Pinhole strength testing plays a crucial role in the evaluation of packaging materials, especially for liquid packaging bags. In the conveying and transportation process, due to shock and vibration, liquid packaging bags are prone to pinholes, which may lead to product leakage and quality problems, causing unnecessary losses. Therefore, it is essential to understand and evaluate the pinhole resistance strength of packaging materials. This paper will introduce the test methods of pinhole strength, including the instrument measurement method and the impact test method, and discuss their application in the evaluation of packaging materials.

1. Instrument measurement method

The instrument measurement method is a test method used to simulate the pinhole strength of the packaging film under the condition of low speed impact. The test device usually consists of a metal cabinet, a cryogenic tank, and a set of test samples. The test process is to load the test sample on a metal cabinet and place it in a cryogenic tank. The sample was heated at a speed of 6cm/min to gradually heat up. A needle made of brass is used to touch the sample, with the front end of the needle being a cone shape with a 70° top Angle. As the sample moves upward, the needle hits the sample and penetrates, creating a pinhole. The load and elongation at failure are measured by the connected detector.

The relationship between failure load and elongation is usually approximated as a linear function. The instrumentation method uses a needle with an acute Angle to touch the packaging film to simulate the strength of the pinhole resistance under low-speed impact conditions. However, in the actual flow process, the impact velocity may be higher, so it is necessary to use the impact test method for testing.

Pinhole strength testing of packaging materials

2. Impact test method

The impact test method simulates the pinhole resistance of the packaging film under the condition of high speed impact. The test device usually consists of a polyvinyl chloride tube with an impact head and a load at the end of the tube. The test process is that when the impact head leaves the horizontal position, there is an impact, resulting in pinholes in the sample. The test load is usually 60g. The impact test method evaluates the properties of packaging films by simulating the pinhole strength under high speed impact conditions. This method is more suitable for the actual flow process, where the impact speed is higher.

Pinhole strength testing is essential for the evaluation of packaging materials, especially for liquid packaging bags. The instrument measurement method and the impact test method are two commonly used test methods to simulate the pinhole resistance under low speed and high speed impact conditions respectively. By understanding the pinhole resistance of packaging materials, manufacturers and packaging engineers can choose the right materials to ensure that the product will not leak and damage during transportation and use, thereby improving product quality and protecting the interests of consumers.