Argotec Fills Industry Need With Thin, Aliphatic-Grade Polyurethane Films

GREENFIELD , MA - Aliphatic-grade thermoplastic polyurethane (TPU) film has become the material of choice for many challenging specialty-film applications because of its inherent toughness, flexibility, weatherability, chemical resistance and adhesive characteristics. Argotec, Inc., of Greenfield, Massachusetts, has perfected the ability to extrude this versatile, high-performance polymer using flat-die technology in thicknesses ranging from 2 to 10 mils and thicker, widths from 40 inches up to 74 inches, and with a variety of surface finishes and roll configurations that are unattainable from blown film extrusion.

Thin, weatherable, aliphatic TPU film on polyethylene carrier

WHO NEEDS THIN ALIPHATIC URETHANE FILM?

Typical users of aliphatic polyurethane film want the ability to purchase hard or soft films that are of consistent gauge, are optically clear, non-yellowing, have low gel content, and are exceptionally clean. The advantage of thin film is lighter weight, conformability, better optical quality and lower cost, while still retaining the physical properties for which aliphatic TPU is known - abrasion, ultraviolet and chemical resistance, elasticity, and bond strength.

Thin aliphatic urethane films are highly desired by laminators who use them as interlayer adhesives between dissimilar substrates. For weatherable films, coaters add adhesive to one side of these films so they can be attached to a surface for use in an ever-growing number of protective applications requiring the inherent qualities of this difficult-to-extrude polymer.

WHY FLAT-DIE EXTRUSION IS PREFERRED

Flat-die extrusion, shown here in Argotec's hard-walled clean-room facility, has numerous advantages over blown film extrusion.

Argotec's ability to manufacture these thin aliphatic films using flat-die extrusion technology is significant because films produced by this method are typically of higher quality than product manufactured via blown film extrusion. Flat-die-extruded films contain less gel - visible pockets of TPU resin that are not completely melted during the extrusion process. The less gel a film contains, the more pleasing it looks.

Flat-die extrusion requires no processing aids that can affect adhesive wetting or the ability of adhesive to be applied uniformly to the film without beading up. It also allows in-line gauge control and roll stock surface finish control; because it utilizes hard finishing rollers, flat-die extrusion is able to impart more consistent matte and gloss surface finishes to the film than other methods. This capability is especially important in producing high gloss films.

Optically clear, polyether-based TPU film is used to bond multiple layers of glass, polycarbonate or other dissimilar substrates together to create impact-resistant security glazing. A ten-layers glass composite is shown below.

When run in Argotec's hard-walled, clean room manufacturing facility, flat-die extrusion eliminates virtually all contaminants, air-borne and otherwise, for the cleanest possible film. And unlike blown film, flat-die extrusion allows thin films to be cast on carriers as well as the insertion of one or more interleafs.

Argotec's aliphatic films are available in three basic grades. Polyether-based polyurethanes have outstanding optical clarity and resist the degrading effects of natural sunlight and ultraviolet radiation without yellowing. They also provide excellent hydrolytic stability. Softer than polyester-based TPUs, they are used primarily as optical interlayers to bond glass to polycarbonate or acrylic, glass to glass, or glass to other substrates to create impact-resistant security glazing found in banks, prisons, aircraft windows and armored vehicles. In addition to serving as an excellent adhesive, the inherent flexibility and elasticity of aliphatic polyurethane film easily absorbs any variance in rates of thermal expansion and contraction between dissimilar glazing materials, thus greatly minimizing the chance of composite delamination.

Aliphatic films made from polyester-based polyurethanes , have stronger physical properties than polyether-based TPUs - tear resistance, elasticity, tensile strength and chemical resistance.

A third aliphatic film type, polycaprolactone polyurethane , utilizes a hybrid ester-type chemistry that also provides excellent hydrolytic stability to create a blend of ether and ester characteristics, bridging the gap between the two grades of TPU.

Matte-surfaced, polyester-based TPU films are used to laminate multiple layers of fabric together, creating super-strong, impact-resistant textile composites.

Another valuable property of aliphatic polyurethanes is that, within each grade – polyether, polyester and polycaprolactone - exist a variety of hard and soft TPU resins from which Argotec can flat-die extrude thin films. The measure of hardness, or Shore durometer, of these flat-die-extrudable resins, is expressed as Shore A (softer) or Shore D (harder), and can range from a low of 70A to a high of 60D .

Soft aliphatic films usually have matte surface finishes that allow better air flow when used in processes employing vacuum lamination. Multiple fabric layers can be laminated together to create impact-resistant textile composites used in personal security applications.

In addition to security glazing, glass laminators also utilize the excellent electrical insulation properties of soft, polyester-based aliphatic TPU film as an adhesive layer between glass and the electronics behind touch-screen monitors. To maximize film cleanness for such critical applications, Argotec has mastered the technique of extruding thin aliphatic film between double polyethylene (DPE) interlayers.

Electrical insulation properties of aliphatic TPU film makes it ideal for use as adhesive layer between glass and electronics of touch-screen monitors

Hard varieties of thin aliphatic TPU films can be made virtually invisible. They are used by coaters who add nearly invisible, “water-clear,” pressure-sensitive adhesives to one side of the film so they can be applied easily to protect vulnerable surfaces from abrasion, chemicals and ultraviolet radiation. The highly conformable nature of aliphatic TPU film is ideally suited to this type of protective application as it allows the material to form around different parts and shapes without wrinkling. Additionally, Argotec's ability to extrude these thin, non-yellowing, weatherable films via flat-die extrusion allows a variety of surface finishes to be imparted to the film that can more closely match the surface to which they are being applied, including an exceptionally high gloss finish that is beyond the capability of blown-film extrusion equipment to produce.

Common applications include affixing protective aliphatic film to exterior surfaces of fabricated metal products, painted metal surfaces, leading edges of aircraft propeller blades, and similar metal-protective applications.

Thin, hard, polyester aliphatic TPU film can be applied to metal surfaces to protect from friction and wear.

Because these films are often so thin, they are frequently extruded - or cast - directly onto carriers of polyethylene film, polyester film, paper, or certain wovens and nonwovens. This gives the film surface a variety of characteristics that allows it to be more easily handled and applied. Additionally, they may be interleafed with similar materials, including DPE double polyethylene interlayers.

Laminators, coaters and converters of thin, aliphatic polyurethane films find the product easy to fabricate using vacuum lamination, adhesive lamination (glues or the TPU film itself), die cutting and laser cutting.

Aliphatic polyurethanes are one of the most difficult polymers to extrude into thin films. Yet Argotec has mastered the technology needed to produce product of the highest quality that still retains the inherent physical attributes of thermoplastic polyurethane - toughness, abrasion and chemical resistance, elasticity, visual clarity and weatherability.

Thin aliphatic TPU film cast on paper carrier.

Often called the best-kept secret in the specialty films industry, Argotec is fast being recognized as one of the leading global suppliers of custom-engineered, high-performance, polyurethane film and sheet for a wide variety of critical applications using flat die, blown film, extrusion coating, multi-layer constructions and cast-on-carrier extrusion technologies. In addition to aliphatic TPU, the company also offers precision film & sheet products made from aromatic polyurethane, copolyesters, copolyamides, ether-amides and other specialty thermoplastic elastomers. Further information may be obtained by calling (413)772-2564, faxing (413)772-2565, e-mailing info@argotecinc.com , or visiting the Argotec website, www.argotecinc.com .

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