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New lightweight film creating markets for nonwoven composites.

New Lightweight Film Creating Markets For Nonwoven Composites

a new low cost film that can breathe yet still resist moisture is now available from Exxon and Shawmut; several applications targeted Recent advances in lamination techniques have been combined with new film technologies to provide a whole new crop of high tech disposable composites.

A classic example of today's lamination/film impact is Exxon's microporous polyolefin film that is "breathable" yet provides an effective barrier against moisture. Called "Exxaire" breathable film, it is lightweight and moisture vapor transmittable. Exxaire films have been evaluated for a number of applications in health care, protective apparel, footwear and construction.

The "Twin-Set" lamination technology from Shawmut Mills, West Bridgewater, MA, has been successfully applied to a number of nonwoven disposable barrier products, including the Exxaire films. This Shawmut process provides several key properties that make it compatible with these products. First, Twin-Set is a completely room temperature process. Since no heat is used, it is possible to work with temperature-sensitive substrates. Second, the process employs minimum pressure so it does not expose delicate substrates to additional stresses.

Third, the process uses discreet bonding patterns and can apply extremely low adhesive add-on weight (down to two grams or less per square meter). The appropriate adhesive lay-down patterns can provide for the subtle drape characteristics of the finished laminate while having little or no effect on the moisture vapor transmission properties of these laminates.

Advanced Lamination

The introduction of lightweight films requiring delicate handling has seen the Shawmut Twin-Set lamination process making significant contributions. Exxon's work with Shawmut Mills on its Exxaire film/nonwoven laminates is an illustration of the use of advanced lamination techniques along with new substrate technology to create new marketing opportunities.

Exxaire breathable film's porosity is a result of the presence of microscopic particles. Upon stretching, a microscopic void is formed adjacent to each particle. When these voids are close together, cell walls rupture, thereby creating many connecting micropores that extend in a very tortuous manner from one film surface to the other. The film will resist liquid water penetration pressure of up to 90 cm of water column, yet water vapor will pass through the film at a rate of 6000-10,000 grams sq. meter/24 hr. at 100 [degrees] F and 100% R.H. difference. Nonporous standard polyethylene films would compare at a rate of 10 grams sq. meter/24 hr.

Working with Exxon, Shawmut has combined Exxaire films with a variety of lightweight nonwoven products. Because Shawmut's process uses virtually no heat or pressure, it does not threaten the film's pore structure. This leaves the millions of tiny pores unobstructed and also helps make the finished laminate extremely soft and drapable.

The Composite Advantage

There are several major reasons why Exxaire is desirable in composite form rather than by itself. These include the fact that adding a nonwoven provides increased tear resistance, which is a plus in sewing conditions.

A composite also produces a more cloth-like hand and increases the comfort factor when the finished fabric is next to the skin. Further, the nonwoven absorbs some moisture and retains it while it is migrating through the film.

Because of the method of manufacturing, Exxaire film cannot be extrusion-coated directly onto a nonwoven, as is the case with some standard polyethylenes. The past few years have seen the introduction of absorb-desorb film technologies and antistatic films from a variety of film manufacturers. Many of these films cannot be extrusion-coated directly to nonwoven substrates but must be extruded and laminated separately.

PHOTO : An electron micrograph illustrates the extreme uniformity of gauge and permeability of the Exxon "Exxaire" breathable film product.
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Title Annotation:breathable, moisture resistant film now available from Exxon Corp. and Shawmut Mills
Publication:Nonwovens Industry
Date:Jun 1, 1991
Words:608
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