1.Substrate Preparation:
The target substrate surface must be clean, dry, and free from dust, oil, mold release agents, or any other contaminants that could interfere with adhesion. For non-porous substrates (e.g., plastics, coated metals), surface activation via corona, flame, or plasma treatment is recommended to increase surface energy and ensure optimal wetting and bonding. Porous substrates such as textiles should be pre-treated to minimize fiber raise and ensure a smooth transfer interface.
2.Coating Application and Drying:
The aqueous coating dispersion must be applied uniformly using a precision Meyer rod, gravure, or slot-die coater. The applied wet layer should be dried immediately in a forced-air oven at 60–80°C to remove water and prevent premature migration of coating components. Incomplete drying may result in poor ink acceptance or reduced release performance. The dried coating should form a continuous, defect-free film with a target coat weight of 5–8 g/m² for the ink-receptive layer and 0.8–1.2 g/m² for the release layer.
3.Printing and Curing:
Pigment-based inkjet inks should be applied using calibrated piezoelectric printheads. After printing, the ink must be fully cured using infrared or forced-air drying (100–120°C) to evaporate water and coalesce the ink film. Incomplete curing will lead to poor transfer efficiency and reduced wash fastness.
4.Transfer Process:
Heat and pressure must be applied uniformly using a calibrated heat press. Typical transfer conditions are 150–160°C, 0.3–0.5 MPa, and 8–12 seconds. The silicone-based release layer undergoes controlled cleavage under heat, allowing the entire printed film to cleanly separate from the PET carrier and adhere to the target substrate through the thermoplastic adhesive layer.
5.Post-Transfer Conditioning:
After transfer, the decorated substrate should be conditioned at room temperature for 2–4 hours to allow the adhesive layer to fully crystallize and develop ultimate adhesion and wash resistance. For textiles, a post-cure at 150°C for 1–2 minutes is recommended to further cross-link the adhesive and enhance durability.
Important Safety and Handling Precautions for PUR Hot Melt Adhesives
1.Aqueous Coating Sensitivity:
DTF coatings are water-based dispersions and are sensitive to freezing and microbial growth. Store in original sealed containers between 5-30°C. Freezing will cause irreversible coagulation of polymer particles and pigment settling, while prolonged high-temperature exposure may lead to premature hydrolysis or microbial degradation, reducing coating performance.
2.Drying and Thermal Management:
Dry applied coatings immediately using forced-air ovens at 60-80°C. Incomplete drying will result in poor film formation and reduced ink adhesion. Avoid exceeding 100°C during drying, as this may cause premature cross-linking in the release layer or degradation of absorbent polymers, compromising transfer performance.
3.Dust and Particulate Control:
Coatings contain nano/micro-scale pigments and polymers. During handling and powder recovery, use NIOSH-approved N95 masks to avoid inhalation of airborne particles. Ensure adequate local exhaust ventilation in coating and drying areas to maintain airborne particulate levels below OSHA PEL limits.
4.Skin and Eye Protection:
While cured coatings are inert, liquid coatings may contain surfactants and organic acids (pH 4-6). Wear chemical-resistant gloves and safety goggles when handling concentrated products. In case of contact, flush immediately with plenty of water for at least 15 minutes.
5.Equipment Cleaning and Maintenance:
Clean application equipment immediately after use with warm water (40-50°C) before coatings dry. Dried coating residues require specialized alkaline cleaners (pH 9-11) for removal. Never use strong solvents that may damage precision coating equipment or leave contaminating residues.
6.Substrate Compatibility Testing:
Always test coating adhesion and release performance on specific substrate batches. Surface energy, porosity, and chemical composition variations may require adjustments in coating formulation, application weight, or transfer parameters to ensure optimal performance.
7.Curing and Performance Development:
Final adhesion and wash resistance develop through physical film formation and crystallization of polymer components. Allow transferred graphics to condition at room temperature for 2-4 hours before subjecting to mechanical stress or wash testing. Full durability is achieved after 24 hours of maturation at 20-30°C and 40-60% RH.
