Method A vs Method B: How to Choose the Right Dart Impact Test for Your Film

Method A vs Method B: How to Choose the Right Dart Impact Test for Your Film

Selecting between Method A and Method B in the falling dart impact test is one of the most common questions for film manufacturers and laboratories. Both methods are defined in standards such as ASTM D1709 and ISO 7765-1, but they target different impact energy ranges and film types. Choosing the wrong method can either waste time (if the film never fails) or yield data that is not meaningful for your actual application.

Method A uses a smaller dart (about 38 mm diameter) dropped from a height of 0.66 m. This combination produces a moderate impact energy range suitable for thin to medium-thickness films with relatively lower toughness. Typical examples include snack bags, small pouches, and general-purpose flexible laminates. Method B, in contrast, uses a larger dart (about 50 mm diameter) dropped from 1.50 m. The higher drop height and larger contact area create a more severe impact suitable for stronger films, thicker structures within the standard scope, and heavy-duty packaging.

In practice, the starting point is always your expected impact performance and film structure. If you are testing standard flexible packaging films below 1 mm that are not specifically designed for extreme abuse, Method A is usually sufficient. If you are testing reinforcement films, pallet wraps, heavy-duty sacks, or any structure marketed as “high toughness,” Method B offers a more realistic challenge. You can confirm your choice by running a few preliminary drops: if all samples fail at very low dart masses in Method B, the film is better suited to Method A; if the film never fails even near the upper weight limit in Method A, Method B is likely required.

Another factor is how your customers and internal specifications are written. Some large buyers explicitly specify Method A or Method B in their material specifications. In those cases, following the specified method is essential for compliance and to ensure results are comparable between suppliers. If the specification only mentions “ASTM D1709” or “ISO 7765-1” without naming a method, you should document your rationale for choosing A or B (film type, expected toughness, historical practice), and keep that rationale consistent in your QC procedures over time.

Finally, it is important to understand that data from Method A and Method B are not directly interchangeable. The geometry, impact energy distribution, and failure behavior differ between the two methods. You should avoid mixing A and B results in the same internal database or combining them into a single trend line. If your product portfolio includes both thin consumer packaging and stronger industrial films, the most robust solution is to equip your lab with a tester that supports both Method A and Method B and to maintain separate specifications and historical data sets for each method.