Causes and solutions for poor waterproof performance of fabrics
Waterproof agent performance:
Cationic waterproofing agents have better stability and better adsorption to fibers, and their waterproofing and oil-repelling properties are better than non-ionic or anionic ones. Product. The smaller the molecular weight of the additives contained in the product and the lower the boiling point of the added solvent, the better the film-forming properties. Commonly used solvents include acetone, dipropylene glycol methyl ether (DPM), tripropylene glycol (TPG), etc., among which acetone’s It has the best film-forming properties, but it is a hazardous chemical.
Waterproof and oil-repellent agent The molecular structure determines the oil-proof performance. The molecules contain active groups that react with fibers, and the products have better oil-proof properties than products without reactive groups.
Usage amount of waterproofing agent:
Under normal processing conditions, the waterproof and oil-proof effect increases with the increase in the dosage of waterproofing agent. Within the cost range, the dosage can be appropriately increased to improve the waterproof and oil-proof properties. However, after reaching saturation, the water-proof and oil-proof effect will increase with the dosage. Improve, the waterproof and oil-proof effect is no longer improved, and the product performance has reached the limit.
Baking conditions:
Polymer waterproofing agent requires high temperature to cross-link to form a film , Insufficient baking will affect the film-forming properties, and the waterproof and oil-proof effect will be poor. In addition, the baking temperature is also critical. The higher the temperature, the more beneficial it is for waterproof and oil-proof processing. In order to avoid large discoloration and yellowing of the fabric The temperature should be limited, but the baking time can be extended to improve the waterproof and oil-proof performance.
Front processing of fabrics:
Incomplete fabric pre-treatment, such as incomplete removal of oil and wax, It is easy to produce a slight waterproof effect on the surface of the fabric, which affects the adsorption amount of the waterproof and oil-repellent agent on the fabric. Even if you use dry cloth to pad or increase the amount of waterproof and oil-repellent agent, the waterproof and oil-repellent effect cannot be improved.
Front fabric processing:
(1) Ordinary polyester fabrics are commonly sizing with polyacrylate, and the amount of oil during spinning is small, so it can be removed with alkali and detergent;
(2) The slurry of polyester ultrafine fabrics is mineral oil, esterified oil, wax, etc. Compound oil agent. If the pre-treatment is insufficient, oil substances will easily remain on the cloth surface. After drying, the surface of the fabric will be water-repellent, and the waterproof and oil-proof effect will be poor. The solution is to strengthen the pre-treatment of the fabric to maintain more than 50% of the fabric. To improve the overprint rate, or add solvents such as isopropyl alcohol (10~20g/L) and n-hexanol (3~6g/L) to the waterproof working fluid to improve the overprint rate of the fabric;
(3) The cotton whitening fabric has not been color-fixed, and part of the anionic whitening agent leaves the fabric during the padding process. The surface enters the mixed liquid and adsorbs with the macromolecules of the waterproofing agent, which reduces the amount of adsorption of the waterproof and oil-repellent agent on the cloth surface, and the waterproof and oil-proof effect becomes worse. Increasing the washing process to remove the floating color of the whitening agent on the cloth surface can improve Waterproof and oil-proof effect;
(4) On cotton printed fabric, the graphics are deep There is often water staining in the colored areas, and the waterproofing does not reach 100 points of the AATCC-22 standard or the oil-proofing in the printed areas is poor. The reason is that there is more sizing in the dark areas, and it is difficult for the waterproofing agent to penetrate into the fibers after the film is formed, and the waterproofing effect is not good. Ideal. Some light-colored fabrics can be improved by adding more reactive blocked isocyanates.
Compounded with other finishing agents:
Compound softeners are often non-ionic and cationic, rather than anionic. Non-ionic softeners The agent has little effect on waterproofing and oil-proofing, but the feel is not ideal; using a small amount of cationic silicone softener will produce a better feel.
It is not suitable to mix Softener situation:
(1) When oil-proof requirements are high, add Softener will reduce oil-proof performance;
(2) Waterproofing agent (self-crossing There are no active groups that react with fibers in the molecular structure of the organic fluorine compound. If the organic fluorine compound molecule contains active groups that react with fibers, the active hydrogen on the siloxane chain in the organic silicon compound molecule can react with the waterproof and oil repellent agent. The addition of double bonds in the molecule can also react with the dehydration of hydroxyl groups in the fiber to form a mixed film on the surface of the fiber. The surface tension of organic fluorine compounds is lower than that of organosilicon compounds, and the increase in the surface tension of the mixed film causes the oil-proof performance of the fabric to decrease.
Add organic silicon compounds to the self-crosslinking waterproofing agent, and the organic silicon molecules The active hydrogen reacts with the fiber to dehydrate, affecting the film-forming uniformity and integrity of the waterproof and oil-repellent agent.
Non-ionic antistatic agents are commonly used. Although cationic agents have better antistatic effects, when used in the same bath with waterproof and oil-repellent agents, their waterproof and oil-repellent properties are significantly reduced, so they should not be used.
Fabric structure ：
Some polyester high-density fabric beltsThe efficiency is often below 30%, and the waterproofness is <100 points under normal dosage. Increasing the dosage of waterproof and oil-proof agent, adding waterproof and oil-proof synergist, or raising the setting temperature can improve the waterproof and oil-proof effect. Blended fabrics such as brocade For polyester and textile fabrics, when the waterproofing agent is used alone, there will be water marks on the fabric surface. Adding 3~5g/L of melamine resin can improve this phenomenon.
Only when the nylon fabric is above the isoelectric point and the potential displayed on the cloth surface is negative charge, can it better absorb the positively charged waterproof and oil repellent agent molecules, showing Better waterproof and oil-proof effect.
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