How should flexible packaging be designed for recycling?
The concept of recyclability
Consumers are increasingly concerned about the environmental impact of packaging waste generated at home. They are looking for alternatives to reduce it, while also considering its effect on the final cost of products.
For their part, companies are working in the same direction, adopting various approaches: reducing the weight and thickness of materials, decreasing the dimensions of packaging, choosing materials that facilitate recycling, etc.
The goal of packaging recycling is to prevent it from becoming waste by giving it a second life. These materials are not always transformed into new packaging; they can be used to manufacture various objects such as containers, automotive parts, street furniture, and many other applications.
What characteristics must flexible packaging have to be recyclable?
Not all flexible packaging is recyclable or recycled in the same way. To guarantee their recyclability, several elements are necessary:
A selective collection system, for example, through yellow recycling bins
An efficient separation system, carried out in sorting centers
A recycling process adapted to the type of material
A market capable of using the recycled material
For this system to work, it must also be economically viable. Although, technically, almost all polymers can be recycled, some processes are so complex and costly that they become impractical.
Thus, packaging must meet certain specific conditions to be processed effectively in recycling systems.
This article explores the factors that make flexible packaging recyclable, according to the guidelines established in the flexible packaging sector.
Recycling processes
These vary depending on the composition of the material and the intended use of the recycled polymer. Here are the main methods:
Mechanical recycling
This process consists of purely mechanical steps, without breaking the polymer chains:
Shredding: reducing the size of the packaging into flakes. Washing: Removal of contaminants using a solution of water and detergents. The flakes are separated by density; polyolefins such as PP and PE float, while PET and PS sink.
Optical separation (optional): Identification and sorting of the flakes.
Drying: Maximum moisture removal.
Decontamination: Heating of the flakes to eliminate unwanted substances.
Granulation: Extrusion of the flakes to produce granules.
Dissolution recycling (physical)
This process dissolves the polymer without altering its molecular structure, removing contaminants. It is often used for polystyrene and sometimes for polyolefins.
Chemical recycling
Also called molecular recycling, it involves depolymerizing polymers into monomers, which can be repolymerized to become the original materials. This process, based on thermal or chemical treatments, allows for the treatment of multilayer plastics or materials that have lost their properties after several cycles of mechanical recycling.
Material design
Material and layer compatibility
Single-layer packaging, composed of a single material, is the most suitable for recycling. In contrast, multilayer packaging, often made of plastics, aluminum, or paper, poses a problem because its components must be separated before recycling, making the process complex and costly.
However, some multilayer structures, such as those composed of polyethylene (PE) and polypropylene (PP), are considered recyclable because they belong to the same family of polymers, the polyolefins. Other polymers, such as EVOH, can be accepted in small quantities (<5%), as they offer good barrier properties with minimal thickness.
Additives, Coatings, and Inks
Additives and coatings used to enhance the barrier properties of packaging
can complicate recycling. It is therefore advisable to minimize their use or
choose alternatives compatible with the base material. For example, reducing
metallic coatings promotes recyclability.
Water-based inks are preferable because they can be washed off,
unlike insoluble inks that contaminate the material.
Other Packaging Components
Features such as resealable zippers or valves should ideally be made
of the same material as the main packaging to avoid additional sorting during
recycling.
