Pam Poppaw

Summary of Standard T 810

Bursting strength of corrugated and solid fiberboard

Pam Poppaw

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Scope

Method for measuring the bursting strength of single wall and double wall corrugated and solid fiberboard. (not paper, paperboard, linerboard, or triple wall corrugated board)

Significance

Bursting strength of combined board is primarily an indication of the character of the materials used in manufacturing a fiberboard box. It does not correlate well with container performance. Bursting strength of combined board is an optional requirement of the various carrier regulations and federal specification for shipping containers. Test is simple and rapid to execute, but it must be recognized that it is subject to serious errors if instrument, diaphragm, and gages are not properly maintained or if improper procedures are used.

Apparatus

Bursting test consisting of:

Clamp test specimen between two planes
a diaphragm requiring a pressure of not less than 159 kPa nor more than 207 kPa
means of forcing liquid into the pressure chamber below the diaphragm at a steady rate of 170 +/- 16 mL/min
a pressure gage of the maximum reading or the lazy hand type
an alternate pressure gage
vernier, caliper with micrometer gage to measure penetration of the upper clamping plate into the board.

Calibration

Calibrate gages frequently to ensure their accuracy (once a week if in constant use or before using if they have been idle for a month or more)
If a gage is accidently subjected to a pressure beyond its capacity, recalibrate it before it is again used

Sampling & test specimens

Solid fiberboard

Obtain & prepare in accordance with TAPPI T 400 at least five 12 x 12 in. specimens or at least enough for 20 bursts

Corrugated board

Obtained in accordance with T 400 five 12 x 12 in specimens or enough to permit a total of 20 bursts

Conditioning

In accordance with TAPPI T 402

Procedure

Solid fiberboard

Place specimen between the clamping ring and diaphragm plate & apply pressure of 100 psi ( specimen must not slip during test)
Apply bursting pressure by forcing the piston forward until the diaphragm ruptures the specimen & record the maximum registered by the gage (return to zero)
Allow a 4 x 4 in. area for each burst to prevent clamping overlapping
Make an equal number of bursts from each side of the specimen
No more than one burst from each side of specimen in the same line of machine formation
Do not test on areas containing wrinkles, creases, or other imperfections
Make a minimum of 6 bursts & a maximum of 10 bursts (12 x 12 in.) to determine the average bursting strength of the material tested

Corrugated board

Insert specimen between clamping ring & diaphragm plate, applying pressure so that the top compression ring moves into the board to a depth of:

"A" flute .082 +/- .002 in.
"B" flute .032 +/- .003 in
"C" flute .12 +/- .006 in..

Specimen must not slip during test, apply bursting pressure by forcing piston forward until the diaphragm ruptures the specimen
Record maximum registered by the gage & gently return the indicator of the gage to zero
A minimum of 6 x 6 in. is required for each burst - a maximum of 4 bursts (2 each direction)
Make a minimum of 20 bursts with not more than one burst each direction in same line

Report

Report test averages in kilopascal to 3 significant figures

Precision

Repeatability (within a laboratory) = 5.7%
Reproducibility (between laboratories) = 13.5%

Additional Information

Effective date of issue: 4/24/92
For flat diaphragm type instrument - an alternative instrument with a hat-shaped diaphragm may be used

To change diaphragm, rotate the operating handle to start the motor pumping cycle & immediately return handle clockwise to its top
Unscrew the lower platen & remove old diaphragm & fiber spacer washer & wipe diaphragm set dry. Insert new diaphragm & place fiber spacer washer on the diaphragm shoulder. Replace the lower platen & tighten. ( if leak occurs add another spacer washer)
Liquid is replaced under the diaphragm by a special liquid gun. A special bleeder tube to remove air from chamber.
The diameter of the upper clamping plate using the hat-shaped diaphragm is slightly smaller than the previous tester

References

Institute of Paper Chemistry, "A Method for Determining the Bursting Strength (Mullen) of Paperboard & Paperboard Products"
McKee, R. C., Root, C. h. and Ayers, L. R. "Instrumental and Operational Variables Influencing Bursting Strength Results,"
Pitman, G.A., "Problems of Entrapped Air in Mullen Testers"

Checklist T 810

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

Apparatus:Use Mullen tester

1. Obtain samples in accordance with T 400 - enough corrugated for 5 specimens at least 12" x 12". (enough for 20 bursts) _______________

2. Condition samples per TAPPI 402. Record temperature. of room_________ &

relative. humidity of room___________

3. Examine clamping mechanism & clamping surfaces for wear or distortion - repair when necessary. Inspect diaphragm frequently for distortion & replace when needed. Make sure gages are calibrated per required frequency__________________

4. Do preliminary tests to determine which pressure gage is needed for test and to determine clamping pressure. 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 .________________

6. Lower the tripod and lower the clamping plate until it rests on top of the sample, then give the clamp wheel one quarter turn 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 maximum registered bursting pressure indicated on the gage and return hand to zero.

9. Repeat

1._________ 2.__________ 3.__________ 4.___________ 5.___________ 6.___________

7. ___________ 8.___________ 9.___________ 10. ___________ 11. __________ 12. __________

13. __________ 14. __________ 15. __________ 16. ___________ 17. ___________ 18. ___________

19. ___________ 20. __________ Average ________________

Avoid overlapping of the clamping areas and disregard any single readings that are not reasonably consistent with those around sample.

If the Mullen Tester looses fluid from its system by leakage or diaphragm breakage air will accumulate and affect the accuracy of the readings. The system will need to be bled. Follow instructions "Bleeding the Gage". (page 6 of manual) There are also instructions for replacing the rubber diaphragm (page 5)