In application scenarios such as automotive sealing strips, wearable electronic devices, and outdoor signs, whether the coating and adhesive can maintain flexibility after being immersed in water directly determines the life of the product. Traditional materials face severe challenges: water penetration triggers a plasticizing effect, resulting in decreased adhesion, re-adhesion, and even cracking. With the tightening of environmental regulations and the complexity of terminal scenarios, high-performance materials that have both the ability to maintain flexibility after immersion in water and low VOC characteristics have become a key breakthrough for industry upgrades.
1. Technical challenges in water immersion: Why is flexibility prone to failure?
Water erosion of coatings mainly leads to performance degradation through two mechanisms:
Plasticization: Water molecules penetrate into polymer chain segments, weakening the intermolecular forces, causing the hardness to drop by more than 30%, and causing re-sticking.
Interface peeling: On metal/plastic substrates, water forms an isolation layer at the interface, causing adhesion to decay. For example, the peel strength of ordinary UV pressure-sensitive adhesives may decay by 40% after being immersed in water for 48 hours.
Typical cases include:
The sealant of the screen of a folding screen mobile phone cracks after repeated bending in a humid environment;
The pressure-sensitive tape of an outdoor metal logo falls off after encountering rain;
Water evaporates during the drying process of the water-based paint film to produce bubbles, which accelerates the aging of the coating.
2. T-7128 resin: molecular design breaks through the limit of water-immersion flexibility
Shenzhen U-Sunny's T-7128 UV resin solves the problem of wet failure through triple structural innovation:
Hydrophobic cross-linking network: the introduction of polysiloxane modified chain segments forms a dense hydrophobic layer after curing, with a water contact angle of >95°, significantly reducing the water permeability.
Dynamic bonding design: the molecular chain contains reversible hydrogen bonds, which are locally reorganized when encountering water stress to avoid permanent deformation. The elongation retention rate after immersion is >85%, far exceeding the 50% of ordinary resins.
Enhanced metal adhesion: carboxyl and epoxy groups work synergistically to form coordination bonds with the metal surface, and maintain a cross-cut adhesion of ≥4B even in a hot and humid environment (ISO 2409 standard).
3. Application scenarios: Comprehensive performance improvement from ink to pressure-sensitive adhesive
(1) Metal decoration UV ink
Challenge: The printed patterns on stainless steel kitchenware and aluminum alloy electronic housings are often exposed to detergents or sweat, and the edges are prone to warping.
Solution: After curing, the ink based on T-7128 forms a "rigid and flexible" structure:
Hardness 3H (pencil hardness) ensures wear resistance;
After immersion in water for 48 hours, the T-bend test can still pass the 2T level bending (GB/T 6742 standard).
(2) UV pressure-sensitive adhesive and waterproof adhesive
Innovative process: Combined with "UV patterning" technology (such as flexible display screen glue layer process), high cross-linking points are constructed in local areas to achieve stress dispersion. After UV curing, the initial peel strength reaches 17 N/25mm, and only decays by 10% after immersion in water (ordinary glue decays ≥30%).
Case: The pressure-sensitive adhesive tape used for outdoor electronic tags passed the -45℃~150℃ hot and cold cycle test without debonding (refer to ASOKLID UV-2202 verification method).
4. Future direction: integration of green and high performance
With the emergence of new materials such as Luoyang Shuangrui flexible polyurethane topcoat and Suzhou Shihua UV tackifier, the industry is evolving towards "zero VOC + adaptive flexibility". The T-7128 resin platform can be designed modularly:
Contact Shenzhen U-Sunny immediately to obtain T-7128 resin samples and water immersion performance test solutions to build core competitiveness for your metal ink and waterproof pressure-sensitive adhesive products!