A. Grain Direction
1. Grain direction should be considered for various binding and finishing operations, including folding, scoring and perforating. It may also impact strength properties as well (see the "Physical Properties" section for more details).

2. Unlike wood based papers, the grain direction of YUPO runs across the width of a roll. However, stock sheet sizes are trimmed with a grain direction normally found in conventional commercial printing paper grades.

3. To determine the grain direction in a sheet of YUPO, make a small cut at the edge of a sheet in the center of the length. Pull on the cut and watch the direction of the tear. If the tear is parallel to the grain direction, it will be very straight. If it's perpendicular to the grain, it will turn toward the grain direction.

B. Temperature Distortion
1. YUPO, a polypropylene plastic paper, will distort when sheet temperatures exceed 170º F (77ºC). In addition, lighter substance weights ofYUPO will distort more readily than heavier weights. Heat can also affect inks and coatings, and a trial should be conducted to evaluate their suitability in converting.

2. YUPO should not be used in heat fixation laser printers or photocopiers. The temperatures generated by their imaging processes may cause YUPO to melt in the equipment. YUPO may be used in flash fixation imaging equipment.

C. Perforating
1. Make perforations in YUPO along the grain direction, rather than across it. Once a tear begins, YUPO tears more easily with the grain direction. Keep tension low during perforating to avoid stretching the sheet.

2. Once an edge is nicked, YUPO tears very easily. When perforating tear-off forms, begin the perforation cut on the edge of the sheet to lower tear resistance. The perforation cut area should be considerably longer than the uncut area to facilitate tearing.

3. Recommended intervals of cut and uncut areas are:
¨ Across the grain ¨ With the grain
Uncut: under 1/16 inch Uncut: 1/8 inch
Cut: from ¼ - ½ inch Cut: from ¼ - ½ inch

D. Scoring and Folding
1. YUPO can be folded thousands of times without cracking or tearing. Before folding YUPO, scoring is recommended for basis weights greater than 57lb. text (FPG 130); scoring lighter basis weights may be necessary to define the fold. YUPO folds more easily in the grain direction, especially with heavier weights: 58 lb. cover (FPG 200) and up.

2. Lighter basis weights and calipers fold easiest in folding equipment. Keep roll pressure even and as high as possible. Sheets must be directly parallel to the guide rolls for even folding. YUPO, when folded, has a memory and will spring back to some degree, particularly for basis weights greater than 74lb. text (FPG 250).

3. To help set the fold, vertical stacking or banding of folded items is recommended after folding is complete. Inks must be completely dry to prevent setoff.

4. YUPO has a low air permeability, so little air passes through the sheet during folding. To minimize the amount of air trapped between sheets, limit the number of folded pages to a maximum of eight. Pretest using YUPO samples that are the same size and caliper as the production run. Unless perforated, a 32-page fold is not possible with YUPO, since air is trapped between the folds and has no way of escaping.

E. Die Cutting
Dies should be made of hardened steel, sharp and free of nicks. Avoid intersecting inside cuts in applications where tear resistance is important. Right angle cuts should be made with a 1/16 inch radius hole to prevent tearing. A sharp corner will act as a nick and tear easily. On matrix die cuts, the points that attach the die-cut item to the skeleton should not exceed 1/64 inch to ensure easy release.

F. Foil Stamping
1. YUPO can be foil stamped. Like wood based papers, three process factors influence its success: temperature, pressure and dwell time. Trials with various foils at varying foil-stamping conditions are required to determine foil compatibility and optimum press settings.

2. Because YUPO is heat sensitive, the temperature of the die in combination with the dwell time (press speed) should not raise the sheet temperature above 170º F (77ºC). Therefore, adhesive coating on foil should have a low activation temperature, or sheet distortion will occur. Calipers above 8.0 mils will show less distortion than thinner weights of YUPO.

3. YUPO has a low surface energy between 30-33 dynes/cm (as measured by the contact angle method). For proper adhesion, foils must be compatible with this measurement. Pre-test the foil on YUPO before running the job.

4. When foil overstamping, inks and coatings must be compatible with the foils. Wax-free inks are necessary when foil stamping over a printed surface; waxes would melt from the heat of the die and create a wet area with poor foil adhesion.

Similarly, coatings may also contain waxes that pose problems to foil stamping. In particular, successful foil adhesion on UV coatings can be especially challenging due to the coatings' low surface energies.

G. Embossing
1. YUPO can be embossed using shallow, rounded edge dies; avoid deep or sharp angle dies that could puncture the stock. Once embossed, YUPO holds the embossing well.

2. Like foil stamping, lower temperature settings are recommended to avoid puckering. Trials can determine the optimum settings for temperature, pressure and dwell time.

3. Heat can generate drier conditions and static. The press area may need to be humidified if the relative humidity falls below 50%.

H. Laminating
1. Laminating is the process of combining two or more layers of a material together with an adhesive. Laminating a clear plastic film over YUPO offers the greatest form of protection for a printed image. Consider laminating it for extremely harsh end use conditions, where overprint coatings may not provide the desired protection. Laminating films are available in a number of thicknesses with glossy or dull finishes.

2. The advantages of film laminating, compared to coating, are:
• film will not crack, coatings may
• the printed surface is completely protected from moisture
• the film has excellent durability, and can be wiped clean easily and without scratching
• fingerprint smudges are less noticeable, especially over dark colors

3. When laminating over preprinted material, inks must be compatible with the process as well. Use wax-free, solvent free, heat resistant inks. Before printing on YUPO, check your ink supplier to ensure ink compatibility with the laminate specified.

4. When laminating over preprinted material, remove excess anti-setoff spray powder; if it becomes trapped, it will cause a rough stipple appearance and interfere with the film's bonding to YUPO. Watch for the formation of air bubbles in the adhesive layer as well. Reducing the laminator speed, increasing the temperature of the combining rolls and reducing the adhesive's viscosity can help prevent air entrapment.

5. Adhesives can be either thermoplastic or thermoset. Thermoplastics (hot melt) such as EVA require lower temperatures to be laminated. However they lack heat resistance, so end use conditions must be considered. Thermoset adhesives cross-link after lamination, which increases heat resistance. These adhesives - polyesters and polyurethanes - contain initiators that speed up the curing reaction.

6. Since YUPO is extremely tear resistant, the thinnest possible film thickness can be used; the film's tear resistance is not critical to the job's overall durability. When laminating is properly executed, the film fuses tightly to the edge of YUPO and an edge seal is not necessary (this also eliminates the need for heavier gauge films). Compared to conventional papers, about half of the laminating material is required to laminate YUPO, and the end product will be more durable.

7. When laminating YUPO minimize web tension (roll laminating) and heat to avoid sheet stretching, distortion and wrinkles. When combining YUPO with another material, mechanical and electrical precision is required to keep the speeds coordinated (in light of the materials' different stretch properties).

Binding

A. Saddle and Side Wire Stitching
Saddle stitched books are bound through the centerfold by staples created from a continuous roll of wire; side stitched books are bound by staples through the side of the booklet, near the spine. To avoid rusting, stainless steel wire staples should be used if the books remain near water or in humid conditions.

B. Spiral and Loose-Leaf: Mechanical Binding
1. Spiral binding threads a wire or plastic comb through prepunched holes. When spiral binding YUPO, use round holes rather than square ones to increase durability and tear resistance. A right angle corner can easily tear.

2. Loose-leaf binders use rings or posts to hold materials together. Since pages can be easily inserted or removed, these binders are ideal for documents that require continuous updating. When drilling holes in YUPO, be sure the inside radius is greater than 1/16 inch and that the drill bit is sharp. Drill no more than a maximum lift height of 1 inch to avoid overheating and melting the stock.

C. Case Binding: Thread Sewing
1. If YUPO is used as case material (the material applied to rigid or flexible boards of hardcover books), a high tack animal adhesive is recommended. The adhesive is applied to YUPO, which is then applied to the board and folded around the edges.

2. The cover is then applied to the bound signatures in a two-step process. With the first step ("casing-in"), the cover is attached to the body of the book by gluing the book's end papers to the cover. With the second step ("building-in"), the cases' adhesives are dried using a series of pressure plates and heated formers. Each set of plates and joint formers quickly clamps the book under extreme pressure and then releases it. The book will pass through a series of clamps depending on the drying needed. The temperature of the heated formers should be adjusted to avoid melting YUPO during machine stoppages.

D. Perfect Binding: Adhesive
1. Perfect binding uses adhesive exclusively as the binding mechanism. The binding edge is trimmed and roughened (milled), or it's cut to make the sheets receptive to the adhesive (usually a hot melt glue). A cover is pressed against the adhesive once it's applied and held in place by the glue. The scratches or cuts on the spine should be deeper than the paper caliper for the adhesive to penetrate.

2. When using a hot melt glue, the unmelted glue must be hot enough in the pre-melter to liquefy and flow. When cooled on the book spine, the hot melt adhesive instantly bonds. During gluing, the temperature level should be kept low enough to prevent distortion of YUPO. Before perfect binding the print job, consult your adhesive supplier for recommendations and conduct your own pre-testing.

3. Solvent-based (vinyl acetate) adhesives may be used instead of hot melt adhesives. They're applied cold and provide a more flexible backbone. These adhesives form a strong, cross-linked bond once the solvent is removed. Some solvents may cause distortion over time, so sensitivity tests should be conducted.