Optimizing pallet stretch wrapping protocol for consistent comparison of stretch film transport performance

Abstract

New legislation, plastic taxes, and eco-modulation will soon require stretch films around pallets to contain multiple recycled polyethylene (PE). To study the impact on stretch film performance during transport, the CORNET project MultiRec (HBC.2023.0176) conducts transport simulations with stretch films varying in recycled content and recycling cycles. For consistent comparisons, a standard pallet was defined for industrial relevance. A Europallet with six column-stacked double-walled cardboard boxes filled with plastic pellets was chosen to achieve a packaging density of 192.2 kg/m³, in line with ASTM D4169 recommendations for average shipping density, resulting in a total load weight of 332 kg. The pallet is finished with cardboard corner profiles and a PE top sheet. A 300% pre-stretch was set on the wrapper based on tensile tests and datasheet values. The wrapper was then adjusted to ensure 300% stretch across the entire pallet, verified by measuring the weight of the wrappings at the base, centre, and top. This resulted in the following settings for the industrial turntable wrapper (Spinny S350; EFFE 3 TI srl): a rotation speed of 75%, an up/down speed setting of 20, and a film tension setting of 18. In the final step, the wrapping pattern was optimized by testing various wrapping patterns while keeping the total number of layers constant at 26. This optimization involved subjecting the pallets, 10 minutes after being stretch-wrapped, to a horizontal collision using a swing that comes to a sudden stop, resulting in a brief but intense acceleration peak (20 ms, max. 15 g). The relative displacement of the layers was determined by video analysis using open-source tracking software (https://physlets.org/tracker/), with minimal displacement considered favourable. This preliminary study describes best practices that can be more broadly applied to systematically setting industrial wrappers.