Evaluating Recycled and Biodegradable Films with the Staircase Method

Evaluating Recycled and Biodegradable Films with the Staircase Method

As brands move toward recycled and biodegradable materials, film producers face a new challenge: how to ensure these environmentally friendly films still deliver the mechanical performance required in real-world logistics. Dart impact testing with the staircase method provides a powerful framework for evaluating toughness and comparing alternative formulations.

Recycled (PCR) films and biodegradable resins often show different crack-initiation and crack-propagation behaviors compared with virgin polyethylenes or polypropylenes. Small inclusions, inhomogeneities, or differences in crystallinity can lead to more brittle behavior under impact. The staircase method, which repeatedly increases or decreases dart mass based on pass/fail outcomes, allows you to determine a statistically meaningful failure mass (M50) for each formulation. This value can then be used as a primary metric for toughness comparisons.

To evaluate recycled or biodegradable films, begin by defining the test matrix. This includes selecting a set of formulations (such as different PCR content levels or different biodegradable grades), choosing Method A or B based on expected toughness, and deciding on conditioning conditions. For packaging films used in cold chains, low-temperature conditioning may be necessary; for room-temperature applications, standard lab conditions can be used. Each formulation should be tested using enough specimens to give a robust M50 estimate.

Once M50 values are obtained, they can be plotted against variables such as recycled content, thickness, or resin blend. In many cases, higher recycled content may correlate with lower M50, but smart formulation (for example, using impact modifiers or optimized blends) can mitigate this effect. Similarly, biodegradable films may initially show lower impact performance, but process and formulation adjustments can close the gap. The staircase method provides quantitative evidence for these improvements, rather than relying on subjective judgments.

It is also important to relate laboratory data to field performance. If possible, pilot-scale or limited field trials should be conducted for promising formulations, and their failure rates compared with conventional materials. Over time, a combination of dart impact M50 and field data will indicate which recycled or biodegradable films are “good enough” for certain applications and where further optimization is needed. This approach helps ensure that sustainability goals do not compromise packaging integrity.