The puncture resistance of film materials is a key indicator to evaluate their ability to resist the puncture of sharp objects during transportation, storage and use. This performance directly affects the protective effect and service life of packaging materials. The puncture test by tensile testing machine can quantitatively evaluate the puncture resistance and energy of the film, providing a scientific basis for material research and development, quality control and application selection. The test method usually follows common standards at home and abroad, and obtains highly repeatable and comparable mechanical data by simulating the actual puncture process.
Test Principle:
Puncture testing typically involves a fixed film specimen that drives the piercing probe vertically through the specimen at a specific speed. The probe is generally cylindrical in shape and has a hemispherical or tapered tip. During the test, the testing machine records the puncture force and displacement curve in real time. Puncture resistance is mainly characterized by the maximum puncture force and puncture energy. The puncture energy can be calculated by the area integral under the force-displacement curve, and its physical meaning is the work required to pierce the specimen.
The relationship curve between puncture force F and displacement s usually includes elastic deformation, plastic deformation up to the rupture stage. Puncture energy W can be calculated by the following formula:
W = ∫0smax F(s) ds
Among them, smaxIt is the total displacement when the specimen breaks. This integral value reflects the material's combined ability to resist puncture.
System composition
The test system is mainly composed of a tensile testing machine, a special puncture fixture and data acquisition and analysis software. The testing machine needs to have stable speed control and high-frequency data acquisition capabilities. The fixture design should ensure that the specimen is flat and clamped without initial stress, and the puncture point is located in the middle of the center hole of the fixture. Key test parameters include probe shape and size, test speed, specimen size and clamping method. These parameters must be clearly defined according to relevant testing standards or practical application scenarios to ensure comparable results.
| Test parameter categories | Typical examples or considerations |
| Probe shape | Hemispherical and conical |
| Probe diameter | According to the standard, there are common 1.0 mm, 2.0 mm, etc |
| Test speed | It is usually set in the range of 50 to 500 mm/min |
| Specimen size | The side length or diameter is greater than the inner hole of the clamp to ensure effective clamping |
| Clamping force | It should be uniform and sufficient to prevent specimen slippage during testing |
| environmental conditions | Temperature, humidity may affect the results, it is recommended to record |
Testing process
The testing process begins with the preparation and conditioning of the specimen. The specimen should be free of creases, bubbles, or obvious defects, and balanced for sufficient time in standard temperature and humidity environments. The specimen is then mounted on the fixture, ensuring that the center is aligned. Start the testing machine and the probe descends at a constant speed until it completely pierces the specimen. The software synchronously records the complete force-displacement curve. Tests often require multiple samples to be repeated to calculate the average and degree of discreteness, ensuring the reliability of the results. After the test, the sample should be checked for rupture morphology, which provides auxiliary information for analyzing the failure mode of the material.
Analysis of results
The maximum puncture force value can be read directly from the force-displacement curve. The puncture energy is obtained by software integration function or numerical calculation method. When analyzing, it is necessary to combine basic information such as material thickness and density for comprehensive consideration. Puncture resistance data can be used to compare the advantages and disadvantages of films of different materials and processes, guide the structural design of composite materials, or as technical indicators in packaging protocols. In practical applications, this property is related to the impact resistance, tear resistance and other properties of the material, but it is not substitute for each other and needs to be combined and evaluated according to the usage scenario.
| Performance metrics | Significance and influencing factors of the project |
| Maximum puncture force | It reflects the peak strength of the material against puncture, which is affected by the stiffness and strength of the material |
| Piercing energy | It reflects the energy absorbed by the material during the whole process from deformation to rupture, which is related to toughness |
| Force-displacement curve pattern | It can analyze the brittleness, ductility and failure process of materials |
| Data dispersion | Evaluate material uniformity and test operational consistency |
Notes:
To ensure the accuracy of the test, the tensile testing machine needs to be calibrated regularly for force value and speed. The tip of the probe should remain smooth and free of wear or deformation. Specimen clamping should be avoided when pre-stretching or wrinkling. Changes in the test environment can have a significant impact on the results of some polymer films, so experimental condition documentation is essential. It is important to recognize that laboratory puncture testing is a simplified simulation of complex real-world puncture scenarios, and the results are primarily used for relative comparison and quality control, and caution is required in predicting the behavior of materials under real-world extreme conditions.
References
ASTM D7192-20, Standard Test Method for High Speed Puncture Properties of Plastic Films Using Load and Displacement Sensors.
ISO 3036:2015, Board — Determination of puncture resistance.
GB/T 10004-2008, Plastic composite film for packaging, bag dry lamination, extrusion lamination.
General technical conditions of tensile testing machine, relevant national metrology and verification regulations.