Introduction
In the quality assessment of packaging materials, the mechanical properties of cardboard are a key indicator. Puncture strength and breaking resistance are two commonly used test parameters that reflect the ability of a material to resist dynamic impact and static pressure, respectively. Although the test principle and loading method are different, both are closely related to the fiber structure, lamination process and raw material characteristics of cardboard. Therefore, exploring the correlation between the two is of practical significance for optimizing quality control, predicting material properties, and simplifying the inspection process. This paper analyzes the correlation between cardboard puncture strength and breaking resistance from the perspectives of test standards, mechanisms and data.
Test methodology
The puncture strength test simulates the resistance of cardboard to being impacted by sharp objects during transportation and handling, usually using a puncture strength meter to record the energy required to completely penetrate the cardboard in joules. The breakage resistance test evaluates the maximum pressure of the cardboard at uniform increasing pressure until it breaks, using a breakage test, and the result is expressed in kilopascals. Both tests follow international and domestic common standards, ensuring consistency in test conditions and comparability of results.
| Piercing strength | Breakage resistance |
| Dynamic impact test | Static stress test |
| Unit: Joule | Unit: kPa |
| Simulate sharp object impacts | Simulate uniform pressure |
| Relevant standards: ISO 3036, etc | Relevant standards: ISO 2758, etc |
From the perspective of material mechanics, the puncture strength and breaking resistance are affected by the bonding strength, fiber length and interlayer bond quality of cardboard fibers. The breaking resistance mainly reflects the in-plane tensile strength and the integrity of the fiber network, while the puncture strength depends more on the toughness and energy absorption capacity of the fiber. Theoretically, cardboard with tight fiber structure and good interlayer bonding may show high values for both indicators. However, due to the difference between the loading rate and the degree of stress concentration, the relationship between the two is not simply linear. The puncture process under dynamic impact involves various failure modes such as shear and tearing, while the breakability test is closer to the biaxial tensile state.
A large number of experimental data can establish a statistical relationship between the two indicators. The common model is an empirical formula, which can be expressed as:
E = k × P + b
Among them, E represents the puncture strength, P represents the breaking resistance, k is the correlation coefficient, and b is the constant term. The coefficient k is affected by factors such as cardboard quantification, slurry type and humidity conditions. It is important to note that this relationship is only established under specific material systems and process conditions, and different paper grades or processing processes may lead to significant deviations.
Influencing factors
In addition to fiber characteristics, many factors can affect the degree of correlation between the two indicators. Increased humidity usually reduces the rigidity of the cardboard, which may lead to a decrease in breakage resistance that is more pronounced than the puncture strength. Additives such as starch or enhancers can improve both properties simultaneously, but the improvement may vary. In addition, the increase of cardboard thickness and layer count tends to increase the puncture strength and breaking resistance at the same time, but the nonlinear growth may lead to a weakening of the correlation. In practical applications, comprehensive evaluation is required in combination with the specific environment and material formulation.
Application:
Understanding the correlation between puncture strength and breakage resistance helps labs efficiently evaluate the overall performance of cardboard. In quality control, potential weaknesses can be quickly inferred based on production batches. Future research can further combine non-destructive detection technology to further reveal the correlation mechanism between microstructure and macroscopic mechanical properties, and provide support for the development of green packaging materials.
References
International standard ISO 3036: Determination of the puncture strength of cardboard
International Standard ISO 2758: Determination of the breakage resistance of cardboard
Review of Mechanical Properties Testing Technology of Packaging Materials, Journal of China Paper Society
Research on the correlation between impact and static properties of fiber matrix composites, packaging engineering