GB/T 9639.1 Explained: Practical Guide for Chinese Film Manufacturers

GB/T 9639.1 Explained: Practical Guide for Chinese Film Manufacturers

GB/T 9639.1 is the Chinese national standard for measuring the impact resistance of plastic films and sheets using the free-falling dart method. For Chinese film manufacturers, especially those exporting packaging materials, understanding this standard is essential for both domestic compliance and alignment with international methods such as ISO 7765-1 and ASTM D1709.

The standard covers flexible plastic films and sheets up to a defined thickness, typically less than 1 mm. It specifies the test apparatus, including a vertical drop tower, a hemispherical dart, a clamping ring, and a release mechanism. It also defines two methods, A and B, similar in concept to those described in ISO 7765-1. Method A uses a lower drop height and smaller dart, while Method B uses a higher drop height and larger dart, thus providing two energy ranges suitable for different film toughness levels.

From a practical standpoint, manufacturers should pay attention to the dimensional and accuracy requirements in GB/T 9639.1. The dart diameters, drop heights, and weight increments all have specified tolerances. Clamping conditions, including the rubber gasket hardness and clamp pressure, are also defined to ensure tests are comparable across different laboratories. Using a tester that is explicitly designed to meet these hardware requirements reduces the risk of non-compliant data and arguments with customers or regulators.

The standard describes how to conduct the staircase method for determining the impact failure mass. Operators must follow the defined sequence of increasing or decreasing dart mass based on pass or fail outcomes until the required number of failures and non-failures is achieved. After the test sequence, a calculation is applied to determine the characteristic failure mass. For consistent results, test conditions such as temperature and humidity should align with related conditioning standards, and sample preparation (including cutting and inspection for defects) must be controlled carefully.

Many international buyers are familiar with ISO 7765-1, so Chinese manufacturers often need to show how GB/T 9639.1 corresponds to this international standard. Fortunately, GB/T 9639.1 is closely aligned with ISO 7765-1 in methodology and apparatus; communicating this equivalence in technical documents and reports can give overseas customers confidence that domestic test results are meaningful. By thoroughly implementing GB/T 9639.1 in internal QC, and documenting how it aligns with ISO and ASTM methods, Chinese film producers can strengthen their position in both domestic and export markets.