Be thankful for the presence of chemistry as it is here to help us remove our stains. Many different molecules are present in stain removers and detergents to help remove grease and dirt, and they have different functions.
Stains can be grouped into several groups: enzymatic, oxidisable, greasy, and particulate. In reality, a stain will have a few components, which may fall into more than one of these categories. As such, stain removers have multi-functions (a mixture of all of the agents), to remove these multi-component stains.
Enzymatic stains are mostly made up of proteins, which includes blood stains and human sweat. Enzymes present in stain remover can be used to break down the protein. Proteases will break down proteins by breaking down the larger molecules into smaller, soluble molecules. Other molecules (fats and starch) that can be broken down by enzymes (lipase and amylase).
Brightly coloured stains is in the oxidisable stain category. These include stains like tea and coffee, as well as red wine. Stain removers contain bleaching agents, most often hydrogen peroxide, which breaks down colour-causing sections of chemical structures, removing the appearance of the stain. The hydrogen peroxide(gas) is usually in the form of sodium percarbonate(solid), which releases hydrogen peroxide when dissolved in water.
However, hydrogen peroxide does not function well at removing stains below 40˚C. It is not an issue if one is washing at or above that temperature, but if you’re washing below, or just wanting to use your stain remover on carpet or furnishings, the hydrogen peroxide needs to get some extra help- an addition of tetraacetylethylenediamine(TAED). TAED reacts with hydrogen peroxide to produce peracetic acid, which makes it a stronger bleaching agent as compared to hydrogen peroxide.
Oils and grease can be broken down by lipase enzymes but they are primarily removed by the use of surfactants. These are commonly long carbon chain compounds with a charged water-soluble ‘head’ and an oil-soluble ‘tail’. Generally, they are either named ‘cationic surfactants’, ‘anionic surfactants’, or ‘nonionic surfactants’ on the stain remover bottle. It refers to the charge on the molecule’s ‘head’. A cationic surfactant has a positive charge, an anionic surfactant a negative charge, while a nonionic surfactant is electrically neutral.
These surfactants remove oil and grease by forming structures called ‘micelles’ around them. The oil-soluble parts of the molecule dissolve in the oil or grease, forming a spherical structure around the oil droplet. The water-soluble parts of the surfactant molecule then stick outwards, which means that that the micelles will be able to dissolve in water, allowing the greasy stain to be removed.
Last but not least, we have particulate stains. There are compounds in the stain remover which are also known as ‘Builders’. These compounds primarily help to soften the water during washes by removing positive metal ions (mainly calcium and magnesium ions) from the water. It is also useful in removing soil stains from clothes, as these stains are often bound to fabrics by calcium ion bridging. Removing the calcium ions therefore helps remove the dirt.
Washing detergents is commonly uses sodium triphosphate as a builder, but due to concerns about its excessive release into the environment, many companies have now swapped it with other agents, such as sodium carbonate or zeolites. Zeolites are crystalline aluminium silicates, inorganic structures that is ready to bond with calcium and magnesium ions. They also possess a number of advantages over other builders, such as inhibiting dye transfer during washes. Generally, builders help improve the cleaning action of other chemicals in the detergent, by preventing cations combining with other charged molecules, such as surfactants. They can also help prevent the redeposition of dirt onto fabrics once it has been removed.