Polyolefins, especially polypropylene, are widely used in various nonwoven applications including hygiene, medical, absorbents, wipes, filters or battery separators. However, polyolefins are hydrophobic which limits their use in applications where wettability is required.

To make polypropylene hydrophilic the polymer surface has to be modified. Surface modification by topical application of hydrophilic spin finishes is well known in the industry. However, fiber finishes are typically not durable and are easily washed off or removed by mechanical forces.

An alternative and improvement over topical application is to melt compound surface-active additives into polyolefins that will migrate to the surface to render the polyolefins hydrophilic.

Ciba® IRGASURF® HL is a new hydrophilic internal additive for polyolefin fibers and nonwovens. It has been developed to provide durable surface properties to polypropylene fabrics.

Ciba® IRGASURF® HL is dispersed in the polymer during the extrusion process. Upon cooling, the polymer crystallizes and the additive will segregate toward the surface.

Different tests are used in the nonwoven industry to measure the hydrophilicity and the durability of the effect. The tests used are essentially on the final application. Thus, hygiene and medical applications, such as diapers, adult incontinence and feminine care products, specify initial strikethrough time and strikethrough times after several insults.

The water absorption capacity is a key requirement for the use of PP fibers in wipes. Nonwovens for technical applications such as filters or battery separators have their own specifications.