Dart Impact Testing of Polyethylene Film per ASTM D1709

Introduction to Dart Impact Testing of Polyethylene Film

Polyethylene films are widely used in packaging due to their durability, flexibility, and lightweight characteristics. However, to ensure performance during shipping and handling, understanding their mechanical behavior—particularly under sudden impact—is essential. Dart impact testing of polyethylene film offers a reliable way to assess a film’s resistance to rupture when struck by a free-falling dart. One of the most recognized standards for this evaluation is ASTM D1709, which defines the methodology and apparatus for the impact dart test.

Overview of ASTM D1709 and Impact Dart Test Methods

ASTM D1709 outlines two standardized procedures—Test Method A and Test Method B—to determine the impact resistance of plastic films. These methods involve dropping a hemispherical dart onto a clamped film sample and assessing failure under defined conditions.

Test Method A uses a 38.10 mm dart head dropped from 0.66 meters, applicable for films breaking under 50 g to 6 kg.
Test Method B uses a 50.80 mm dart head dropped from 1.52 meters, suitable for 0.3 kg to 6 kg impact levels.

The primary result is the impact failure weight (WF)—the weight at which 50% of tested specimens fail—offering a quantitative measure of the film’s impact resistance.

Test Setup and Sample Conditioning

Proper conditioning and sample preparation ensure test accuracy and repeatability. According to ASTM D1709:

Condition films at 23°C ±2°C and 50% ±10% RH for at least 40 hours before testing.
Specimens must be free of defects (pinholes, folds, or wrinkles) and large enough to extend past the clamp gaskets.
Choose the test method (A or B) based on the expected strength range of the film.

For reliable results, testing should be conducted in a controlled environment using calibrated and properly aligned equipment.

Dart Impact Testing Procedure: Staircase Method vs. Group Method

Two techniques are permitted under ASTM D1709: the staircase (up/down) method and the alternative group method. Both aim to find the dart weight that causes 50% of samples to fail.

Staircase Method: Adjust the dart weight incrementally after each test based on whether the previous specimen passed or failed. Testing continues until 10 failures and 10 non-failures are obtained.
Group Method: Test samples in groups of 10 at the same weight, then change the dart mass for the next group. This method requires at least five data points ranging from 0% to 100% failures.

WF (impact failure weight) is calculated mathematically or via graphical interpolation to identify the weight that corresponds to a 50% failure rate.

Why Dart Impact Testing of Polyethylene Film Matters

This test simulates real-world scenarios such as drops during shipping or loading, helping manufacturers:

Select appropriate film thickness and formulations
Predict field performance
Ensure product protection in transit
Comply with industry and regulatory standards

It also assists in quality assurance and R&D by identifying mechanical weaknesses before packaging enters production or the supply chain.

Choosing the Right Equipment: FDT-01 Dart Impact Tester from Cell Instruments

To execute dart impact testing of polyethylene film in accordance with ASTM D1709, precision and reliability in test equipment are critical. Cell Instruments’ FDT-01 Dart Impact Tester is specifically engineered for this purpose, offering:

Support for both Test Methods A and B
Adjustable dart release heights and heads
User-friendly interfaces for rapid setup and data recording
Compliant design with ASTM and ISO standards

Whether you’re in packaging R&D, quality control, or production, the FDT-01 ensures that you get consistent, reproducible results critical for decision-making.

Best Practices and Considerations

To maximize the effectiveness of dart impact testing:

Always verify dart head condition for scratches or wear.
Ensure accurate alignment of the dart for centered impact.
Avoid excessive passive voice in reporting to maintain clarity.
Record all results systematically to calculate WF precisely.

Note that test results are highly dependent on material properties, including thickness, clarity, additives, and uniformity. Only compare data from films of similar structure and thickness (±25%) to ensure valid benchmarking.

Conclusion

Understanding and applying dart impact testing of polyethylene film using ASTM D1709 ensures that packaging materials meet rigorous impact resistance requirements. By employing standardized testing and precision instruments like the Cell Instruments FDT-01, packaging professionals can confidently validate film durability, reduce product loss, and enhance end-user satisfaction.

FAQs

What does dart impact testing measure in polyethylene films?
It measures the energy required to cause failure (rupture) of a film under a free-falling dart, expressed as the weight causing 50% failure.
What is the difference between Test Method A and B in ASTM D1709?
Method A uses a smaller dart (38.10 mm) dropped from 0.66 m, while Method B uses a larger dart (50.80 mm) from 1.52 m, covering different film strength ranges.
Why is the staircase method often preferred in dart impact testing?
It offers a more efficient determination of the 50% failure weight with fewer specimens compared to fixed-weight group testing.
How should I condition polyethylene film samples before testing?
Condition at 23°C ±2°C and 50% ±10% RH for at least 40 hours to stabilize film properties before testing.
Can dart impact results be compared between different film types?
Only films of similar structure and thickness (within ±25%) should be compared, as formulation and thickness significantly affect impact performance.