What is a Bursting Strength Tester and Why is It Vital?

During transport, stacking, and handling, packaging materials like corrugated shipping boxes or heavy-duty paper sacks are continuously subjected to localized internal or external impact forces. If the material’s bursting resistance is insufficient, structural failure occurs, leading to torn packages and damaged merchandise.

A Bursting Strength Tester (frequently referred to as a Mullen Tester) is the standard mechanical instrument used to determine this structural threshold. The testing sequence involves securely clamping a flat material specimen over a circular opening. An internal hydraulic system then pumps fluid (typically glycerin) at a controlled, constant rate to expand a high-elasticity rubber diaphragm like a dome against the sample. The system increases hydraulic pressure until the material ruptures. The digital processor captures and locks the maximum pressure achieved, providing engineers with a critical metric to evaluate the material’s structural integrity.

Standard Specifications: Paper Testing vs. Corrugated Board Testing

When selecting a Bursting Strength Tester, configuring the machine to match your raw material matrix is vital, as international protocols specify distinct pressure ranges and components:

• Paper and Paperboard Testing (ISO 2758 / TAPPI T403): Tailored for single-layer sheets, linerboards, and kraft papers. This setup utilizes fine-resolution hydraulic controls and flexible diaphragms optimized to precisely capture low-to-medium rupture limits.

• Corrugated and Solid Fiberboard Testing (ISO 2759): Specially engineered for heavy-duty multi-wall corrugated board, industrial cardboard, and thick liners. This configuration utilizes high-capacity hydraulic cylinders and heavy-duty reinforced rubber diaphragms designed to withstand massive pressures before the corrugated fluting matrix gives way.

Frequently Asked Questions About Bursting Strength Testers (FAQ)

Q: Is there any difference between a Bursting Strength Test and a Mullen Test? > A: No, they refer to the exact same test. The term “Mullen Test” is widely used in the global packaging industry in honor of B.F. Mullen, who commercialized the very first hydraulic bursting apparatus. Therefore, when customer spec sheets request either a Mullen rating or Bursting Strength data, a standard Bursting Strength Tester is the exact tool required.

Q: How often does the rubber diaphragm need replacement, and does it impact accuracy? > A: The rubber diaphragm is a critical consumable component that experiences intense mechanical stretching during every test cycle, meaning its physical condition directly impacts data accuracy. Over time, the rubber can oxidize, stiffen, or develop micro-tears, which alters its intrinsic resistance and skews the test results. To secure valid, repeatable data, lab managers must calibrate the machine regularly, verify the diaphragm’s raw pressure resistance, and replace it according to the test cycles specified in the operating manual.