As a widely used packaging material, the impact resistance of corrugated cardboard is directly related to the ability to protect the contents during transportation. Puncture strength is a key metric for evaluating corrugated cardboard's ability to resist dynamic impacts, punctures, or tears, simulating sudden impacts or sharp object puncture scenarios that the packaging may encounter during circulation. Unlike static strength testing, puncture strength testing focuses more on the energy absorption and failure behavior of a material under instantaneous impact energy, which is essential for evaluating the reliability of packaging in real-world logistics environments.
Principle
The puncture strength tester mainly uses a pendulum system to simulate the impact process. When the instrument works, the pendulum is released from a predetermined height, and the triangular tapered poke head at its end strikes with specific kinetic energy and penetrates the corrugated specimen fixed to the fixture. The instrument measures and records the energy consumed during the penetration process, which is the puncture intensity, usually expressed in joules (J) or kilojoules per square meter (kJ/m²). The core calculation formula is as follows:
E = m * g * (h₁ - h₂)
Among them, E is the energy consumed through the puncture, m is the mass of the pendulum, g is the acceleration of gravity, h₁ is the initial height of the pendulum, and h₂ is the maximum height reached by the pendulum after penetrating the specimen. The main structure of the instrument includes the base, specimen fixture, pendulum release mechanism, energy indicator device, and friction loss calibration system to ensure the accuracy and repeatability of test results.
Test Standards
The puncture strength test follows a number of international and domestic standards, which uniformly stipulate the specimen size, pretreatment conditions, test environment and instrument calibration to ensure the comparability and reliability of the test data. Key test parameters include pendulum capacity, puncture head geometry, specimen holding force and test speed. Before testing, the specimen should be balanced under standard temperature and humidity conditions to eliminate the influence of ambient temperature and humidity on the performance of the cardboard.
| Common international standards | ISO 3036, TAPPI T803 |
| Common domestic standards | GB/T 2679.7 |
| Key test results: | Puncture energy (J), puncture strength (kJ/m²) |
| Typical specimen size | Not less than 175mm × 175mm |
| Regular pretreatment environment | 23°C ± 1°C, 50% ± 2% RH |
Application in packaging inspection processes
In the packaging quality testing laboratory and production quality control link, the application of the piercing strength tester runs through the whole process of material screening, process optimization and finished product verification. Determining the puncture strength of corrugated board made from different paper mixings, flutes, or composite processes can provide critical data support for packaging design and help optimize material costs while meeting protection requirements. In addition, regular sampling of puncture strength of inbound base paper or outgoing cartons is an effective means to monitor the quality stability of the supply chain. The test data can be used to establish product specifications and serve as a technical basis for resolving disputes over transportation damage.
Operational precautions
In order to ensure the accuracy of the measurement results, the following points should be paid attention to during operation: the specimen should be clamped flat and without initial stress; Before testing, the zero point and friction loss of the instrument must be checked and calibrated; After each test, wait for the pendulum to come to a complete standstill before proceeding with the next operation. Routine maintenance of the instrument includes regular cleaning of the guide rails and shafts, checking the flexibility of the pendulum pointer, and lubricating critical moving parts. It is recommended to conduct comprehensive calibration and verification by professionals regularly according to the frequency of use to meet the requirements of the quality management system.
Epilogue
The puncture strength tester provides a straightforward and reliable method for quantitatively evaluating the dynamic impact resistance of corrugated cardboard. It plays an important role in packaging research and development, quality control, and standard compliance verification. An in-depth understanding of its principles and strict compliance with standards for operation and maintenance can lay a solid technical foundation for the scientific evaluation and rational application of packaging materials, thereby helping to improve the overall reliability of logistics packaging.
References
GB/T 2679.7-2005, Cardboard - Determination of puncture strength.
ISO 3036:1975， Board — Determination of puncture resistance.
TAPPI T803 om-22， Puncture resistance of paperboard.