Core performance requirements for sodium carboxymethyl cellulose (CMC) in warp sizing include:
Solubility in cold or hot water, no lumps, and a transparent solution to avoid uneven sizing (sizing spots or exposed fibers);
Degree of substitution (DS) should be controlled between 0.6 and 0.9 with high uniformity to ensure water solubility and sizing film flexibility (too low a value makes it difficult to dissolve, while too high a value makes it brittle);
Viscosity should be between 50 and 500 mPa·s (2% aqueous solution), with low viscosity used for fine yarns and high viscosity for coarse yarns. This allows for controlled sizing, balancing sizing penetration and film thickness;
Purity should be ≥95%, ash content ≤5%, and salt content ≤3% to prevent sizing film shedding and fabric contamination; the film should possess strength (tensile strength), toughness (resistance to brittleness), and abrasion resistance to minimize weaving breakage.
The main functions of sodium carboxymethyl cellulose in warp sizing are:
First, it protects the yarn and prevents breakage. It can adhere to the hairiness on the yarn surface, forming a uniform sizing film, isolating friction, enhancing yarn strength, and reducing end-of-weaving breakage rates.
Second, it optimizes sizing by adjusting the viscosity of the mixed sizing (to suit different yarn counts), preventing sizing stratification and sedimentation, and is compatible with a variety of fibers, including cotton and chemical fibers.
Third, it facilitates desizing. Because it is cold-water soluble, subsequent desizing is simple, reducing fabric damage and wastewater pollution.
In practical applications, sodium carboxymethyl cellulose (CMC) is often used in combination with starch, PVA, and other materials. The key is to achieve "yarn protection + sizing," balancing warp yarn weaving performance with processing convenience.
