Are mono-materials guarantors of recyclability?

On September 17, the “Recyclable Mono-Material Packaging Solutions” conference was held, organized by the Center for Management Technology (CMT), within its cycle of conferences to promote debate in the industry and find solutions to optimize recycling processes. Among the speakers there were ECOSENSE companies such as SP Group and AMB, benchmarks in the sheet manufacturing market in Europe.

During the conference, which was mainly focused on flexible PE solutions, several innovations were presented such as the improvement of the barrier with additives in PE films and new technologies for the use of monomaterial PET trays for MAP applications (protein foods), without the use of PE sealing layer.

One of the main objectives of the value chain is to provide packaging that maintains the properties of food in order to extend its shelf life and that, in addition, is easily recyclable. The plastics sector has been working on monomaterial solutions, which are those made with a single plastic material instead of a mixture of several, whether with a multilayer structure or not. In principle, having a single material simplifies the film and sheet manufacturing process and eliminates the need to separate and recover the different polymers in the recycling process. Another question would be whether it is legal to speak of monomaterial in multilayer structures using EVOH.

However, there are still many technical limitations in the field of thermoformed PET containers. On the one hand, certain food such as sliced cooked ham requires preservation requirements that are compromised with monomaterial solutions (even if they are multilayer) and in which the effective barrier function is currently only achieved with structures of various materials such as PET / PE or PET / EVOH / PE solutions.

On the other hand, the cumulative impact of certain additives in PET, such as oxygen scavengers based on cobalt salts, must be taken in consideration as well as how the concentration can negatively affect the recycling stream and the recyclability and quality of the material itself. Taking into account, in addition, that oxygen scavengers provide a barrier to O₂ but not to CO₂, which is necessary to control when packaging in a controlled atmosphere and in a modified atmosphere.

Sustainability is a clear commitment of the sector: thermoformed multilayer PET containers have been on the market for years because they have proven to be a totally effective solution in terms of sealing and barrier function. In this way, the conservation and avoided food waste are joined by the eco-design measures that the value chain is applying following the guidelines to guarantee its recyclability published by the Plastic Sense Foundation. In the same way, monolayer PET containers have been on the market for years for applications that do not require these functional requirements. The use of additives to achieve the same barrier function that multimaterial structures is a technological challenge that should not compromise the value chain for recycling and, therefore, the sustainability for which this sector is committed.