Optimizing Warp Sizing Polymer Add-on Levels for Air-Jet Weaving Efficiency
Optimizing sizing polymer add-on levels balances yarn hairiness reduction against shed dusting to maximize air-jet loom efficiency and lower desizing costs.
Size Film Plasticizer Content
Chemical Composition
Sizing agents applied to warp yarns must form a protective barrier that is both tough and flexible to withstand the stresses of high-speed weaving. The size film plasticizer content represents the proportion of softening additives incorporated into the starch or synthetic polymer mixture to modify the mechanical properties of the dry coating. This value determines the brittleness and elasticity of the protective shell.
Film Flexibility
Pure starch or polyvinyl alcohol films tend to become extremely brittle when dry, especially under the low humidity conditions often found in weaving sheds. A high size film plasticizer content prevents the protective coating from cracking or flaking off the yarn surface when it is bent or tensioned. Additives like urea, glycerol, or animal fats lodge between the polymer chains of the sizing agent, increasing the free volume and allowing the chains to slide past one another.
This modification reduces the glass transition temperature of the film, making it more pliable and resilient under cyclic stress.
Weaving Protection
Optimizing the concentration of these softening agents is necessary to avoid issues during both weaving and desizing. If the size film plasticizer content is too low, the protective film will shatter under the action of the heddles and reeds, leading to a loss of abrasion resistance and an increase in warp breaks. Conversely, an excessive concentration of plasticizers makes the film soft and tacky, causing the yarns to stick together on the warp beam or accumulate sticky residues on the loom parts.
This stickiness can cause yarn cling, uneven shedding, and fabric defects.
Industrial Determination
Mill laboratories analyze this parameter by casting free films of the sizing mix in shallow dishes and testing their mechanical properties. The size film plasticizer content is adjusted based on these measurements to match the specific fiber blend and yarn count being processed. For example, fine cotton yarns woven on air-jet looms require a different balance of strength and flexibility than coarse synthetic yarns.
Regular monitoring of the plasticizer ratio ensures that the warp yarn remains protected throughout the weaving process without causing build-up on the machinery.