Shortening by beating the typically 27 mm cotton fiber is necessary since long cotton fibers flocculate in the dispersion process. To use cotton meaningfully in wet-laid nonwovens, it is believed desirable to maintain a fiber length of 6 to 15 mm. The fibers used in this investigation have an average length of 14 mm. Such fibers are available as comber noils, a by-product of the combing operation during combed cotton yarn manufacturing. Separation of cotton fibers is a limiting factor in their successful implementation in the wet-laying process.
Entangled fibers result in fiber bundles and holes in wet-laid webs.
In this work, the degree of entanglement has been associated with the viscosity of the dispersion, the concentration of fiber in the dispersion, the amount of associative thickener present, the amount of agitation of the dispersion, mixer blade and shaft dimensions, and the amount of initial entanglement of the fibers before they are added to the stock. Blending makes dispersal of the cotton easier, since cotton can be present at lower concentrations. In the later case, the hydrophobic synthetic fibers are dispersed through the aid of associative thickeners. Associative thickeners are block co-polymers with blocks having a hydrophobe on one end and a hydrophil on the other. In the present case, the hydrophobic end associates with the waxy layer of the unbleached cotton fiber, while the hydrophil end associates with the water phase.