Popular brand names include Lenor, Downy, Snuggle, Bounce and Comfort. Most newer washing machines have a dispenser to add liquid fabric softener to the load of laundry automatically on the final rinse; in launderettes it may need to be added manually. Some brands of washing powder have fabric conditioning built-in which is claimed to save money when compared to buying ordinary washing powder and fabric softener separately. There are some fabric softeners that besides softening clothes also claim to make ironing easier whereas some claim to make clothes dry faster. The use of fabric softener may however reduce the water absorption capabilities of the fabric, and is contraindicated in some articles like microfibre textiles. For best results, un-diluted liquid fabric softener should not be poured directly onto clothes.
In the form of dryer sheets, these are added to clothing in the tumble dryer to soften the fabrics and prevent static. Dryer sheets, or dryer anticling strips, can also be used to keep clothes smelling good while being stored. Many alternative uses of dryer sheets have been suggested by users, for example as posted in a Bounce website There may be other online sources for alternative uses.
Fabric softeners work by coating the surface of the cloth fibers with a thin layer of chemicals; these chemicals have lubricant properties and are electrically conductive, thus making the fibers feel smoother and preventing buildup of static electricity. Other functions are improvements of iron glide during ironing, increased resistance to stains, and reduction of wrinkling.
Cationic softeners bind by electrostatic attraction to the negatively charged groups on the surface of the fibers and neutralizing their charge; the long aliphatic chains are then oriented towards the outside of the fiber, imparting lubricity. Vinegar works on some materials in a similar way, as the hydrogen ions bind to the anionic groups on the fibers.
The disadvantage of coating fibers by hydrophobic layer is in decreasing the water absorption properties of the fabric, which may be an issue with towels and diapers. Therefore the cationic softeners are often combined with other chemicals with lower affinity to the fibers.
The earliest fabric softeners were developed during early 20th century to counteract the harsh feel which the drying methods imparted to cotton. The cotton softeners were typically based on water emulsion of soap and olive oil, corn oil, or tallow oil.
Contemporary fabric softeners tend to be based on quaternary ammonium salts with one or two long alkyl chains, a typical compound being dipalmitoylethyl hydroxyethylmonium methosulfate. Other cationic compounds can be derived from imidazolium, substituted amine salts, or quarternary alkoxy ammonium salts. One of the most common compounds of the early formulations was dihydrogenated tallow dimethyl ammonium chloride (DHTDMAC).
Anionic softeners and antistatic agents can be eg. salts of monoesters and diesters of phosphoric acid and the fatty alcohols; these are often used together with the conventional cationic softeners. Cationic softeners are incompatible with anionic surfactants presenting the bulk of surfactants used in detergents, with whose they form inefficient precipitate; therefore they can not be mixed with the detergent, but have to be added during the rinse cycle instead. Anionic softeners can be combined with anionic surfactants directly. Other anionic softeners can be based on smectite clays. Some compounds, eg. ethoxylated phosphate esters, have properties of both softening, anti-static, and surfactant.
The softening compounds differ in affinity to different materials. Some are better for cellulose-based fibers, others have higher affinity to hydrophobic materials like nylon, polyethylene terephthalate, polyacrylonitrile, etc.
Silicone based compounds, eg. polydimethylsiloxane, are one of the new softeners that work by lubricating the fibers. Silicone derivates are used as well, eg. modified to contain amine or amide groups; they bind better to the fabrics and have much improved feel. They have essentially the same role as oils had in the early formulations.
As the softeners themselves are often of hydrophobic nature, they are commonly occurring in the form of an emulsion. In the early formulations, soaps were used as emulsifiers. The emulsions are usually opaque, milky fluids. However there are also microemulsions where the droplets of the hydrophobic phase are substantially smaller; the advantage of microemulsions is in the increased ability of the smaller particles to penetrate into the fibers. A mixture of cationic and non-ionic surfactants is often used as an emulsifier. Another approach is using a polymeric network, an emulsion polymer.
Other compounds are included to provide additional functions; acids or bases for maintaining the optimal pH for adsorption to the fabric, electrolytes, carriers (usually water, sometimes water-alcohol mixture), and others, eg. silicone-based anti-foaming agents, emulsion stabilizers, fragrances, and colors. A relatively recent form on the market are the ultra-concentrates, where the amount of carriers and some other chemicals is substantially lower and much smaller volumes are used.
In recent years, the importance of delivering perfume onto the clothes has exceeded that of softening. The perfume levels in fabric softeners has gradually increased, requiring high shear mixing technology to be used to incorporate greater amounts of perfumes within the emulsions. Long term release of perfume on the fabric is a key technology now being utilised. Each country tends to have different perfume requirements and brands may have different softener/perfume ratio depending on the country.