Silicone heat transfer labels: layer build-up, cure and adhesion
Silicone labels and 3D logos are popular on sportswear and footwear because silicone stays flexible over a wide temperature range. The same chemistry makes them demanding to produce: each layer has to cure properly, and silicone does not bond easily to other materials.
What silicone brings to a label
Silicone rubber is flexible and resists extreme temperatures; reference figures give a range of about −55 to 300 °C. Silicone is used in apparel such as undergarments, sportswear and footwear.
For a heat transfer label this means the print can move with stretch fabric and survive the heat press. It does not mean every silicone label passes every wash test: the result still depends on the cure, the adhesive and the fabric.
Building height layer by layer
In screen printing one layer is printed at a time through a screen, and printed layers are allowed to dry between passes. Raised silicone marks are built the same way, pass by pass on the release carrier, until the agreed height is reached.
In its uncured state silicone rubber is a highly adhesive gel or liquid. Each layer therefore has to be cured far enough before the next one is printed, or the stack smears and stays tacky. Record the number of passes, the mesh and the cure between passes for every approved sample.
Cure and contamination
Silicone rubber can be cured by several systems, including platinum-catalysed, peroxide and condensation cures. For the platinum-catalysed system, heat or pressure can accelerate curing and the reaction has no byproducts, but it is easily inhibited by elemental tin, sulfur and many amine compounds.
Ask the ink supplier which cure system the silicone uses. If it is platinum-cured, keep inhibiting materials away from screens, squeegees, carriers and other inks on the line, and check a cure sample whenever a material in contact with the silicone changes.
Bonding the label to the fabric
Most materials do not adhere to silicone, and silicones do not have long-term adhesion to plastics. The layer that joins the silicone mark to the garment is therefore a separate design decision, not an afterthought.
Use the adhesive system recommended for the silicone ink, then press samples on the actual fabric and check peel, edge lift, stretch and wash results. Repeat the test when the fabric, silicone grade or adhesive changes.
Related process and equipment
- Agree the label height, hand feel and fabric before sampling.
- Confirm the silicone cure system and its inhibitors with the ink supplier.
- Record passes, mesh and cure between layers for each approved sample.
- Test the adhesive on the real fabric with peel, stretch and wash.
Silicone heat transfer labels and 3D logos · How heat transfer film is screen printed: layer order from release film to adhesive · Hot-melt powder or printed adhesive layer: choosing the glue for heat transfers · Wash testing heat transfer labels: ISO 6330, ISO 105-C06 and AATCC 61 · LC-6080SYJ-C roll-to-roll CCD screen printer
Frequently asked questions
Why does a printed silicone layer stay tacky?
Uncured silicone rubber is a sticky gel or liquid. A tacky layer usually means incomplete cure; with platinum-cured silicone, tin, sulfur or amine compounds can also inhibit the cure. Check cure settings and contact materials with the ink supplier.
Can any adhesive bond a silicone label to fabric?
No. Most materials do not adhere to silicone, so use the adhesive system specified for the silicone ink and confirm it with peel and wash tests on the production fabric.
Technical references
Related process and equipment
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