WATER FREE FINISHING TECHNOLOGY
The GTT Dry Finishing Technology consists of only 2 steps. At GTT, we design and sell the premixed chemical formulation designed for plasma or thermal curing.
STEP 1: Chemical Application
The ChemStik® formulation contains a complete finishing chemistry package: monomers, cross-linkers, adhesion agents, and optional additional attribute components, such as anti-microbial or UV-absorbing, plus the trigger required to start polymerization and permanently bond the polymer to your fabric when it is thermally cured. Plus, it is environmentally-safe, produces very little waste and is cost competitive with your current wet finishing process.
Liquid coating (water-free) of the roll goods, finished apparel or footwear is the first step. Three recommended application methods are shown below.
Spray Coating - Chemical coating of the fabric is easily done using commercial sprayers. This approach is inexpensive and provides reasonably good uniformity. Overspray causes some chemical loss. This approach is practical for widths as large as 2m or more. We use 5 spray heads for 1.8 m fabric width. Confinement of the spray zone is recommended.
Gravure Coating - Gravure coating provides a means for uniform application of a precise chemical coating. The liquid chemical is picked up by a rotating roller with a finely machined texture and the roller presses the chemical mixture into the fabric with variable pressure. Thus, the amount of depth penetration is variable, as is the applied chemical dosage. Gravure coating can be done on full width fabrics and on one or both sides at the same time.
Water-Free Padding - Padding is a third option. For this the fabric is immersed in the ChemStik formulation and then is squeezed between nip rollers and/or vacuumed out to reduce the chemical loading. Padding tends to put too much chemical into the fabric, so an efficient vacuum removal method is needed to lower the chemical loading.
STEP 2: Thermal Curing
After fabric or footwear coating, next the treated roll goods, fully-finished apparel or footwear, are thermally cured. Exposure to heat releases free radicals from the polymerization initiator that is added to the ChemStik formula, triggering the polymerization process. The crosslinkers also bond the polymer to the fabric through a free radical polymerization process.
One of the simplest approaches to polymerizing an applied chemical treatment (often called "curing") is done just by heating the fabric. For this. the ChemStik® treatment has a thermally-triggered polymerization initiator. The initiator decomposes at a set temperature, releasing free radicals, which initiate monomer and crosslinker polymerization.
Different ChemStik formulations are typically used for different finishing treatments, and, in some cases, for different fabrics. Only several seconds of heat treatment is needed to trigger polymerization.
At GTT, we will provide the chemical mixture, the hardware and a process recipe that includes how much thermal curing is required and what temperature is required for finishing treatment requirement. This makes the transition to dry finishing painless and inexpensive.
Thermal curing may be done at high pressure - at GTT, we have used up to 35 Bar (500 psi = 3.4 MPa) to pressurize coated roll goods or footwear before polymerization.
For this, the fabric or footwear is first coated, then it is placed into the pressure "Pod" where it is pressurized at room temperature. The pressure causes the chemical formulation to be squeezed into the twisted yarn, providing a highly uniform, thin coating of monomer + crosslinkers. Then, the Pressure Pod is heated, resulting in polymerization and crosslinking. The polymeric film retains its position inside the twisted yarn and fibers once cured and returned to atmospheric pressure.
For footwear, the pressure pushes the chemical into the sewn seams and deep within the shoe material. This provides a better water-proofing treatment and better abrasion resistance than be obtained by wet or dry means at atmospheric pressure.