Understanding Impact Resistance in Plastic Film Testing
Plastic packaging must endure various mechanical stresses during handling, transportation, and storage. One crucial property to evaluate is impact resistance, which refers to a material’s ability to absorb energy during sudden impacts without fracturing. An impact testing machine designed for plastic films ensures objective, repeatable assessments of this characteristic. Specifically, ASTM D1709 is the industry-standard test method for determining the energy required to puncture a plastic film using a free-falling dart.
Plastic Impact Testing Machine and ASTM D1709
The plastic impact testing machine evaluates the dynamic puncture resistance of plastic films under controlled conditions. ASTM D1709 specifies two testing methods:
- Test Method A: Utilizes a 38.10 mm dart dropped from 0.66 m
- Test Method B: Utilizes a 50.80 mm dart dropped from 1.52 m
Both test methods aim to identify the dart weight at which 50% of specimens fail, providing a quantitative measure of impact strength. The Cell Instruments FDT-01 Impact Testing Machine supports both Test Methods A and B and offers programmable drop control, dart head interchangeability, and precise height adjustments.
Test Setup and Specimen Preparation
To ensure reliable data, follow strict preparation protocols:
Conditioning and Environment:
- Maintain 23 ± 2°C and 50 ± 10% relative humidity for at least 40 hours before testing.
- Conduct tests in the same environmental conditions to prevent variations in test results.
Specimen Integrity:
- Use defect-free specimens—no pinholes, folds, or wrinkles.
- Ensure the film extends beyond clamp boundaries to avoid slippage.
Apparatus Configuration:
- Confirm dart diameter and drop height match the selected test method.
- Inspect dart heads for scratches; replace if imperfections are found.
- Verify the dart release mechanism centers the dart accurately on the film specimen.
Staircase Testing Method – A Step-by-Step Guide
This is the primary technique described in ASTM D1709:
- Estimate a starting dart weight near the expected failure threshold.
- Clamp the specimen securely between the annular clamps.
- Drop the dart and observe whether the specimen fails.
- Adjust the dart weight up or down based on the previous result.
- Continue until 20 specimens are tested, then analyze the results to calculate the failure weight.
Impact Failure Weight (WF) is calculated using the formula:WF = W0 + ΔW × (N/A − 0.5)
Where W0 is the base weight, ΔW is the weight increment, N is the total number of failures, and A is the sum of weighted failure indices.
Alternative Testing Method
In contrast, the alternative approach tests groups of 10 specimens with one dart weight per group. The missile weight changes across groups to cover a full failure range (0% to 100%). The impact failure weight is derived by plotting results on a probability scale or using weighted averages. This method is especially useful for quality control when fewer specimens are available.
Choosing the Right Equipment
An accurate impact testing machine must meet the following criteria:
- Support both dart head sizes and drop heights per ASTM D1709
- Minimize specimen slippage and offer uniform clamping
- Allow precise control of dart release and weight adjustment
The Cell Instruments FDT-01 is tailored for such requirements. It allows users to switch seamlessly between methods A and B, features a vented dart holder, and ensures consistent test conditions. Its data output supports both manual and automated analysis workflows—making it a reliable solution for laboratories, film manufacturers, and packaging quality assurance teams.
Why Impact Resistance Testing Matters
Plastic film failures during transport can result in contamination, leakage, or product loss. Testing helps:
- Benchmark film performance during R&D
- Ensure compliance with packaging specifications
- Minimize failure-related costs in logistics
- Improve customer satisfaction and product shelf life
Final Thoughts
Performing impact resistance tests using a compliant impact testing machine following ASTM D1709 protocols is essential for quality control in film manufacturing. Both the staircase and alternative methods offer valid paths to reliable data. For accurate, efficient, and standard-compliant testing, the Cell Instruments FDT-01 Impact Tester is an excellent choice to support production and R&D teams alike.