T 494 om-06
SUGGESTED METHOD – 1964
OFFICIAL STANDARD – 1970
OFFICIAL TEST METHOD – 1981
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CORRECTED – 1982
REVISED – 1988
REVISED – 1996
REVISED – 2001
REVISED – 2006gary oldman
©2006 TAPPI
The information and data contained in this document were prepared
by a technical committee of the Association. The committee and the
Association assume no liability or responsibility in connection with
the u of such information or data, including but not limited to any
liability under patent, copyright, or trade cret laws. The ur is
responsible for determining that this document is the most recent
edition published.
Approved by the Standard Specific Interest Group for this Test Method
TAPPI
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 the is to alert the ur of the method to safety issues related to such u. The ur is responsible for determining that the safety precautions are complete and are appropriate to their u of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the u, disposal, or both, of chemicals which may prent rious health hazards to humans. Procedures for the handling of such substances are t 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 u of this method, the ur must determine whether any of the chemicals to be ud or dispod 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 u and disposal of the chemicals.
Tensile properties of paper and paperboard
(using constant rate of elongation apparatus)
1. Scope
1.1 This test method describes the procedure, using constant-rate-of-elongation equipment, for determining four tensile breaking properties of paper and paperboard: tensile strength, stretch, tensile energy absorption, and tensile stiffness.
1.2 This procedure is applicable to all types of paper and paperboard within the limitations of the instruments ud, whether the instruments perform horizontal or vertical tests or whether they are manually operated or computer controlled. It is also applicable to handsheets, with modifications, as specified in TAPPI T 220 “Physical Testing of Pulp Handsheets.” It does not apply to combined corrugated board.
2. Definitions
2.1 Tensile strength, the maximum tensile force developed in a test specimen before rupture on a tensile test carried to rupture under prescribed conditions. Tensile strength (as ud here) is the force per unit width of test specimen.
2.2 Stretch, the maximum tensile strain developed in the test specimen before rupture in a tensile t
est carried to rupture under prescribed conditions. The stretch (or percentage elongation) is expresd as a percentage, i.e., one hundred times the ratio of the increa in length of the test specimen to the original test span.
2.3 Tensile energy absorption (TEA), the work done when a specimen is stresd to rupture in tension under prescribed conditions as measured by the integral of the tensile strength over the range of tensile strain from zero to maximum strain. The TEA is expresd as energy per unit area (test span × width) of test specimen.isa rver
2.4 Tensile stiffness, the ratio of tensile force per unit width to tensile strain within the elastic region of the tensile-strain relationship. The elastic region of the tensile-strain relationship is the linear portion of the load-elongation relationship up to the elastic limit. The elastic limit is the maximum tensile force above which the load-elongation
T 494 om-06 Tensile properties of paper and paperboard / 2
(using constant rate of elongation apparatus) relationship departs from linearity. (Tensile stiffness is numerically equivalent to E•t, where E is the modulus of elasticity and t is sample thickness.)
2.5 Breaking length, the calculated limiting length of a strip of uniform width, beyond which, if such a strip were suspended by one end, it would break of its own weight.
index, the tensile strength in N/m divided by grammage.
2.6 Tensile
NOTE 1:ISO/TC6 recommends the u of tensile index over breaking length. See TAPPI T 1210 or TIP 0800-01 “Units of Measurement and Conversion Factors.”
3. Significance
3.1 Tensile strength is indicative of the strength derived from factors such as fiber strength, fiber length, and bonding. It may be ud to deduce information about the factors, especially when ud as a tensile strength index. For quality control purpos, tensile strength has been ud as an indication of the rviceability of many papers which are subjected to a simple and direct tensile stress. Tensile strength can also be ud as an indication of the potential resistance to web breaking of papers such as printing papers during printing on a web fed press or other web fed converting operations. When evaluating the tensile strength, the stretch and the tensile energy abso
rption for the parameters can be of equal or greater importance in predicting the performance of paper, especially when that paper is subjected to an uneven stress such as gummed tape, or a dynamic stress such as when a sack full of granular material is dropped.
3.2 Stretch (sometimes evaluated in conjunction with bending resistance) is indicative of the ability of paper to conform to a desired contour, or to survive nonuniform tensile stress. It should be considered important in all papers, but is of particular importance in papers where stress-strain properties are being modified or controlled. This includes creped paper, pleated paper, air-dried paper, and paper that has been made extensible through mechanical compaction. Stretch may be ud as an indication of the amount of crepe in tissues, towels, napkins, and similar grades. Stretch is evaluated in decorative papers and certain industrial grades such as paper tapes and packaging papers, both as an index of how well the paper will conform to irregular shapes and, along with tensile energy absorption, as an indication of the paper’s performance under conditions of either dynamic or repetitive straining and stressing. Stretch has also been found important in reducing the frequency of breaks on high-speed web fed printing press such as are ud to print newspapers.
3.3 Tensile energy absorption is a measure of the ability of a paper to absorb energy (at the strain rate of the test instrument), and indicates the durability of paper when subjected to either a repetitive
or dynamic stressing or straining. Tensile energy absorption express the “toughness” of the sheet. An example of this is a multi-wall sack that is subject to frequent dropping. In packaging applications such as multi-wall sacks, favorable drop tests and low failure rates have been found to correlate better with tensile energy absorption than with tensile strength.
3.4 Tensile stiffness tells of the stiffness of the sheet and often gives a better indication of the mechanical respon of the sheet to converting forces than does failure criteria.
4. Apparatus
4.1 Tensile testing machine1, a constant-rate-of-elongation type (1), meeting the following requirements:
4.1.1 Two clamping jaws, each with a line contact for gripping the specimen, with the line contact perpendicular to the direction of the applied load and with means for controlling and adjusting the clamping pressure.
NOTE 2:“Line contact” describes the clamping zone resulting from gripping the specimen between a cylindrical and a flat surface or between two cylindrical surfaces who axes are parallel (2).
NOTE 3:For certain grades of paper “line contact” jaws may not be appropriate and it may be necessary to substitute flat gripping surfaces.
Certain grades are damaged by the “line contact” loading between cylindrical and flat surfaces. The u of emery cloth on flat
gripping surfaces will help minimize slippage for some board grades.
4.1.2 The clamping surfaces of the two jaws shall be in the same plane and so aligned that they hold the test specimen in that plane throughout the test. The clamping lines shall be parallel to each other within an angle of ± 1°, and
1
哥伦比亚大学校训Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list in the t
of TAPPI Test Methods, or may be available from the TAPPI Quality and Standards Department.
3 / Tensile properties of paper and paperboard T 49
4 om-06 (using constant rate of elongation apparatus)
shall not change more than 0.5° during the test. The applied tensile force shall be perpendicular to the clamp lines within ± 1° throughout the test.
4.1.3 The distance between line contacts at the start of the test shall be adjustable and rettable to ± 0.5 mm (nominally 0.02 in.) for the specified initial test span (6.4). (See 11.3.)
4.1.4 The rate of paration of jaws shall be 25 ± 5 mm/min (nominally 1.0 in. /min), or as otherwi noted (6.5) and once t shall be rettable and constant to ± 4%. (See 11.3.)
4.1.5 Recorder or indicator capable or indicating the actual force on the specimen within 1% or 0.1 N, whichever is greater.
4.1.6 Recorder speed or indicator shall be adjustable to provide a readability and accuracy of ± 0.05% stretch.
jig (optional) (2) to facilitate centering and aligning the specimen in the jaws, so that the
4.2 Alignment
clamping lines of contact are perpendicular to the direction of the applied force and the center line (long dimension) of the specimen coincides with the direction of applied force.
or integrator, respectively, to measure the area beneath the load-elongation curve or to
4.3 Planimeter韩国字转换器
compute directly the work to rupture, with an accuracy of ± 1%.
cutter, for cutting specimens of the required width, with straight parallel sides (5.3).
4.4 Specimen
4.5 Magnifier and scale or optical comparator, capable of measuring the specimen width to the nearest 0.1 mm (0.004 in.).
NOTE 4:Fully automated laboratory management and/or data acquisition systems are available which perform veral functions such as: automatic calibration check, pre-tting and storing a variety of test programs, cutting the test strip, acquiring test data, and
accurately determining the tensile breaking properties of paper and paperboard. The tests may be performed with the test strip
horizontal or vertical by such equipment. Such equipment may be suitable for u in performing this method; however, the ur is
responsible for making independent asssment of this fact on the basis of data generated using specific equipment.
5. Sampling and test specimens
5.1 For sampling for acceptance of a lot of paper, paperboard, related product, without prior agreement between buyer and ller, u TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard, or Related Product.”
5.2 For sampling for quality control and other purpos, u accepted and agreed upon company and laboratory sampling practices.
5.3 Precondition, then condition, the sample in accordance with TAPPI T 402 “Standard Conditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and Related Products” prior to cutting
the specimens.
NOTE 5:The exposure of the paper to a high relative humidity before preconditioning and conditioning can lead to erratic results varying from a decrea in stretch and tensile to a substantial increa (30% increa in stretch not uncommon) in the properties.
Conquently, TEA is similarly affected. Careful protection of the sample from the time of sampling until testing is therefore very
important.
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5.4 Cut 10 test specimens from each test unit of the sample in each principal direction of the paper 25 ± 1 mm (nominally 1.0 in.) wide with sides parallel within 0.1 mm (nominally 0.004 in.) and long enough to be clamped in the jaws when the test span is 180 ± 5 mm (nominally 7.0 in.), leaving enough length so that any slack can be removed from the strip before clamping. (See 11.3.) Insure that strips are free from abnormalities, creas, or wrinkles. In some cas, it may be impossible or impractical to obtain a test specimen having a length long enough to be clamped in the jaws having the test span specified here. In such cas, e Appendix A.3.1 for special considerations and procedures required for testing samples at smaller test spans.
6. Procedures
abnt minded6.1 Perform the test in the testing atmosphere specified in T 402.
6.2 If the test specimen width is not known to 0.1 mm (nominally 0.004 in.) (i.e., if a previously evaluated precision cutter is not ud), determine width and parallelism using magnifier and scale. Lack of parallelism is indicated by a difference in width of the two ends of the specimen.
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6.3 The testing machine shall be calibrated and adjusted as described in Appendixes A.1 and A.2.
6.4 Set the clamps to an initial test span (distance between line contacts) of 180 ± 5 mm (nominally
7.0 in.). Determine and always ret this distance within ± 0.5 mm (nominally 0.02 in.). (See Appendix A.1.3.)
T 494 om-06 Tensile properties of paper and paperboard / 4
(using constant rate of elongation apparatus)
6.5 Set the controls for rate of paration of the jaws to 25 ± 5 mm/min (nominally 1.0 in./min). (See 11.3.) In cas where the time required to break a single strip exceeds 30 s, a more rapid rate of jaw paration shall be ud, such that the time to break a single strip will be between 15 and 30 s. In such cas, the speed of the instrument must be reported, along with the test data.ratrace
NOTE 6:For purpos of determining shipping sack and shipping sack paper TEA compliance with Carrier and Federal requirements, Uniform Freight Classification Rule 40, National Motor Freight Classification, Item 200, UUS 48 and Department of
Transportation 178.236, 4.8 in. (122 mm) between the jaws and 1 in. (25 mm) per minute jaw paration should be ud.
6.6 Select recorder speed or indicator to give a readability equivalent to 0.05% stretch.
6.7 Select the full-scale reading, if possible, so that breaking force can be read in the upper three-fourths of the scale. Make preliminary trial tests if necessary to determine full-scale load.
NOTE 7:If, for any reason, any of the testing conditions specified above (specimen length, rate of jaw paration, sample width, etc.) cannot be followed becau of the small sample size or other reason, the method variance must be stated in the report.
6.8 Align and clamp the specimen first in one jaw and then, after carefully removing any noticeable slack, but without straining the specimen, in the cond jaw. While handling the test specimen, avoid touching the test area between the jaws with the fingers. U a clamping pressure determined to be satisfactory (Appendix A.1.4), i.e., so that neither slippage nor damage to the specimen occurs. Automated instruments for which both jaws clo simultaneously are within the context of this method.
6.9 Test 10 specimens in each principal direction for each test unit.
6.10 Reject any value in which the test specimen slips in the jaws, breaks within the clamping area, or shows evidence of uneven stretching across its width. Also reject any values for test specimens which break within 5 mm of the clamp area if further inspection indicates the break location is due to improper clamping conditions or misalignment. If more than 20% of the specimens for a given sample are rejected, reject all readings obtained for that sample, inspect the apparatus for conformance with specifications, and take any steps necessary to correct the trouble.
6.11 If determining tensile strength and stretch, read and record the breaking force to 0.5% of full scale and the elongation at break to the equivalent of 0.05% stretch.
6.12 If determining tensile energy absorption, record the integrator reading or u the planimeter to determine the area under the load-elongation curve from zero load to the breaking load.
NOTE 8:For the purpo of terminating integration, the specimen will be deemed broken when maximum tensile load has been reached and the tensile load has dropped no more than 0.25% of the full-scale load below the maximum load. This procedure is applicable in
the determination of TEA as long as maximum strain occurs at rupture, which is usually the ca.
6.13 If determining tensile stiffness, measure the strain at two force levels within the elastic region of the tensile force-strain relationship. The lower of the two force levels must be at least 5% of the apparent elastic limit, the higher not more than 75%, and the two force levels must be parated by at least 20% of the apparent elastic limit. For purpos of this measurement, the apparent elastic limit is defined as the point at which the tensile force-strain relationship departs from linearity. Alternately, the slope can be continuously monitored, and the maximum value taken as the measure of tensile stiffness. Determine the tensile stiffness, S t, from:
S t= (Δf•L) / (w•ΔL)
where:
S t = Tensile stiffness, kN/m
Δf= difference between two force levels, kN
天津新东方英语学校L= initial test length, m
w= initial specimen width, m
ΔL = change in length corresponding toΔf, m
7. Calculations
7.1 For each test unit and in each principal direction, calculate from the recorded values the average breaking force, average elongation at break, average integrator or planimeter value, and the average elastic slope, as required.
5 / Tensile properties of paper and paperboard T 494 om-0
6 (using constant rate of elongation apparatus)
Correct the instrumental results, if necessary, according to the correction curve described in the App
endix (A.2.2). Corrections for instrumental deflection need to be applied to both the elongation and energy measurements. Determine the range or standard deviation in each ca.
7.2 Divide the average breaking force by the specimen width (as determined in 6.2) to obtain the tensile strength. If this has been measured in pounds and inches, convert to kN/m by multiplying by 0.1751. If this has been measured in kg/mm, convert to kN/m by multiplying by 9.807.
NOTE 9:To calculate the breaking length (air dry) in meters u the following formula:
BL = 102,000 (T/R ) = 3658 (T´/R´)
To calculate the tensile index in newton meters per gram u the following formula:
TI = 1000 (T/R ) = 36.87 (T´/R´)
where
TI = tensile index, N ● m/g
BL = breaking length, m
T= tensile strength, kN/m
T´= tensile strength, lbf/in.
R= grammage (air dry), g/m2
R´= mass per unit area (air dry), lb/1000 ft2
7.3 To calculate the percentage stretch, divide the average elongation at break by the initial test span (as determined in 6.4) and multiply by 100.
7.4 Multiply the average integrator or planimeter value by the appropriate factor for the equipment and ttings ud to obtain the area under the load-elongation curve (Note 8) in energy units, joules (preferred) or inch-pound force. Then calculate the tensile energy absorption, according to one of the following formulas (e Appendix A.4 for proof of constants):
TEA = 1 × 106A/LW or 9.807 × 104A´/LW or 175.1 a/lw
tea = 12 a/lw
where:
TEA = tensile energy absorption, J/m2
L= initial test span, mm
W= specimen width, mm
A= area under load-elongation curve, J
A´= area under load-elongation curve, kgf •cm
tea = tensile energy absorption, ft • lbf/ft2
a = area under load elongation curve, lbf • in.
l= initial test span, in.
w= specimen width, in.
To convert tensile energy absorption in ft • lbf/ft2 to J/m2, multiply by 14.60.
NOTE 10:The “area under the load-elongation curve” is the area between the curve and the elongation axis.
7.5 Divide the elastic slope by the specimen width to obtain the tensile stiffness. If the slope has been measured in pounds and inches, convert to kN/m by multiplying by 0.1751.
7.6 Determine the corresponding ranges or standard deviations from the ranges or standard deviations of the measured values (7.1).
NOTE 11: Hardware/software systems are available that will perform all calculations required in the desired units of measurements.
