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Specifications for Pressure Sensitive Adhesive Labels for Application to Text Pages of Bound Books for Use in Thermal Transfer Printers

Specification Number 700-714-9/5/00

This specification is provided as a public service by the Preservation Directorate of the Library of Congress. Any commercial reproduction that implies endorsement of a product, service or materials, in any publication, is strictly prohibited by law. This Specification is written for L.C. purchasing purposes and is subject to change when necessary.

I. General Specifications - II. Product Requirements - III. Inspection

I. GENERAL SPECIFICATIONS

A. Face Stock

  1. Composition Options
    1. Polyester: White opaque film, 1-2 mil thick. The polyester must be biaxially oriented, non-recycled film with no plasticizers added.
    2. Polypropylene: White opaque film, 1-2 mil thick. Biaxial orientation preferred.
    3. Paper:
      • pH: 8.0 - 9.5, (TAPPI T 509 om-88), cold extraction, slurried pulp
      • Alkaline Reserve: between 2 and 5% calculated as calcium carbonate (ASTM D4988)
      • Lignin: Kappa number of 5 or less (TAPPI T236 cm-85)
      • Sizing: only neutral or alkaline sizing should be used.

    The Procurement Request will clearly identify which of these face stock materials is to be used for the particular application intended by the purchaser.

  2. Degree of Whiteness
    White pigmented label face-stocks must have a minimum brightness of 82% as measured by directional reflectance at 457 nm (TAPPI T452 cm-92).
  3. Brightness Retention
    Accelerated Aging: The color of the face stock must not change more than 10 points of brightness as measured by directional reflectance at 457 nm when exposed for 28 days at 90°C and 50% RH. The brightness will be measured according to TAPPI T452 cm-92.

B. Adhesive

  1. Composition
    The pressure-sensitive adhesive layer must possess high permanence characteristics such that labels, once applied, remain attached permanently and can be removed only with difficulty. The adhesive must be clearly identifiable as an acrylic polymer or copolymer by its infrared spectrum.
  2. Bond Strength
    The adhesive must demonstrate sufficient initial bond strength for the label to support a test weight of 200g for 10 minutes.
  3. Test Method: This procedure is a 90-degree peel test, modified from ASTM D2860M-90. The bonding strength of the adhesive to two different substrates is assessed. These two test panels, designated LC Standard Test Panels PP-1 and PP-2, consist of two different papers applied to 3" x 6" sections of 60 pt. binder's board. The materials used on these LC Standard Test Panels have been selected to represent the surface characteristics of papers commonly found in General Collection books.
    A set of three labels, size 1" x 2 1/2", is applied to each of the two Test Panels over a Mylar window that permits only a one inch square area of the adhesive side of the label to be in contact with the substrate, as illustrated in ASTM D2860M-90, procedure B. The labels are set in place by applying firm pressure with the edge of a 3M plastic applicator, model no. P.A.-1., to the labels in four downward strokes. The test samples are then allowed to cure for 7 days in an environmental chamber conditioned to 73°F and 50% RH.
    At the end of this dwell time a 200 gram weight is suspended from the free end of the label and timed for 10 minutes. At the end of this test period, labels must not have peeled away from the substrate by more than 10 millimeters. Failure of this test with any of the two test panels will disqualify the stock and no further testing need be performed.
  4. Bond Strength after Accelerated Aging
    The adhesive, once set after the initial 7-day dwell time, must remain permanently affixed to both the face-stock and the substrate with no loss of adhesive strength for the life of the object to which it is applied, under conditions of normal use.
    Test Method: This procedure is a 90-degree peel test, modified from ASTM D2860M-90.
    A set of three labels is applied to each of the two Test Panels in the same manner as described under Item 2 above. The labels are then subjected to accelerated aging at 80°C and 50% RH for 28 days. At the end of the aging period the test samples are placed in an environmental chamber conditioned to 73°F and 50% RH for 24 hours.
    At the end of the conditioning period a 90° peel test is performed as in Item 2 above. At the end of this test period, labels must not have peeled away from the substrate by more than 10 millimeters.

C. Other Label Properties

  1. Curling/Lifting/Ooze
    The labels must not show any sign of curling, lifting, buckling, or puckering, nor any evidence of the adhesive oozing beyond the label edges.
    Test Method: A set of three labels, size 1 1/4" x 1 1/4", is applied to LC Standard Test Panels PP-1 and PP-2 so that the entire adhesive side of the label is in contact with the substrate. The labels are set in place by applying firm pressure with the edge of a 3M plastic applicator, model no. P.A.-1, to the labels in four downward strokes.
    The labels are then subjected to accelerated aging at 80°C and 50% RH for 28 days. At the end of the aging period, the labels are examined visually.
  2. Migration and Staining
    The label adhesive must not migrate into and discolor the substrate and/or cause staining of the substrate after aging.
    Test Method: One label, size 1 1/4" x 1 1/4", is applied to each of 5 separate strips of LC Standard Test Paper P-3 (Whatman No. 1 filter paper) and LC Standard Test Paper P-4 (an acidic newsprint paper) and aged at 80°C and 50% RH for 28 days.
    After aging, a fresh label is placed on the test paper alongside, but not touching, the aged label. The side of the test paper behind the labels is measured for brightness. The area behind the aged label must not show any visual evidence of discoloration of the test paper as compared to the paper behind the fresh label. Visual evidence of discoloration, confirmed by a brightness change of more than 3 points, constitutes a failure. This brightness change must be clearly attributable to discoloration of the paper substrate, rather than to discoloration of the label face-stock or yellowing of the adhesive.
  3. Damage to Adjacent Pages
    Neither the face-stock nor the adhesive must cause discoloration, stick to, or otherwise cause damage to adjacent pages.
    Test Method: One label is applied to each of five strips of two different test papers, each measuring 22mm x 120mm. The two test papers are LC Standard Test Paper P-2 (a clay-coated alkaline paper) and LC Standard Test Paper P-3 (Whatman No. 1 filter paper). Each of these labeled Test Papers is faced with one strip of the same paper, backed up with 4 more strips of the same paper, so that the face stock is facing the first strip and is in contact with that strip.
    Each stack of samples of each of the two Test Papers is placed, together, in a stainless steel test jig to hold the papers in the stack. Each stack of paper is separated by a strip of polyester. The stack of samples will be topped with a glass slat of the same size as the strips. Enough stainless steel slats measuring 22mm x 120mm are placed on top of the glass slat to come to a total weight (glass and metal) of 200g. The samples are then subjected to accelerated aging at 90°C and 50% RH for 28 days.
    At the end of the aging period the labeled test strips must separate cleanly and easily from the facing paper strips. First degree blocking, as defined by ASTM D1146-88, is acceptable. However, if either the face stock, or edge-ooze of the adhesive, has caused second degree blocking, the label will fail the test.
    The brightness of the facing paper strips is measured according to TAPPI T452 cm-92. The brightness of the area of the facing paper strip which was in contact with the face-stock on the facing strip is also measured. The two brightness measurements must not differ by more than 3 points.
  4. Print Fastness
    The label stock must be able to accept and retain a clean, legible image from a thermal transfer printer.
    The label stock will be printed with a test pattern consisting of a sample phrase or barcode centered on each label using a printer selected by the Library. The printer model to be used in this test will be noted on the purchase order. Inability to print the stock on the selected printer, obtain a clear, crisp and complete image, or read the barcode with a scanner will constitute a failure. Any failure of the label stock during the printing process will disqualify the stock and no further testing will be performed.
    Test Method: A strip of 3M Tape #230 is applied over the printed test pattern on the label by rubbing down the tape using three fingers in six firm strokes. The tape is then peeled back at a 180° angle. Legible characters visible on the test tape, and/or degradation of the printed image on the face stock, constitute a failure. (This method is described in Archival Copies of Thermofax, Verifax and Other Unstable Records, Technical Information Paper No. 5, Washington, D.C., National Archives and Records Administration, 1990).
  5. Off-setting of Ink to Adjacent Pages
    The printed image on the label must not rub off, transfer, or otherwise disfigure the paper facing the label.
    Test Method: A printed label is applied to each of two different test papers, LC Standard Test Papers P-1 and P-3, and tested by rubbing with that same Test Paper on a Sutherland Rub Tester according to GPO Test Method P-11, Rub Resistance of the Printed Image. Density changes of 0.02 or above, recorded on the receptor stocks, constitute a failure. (This method is described in GPO Publication 310.1, Government Printing Office Contract Terms Quality Assurance Through Attributes Program for Printing and Binding, December 1992 edition.)
  6. Effect on Photographic Material
    If specified on the purchase order for use with collections of photographic materials, the labels must pass the Photographic Activity Test. Both the face stock and adhesive side of the label will be tested. Test to be conducted and results reported as described in ANSI IT9.16-1994, or latest revision. This test can be performed by the Image Permanence Institute (c/o Rochester Institute of Technology, Frank E. Gannett Memorial Building, P.O. Box 9887, Rochester, NY 14623-0887. Tel.: 716-475-5199, FAX: 716-475-7230) or other pre-approved laboratory.
  7. Suitability for Cold Storage
    The labels must be able to pass all of the tested properties listed above after being exposed to conditions of 0°C for 24 hours, followed by 24 hours at 73°F and 50% RH.

II. ADDITIONAL PRODUCT REQUIREMENTS:

A. Thermal Transfer Ribbon Compatibility

The label stock must be compatible with hard-resin thermal transfer ink ribbons. Wax ribbons or wax-resin ribbons are not acceptable. The vendor must recommend compatible printing ribbons for the label stock, provide specification sheets (and/or performance data), a sample to be used in the printer for use in testing, and purchasing information for each ribbon recommended.

B. Odorlessness

The label stock must not emit odors deemed objectionable or hazardous to the work environment by the Library of Congress according to TAPPI T483.

C. Liner

The release liner under all label configurations must allow for easy and complete peeling of the face-stock without shearing of the adhesive layer.

D. Workmanship

All label edges will be cut square and clean, and sizes accurate to specification.

E. Shelf-Life

The adhesive must have a one year usable shelf-life such that the initial adhesion strength will be the same for labels applied up to one year after the original delivery date under ambient storage conditions. The labels must also maintain their capacity to be printed upon.

F. Dimensions

Dimensions will be specified on the purchase order.

G. Packaging

The items must be packed in standard commercial containers which are constructed to ensure that they are received in perfect condition - dry, undamaged and without kinks or creases. The outside of each container must be identified by type, size and number of items within, manufacturing run or batch number and Purchase Order number or Contract number.

III. QUALITY ASSURANCE INSPECTION:

A. Testing

  1. Responsibility
    The supplier is responsible for meeting all the requirements specified herein. The Library of Congress has the right to perform any of the tests set forth in the specification where such tests are deemed necessary to ensure that supplies conform to prescribed requirements
  2. Sampling
    To sample for testing, shipments will be sampled according to MIL-STD-105E at inspection level S-2 with an acceptable quality level of 2.5 percent defective from each lot offered. Copies of MIL-STD-105E are available from Naval Publications and Forms Center; Standardization Document Order Department, Building 4, Section D; 700 Robbins Avenue; Philadelphia, Pennsylvania 19111-5094.
  3. Materials
    The following materials are required to perform the tests in this specification:
    • LC Standard Test Panel PP-1
    • LC Standard Test Panel PP-2
    • LC Standard Test Paper P-1
    • LC Standard Test Paper P-2
    • LC Standard Test paper P-3
    • LC Standard Test Paper P-4
    • Polyester (Mylar D)
    • 3M Tape #230
    • Carey Lea Silver Test Film
    • Elite Photographic Paper
    • Whatman No. 1 filter paper
  4. Methods
    Tests will be conducted in accordance with specified test methods of the American National Standards Institute (ANSI), the American Society for Testing and Materials (ASTM), and the Technical Association of the Pulp and Paper Industry (TAPPI) and/or as described. Publications describing these tests may be ordered directly from the technical associations:
    • ANSI, 1430 Broadway, New York, NY 10018
    • ASTM, 100 Barr Harbor Drive, W. Conshohocken, PA 19428-2959
    • TAPPI, One Dunwoody Park, Atlanta, GA 30348
  5. Tests
    Requirements
    		 Test Method
    pH (paper face-stock) 8.0 - 9.5 TAPPI T509 om-88
    Alkaline Reserve (paper) 2-5% ASTM D4988
    Lignin (paper) Kappa < 5 TAPPI T236 cm-85
    Brightness, initial > 82% TAPPI T452 om-92
    Brightness, after aging < 10 pts. change TAPPI T452 om-92
    Adhesive ID acrylic infrared spectrum
    Bond Strength 200g, < 10 mm peel ASTM D2860M-90 (modified)
    Bond Strength - Aged 200g, < 10 mm peel ASTM D2860M-90 (modified), after aging
    Curling/Lifting/Ooze none visual, after aging
    Staining < 3 points TAPPI T 452 om-92, after aging
    Damage to Adjacent Pages no blocking; no discoloration TAPPI T 452 om-92, after aging
    Print Fastness no legible characters on tape NARA Technical Information Paper No. 5
    Off-setting of Ink < 0.02 pts density GPO Test Method P-11
    Photo Activity Test pass ANSI IT9.16-1994

FAILURE TO MEET ANY OF THE SPECIFICATIONS WILL BE CAUSE FOR REJECTION.