Information on Tyvek by du Pont

Du Pont's web page Tyvek® for Graphics features a description of Tyvek®'s properties and possible uses for that material. There is no suggestion for the use of Tyvek® in the production of bank notes. Nevertheless, the web page gives a general idea about Tyvek® that had been used for printing banknotes in 1980s. Below are some excerpts from that web page.

Tyvek®—creating new dimensions in graphics

Tyvek® is ...

Tyvek® brand protective material is a miracle of science from DuPont. It is a family of tough durable sheet products of high-density polyethylene fibers. The sheet is formed first by spinning continuous strands of very fine interconnected fibers, and then bonding them together with heat and pressure.

Tyvek® is white, non-toxic, chemically inert and contains no binders. The non-woven sheet, after bonding, combines a good printing or coating surface, high opacity and toughness to a degree unique among sheet products of similar weight and price.

Tyvek® is produced in three different types, namely 10, 14 and 16. The fibers in Type 10 Style are bonded to form a tough, dense, opaque sheet. The dense packing of the fine, interconnected fibers produces a smooth surface, high opacity and whiteness. The large number of bonds per unit area results in a stable and abrasion resistant surface with a stiffness similar to paper. Fiber bonding of Types 14 and 16 is restricted to discrete points in the non-woven sheet, producing a high degree of fiber mobility, and giving the non-woven a fabric-like drape.

Made by bonding webs of fine fibers with heat & pressure, nonwovens are an incredibly durable printing surface.

A unique, proprietary manufacturing process perfected by DuPont over 24 years ago makes Tyvek® ideal for a variety of applications.

Working with Tyvek®

Tyvek® is a unique nonwoven printing medium. It's not paper. It looks different from paper. Its not like synthetic films. It feels more natural, with flat, precision folding qualities. Its not a fabric, although it can be used like fabric.

Made by bonding webs of fine fibers with heat and pressure, nonwovens are an incredibly durable substrate. Tyvek® blends the best traits of fabric, film and paper. Account for the differences Tyvek® brings and get reliable printing results every time.

Prepress—planning for success

• Tyvek® with antistatic and corona treatment is strongly recommended for improved adhesion of inks, coatings and adhesives.

• Pretest ink and Tyvek® interaction before the production run.

• For a reasonable color match, select Pantone® colors from the uncoated color set. For an exact color match, prepare a sample using the match ink directly on Tyvek®.

• Depending on the style of Tyvek®, dot gain will increase 15 to 20% compared to coated paper.

• Dot gain is more prevalent from the 35% to 50% dot area. This is different from paper where dot gain is normally maximized at the 50% dot

• Adjust the reproduction curve for 80% in the maximum areas. Allow for corresponding lightening in the other tonal areas.

• Minimize the highlight dot. Allow specular highlights to go to zero.

• UCR and GCR should be used as much as possible.

• Opaque inks are best for tints.

• Fiber swirl is an artifact of the strength of Tyvek®. This should be kept in mind when designing artwork for printing on Tyvek®.

• In general, you will need 15% more ink to achieve color densities similar to uncoated paper.

• Test the compatibility of solvents in inks, coatings and adhesives by placing two or three drops on Tyvek®. Check for any distortion after 20 minutes.

• Because Tyvek® absorbs little or no moisture, plan on longer drying times than paper. As with any printing, allow more drying time with heavier ink coverage.

• During any phase of processing do not expose Tyvek® to temperatures above 175°F. In general, the higher the temperature the more Tyvek® will distort.

• To avoid static, maintain a relative humidity of 50% or greater.

• For critical print clarity, print on the smoother side of Tyvek®.

Printing

Tyvek® can be printed by all conventional printing processes—letterpress, offset lithography, heat-set web offset, flexography, gravure, and screenprinting.

Tyvek® is also thermal transfer printable. For best thermal transfer results, printing on the smooth side of Tyvek® Brillion™ styles is recommended.

For wide format ink jet printing, a Tyvek® with an ink jet receptive coating is required in order to achieve acceptable results. Numerous companies offer ink jet compatible Tyvek® based products.

Hot process laser printing and photocopying are not suitable with Tyvek®.

Converting

DuPont Tyvek® is composed of 100% high density polyethylene fibre. It is a tough, durable, tear-resistant material that is unaffected by water. Tyvek® retains its flexibility to -73°C (-100°F) but being a thermoplastic material it melts at 135°C (275°F). Tyvek® can be converted in much the same way as paper or plastic films and on the same equipment. If you understand the properties of Tyvek® , you will find converting to be much easier.

All styles of Tyvek® with a "D" or a "R" suffix are antistated and permanently corona treated.

Tyvek® will stretch up to 30% before breaking. To minimize distortion or neck down during roll fed converting, keep tension less than 1.4 N/cm (0.75 pounds/inch.) A floppy web is recommended. This is particularly true when die cutting Tyvek® business forms with rotary punched sprocket holes.

Slitting, Sheeting, Cutting

Because Tyvek® fibres are very strong, each must be completely severed; hangers will not break off. Knives, dies and punches must be set to close tolerances. A sharp, slightly rounded edge gives longer service than a pointed edge for crush cutting, but a sharp edge is preferred for other slitting methods.

Rotary Die Punching

Because soft steel male/female rotary dies dull quickly when Set to the close tolerances required to punch Tyvek® cleanly, the use of rotary dies made of hardened tool steel or tungsten carbide is recommended. A list of manufacturers of these dies for Tyvek® is available from your Tyvek® Technical Specialist.

Die Cutting

Tyvek® can be die-cut using either steel rule, male/female or closed dies. Tyvek® fibres must be completely cut and dies must be in good condition with sharp, nick-free edges. Dull dies cause edges to curl. When using closed dies, the use of a side cutter with internal relief is recommended. Deaerate and keep lift height below 7.6 cm (3 inches) when die cutting to avoid oversizing to blanks.

Punching

Tyvek® can be punched on tag, letterpress and rotary line-hole equipment. Best results are obtained for sharp, well registered and closely fit punches. Punches may be either smooth or serrated and cut best if ground concave on the ends. A soft self-honing male punch in a hardened female die is recommended.

Folding

Tyvek® will take a dead fold and can be folded on conventional bindery folders. An increase in roller and spring tension will produce sharper creases. Due to the inherent slippery surface of Tyvek®, soft, rubber-covered rollers will aid feeding.

Perforating

For clean-tearing perforations, use the maximum practical number of cuts with the smallest land (reserve) between them. An 8:1 ratio (1/4” [6.4mm] cut with 1/32” [0.8mm] reserve) is recommended.

Embossing

Tyvek® can be embossed with either high or low pressure equipment. Cold embossing does not significantly reduce the strength of Tyvek®. It does, however, reduce opacity. Embossing cylinders used for Tyvek® usually are very shallow, having a depth of only 0.13-0.65 mm (5-25 mils.). A Shore "D" hardness of 70-80 for the rubber back-up cylinder is preferred.

Foil stamping

This is readily accomplished on Tyvek® due to its thermoplastic nature. A variety of foils is available from suppliers for label and book cover applications. A foil that will transfer cleanly to Tyvek® between 135-160°C (275-325°F) should be chosen. Large, solid foil-stamped areas tend to pucker and distort Tyvek® and should be avoided.

Coating

When coating or laminating Tyvek®, the web temperature should not exceed 79°C (175°F). Coatings are used to color, improve print fidelity, add gloss or mask the fibre pattern of Tyvek®. Air-knife coating is preferred for aqueous coating because it applies a uniform thickness of coating on Tyvek®. Usually an increase in binder content is needed to achieve acceptable coating adhesion to Tyvek®. The air knife also produces a very smooth surface which is ideal for printing. Gravure coating is preferred for solvent-based systems, particularly where deep coloration is required.

Dyeing

Conventional textile dyeing processes do not impart permanent color to Tyvek®. For this reason, Type 14/16 Tyvek® is usually printed by the flexographic or gravure process using either solvent or water base inks. Sublistatic printing of Tyvek® is not recommended because of the high temperatures used.

Laminating

Tyvek® can be extrusion, adhesive and calender laminated. Extruded, branched polyethylene is an excellent adhesive for laminating foil and film to Tyvek®. Polyurethane adhesives can be used to adhere a variety of films and fabrics to Tyvek®. When laminating Tyvek® to paper or board, it is important to completely cover Tyvek® with adhesive to prevent bubble formation.

Heat Sealing/Dielectric Sealing/Ultrasonic Sealing

Heat sealing Tyvek® to itself or other films is usually accomplished by applying a heat seal coating such a branched polyethylene to one of the materials. High seal strength can be achieved using hot-bar or impulse techniques. Tyvek® cannot be dielectrically sealed under ordinary conditions because it is non-polar. Recent developments in ultrasonic sealing have demonstrated seals almost equivalent to heat seals.

Gluing

Natural product adhesives based on dextrin, casein or animal byproducts can be used to adhere Tyvek® to itself and a variety of paper materials. Water based synthetic lattices such as the ethylene/vinyl acetate adhesives form fibre tearing bonds with Tyvek®. Hot melt polyamide adhesives are available which form good bonds to Tyvek® with a variety of materials. Acrylic pressure sensitive adhesives are commonly used with a release liner.

Sewing

Tyvek® can be sewn on conventional sewing machines. Best results are obtained with machines equipped with puller or drop-feed. Smooth, rubber covered rolls should be used rather than knurled metal rolls which tend to leave impressions on Tyvek®.

Stitching

When stitching the Type 10 styles of Tyvek®, 2-3 stitches/cm (4-5/in.) and the smallest needle practical should be used to avoid postage stamp tears. On soft type 14/16 Tyvek®, it is recommended to sew rough side to rough side.

Finishing

• Keep cutting parts clean and sharp, with true, well supported, nick-free edges.  

• For crush cutting, a sharp, slightly rounded edge gives longer service than a pointed edge.  

• When using non-antistatic styles of Tyvek®, use conductive tinsel or ionized air.  

• Die-cut with either steel rule (sharp edge) of male/female dies. Dies must be set up to completely cut the Tyvek® fibers. An incomplete cut will not allow the die-cut Tyvek® to release properly.  

• A soft, self-honing male punch in hardened female die is recommended for punching.  

• For clean-tearing perforations, use the maximum practical number of cuts with the smallest land (reserve) between them. An 8:1 ratio (1/4" [6.4mm] reserve) is recommended.  

• Use conventional bindery folders. Increase roller and spring tension for sharper creases.  

• Tyvek® can be extrusion, adhesive and calender-laminated.  

• For gluing Tyvek®, water-based adhesives that provide quick tack and fast drying are best. 

• Embossing cylinders for Tyvek® should be very shallow. 5 to 25 mil (0.13 to 0.65mm) is recommended.

• Keep foil stamping area under 2" x 2" (50mm x 50mm) to avoid distortion.  

• When stitching Tyvek®, use the least number of stitches per inch and the smallest needle practical for maximum tear resistance.

Recycling

Reduce.

Tyvek® offers superior strength and durability relative to its light weight. Tyvek® typically weighs half as much as other printing substrates. Tyvek® provides significant source reduction opportunities, helping to meet resource conservation goals. It simply takes less material to make Tyvek® when compared to other film and paper substrates. The reduced weight offered by Tyvek® can result in fuel savings during the transportation of roll and sheet deliveries.

Reuse.

If reuse or recycling is not an option, Tyvek® can be cleanly incinerated, and the high energy value can be utilized. Also, because Tyvek® is chemically inert without binders, it can be safely disposed of in landfills.

Recycle.

Tyvek® is made entirely of high-density polyethylene (HDPE), one of today's most commonly recycled plastics. More than 70 facilities in North America are available to recycle Tyvek®. Tyvek® can be recycled into durable goods, such as drainage pipes, plastic lumber, park benches and even fishing lures—continuing a cycle of resource conservation.