Ring crush of paperboard (flexible beam method) (REAFFIRMATION of Classical Method T 818 cm-07) (No changes from previous drafts)

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1 NOTICE: This is a DRAFT of a TAPPI Standard in ballot. Although available for public viewing, it is still under TAPPI s copyright and may not be reproduced or distributed without permission of TAPPI. This draft is NOT a currently published TAPPI Standard. WI T 818 DRAFT NO. 4 - SARG DATE October 3, 2018 WORKING GROUP CHAIRMAN Walter Rantanen SUBJECT CATEGORY RELATED METHODS Fiberboard Shipping & Container Testing See Additional Information CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is responsible for determining that the safety precautions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serious health hazards to humans. Procedures for the handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the use of this method, the user must determine whether any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemicals. Ring crush of paperboard (REAFFIRMATION of Classical Method T 818 cm-07) (No changes from previous drafts) 1. Scope 1.1 The ring crush test correlates with edgewise compression strength of paperboard (1). 1.2 This method is intended for paperboard between 0.28 mm (0.011 in.) and 0.51 mm (0.020 in.) thick. It may be used with less reliability for paperboard as thin as 0.18 mm (0.007 in.), and as thick as 0.76 mm (0.030 in.). The short span compression test, TAPPI T 826 Short Span Compressive Strength of Paperboard, measures edgewise compressive strength over a broader range of thickness. 1.3 Ring crush is also measured in TAPPI T 822 Ring Crush of Paperboard (Rigid Support Method), which uses a rigid platen compression machine instead of the flexing beam of this method. T 822 has a tighter precision. 2. Significance Approved by the Standard Specific Interest Group for this Test Method TAPPI

2 T 818 cm-07 Ring crush of paperboard / 2 The edgewise compression strength of corrugated board is a principal element in determining the dynamic compression strength of the container made from that board. Since fiberboard shipping containers are frequently subjected to loads which are resisted by compression strength, this property is an important measure of the performance characteristic of corrugated board, useful in controlling the manufacturing process and in measuring the quality of the finished product. Since edgewise compression can be estimated by a summation of the ring crush strengths of the liners and the medium, this test becomes a useful one for the corrugated boxmaker. 3. Summary A compressive force is exerted on a specimen held in ring form in a special jig and placed between two platens of a compression machine, by causing the upper platen to approach the lower platen at a uniform speed until the specimen collapses. 4. Apparatus 4.1 Compression machine 1, having upper and lower platens The lower platen rests on a beam which flexes on loading The compressive force applied is developed at a rate equivalent to 111 ± 22 N/s (25 ± 5 lbf/s) when the machine is under load with the platens in contact The surfaces of the platens are smooth, flat, and parallel to each other to within one part in 2000 throughout the test. That is, for mm (4 4 in.) platens, the difference in clearance between the platens shall not exceed 0.05 mm (0.002 in.) when a simulated load is applied. NOTE 1: The use of emery or crocus cloth on the platens, as in flat crush testing, is not permissible The platens are held rigidly with a maximum permissible lateral movement of 0.05 mm (0.002 in.) The beam, having a capacity of either 1112 N (250 lbf) or 2224 N (500 lbf), on loading operates a scale indicating the maximum deflection (at the beam's center). This deflection is linearly related to the force applied to the beam's center via the platens, and the scale is calibrated in units of force. The beam is supported so that it can be accurately calibrated with dead weights. NOTE 2: For calibrating, see Appendix A of TAPPI T 808 Flat Crush Test of Corrugated Board. 4.2 Specimen holder, composed of a circular block, having an annular square cut groove, 6.4 ± 0.25 mm (0.25 ± 0.01 in.) deep and 49.3 ± mm (1.940 ± in.) outside diameter. The bottom of the annular groove is required to be parallel with the base of the block ± 0.01 mm (± in.), with the sides of the groove at right angles. A branch groove tangent to the annular groove, of the same depth and extending to the edge of the block, is 1 Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list in the set of TAPPI Test Methods, or may be available from the TAPPI Technical Operations Department.

3 3 / Ring crush of paperboard T 818 cm-07 provided to insert the specimen and is not wider than 1.27 mm (0.050 in.) at its entrance to the annular groove. The center island created by the annular groove is removable and replaceable with disks of different diameters, so that the width of the groove may be adjusted to be at least 150% but not more than 175% of the nominal caliper of the specimen being tested. Each disk has a central hole to fit a receiving pin central to the annular groove and is free to turn as the specimen is inserted through the branch groove. Scribe or otherwise mark one point on the perimeter of the annular groove at some distance away from, preferably opposite, the branch groove. 4.3 Punch and die cutting device, capable of accurately cutting the test specimens to exact dimensions with clean, sharp, parallel edges. 5. Sampling and test specimens 5.1 Obtain the sample in accordance with TAPPI T 400 Sampling and Accepting a Single Lot of Paper, Paperboard, Fiberboard, or Related Product. 5.2 From each test unit, carefully die-cut test specimens felt side toward the male portion of the die , mm ( , in.) wide, , -0.2 mm ( , in.) long. Cut, so that the long dimension is perpendicular to the machine direction of the board for MD specimens, and the long dimension is parallel to the machine direction of the board for CD specimens. In cutting the specimens, take care to ensure that: The long edges are parallel, such that the widths at opposite ends are within mm ( in.) of each other The long edges are parallel (or perpendicular) to the machine direction of the board The edges are cleanly cut, without tears or frays. NOTE 3: Die cutting of single sheets is the proper way to cut the test specimen, meet the requirements of this section, and give test results within the precision stated. 5.3 For the purposes of this method, test a minimum of 10 specimens. 5.4 Periodically inspect a cut specimen under a low magnification to check for proper dimensions (5.2 and 5.2.1) and to insure that cuts are clean and sharp. 6. Procedure 6.1 Precondition, condition, and test the specimens in the atmosphere as specified in TAPPI T 402 Standard Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and Related Products. 6.2 Wearing rubber or plastic gloves, carefully insert each specimen in the holder, locating the ends so that they are at the scribed mark (4.2) (they do not coincide with the tangential groove). Alternately place the specimens in the holder so that half are tested with the felt side facing inward and half with the felt side facing outward.

4 T 818 cm-07 Ring crush of paperboard / 4 NOTE 4: It is important to use care when inserting the specimen in the holder to insure that the island does not rise and allow the specimen to get beneath the island. This would cause lower test results. 6.3 Place the holder with the test specimen on the center of the lower platen of the compression machine. It is desirable to fix stop blocks on the lower platen to insure the proper placing of the holder, but the holder can always be centered with care if the platen is marked or scribed. Position the holder so that the meeting specimen ends are always in the same position, i.e., directly in front of the operator. 6.4 Apply a load to the specimen by driving the upper platen downward until a maximum force is sustained. Immediately after reaching the maximum, the specimen will fail in the area projecting above the holder. Record this maximum load. 6.5 For mm (6.00-in.) test specimens, to convert test values to kilonewtons per meter, multiply readings in pounds force (lbf) by , readings in kilograms force (kgf) by and readings in newtons by For between-laboratory comparisons, collect the test specimens and determine their moisture content as a composite according to TAPPI T 412 Moisture in Paper. NOTE 5: The ring crush test is extremely sensitive to the moisture content of the paperboard under test. Since paperboards do not always condition to ideal moisture contents, knowledge of the latter will sometimes explain differences in between-laboratory results. 7. Report 7.1 Report separately the MD and CD test results (each an average of a minimum of ten determinations of the force per unit specimen length required to crush the specimens) in kilonewtons per meter to three significant figures (or in pounds force for 6-in. specimens to the nearest pound). 7.2 Include, for a complete report, the total number of specimens tested. 7.3 Report the moisture content if determined. 8. Precision 8.1 Repeatability (within a laboratory) = 5.2% MD, 6.6% CD (10 specimens/average). 8.2 Reproducibility (between laboratories) = 32% (each direction) (10 specimens/average). 8.3 The above data are in accordance with definitions of these terms in TAPPI T 1206 Precision Statement for Test Methods. 8.4 Ring crush testing using a fixed platen and load cell system (T 822) has significantly less variability than the current method and has supplanted this test method in much of the industry. Given the significant betweenlab variation of this test method, associated primarily with the use of the flexible-beam compression test equipment, this method is primarily useful for internal comparisons and measurements at a single facility.

5 5 / Ring crush of paperboard T 818 cm Keywords Compressibility, Ring crush tests, Corrugated boards, Paperboard, Fiberboards, Compression tests, Edge crush resistance 10. Additional information 10.1 Effective date of issue: to be assigned 10.2 Several changes have been made to this document since the 1987 revision as a classical method For cm-97, a correction was made in the conversions in and in the tolerance of the specimen holder (4.2). The wording in 6.1 was changed slightly For cm-07, text was added in 1.3 and 8.4 regarding the precision of the method relative to T 822. References to nonexistent organizations, test methods, or sections of test methods were removed. The diameter of the specimen holder in metric units (4.2) was corrected to 49.3 mm. Sample orientation in 5.2 was clarified to follow T This method was formerly TAPPI T 472 Compression Resistance of Paperboard (Ring Crush Test) Related methods: TAPPI T 822 and T 826; ASTM D 1164, Standard Test Method for Ring Crush of Paperboard ; Australian, APPITA P407, Ring Crush Test ; PAPTAC Standard D.33P, Ring Crush of Paperboard ; ISO Compressive strength ring crush method This method, formerly T 818 om-82, has been reclassifed as a Classical Method. Such procedures are no longer in common use or have been superceded by advanced technology; they are techically sound, have a history of use, and contain a body of literature references that make their preservation valuable. Reference 1. Koning, J.W., Jr., A Short Column Crush Test of Corrugated Fiberboard, Tappi 47(3): 134 (1964). Your comments and suggestions on this procedure are earnestly requested and should be sent to the TAPPI Standards Department.