A fabric softener (American English) or fabric conditioner (British English) is a
conditioner that is applied to
laundry during the rinse cycle in a
washing machine
A washing machine (laundry machine, clothes washer, washer, or simply wash) is a home appliance used to wash laundry. The term is mostly applied to machines that use water as opposed to dry cleaning (which uses alternative cleaning fluids and ...
to reduce harshness in clothes that are dried in air after machine washing. In contrast to
laundry detergent
Laundry detergent is a type of detergent (cleaning agent) used for cleaning dirty laundry (clothes). Laundry detergent is manufactured in powder (washing powder) and liquid form.
While powdered and liquid detergents hold roughly equal share o ...
s, fabric softeners may be regarded as a kind of after-treatment laundry aid.
[
A wrinkle releaser is a similar, more dilute preparation meant to be sprayed onto fabric directly.
]
Mechanism of action
Machine washing puts great mechanical stress on textiles, particularly natural fibers such as cotton and wool. The fibers at the fabric surface are squashed and frayed, and this condition hardens while drying the laundry in air, giving the laundry a harsh feel. Adding a liquid fabric softener to the final rinse (rinse-cycle softener) results in laundry that feels softer.
In the US and UK laundry is mostly dried in mechanical dryers, and the tumbling of the laundry in the dryer has its own softening effect. Therefore, fabric softeners in the US and UK are used rather to impart antistatic properties and a pleasant smell to the laundry. Fabric softeners are usually either in the form of a liquid, which is added to the washing machine during the rinse cycle (either by the machine itself or through use of a dispensing ball); or as a dryer sheet which is added to the moist laundry at the beginning of the dryer cycle. Liquid fabric softeners can be added manually during the rinse cycle or automatically if the machine has a dispenser designed for this purpose. Liquid fabric softeners may also be poured onto a piece of laundry to be dried, such as a wash cloth, and it will be distributed as the laundry is tumbled.
Fabric softeners coat the surface of a fabric with chemical compounds that are electrically charged, causing threads to "stand up" from the surface and thereby imparting a softer and fluffier texture. Cationic
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
softeners bind by electrostatic attraction to the negatively charged groups on the surface of the fibers and neutralize their charge. The long aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, ...
chains then line up towards the outside of the fiber, imparting lubricity
Lubricity is the measure of the reduction in friction and/or wear by a lubricant. The study of lubrication and wear mechanisms is called tribology.
Measurement of lubricity
The lubricity of a substance is not a material property, and cannot be me ...
.
Fabric softeners impart antistatic properties to fabrics, and thus prevent the build-up of electrostatic charges on synthetic fibers, which in turn eliminates fabric cling during handling and wearing, crackling noises, and dust attraction. Also, fabric softeners make fabrics easier to iron and help reduce wrinkles in garments. In addition, they reduce drying times so that energy is saved when softened laundry is tumble-dried. Additionally, they can also impart a pleasant fragrance to the laundry.[
]
Fabric softeners
Early cotton softeners were typically based on a water emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...
of soap
Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...
and olive oil, corn oil, or tallow
Tallow is a rendered form of beef or mutton fat, primarily made up of triglycerides.
In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, includ ...
oil. Softening compounds differ in affinity to various fabrics. Some work better on cellulose
Cellulose is an organic compound with the formula , a polysaccharide consisting of a linear chain of several hundred to many thousands of β(1→4) linked D-glucose units. Cellulose is an important structural component of the primary cell w ...
-based fibers (i.e., cotton), others have higher affinity to hydrophobic materials like nylon
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from pe ...
, polyethylene terephthalate, polyacrylonitrile
Polyacrylonitrile (PAN), also known as polyvinyl cyanide and Creslan 61, is a synthetic, semicrystalline organic polymer resin, with the linear formula (C3H3N)n. Though it is thermoplastic, it does not melt under normal conditions. It degrades bef ...
, etc. New silicone-based compounds, such as polydimethylsiloxane
Polydimethylsiloxane (PDMS), also known as dimethylpolysiloxane or dimethicone, belongs to a group of polymeric organosilicon compounds that are commonly referred to as silicones. PDMS is the most widely used silicon-based organic polymer, as its ...
, work by lubricating the fibers. Manufacturers use derivatives with amine- or amide-containing functional groups as well. These groups improve the softener's binding to fabrics.
As softeners are often hydrophobic, they commonly occur in the form of an emulsion
An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Altho ...
. In the early formulations, manufactures used soap
Soap is a salt of a fatty acid used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing, bathing, and other types of housekeeping. In industrial settings, soaps are use ...
s as emulsifiers. The emulsions are usually opaque, milky fluids. However, there are also microemulsion Microemulsions are clear, thermodynamically stable isotropic liquid mixtures of oil, water and surfactant, frequently in combination with a cosurfactant. The aqueous phase may contain salt(s) and/or other ingredients, and the "oil" may actually be ...
s, where the droplets of the hydrophobic phase are substantially smaller. Microemulsions provide the advantage of increased ability of smaller particles to penetrate into the fibers. Manufacturers often use a mixture of cationic and non-ionic surfactants as an emulsifier. Another approach is a polymeric network, an emulsion polymer.
In addition to fabric softening chemicals, fabric softeners may include acids or bases to maintain optimal pH for absorption, silicone-based anti-foaming agents, emulsion stabilizers, fragrances, and colors.
Cationic fabric softeners
Rinse-cycle softeners usually contain cationic surfactant
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
s of the quaternary ammonium
In chemistry, quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group. Unlike the ammonium ion () and the primary, secondary, or tertiary ammonium cations ...
type as the main active ingredient. Cationic surfactants adhere well to natural fibers (wool, cotton), but less so to synthetic fibers. Cationic softeners are incompatible with anionic surfactant
Surfactants are chemical compounds that decrease the surface tension between two liquids, between a gas and a liquid, or interfacial tension between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming ...
s in detergents because they combine with them to form a solid precipitate. This requires that the softener be added in the rinse cycle. Fabric softener reduces the absorbency of textiles, which adversely affects the function of towels and microfiber cloth
Microfiber (or microfibre) is synthetic fiber finer than one denier or decitex/thread, having a diameter of less than ten micrometers. A strand of silk is about one denier and about a fifth of the diameter of a human hair.
The most common ty ...
.
Formerly, the active material of most softeners in Europe, the United States, and Japan, was distearyldimethylammonium chloride
Dimethyldioctadecylammonium chloride also commonly distearyl dimethyl ammonium chloride is an organic compound classified as quaternary ammonium salt. The nitrogen center substituted with two methyl groups and two stearyl groups. The combinatio ...
(DSDMAC
Dimethyldioctadecylammonium chloride also commonly distearyl dimethyl ammonium chloride is an organic compound classified as quaternary ammonium salt. The nitrogen center substituted with two methyl groups and two stearyl groups. The combinatio ...
) or related quat salts. Due to their poor biodegradability
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
, such tallow-derived compounds were replaced by the more labile ester-quats in the 1980s and 1990s.
Conventional softeners, which contain 4–6% active material, have been partially replaced in many countries by softener concentrates having some 12–30 % active material.
File:AltDiesterquatCl.png, Diethyl ester dimethyl ammonium chloride (DEEDMAC)
File:Redrawn diesterquat salt (methanesulfonate anion) related to fabric softeners.png, TEAQ (triethanolamine quat)
File:DiesterCl.png, HEQ (Hamburg esterquat)
File:C18x2Me2Cl.png, Distearyldimethylammonium chloride
Dimethyldioctadecylammonium chloride also commonly distearyl dimethyl ammonium chloride is an organic compound classified as quaternary ammonium salt. The nitrogen center substituted with two methyl groups and two stearyl groups. The combinatio ...
(DSDMAC)
Anionic fabric softeners
Anionic softeners and antistatic agent
An antistatic agent is a compound used for treatment of materials or their surfaces in order to reduce or eliminate buildup of static electricity. Static charge may be generated by the triboelectric effect or by a non-contact process using a high ...
s can be, for example, salts of monoesters and diesters of phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
and the fatty alcohols. These are often used together with the conventional cationic softeners. Cationic softeners are incompatible with anionic surfactants in detergents because they combine with them to form a solid precipitate. This requires that they be added in the rinse cycle. Anionic softeners can combine with anionic surfactants directly. Other anionic softeners can be based on smectite
A smectite (from ancient Greek ''σμηκτός'' smektos 'lubricated'; ''σμηκτρίς'' smektris 'walker's earth', 'fuller's earth'; rubbing earth; earth that has the property of cleaning) is a mineral mixtures of various swelling sheet sil ...
clays. Some compounds, such as ethoxylated phosphate esters, have softening, anti-static, and surfactant properties.
Risks
As with soaps and detergents, fabric softeners may cause irritant dermatitis. Manufacturers produce some fabric softeners without dyes and perfume
Perfume (, ; french: parfum) is a mixture of fragrant essential oils or aroma compounds (fragrances), fixatives and solvents, usually in liquid form, used to give the human body, animals, food, objects, and living-spaces an agreeable scent. Th ...
s to reduce the risk of skin irritation. Fabric softener overuse may make clothes more flammable, due to the fat-based nature of most softeners. Some deaths have been attributed to this phenomenon, and fabric softener makers recommend not using them on clothes labeled as flame-resistant.
Additional reading
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References
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