Why brands are asking for fluorine-free repellents
Water-repellent finishes were based on fluorocarbon chemistry for decades: C8 resins first, then C6. That is ending. PFAS restrictions keep expanding in Europe and the United States, and most international brands already include perfluorinated compounds (PFC) in their restricted substances lists (RSL). A mill that produces for export has to comply with those lists, so what customers are asking for now is a C0 repellent: fluorine-free chemistry, generally based on paraffins, silicones or hydrocarbon-functional polymers.
The problem showed up quickly: many C0 repellents give a good initial effect but lose it after a few washes.
Why many C0 repellents do not survive laundering
A repellent finish covers the fiber with a layer of low surface energy, so water forms drops that roll off instead of wetting the fabric. Fluorocarbons did this very well and held up reasonably well to laundering.
With fluorine-free chemistry, the initial spray rating is usually not the issue. The weak point is anchorage: if the polymer only sits on the fiber surface, the surfactants, alkalinity and mechanical action of each wash cycle remove part of it. After five or ten domestic washes the fabric wets out again.
For the effect to last, the polymer has to bond to the fiber during curing. Three things decide it:
- The polymer. Cationic emulsions have affinity for the fiber surface, which is negatively charged. They deposit evenly and crosslink during curing into a continuous film instead of a loose deposit.
- The curing. The repellent barrier forms on the stenter. If curing temperature or time falls short, part of the reactive groups never react and durability is lost. Typical conditions are drying at 110 °C and curing at 170 °C.
- The crosslinker. For specifications of 20 or 30 washes, a crosslinker (booster) increases the bonds between polymer and fiber. Ask the supplier which system they recommend for their product.
Water repellency, not oil repellency
One thing needs to be said clearly: fluorine also gave oil repellency, and no C0 chemistry replaces that completely. A fluorine-free repellent protects against water, rain, splashes and aqueous soiling, not against oils and greases. For the end uses affected by PFAS restrictions (outerwear, uniforms, textile footwear, tents and awnings, linings, technical fabrics), water protection is what is being asked for. If a specification requires oil repellency, that has to be discussed before the trial, not after.
Application recommendations
A C0 repellent of this type is applied by padding, in the usual impregnation, drying and curing sequence. In the mill, these points decide the result:
- Pretreatment. The fabric must be well scoured and free of surfactant residues. Residual wetting agents are hydrophilic and work against the repellent.
- Bath preparation. Adjust to pH 5 to 7 with acetic acid before adding the product, and prepare with as little turbulence as possible. Cationic emulsions form coagula under strong agitation, and coagula end up as spots on the fabric.
- Dosage. As a reference for our product: 30 to 50 g/L on polyester and 80 to 100 g/L on cotton, with 50 to 70% wet pick-up. Cotton needs more product because its surface is hydrophilic.
- Compatibility. It can be combined with cationic and nonionic auxiliaries; with anything else, run a compatibility test in the lab first. It can also share the bath with antistatic agents, which is useful in linings and technical fabrics.
- Evaluation. Water repellency is measured with the AATCC 22 spray test (ISO 4920 is equivalent). Measure after curing and measure again after laundering; the initial rating alone says little about how long the effect lasts.
What we measured in our laboratory
We developed Casdishield DFF, a cationic polymer repellent free of perfluorinated compounds, for this requirement. In our applications laboratory we treated fabric with it, put it through 30 domestic wash cycles and repeated the spray test: the water still beads and rolls off, and the fabric stays dry. We ran the trial on polyester, nylon taffeta, nylon taslan and cotton, and recorded it on video. The video is available on request.
More information on our water repellent page and on the Casdishield DFF product page. To request the video, a sample or a recipe recommendation for your substrate, contact our technical team.