T220

TENTATIVE STANDARD – 1942OFFICIAL TEST METHOD – 1946

REVISED – 1971

OFFICIAL TEST METHOD – 1983

REVISED – 1988

STANDARD PRACTICE – 1996

CORRECTED – 1997

© 1996 TAPPI

The information and data contained in this document were preparedby a technical committee of the Association. The committee and theAssociation assume no liability or responsibility in connection with theuse of such information or data, including but not limited to anyliability or responsibility under patent, copyright, or trade secret laws.The user is responsible for determining that this document is the mostrecent edition published.

Physical testing of pulp handsheets

1.

Scope and significance

1.1This procedure describes the testing of pulp handsheets, prepared in accordance with TAPPI T 205“Forming Handsheets for Physical Tests of Pulp,” for their strength and other physical properties as well as their light-scattering coefficient.

1.2 Information derived from handsheet testing indicates pulp quality and is a measure of the potentialcontribution of the pulp to the strength of the finished paper product.2.

Summary

2.1The measurements of handsheet properties to be described are as follows: mass per unit area(grammage), thickness, specific volume, apparent density, scattering coefficient, tensile strength, stretch, tensile energyabsorption, bursting strength, tearing resistance, and MIT folding endurance.

2.2Five sheets are generally enough for routine control work in a mill on a specified pulp. Ten sheets shouldbe used wherever possible and when testing mechanical pulp in order to provide enough paper to make four tears of tenstrips each. This makes it possible to use five sheets for tearing resistance and five other sheets for all other strengthtests. Ten sheets cannot be made when testing pulp from TAPPI T 200 “Laboratory Processing of Pulp (Beater Method)”because not enough sample is available and taking a larger sample will change the amount of pulp in the beater and,therefore, change the beating time.

2.3Results are reported in SI units and strength indexes are calculated on conditioned weight.3.

Conditioning

Inspect the sheets and discard any that are abnormal, (e.g. containing holes, uneven thickness, damaged, containingcontaminants such as dirt, plastic, metal bits). Condition in an atmosphere in accordance with TAPPI T 402 “StandardConditioning and Testing Atmospheres for Paper, Board, Pulp Handsheets, and Related Products” and test the sheetsfor each characteristic of interest according to the appropriate TAPPI test method for paper but with modifications asspecified below.

Approved by the Pulp Properties Committee of the Process and Product Quality Division

TAPPI

T 220 sp-9.

Mass per unit area (grammage)

Physical testing of pulp handsheets / 2Determine the average mass per unit area of five conditioned sheets by weighing them together on a balancesensitive to 0.001 g. The area of each sheet is approximate and is taken to be 200 cm2. The grammage is ten times theweight of the five sheets.5.

Thickness5.1

Apparatus1

Fig. 1.Division of sheets for testing.

5.1.1Micrometer, see TAPPI T 411 “Thickness (Caliper) on Paper and Paperboard.”5.2Procedure5.2.1Before cutting the test sheets, obtain their average thickness as follows: Place five sheets in a pile withtheir glazed surfaces in one direction. Using a motor-driven micrometer as specified in T 411, measure the thicknessof the pile of sheets at ten randomly selected points recording the thickness at each point to the nearest 2 󰀁m (0.0001 in.).

5.2.2If any reading is more than 5% above the others, make a measurement on an adjacent spot to determineif the high reading is caused by a shive, speck, foreign materials such as dirt, glass, plastic, etc. or fiber bundles resultingfrom a short disintegration time. If so, discard the high reading.6.

Light-scattering coefficient

6.1Apparatus16.1.1Opacimeter, see TAPPI T 425 “Opacity of Paper (15°/Diffuse, Illuminant A) % Reflectance Backingand Paper Backing.”

6.1.2Working standard of reflectance, calibrated to absolute scale as described in T 425.6.2Procedure6.2.1Place the working standard over the opening of the opacimeter and adjust the instrument reading to thevalue of the absolute reflectance of the working standard.

6.2.2Obtain the reading R0 by placing each sheet in the opacimeter with its smooth side against the black bodyand reading the reflectivity without adjustment of the instrument.

6.2.3Place the pile of five sheets in the opacimeter with the smooth sides toward the specimen holder and takea reading. Increase the number of sheets in the pile by inserting five more sheets of the same test or, if these areunavailable, sheets from another test that are similar in reflectance between the pile and the specimen holder. Takeanother reading. If there is a significant difference between the two readings, add additional sheets to the pile until no

Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list in the bound

set of TAPPI Test Methods, or may be available from the TAPPI Technical Services Department.

1

3 / Physical testing of pulp handsheetsT 220- sp-96significant change occurs with the addition of five more sheets. Using this pile of sheets, measure the reflectivity R󰀁 ofeach of the five test sheets keeping the other four test sheets immediately behind the sheet being tested.

6.2.4Use the average values of R0 and R󰀁 to calculate light scattering coefficient as described in 13.3.4.

NOTE 1:

For greater accuracy, the two measurements should be made on the same specimen area and the weight per unit area of the actual

test area used.

The R󰀁 value must be obtained using the opacimeter as described. A brightness reading cannot be used.

NOTE 2:

7.Cutting the sheets for remaining physical tests

7.1Apparatus17.1.1Double-knife, 15 mm (0.59 in.) wide cutter, or a single-knife cutter equipped with a guide to give a strip15 mm wide.

7.2Procedure7.2.1Place the pile of five sheets on the cutting anvil with the diameter of the pile accurately situated alongone of the anvil's edges.

7.2.2Cut the sheets as shown in Fig. 1. By testing the folding endurance with an MIT tester at one end of astrip, with care, the longer part of the remnant is not appreciably damaged and is quite suitable for another fold test ifit is inserted in the tester in such a manner that the folding test is made on the part of the strip that protruded above thetop clamp. The strip should not be used for a tensile test as the tension placed on the strip in making the fold test willchange the characteristics of the paper.8.

Tensile strength (stretch and tensile energy absorption)

8.1Apparatus18.1.1Tensile tester, see TAPPI T 494 “Tensile Breaking Properties of Paper and Paperboard (Using ConstantRate of Elongation Apparatus).”

8.2Procedure8.2.1Use at least one specimen strip from each of the five test sheets, cutting each strip 15 mm wide. Set thejaws of the tensile tester 100 mm apart.

8.2.2Determine the tensile strength, stretch, and tensile energy absorption simultaneously in accordance withT 494 except for the size of the specimen.

NOTE 3:

TAPPI T 404 “Tensile Breaking Strength and Elongation of Paper and Paperboard (Using Pendulum-Type Tester)” may be usedto determine tensile strength, but this should be noted in the report.

9.Bursting strength

9.1Apparatus19.1.1Bursting tester, see TAPPI T 403 “Bursting Strength of Paper.”9.2Procedure9.2.1Determine the bursting strength by making at least ten bursts one at a time on the segments of five testsheets, the glazed side of each sheet being clamped toward the diaphragm, otherwise in accordance with T 403.10.

Tearing resistance

10.1Apparatus1

10.1.1Elmendorf tearing resistance tester, see TAPPI T 414 “Internal Tearing Resistance of Paper.”10.2Procedure

10.2.1Determine the tearing resistance as described in T 414, with modifications indicated below. Clamp thesheets so that their smooth sides face the axis of the instrument and the greater part of the specimen is held in the fixed,not the moving, jaw.

10.2.2For chemical pulps, cut sections from five test sheets in the manner shown in Fig. 2 and test the fivesections (plys) together, making four tears across the width of the sections, each being through a total tearing distance

T 220 sp-96Physical testing of pulp handsheets / 4of 215 mm (5 x 43 mm). If the scale on the tearing resistance tester is in grams, multiply the average reading on thestandard tester by 3.2 (i.e., 16/5) to obtain the force in grams required to tear a single sheet. If the specimens should besuch that five sheets together give a reading above 60, reduce the number of sheets torn together to two and multiply theobserved reading by 8 to give the force in grams to tear a single sheet. If the instrument scale is in millinewtons, dividethe reading by the number of sheets torn.

10.2.3For mechanical pulps, use ten sheets (plys) and multiply the average reading by 1.6 to obtain the forcein grams required to tear a single sheet.

NOTE 4:

Accuracy is enhanced, especially if the segments of sheets are cut somewhat narrow, if a template is used to draw a pencil line 47.0mm from the centrally cut edges of the pack of specimens as shown in Fig. 2. When it is clamped in the jaws of the instrument,align the pack so that the scribed line coincides with the top edges of the jaws. The knife should be checked to cut 4.0 mm abovethese edges, to give the standard tearing distance of 43.0 mm. If an instrument’s digital display limits the number of available testplies (i.e., 1, 2, 4, 8, 16 plies), test the number of plies closest to the recommended number in the method and keep the total tearingdistance for all test specimens for a given sample constant (i.e., 5 each, 4-ply tears for chemical pulps). Note any modifications inthe report.

11.Folding endurance11.111.1.111.211.2.1

Apparatus1

MIT folding tester, see TAPPI T 511 “Folding Endurance of Paper (MIT Tester).”Procedure

Determine the folding endurance of the 15-mm-wide strip of paper cut as shown in Fig. 1.

Fig. 2. Detail of tearing test

11.2.2With the MIT tester, only a 10-mm portion or so of the strip needs to be clamped in the lower (moving)jaw and the exact tension of 1 kg applied, leaving the extra length of the strip projecting through the upper jaw. Becausethe part of the strip above the upper clamp is not appreciably affected by the test, the upper end of the strip can be usedfor another fold test making the fold in the part of the strip that was above the clamp.

11.2.3For a referee test, make 20 determinations using 10 strips and making two tests on each strip.

NOTE 5:

The folding test is very sensitive to moisture. Accordingly, avoid touching the vicinity of the fold line with the fingers. The foldtester should be equipped with a fan to draw room air across the head to keep it cool (see T 511).

5 / Physical testing of pulp handsheets12.

Moisture content

T 220 sp-9612.1Apparatus1

12.1.1See TAPPI T 550 “Determination of Equilibrium Moisture in Pulp, Paper, and Paperboard for ChemicalAnalysis.”

12.2Procedure

12.2.1Determine the moisture content using the procedures described in T 550 on scrap samples of the pulphandsheets being tested.13.

Other tests

If desired, other tests, such as porosity (air pressure, applied to the glazed side of the sheets), stiffness, zero span,etc., may be made according to accepted procedures.14.

Report

14.1Report results in terms of their derived units to three significant figures. If the direct test results arereported, i.e., the actual instrument readings, either (a) metric, (b) English, or (c) SI units may be used as is commonpractice, the units being stated in each case. For derived units, however, such as the various strength indexes, only theSI units are acceptable.

14.2Calculate and report all the results on the conditioned mass per unit area of the test sheets.14.3The calculations of the various items reported are shown below by formulas in which:

r = mass per unit area, g/m2t = single sheet thickness, µm

T = single sheet thickness, 0.001 in.b = bursting strength, kPaB = bursting strength, lbf/in.2

p = tensile break load, kgf on a 15-mm stripP = tensile break load, lbf on a 0.59-in. stripe = force to tear a single sheet, g

14.3.1Mass per unit area: in g/m2.

14.3.2 Specific volume (bulk): calculated as cm/g: from t/r or 25.4 T/r.

3

NOTE 6:

The result compares the bulk of the test sheets (measured under the prescribed pressure) to water, which has a “bulk” of 1.0 cm3/g,about the same as a dense glassine.

14.3.3Apparent density: calculate as g/cm3 from r/t or r/25.4 T.

14.3.4Light scattering coefficient: obtain the value of sW from the chart in T 425 using the values obtained forR0 and R󰀁. Scattering coefficient = sW/r.

14.3.5Folding endurance: correct for variations in basis weight by multiplying the average folding enduranceobtained by 65/r.

14.3.6Logfold: obtain the logarithm to the base 10 for each folding endurance measurement. Average thelogarithms and correct for variations in basis weight by adding (1.813-log r) to the average log. Report as the log foldingendurance.

14.3.7 Bursting strength, kPa, from the formula 6.B.14.3.8 Tearing resistance, mN, from the formula 9.807e.

14.3.9 Tensile strength, kN/m, from the formula 0.6538 p or 0.2966 P.14.3.10 Stretch, %.

14.3.11 Burst index, kPa m2/g, from the formula b/r or 6. B/r.14.3.12 Tear index, mN m2/g from the formula 9.807 e/r.14.3.13 Tensile index, N m/g from 653.8 p/r or 296.6 P/r.

14.3.14Breaking length, km, calculated from the formula 200p/3r or 30.24P/r.14.3.15Percent moisture content on conditioned weight basis.

T 220 sp-96NOTE 7:

Physical testing of pulp handsheets / 6The breaking length corresponds to the length in kilometers of a uniformly wide strip of paper which, if held at one end (e.g., freelysuspending a coil of that paper by its tab end), would just cause the strip to break under its own weight.

15.Precision

A precision statement for this standard practice is not applicable as precision statements accompany each of thereferenced test methods.16. Keywords

Pulp, Handsheets, Physical tests.17.

Additional Information

17.1Effective date of issue: February 9, 1996.17.2This revision has been reissued as a standard practice with the inclusion of the determination andreporting of the moisture content. This revision specifies all test results will be reported on the basis of conditionedweight rather than oven dry weight, substitutes the terms “burst index” and “tear index” for the old terms of “burst factor”and “tear factor,” and introduces the use of SI units. A formula for correcting folding endurance for variations in basisweight has been introduced. Folding endurance is reported as the log fold.

17.3Related methods: Canadian, CPPA D 12; Australian and New Zealand, APPITA P 208; German,VZUPCI.V. 10-13; Scandinavian SCAN C 28:76.References1.2.3.4.

Clark, J. d'A., “The Bulk of Pulp Test Sheets,” Tappi 53 (7): 1340 (1970).

Clark, J. d'A., “Measuring Stretch Accurately with a Pendulum Tensile Tester,” Tappi 53 (3): 503 (1970).Brandon, C. E., “Effect of Basis Weight on Folding Endurance,” Tappi 49 (6): 233 (1966).

Brandon, C. E., “The Precision of the TAPPI Standard Beater Test,” Tappi 41 (9): 129A (1958).

Your comments and suggestions on this procedure are earnestly requested and should be sent to the TAPPI Technical

󰀂Divisions Administrator.