGENT WORK & FACTORS THAT AFFECT CLEANING

2. THE CHEMISTRY OF CLEANING
In the process of cleaning there are a lot of technical words and terms used to describe the contents of the cleaning chemical formulations and their actions.
Most detergents contain several different components, which can usually be placed into groups having similar functions. The groups of chemicals used in detergent formulations are:
SURFACTANTS - Wetting agents that help “wet” the surface.
ACIDS & ALKALIS
SEQUESTRANTS - Mop up hard water ions and facilitate the surfactant.
SOLVENTS - Dissolve oils & greases to help the surfactant work.

3. SURFACTANTS The word “surfactant” is a shortened, easy to remember name for “surface active agent” - surfactants act on surfaces.
SURFACTANT ACTIONS
Wetting
Emulsification
Solubilisation
Solubilisation versus Emulsification
Foaming / Defoaming
Dispersion

4. SURFACTANT STRUCTURE Surfactants have a chemical structure comprising:
an oil-loving “tail” and a water-loving “head” and may be considered as looking something like a tadpole. This structure gives surfactants the ability to align themselves at surfaces between water and oil and / or air.
The water-loving head protrudes into the water phase and the oil-loving tail protrudes into the oil phase or air (or even onto a solid surface). In all cases, the oil-loving tail tries to escape from being in the water phase. This property is used extensively in detergent formulations to impart specific actions.
IN BRIEF: The oil-loving head sticks to the grease and the surfactant acts as a glue between the oil and the water and makes the oil soluble in water

5. SURFACTANT TYPES
The major types of surfactants used in detergents are:
Anionic (neg-charge) 90% Detergents etc
Cationic (pos-charge) 10% Polishes/Finishes
Non-ionic
The charges on the different surfactant types place restrictions on blending of different surfactant types in formulations.
Opposite charges attract and, if anionic and cationic surfactants are blended together - neutralize one another.
This results in no surface activity and no cleaning ability.
Balance of cost of cleaning versus cleaning performance. Many products have a great cost but don’t perform very well

6. SURFACTANT ACTIONS Wetting
At water / air surfaces, the alignment of surfactants with their oil-loving tails out of the water surface breaks down the
“surface tension” of the water
the “skin” on the surface of water that allows insects to walk on water and that pulls water droplets into beads on oily surfaces.
The ability of surfactants to reduce the surface tension of water allows water droplets to spread and “wet” oily surfaces, hence the other common name for surfactants – “wetting agents”.

7. SURFACTANT ACTIONS Emulsification
When oil droplets are dispersed in water the oil quickly floats to the surface to form a continuous oil film. When surfactants are added to the water:
the surfactants adsorb onto the surface of the oil droplets
with their oil-loving tails in the oil droplet
with their water-loving heads extending into the water.
This gives the surface of the oil droplets a water-loving “skin” which allows the droplets to remain dispersed in the water.
This property of surfactants, to keep oil droplets dispersed, is called “emulsification”
The stable dispersion of oil droplets in the water is called an “emulsion”
When oil droplets are dispersed in a continuous water phase, the emulsion formed is called an “oil in water” emulsion, frequently shortened to o/w emulsion.

8. SAPONIFICATION
When animal and vegetable fats and oils are reacted with a strong alkali such as caustic soda (sodium hydroxide), the fatty acid groups are split off and neutralized by the alkali to make soap – the salt of the fatty acid.
NOTE: Animal and vegetable fats and oils all belong to the same chemical family. The only “difference” between them are that at room temperature:
fats are solid
oils are liquid

9. pH
No discussion on acids and alkali would be complete without reference to “pH”.
The pH scale is a measure of the amount of acidity or alkalinity in water.
Due to the mathematical nature of the pH scale
each one-unit decrease in pH, requires a tenfold increase in the hydrogen ion concentration.
each one-unit increase in pH, requires a tenfold decrease in the hydrogen ion concentration, brought about by a tenfold increase in the hydroxide ion concentration
This means that a liquid with a:
pH of 9.0 is ten times more alkaline than a liquid with a pH of 8.0
pH of 10.0 is 100 times (10x10) more alkaline than a liquid with a pH of 8.0
The same works in reverse for Acids – pH 4.0 is ten times more Acidic than pH 5.0

10. pH – pictorial examples
Source: Wikipedia

11. ALKALINITY IN CLEANING
In general detergents are formulated to be either:
neutral
alkaline.
Many soils will be acidic therefore alkalinity in the detergent assists in their removal by neutralizing them to make soluble salts. 
Functions of the alkalinity in the detergent include :
saponifying fats and oils
breaking down and solubilising proteins
neutralizing acids present in soils
removal of acidic metal oxides from surfaces
alkalinity also assists in wetting of surfaces and dispersing and suspending solid soils 

12. ACIDS IN CLEANING Acids, in general will attack and dissolve many:
metals, basic metal oxides and alkaline metal salts
concrete, mortar and grout.
The most frequently encountered examples of basic metal oxides and alkaline metal salts are:
iron oxides “rust”
calcium / magnesium carbonate “water scale”
The specific type and concentration of acid used and the presence of corrosion inhibitors and other additives will all affect the degree of acidic attack. 

13. SEQUESTRANTS
Sequestrants are special chemicals added to detergent formulations to:
prevent dissolved metal ions present in the cleaning solution from causing scaling and from
reacting with, and inactivating, other cleaning chemicals.
Sequestrants do this by preferentially reacting with the problem metal ions to prevent their interaction with the other chemicals.
 The major source of dissolved metal ions is the water used to prepare the cleaning solution.
The main metal ions in the water are:
calcium and magnesium hardness
but can also contain iron, manganese, copper, and minor levels of other metals ions.
Dissolved metal ions can also be introduced into the detergent formulation or cleaning solution, as contaminants of other cleaning chemicals.

14. SOLVENTS
When the word “solvent” is mentioned, most people immediately think of petroleum solvents like paraffin and white spirit or chlorinated solvents like methylene chloride and trichloroethylene. However, a solvent is simply a liquid that dissolves another substance.
Using this general definition it become obvious that water is the most common solvent used in cleaning, although it is usually excluded when “solvents” are mentioned.
 The range of solvents that are employed in cleaning processes is extensive. Some of the many types include:
hydrocarbons
chlorinated solvents
natural oils
alcohols
ketones, esters, ethers, glycols and glycol ethers

15. SOIL TYPE
Identifying the soils to be removed is a major consideration in selecting an appropriate detergent formulation for a cleaning application.
Most soils tend to be combinations of different soil types and compromises are often required in selecting an “optimum” formulation, based on:
relative levels of soil types present
the type of surface being cleaned and method of cleaning to be used.

16. WATER HARDNESS
A detergent formulation to be used in hard water areas will require higher levels of sequestrants than a similar detergent for use in soft waters.
These higher levels are necessary to handle the higher levels of:
calcium
magnesium present in the water.
 Water hardness salts become less soluble as the alkalinity level increases and start to precipitate at pH greater than 7.6, unless appropriate sequestrants are present in solution to prevent this from occurring.
In multi-stage cleaning processes this can present problems:
carryover of alkalinity into the rinse water will rapidly increase the pH above this threshold
whilst there will be insufficient sequestrant carryover to maintain the water hardness salts in solution
resulting in scaling problems in the rinse area.