\which of this is relevant to the above average carpet cleaning tech.
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So tell me Ron, which of this is relevant to the above average carpet cleaning tech.
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2.3 Chemical Process of Cleaning
Cleaning carpet involves both physical and chemical processes. The cleaning technician must understand both to remove the most soil without damaging the carpet. The relative balance depends on the method used. The chemistry of carpet cleaning is based on:
Physical reactions involve a change that removes soil or makes a soil easier to remove but does not create any new substance. Physical changes include:
change of state: an example would be a solid becoming a liquid;
dissolving: soluble soils are dissolved, using wet or dry solvents. Soils are then extracted;
suspension/emulsification action: surfactants are used to break down and suspend soils. Soils are then extracted;
encapsulation: encapsulation detergents are used to dissolve soluble soils, emulsify oily soils, or suspend insoluble soils. They then form films that hold soils in suspension until they can be removed.
chemical reaction: a reaction changes the soil or staining agent into another substance. Extraction may be used to remove this new substance or it may be left in place if it is volatile and will evaporate or is innocuous (e.g, using a volatile oxidizer such as hydrogen peroxide, on food dyes), and
2.3.1 Chemical Reactions
Common chemical reactions that occur during cleaning are ionization, reduction/oxidation, and biological.
2.3.1.1 Ionization is the process by which a substance acquires a charge by gaining or losing electrons or protons. Thus, ionic substances have an unequal number of protons and electrons. This creates a propensity for a reaction to occur and a new substance to be created. Within many substances, including water, individual molecules may be gaining or losing electrons or protons.
Substances which are proton donors (tend to give up protons) are said to be acids. The pH scale is a measurment of a substances potential to be acidic. There is also a pOH sclae which measures a substance’s potential alkalinity.
Under standard conditions of temperature and pressure, the number of available electrons and protons in pure water is equal. Both pH and pOH would be 7 or neutral. pH does vary with temperature and pressure. The pH scale ranging from 0 to 14 with 7 as neutral is useful when measuring pH values of carpet fibers or cleaning solutions.
Adding pH and pOH will total 14. Thus knowing pH allows one to also know pOH. Rather than measure both pH and pOH, it is common in the cleaning industry to measure only pH.
Electronic pH meters compensate for variations in temperature and adjust readings to a normalized neutral of 7. The pH read from the fiber using a meter can be very useful for understanding the condition of carpets as well as for spot and stain removal.
Cleaning technicians must understand that pH only partially describes the likelihood and strength of a chemical reaction. The make-up of the ions involved, the presence or absence of buffering agents which stabilize pH and other factors also govern. Therefore, knowing only the pH of a cleaning product is insufficient to know its compatible with a fiber being cleaned.
- Reduction/oxidation (or Redox) is a process where one substance loses electrons (oxidation) and another gains those electrons (reduction) forming new substances. This often, but always, is the result of oxygen moving from a molecule of one substance to another. Oxidation and reduction happen together. One substance is oxidized when another is reduced.
A substance that removes oxygen from another substance, it is referred to as a reducer. When a substance adds oxygen to another substance, it is referred to as an oxidizer. In cleaning, oxidizers and reducers are called bleaches. Bleaches may whiten, brighten or remove color. Some bleaches kill microorganisms and thus eliminate or reduce some odors.
Bleaches are common ingredients in dye-stain removers. Milder types can be additives to detergents.
Oxidizers gain strength from absorbing UV light. Reactions may gain strength from heat.
Fading due to ozone or fumes are examples of redox reactions.
- Biological reactions are actions of bacteria and enzymes. Enzymes are biological proteins that act as catalysts to greatly speed up chemical reactions involving organic materials. They speed up digestion and decomposition of things like animal waste. Enzymes are not consumed in the process of breaking down substrates. Enzymes used in cleaning may be produced by bacteria or in laboratories. They work best within a limited range of temperature and pH. Their activity can be inhibited by the presence of some solvents.
Enzymes are specific on which substrates (the materials they break down) they operate.
The types of enzymes used to clean carpet are commonly referred to as digestive enzymes and include:
- Amylase which breaks down starch into sugars which are water soluble.
- Protease enzymes break down proteins into amino acids.
- Lipase enzymes break down lipids (fats and oils) into fatty acids and glycerol.
2.3.2 Physical Changes
Although soils can be dissolved, suspended, or encapsulated by various means, many physical changes are accomplished with the aid of surfactants.
2.3.2.1 Surfactants
Technicians should be aware of why surfactants are used and the possible consequences of over-use or failing to thoroughly remove them. Surfactants are used in many cleaning products. Certain residues left behind after cleaning can cause the carpet to resoil more readily. This is because surfactant residue is often sticky which can attract and bind soil.
There are four types of surfactants available to today’s formulation chemist:
nonionic surfactants: carry no charge and are the most effective for cleaning purposes, particularly where oily soils are present. They are the most widely used surfactants in our industry;
cationic surfactants: carry a positive charge and have limited effectiveness in cleaning. Cationic surfactants are commonly used as antimicrobials, disinfectants, sanitizers, and antistats;
anionic surfactants: carry a negative charge on the main body of the molecule, and are the most effective type of surfactant with respect to cleaning efficacy where particle soils need to be separated from fibers and suspended in water. Most anionic surfactants foam readily and therefore are used in shampoo or foam cleaning solutions, and
amphoteric surfactants: both anionic in basic solutions and cationic in acid solutions, thereby combining detergent and disinfectant properties. The current percentage of use is relatively small, but they are mild surfactants, so their usage may see an increase in coming years.
Surfactant molecules normally are dispersed in water for use. Surfactants are normally not soluble in water and thus form micelles. When diluted and applied to a soiled surface, surfactant micelles surround or engulf soils and carry them into the water, away from a fiber surface, thereby cleaning the surface (see figure 1). Some soil is hydrophilic or soluble, and is easily dispersed into water. For oily soils, non-ionic surfactants are most effective. The surfactant forms the micelle around the soil particle with its charged hydrophilic or water-loving sodium (Na) end out in the water, and the oil loving end nearest the soil particle (see figures 2 and 3).
View attachment 94606
Alkaline surfactants (i.e., pH is above 7) are most often chosen to remove soil. However, if the pH of the surfactant is too high, the stain-resistant treatment on nylon carpet fibers could be removed or the dyes on natural fibers, such as wool or silk, can be adversely affected so as to cause dye bleeding.
Surfactants are typically used in cleaning products. Certain residue left behind after cleaning can cause the carpet to resoil more readily. This is because sticky surfactant residue can attract and bind soil. Surfactants decrease the surface energy of water, thereby making the carpet more easily wet and stained. If, by design, the process or cleaning system leaves a significant surfactant residue to dry upon the fiber, specialty types of surfactants that are either less prone to attract soil or are easily removed from the fibers by dry vacuuming are often utilized.
2.3.2.2 pH Effects
Cleaners should select and use cleaning chemicals with acidity or alkalinity characteristics consistent with available textile manufacturer’s compatibility recommendations.
The acidity or alkalinity of soiled textile fibers and the chemistry employed in cleaning reveal two primary, and sometimes conflicting, concerns. First, is the potential reliance of certain acidity or alkalinity quantities to provide both economical and effective cleaning reactivity. Second, is the reactivity of this same chemistry on the state of the fiber, dyes, or stain protection, which may be adversely affected by the reactivity of the acid or alkaline state.
Therefore, the same alkalinity, which is often employed to enhance cleaning, can be deleterious to fibers, dyes, or the applied stain protection.
pH can still be of value, as long as it is used in testing and evaluation of targets set by the textile manufacturer for cleaning chemistry limitations, and preferred end state. Although pH alone may not be useful in determining cause and effect, measurement of a soiled textile’s pH, when taken directly from a water-moistened fiber, provides data helpful for identifying spots or stains. Also, it may provide supporting data when the possibility exists for identifying a spill or determining the inappropriate previous use of a strongly basic or acidic product.
2.3.23 Detergent’s Effect on Soils
Cleaners should understand how various detrgents perform their function.
- saponification: the process of converting fat into soap by treating it with an alkali. Saponification rate is dependent not only on the temperature, but also the concentration of the caustic substance. A substantial part of oily and greasy soil is composed of saponifiable fats. These can react with the active alkalinity of the cleaning agent converting it to soap. The minimal amount of soap generated supplements the surfactant present and aids somewhat in soil removal;
- emulsification: whereas fatty soil obtained from animal or vegetable sources form soap with alkalis, paraffinic, or mineral oils, like motor oils, are not reactive to alkalis and cannot be saponified. However, they can be emulsified. Caustic soda and soda ash containing detergents can form reasonably good emulsions with motor oils, but they are difficult to rinse from the fiber. Silicates and phosphates not only make effective emulsions, but also are easily rinsed; therefore, they are the preferred agents, and
- buffering: the ability of the substance to stabilize pH (e.g., alkalinity or acidity) during the cleaning process. The ability of a detergent mixture to stabilize pH on the alkaline side is considered important not only for the purpose of saponification, but also for the sequestration of calcium ions, and to soften the water. However, a strongly buffered cleaning agent, which is alkaline, can have a significant detrimental effect on the colorfastness of nylon and wool fibers and on stain-resist treatments. This has a pH dependence and deterioration effect increases at high pH levels.
