Board – Analyzing Bursting Strength

The evaluation of paper or paperboard's bursting strength is a composite measure influenced significantly by various factors, notably tensile strength and stretch. Its determination hinges upon the intricate interplay of fiber composition, preparation techniques, refining processes, sheet formation dynamics, and additive integration. Employing a Mullen tester, the assessment involves subjecting a secured test specimen to escalating hydraulic pressure via a rubber diaphragm until rupture occurs. The pressure registered at the point of rupture defines the bursting strength, typically measured in pounds per square inch or "points". Commonly termed the "Mullen", "pop test", or simply the "burst", this measurement technique differs notably for paperboard compared to lighter papers due to the utilization of a heavier Mullen tester and a larger diaphragm opening.

• Bursting Strength Testing:
  

The Bursting Strength Tester, often referred to as the Mullen Test, is instrumental in evaluating the resilience of corrugated board walls under applied force. This procedure involves utilizing hydraulic pressure to expand a rubber diaphragm against the corrugated box walls until rupture occurs, measuring the bursting strength in Kilograms per square centimeter. Calculating the Bursting factor involves multiplying the bursting strength by a thousand and dividing it by the grammage of the board.

XD-A02 Bursting Strength Tester

• Determining Bursting Strength in Corrugated Sheets:
  
  

The Mullen test serves as an efficient means of assessing various materials, including paper, cardboard, corrugated sheets, and fabrics. It serves as a critical tool for evaluating the strength and quality of containers made from these materials. By precisely measuring the force needed to rupture a material sheet, the Mullen test assists in gauging its endurance and strength. However, it's essential to note that the test results do not directly correlate to the weight or product capacity per inch of the box; additional tests like edge crush, ring crush, and box compression are necessary for a comprehensive evaluation.

• Bursting Strength Test and Formulas:
  
  

The Mullen test yields the specimen's bursting strength, a pivotal parameter for assessing strength and determining the bursting factor—an indicator of endurance. The bursting factor is derived from a formula that considers bursting strength and the material's grammage.

Burst factor = Burst strength (gf/cm²) / Grammage (grams/m²)

The bursting strength value originates from the Mullen test, while Grammage represents the material's GSM. Similarly, the formula for bursting index also utilizes bursting strength and grammage, but expresses pressure in kPa:

Burst Index = Burst strength (kPa) / Grammage (Kg/m²)

This formula converts the bursting strength from gf/m² to kPa, with GSM measured in kg/m², typically determined using a GSM cutter and a weighing scale. These calculated values provide critical insights into material strength, facilitating optimization for enhanced performance.