Summary of Standard D774

Method for Bursting Strength of Paper

Pam Poppaw

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Scope

• Measurements of the bursting strength of paper & paper products occurring as single of laminated flat sheets not over .025 in. thick, having a bursting strength of 30 kPa up to 1400 kPa (This test is not for testing corrugated boxboard, liner board, or hardboards)

Safety

• Follow all Lab safety rules.

Reference

• ASTM standards D585, D646, & D685

Terminology

• Bursting strength - The hydrostatic pressure in pounds per sq inch (or pascals) required to produce rupture of the material when the pressure is applied at a controlled increasing rate through a rubber diaphragm to a circular area 1.2 " in diameter, the area of the material under test being initially flat & held rigidly at the circumference but free to bulge under the increasing pressure during test.
• Points- interchangeable with pounds per sq. inch ( the unit of measure for bursting strength)

Significance and Use

• Used as a measure of the resistance to rupture in many kinds of paper (easy & simulates use)

Apparatus

• Bursting Tester - with a clamp to firmly secure test specimen and diaphragm plate, with controlled, increasing hydrostatic pressure by a fluid (USP 96% glycerin) at a rate of 95 +/- 5mL/min to the underside of the diaphragm until the specimen bursts and have a pressure gage ) diaphragm to be inspected frequently for distortion and replace is distorted.

Calibration and Maintenance

• Calibrate device with a dead-weight tester of the piston type in normal position at least once a month.

Procedure

• Sample in accordance with Method D 585
• Not less than 20 specimens, each at least 2.5 by 2.5 in. from each test unit of the sample
• Condition the sample in accordance with Method D 685
• Do a Preliminary test to determine the required capacity of the measuring device being used
• Clamp specimen securely in position, apply the hydrostatic pressure steadily until specimen ruptures
• Do at least ten acceptable tests ( not on areas containing watermarks, creases, imperfections, or visible damage)

Calculation

• Calculate bursting strength as the mean of the test results on each sample
• Convert burst in psi to burst in kPa : burst (psi) X 6.8948 = burst (kPa)
• Determine grammage (basis weight) as in Test Method D 646

Report

• Report - Bursting strength in kPa ( psi) - Number of tests - Max & Min values - Instrument used

Precision and Bias

• Precision - Repeatability = 5.4% - Comparability = 9.5% - Reproducibility = 14.3%
• Bias - This test method has no bias because the value of bursting strength is defined only in terms of the test method

Keywords

• Bursting strength
• Mullen test
• Paper & paper products

Checklist D744

The purpose of this test is to determine the mean bursting strength of paper.

Apparatus:

Use Mullen tester

1. Obtain samples per standard D585 - enough paper for 20 specimens at least 4" x 4"._______________

2. Condition samples per D 685. Record temp. of room_________ & rel. humidity of room___________

3. Examine clamping mechanism & clamping surfaces for wear or distortion - repair when necessary. Inspect diaphragm frequently for distortion & replace when needed. __________________

4. Do preliminary test to determine which pressure gage is needed for test. Always start with the high gage if unsure of bursting strength. ________________ Shut off air to gage not being used.

5. Raise the tripod and upper clamping plate by rotating the clamp wheel. Place sample to be tested over diaphragm and lower the clamping plate. _______________

6. Lower the tripod and plate, applying sufficient clamping pressure to prevent slippage of the sample between the plates during the test. Set the hand on the gage at zero. ________________

7. Start the motor and move the ball-handled control lever to the left. Keep hand on the lever to stop or reverse the machine at any time during the test. When burst occurs move the control lever as far as it will go to the right and release. ________________

8. Record the bursting pressure indicated on the gage and return hand to zero.

9. Repeat

1._________ 2.__________ 3.__________ 4.___________ 5.___________

6.___________ 7. ___________ 8.__________ 9.___________ 10. ___________

Average ________________