Guides

What are semi-synthetic fabrics?

Fibers made from plants, but dissolved in chemicals and spun again. Not natural, not plastic: in between.

1. Made from plants, rebuilt in a factory

Semi-synthetic fibers start as cellulose, the stuff plant cell walls are made of, usually from wood pulp. The pulp is dissolved with chemicals and pushed through tiny holes to form brand-new fibers. The plant is the raw material, but the fiber itself is made in a factory, which is why US labeling rules treat them as manufactured fibers with their own names, not as plant fibers like cotton or linen.¹

That puts them between the two other kinds of fiber TruTag shows:

• 🌿 Natural: grown and spun as they are, like cotton, linen, wool and silk.
• 🧪 Semi-synthetic: plant cellulose, chemically processed into new fibers.
• 🏭 Synthetic: made from oil, like polyester, nylon and acrylic.

2. The names you'll see on labels

• Rayon, also called viscose: the most common one, usually from wood pulp. Soft and drapey, and it wrinkles easily.
• Bamboo: almost always rayon made from bamboo pulp, which the FTC says should be labeled "rayon made from bamboo."² More on bamboo.
• Modal: a stronger, softer kind of rayon, often made from beech wood. Common in t-shirts and underwear.
• Lyocell (often sold as Tencel): a kind of rayon that US rules define as its own subcategory.¹ It's made with a different solvent, recovered and reused in a closed loop.³
• Cupro: silky, made from the short fuzz left on cotton seeds.
• Acetate: shiny, made from wood pulp, used mostly for linings and dressy fabrics.¹

3. How they feel and wear

Semi-synthetics are usually soft, smooth and breathable, and they drape nicely, which is why they're everywhere in dresses, tees and loungewear. The trade-offs: rayon and viscose are weaker when wet, can shrink or lose their shape in the wash, and wrinkle more than cotton. Modal and lyocell hold up better than ordinary rayon.

4. The catch: the chemicals

Ordinary rayon and viscose are made with carbon disulfide. The FTC notes that rayon is typically made "using environmentally toxic chemicals in a process that emits hazardous pollutants,"² and the CDC lists carbon disulfide as a workplace hazard that affects the nervous system and heart, among other organs.⁴ Lyocell is the cleaner exception: its solvent is recovered and reused instead of released.³

5. Better or worse than polyester?

It depends on what matters to you. Semi-synthetics are cellulose, not plastic, so they can break down where polyester can't. But they aren't natural either, and making ordinary rayon is hard on workers and the places it's made. Lyocell is generally the best of the group.

How TruTag handles them

TruTag labels all of these 🧪 semi-synthetic. The Natural fibers filter leaves them out; No synthetics lets them in while still keeping out polyester, nylon and acrylic. In the TruTag app you can also make your own filter that allows just the ones you're happy with, like lyocell and modal but not rayon. More label terms: Decoding clothing labels.