How to improve the waterproofing ability of fluorine-free water repellents?

1. Optimizing the finishing process

Optimizing the finishing process is a very direct and important step in improving the waterproofing effectiveness of fluorine-free water repellents.

Ensure adequate fabric pretreatment:

Fabric pretreatment (such as scouring and bleaching) aims to remove natural impurities, sizing agents, oils, waxes, and other impurities from the fibers. These impurities can severely hinder effective contact and bonding between the water repellent and the fibers. After pretreatment, the fabric must be thoroughly cleaned and neutralized. Any residual acid, alkali, or surfactant will affect the cross-linking and film formation of the water repellent, resulting in reduced waterproofing effectiveness and a shorter-lasting effect.

Control the working solution concentration and pH:

Strictly follow the water repellent supplier's recommended concentration. Too low a concentration will not form a complete and effective water repellent film; too high a concentration may result in a hard feel, increased costs, or even "water repellency" (self-association). Most fluorine-free water repellents have an optimal pH range. Too acidic or alkaline conditions may affect their stability or cross-linking reaction. For example, some silicone water repellents perform better in slightly acidic conditions (pH = 5.5-6.5).

Select appropriate curing/curing conditions:

Adequate curing temperature and time are crucial for the formation of a waterproof film. This allows the water-repellent molecules to fully crosslink and securely adhere to the fiber surface. Excessively low temperatures or short curing times will result in incomplete crosslinking, a weak waterproof film, and poor washability. Excessively high temperatures may damage the fabric or decompose the water-repellent. Be sure to follow the supplier's process specifications and ensure uniform temperatures across all parts of the curing equipment.

Consider the application method: Pad-Dry-Cure is currently the most popular and effective application method, ensuring precise and even distribution of the water-repellent on the fabric. For finished products with localized treatments or where padding is not feasible, spraying is an option, but proper application uniformity is crucial, as otherwise it can lead to uneven water-repellent results.

2. Additive Combinations and Compounding

Skillful use of other additives can often achieve a "1+1>2" effect.

Adding a crosslinker:

Crosslinkers (such as blocked isocyanates and epoxy crosslinkers) can bridge the gaps between water repellent molecules and between the water repellent and fibers, forming a stronger, denser, three-dimensional network film. This significantly improves the durability and wash resistance of the water repellent. ️ Note that crosslinkers may affect the feel (possibly causing a hardening effect).

Combining with durability enhancers:

Special polymers (such as certain modified polyurethanes) can enhance the adhesion of the water repellent to fibers and improve film-forming properties, thereby increasing the durability of the water repellent.

Avoid using with anionic additives in the same bath:

Most fluorine-free water repellents are cationic or weakly cationic.  Avoid using with anionic additives (such as certain dispersants, detergents, and softeners) in the same bath. Otherwise, charge neutralization can occur, leading to flocculation and demulsification, resulting in water repellency failure and even problems such as sticking and color spots. If using in the same bath, be sure to conduct a compatibility test first.