Azlon / protein fiber

Overview

Manufactured fiber formed from regenerated protein, historically including casein, soy and other sources.

Feel and behavior

Variable; often intended to resemble soft animal fibers.

Where you find it

Historical textiles, specialty yarn and experimental blends.

Source and geography

Azlon covers manufactured fibers spun from proteins recovered from other products. Historic feedstocks included casein precipitated from skimmed milk, peanut protein, corn zein and soybean protein, and regenerated protein fibers were also made from poultry feathers. The feedstock was usually a byproduct of dairy, oilseed or grain processing. Modern soybean protein fiber is commonly a blend of soy protein residue from oil extraction with polyvinyl alcohol (PVA), and in many products PVA is the predominant component.

Worth knowing

• A review of soybean protein fiber reports that commercial SPF can contain as little as about 5 percent soy protein, with the rest polyvinyl alcohol.
• Qmilch, founded in Germany in 2011, uses casein from milk that is no longer fit for sale, reviving an idea first commercialized in the 1930s.

Types, grades and fabrics

Types and grades

Azlon today covers two quite different kinds of product. Historic azlons such as Lanital and Aralac were mostly regenerated casein or other proteins hardened by cross-linking. Modern soybean protein fiber (SPF) is a bicomponent fiber in which soy protein is combined with polyvinyl alcohol (PVA); a technical review of SPF reports compositions of about 5 to 23 percent soy protein and 77 to 95 percent PVA, stabilized by acetalization. Modern milk fibers vary: some trade descriptions combine casein with an acrylic polymer, while the German company Qmilch, founded by Anke Domaske in 2011, says its fiber is made largely of casein from surplus milk. Because proportions vary so widely, the protein content, not the name 'milk' or 'soy', defines what the buyer is getting.

Fabrics and products

Soybean protein fiber is spun into soft yarns for T-shirts, underwear, baby clothes, scarves and knitting yarns, often blended with cotton, wool, silk or bamboo viscose. Milk fiber appears in knitting yarns, underwear and socks, usually blended with cotton or other fibers. Historically, casein azlons were blended with wool in suitings, hats and felts during periods of wool shortage. Most modern azlon-type yarns are staple fibers in ring-spun blends rather than filament fabrics, and they are marketed for their soft, silky hand and sheen.

Buying and care

How to judge quality

Read the fiber content: under US and EU rules, a yarn that is mostly PVA or acrylic should list that polymer by its generic name. If a 'soy silk' or 'milk' yarn is labeled only with a descriptive name, ask the seller for the percentage of protein and carrier polymer. Good soy yarn has an even sheen, low fuzz and no weak spots when you tug gently. Expect some pilling in soft blends. Very low prices with vague 'natural protein' claims are red flags. Qmilch and similar producer claims about chemical-free processing should be read as marketing until independent data are available.

Care in detail

Follow the label, since blends vary. Many soy and milk blend yarns can be hand washed or machine washed on a gentle cycle in cool to lukewarm water with a mild detergent, ideally one suited to wool or delicates. Avoid bleach and strong alkaline detergents, which can damage protein components. Do not wring; press out water with a towel and dry flat away from direct heat. Iron on a low to medium setting on the reverse if needed. Store clean and dry, and check for moths in blends with wool, since protein fibers can attract clothes moths.

Care at a glance

Follow the complete product’s care label. Blends, dyes, finishes and construction can change suitable washing, drying and storage.

Environmental and social footprint

Azlon's environmental case rests on using byproducts: soy protein residue from oil extraction and casein from surplus or waste milk. However, when PVA makes up most of a soybean protein fiber, as reported in the technical literature, the product's footprint and end of life depend largely on that synthetic carrier, including the energy and chemicals used to make PVA and the acetalization step, which traditionally uses formaldehyde. Casein fibers use milk that has already consumed feed, land and water, so their footprint depends on how allocation is handled in any life cycle study. Independent life cycle assessments for current soy and milk fibers are scarce, so claims of 'natural' or 'eco-friendly' status should be checked against content and producer data.

Tradeoffs

Origin, processing inputs, labor, product construction and useful lifetime all need specific evidence. The name alone does not establish responsible production.

A useful question to ask: What exact material, product form and documented producer stand behind this name?

Science

Reformed protein material

A protein feedstock is processed and formed into a manufactured fiber.

Structure and chemistry

Proteins are polyamides built from amino acids joined by peptide bonds, but in azlon the native folded structure is destroyed during extraction and dissolution. The protein is denatured, dissolved (usually in alkali), extruded and then chemically hardened, or cross-linked, so the filament does not swell and disintegrate in water. The resulting fibers are largely amorphous and poorly oriented compared with wool or silk. Research on soybean protein and PVA blend fibers found that fibers with less than about 40 percent PVA were unoriented and amorphous, while higher PVA contents showed the crystalline structure of PVA.

From source to yarn

The protein is separated from its source, for example by acid precipitation of casein from skimmed milk, then purified, dried and dissolved in an alkaline solution to form a spinning dope. The dope is aged to a suitable viscosity and extruded through spinnerets into an acidic coagulating bath (wet spinning). Filaments are stretched to improve orientation and then hardened in a cross-linking treatment to reduce water sensitivity. They are washed, dried, crimped and usually cut to staple, because azlons were typically designed to be blended with wool or other fibers in woollen-type yarns.

Performance in use

Historic azlons were warm, soft and wool-like in handle, and they took acid and other wool dye classes because they carry amino acid side groups. Their weaknesses were low tenacity, especially when wet, poor abrasion resistance and a tendency to lose shape during wet processing, which confined them largely to blends. As protein fibers they could be vulnerable to the same pests and alkali damage as animal fibers. Modern soy and milk fibers that contain PVA or other synthetic carriers behave according to that blend, so performance should be read from the specific product data.

How it is identified

Burn tests are indicative only: a largely protein azlon typically smolders, smells like burning hair or feathers and leaves a crushable ash, much like wool, so it is easily mistaken for wool. Microscopy separates them because azlon lacks scales. FTIR shows amide bands, and a synthetic carrier such as PVA can be detected by its own spectrum. Products sold as 'milk' or 'soy' fiber should be checked for the proportion of protein versus carrier polymer.

History

Timeline

1. 1935Antonio Ferretti received an Italian patent for a casein fiber. [1]
2. 1936SNIA Viscosa began marketing Ferretti's casein fiber as Lanital. [1]
3. 1941Henry Ford was photographed on his 78th birthday in a suit containing soybean protein fiber developed at Ford. [2]
4. 2011Qmilch was founded in Germany to make fiber largely from casein recovered from milk unfit for sale. [3]

Protein-based artificial fibers were explored in the twentieth century, including during periods of raw-material constraint. A modern milk- or soy-named yarn may contain other polymers or fibers.

The deeper record

Italian chemist Antonio Ferretti developed a workable casein fiber and received an Italian patent in 1935. SNIA Viscosa marketed it from 1936 as Lanital, from lana (wool) and Italia, as part of Fascist Italy's drive for autarky, or self-sufficiency, in textile raw materials. Similar fibers followed: Aralac (casein, United States), Ardil (peanut, England), Fibrolane (Courtaulds, England), Merinova (Italy), Chinon (Toyobo, Japan) and Vicara, a corn zein fiber from the Virginia-Carolina Chemical Corporation. At Ford Motor Company, chemist Robert Boyer developed soybean fiber, and Henry Ford was photographed in a suit containing it on his 78th birthday, 30 July 1941. Competition from stronger synthetic fibers after the war contributed to the decline of commercial azlon production.

Labeling and law

In the United States, 16 CFR 303.7 defines azlon as a manufactured fiber whose fiber-forming substance is composed of any regenerated naturally occurring proteins. Regulation (EU) No 1007/2011 includes a separate 'protein' fibre name. Because modern soy and milk yarns often contain PVA or other polymers, labels must disclose fiber content by generic names, and descriptive words such as milk or soy do not substitute for that disclosure.

This describes what rules and standards cover. It is not legal advice; jurisdiction, product form and current rule text control.

Frequently asked

Is soy fabric made only from soybeans?

Usually not. Technical studies of soybean protein fiber report that polyvinyl alcohol makes up the majority, often around 77 to 95 percent, with soy protein as the minor component. Check the label or ask the seller for the protein content.

What is milk fiber?

Milk fiber is a regenerated protein fiber based on casein. Some modern milk yarns combine casein with acrylic polymers, while companies such as Qmilch describe fibers made largely of casein from surplus milk. Content varies, so the fiber label matters.

Is azlon still made?

The US generic name azlon remains in the FTC rules, but large-scale production of pure regenerated protein fibers largely ended after synthetic fibers took over. Today, soy and milk fibers are niche products, often blended with synthetic polymers.

Are soy and milk yarns vegan?

Soy fiber contains plant protein and PVA, so it is animal free unless blended with wool or silk. Milk fiber contains casein from cow's milk, so it is an animal-derived product even though it is not wool or silk.

Sources

• Museum of Fine Arts, Boston: Manufactured-fiber reference
• eCFR: 16 CFR 303.7, Generic names and definitions for manufactured fibers
• MFA Boston CAMEO: Azlon fiber
• MFA Boston CAMEO: Lanital
• The Henry Ford: Henry Ford wearing soybean suit on his 78th birthday
• Wiley, Textile Fiber Microscopy: Regenerated Cellulosic and Protein Fibers
• Rijavec and Zupin, InTech: Soybean protein fibres (SPF)
• Fibers (MDPI): Development of eco-friendly soy protein fiber, a comprehensive critical review and prospects
• Biooekonomie.de: Milking it, textiles made from casein (interview)

Cite this page

Chaos. (2026). Azlon / protein fiber. In Fibers of Earth: An independent textile atlas. https://www.hendrickresearch.com/fibers/materials/azlon/