- Bubble extrusion and flexible packaging: the strategic role of recycled materials
- Single-layer blown film systems: limitations and opportunities with recycled polymers
- Double- and three-layer blown film: managing the variability of recycled material
- 5- and 7-layer systems: plant complexity and integration of recycled materials
- Critical parameters of bubble extrusion: temperatures, compression and L/D ratio
- Melt filtration and mesh change in blown film extrusion with recycled material
- Effects of recycled polymers on bubble stability and film orientation
- Operational strategies and process windows for stabilizing recycled blown film
A guide to single- and multilayer blown film extrusion with recycled polymers: systems, process control, operational criticalities, and film quality
System types: single, double, triple, 5 and 7 layers
Blown extrusion is one of the most widespread and versatile technologies for producing plastic films for flexible packaging. Its industrial relevance stems from its ability to produce thin, continuous, and oriented materials, adaptable to a wide range of applications. In the context of recycled materials, however, the choice of plant type takes on even more strategic importance, as it directly impacts process stability, film quality, and the ability to manage the inherent variability of the raw material.
Blown film extrusion systems can be classified based on the number of layers of film produced. This classification isn't just a design distinction, but reflects profoundly different production philosophies, especially when working with recycled polymers. Each system configuration has advantages, limitations, and levels of complexity that must be evaluated based on the material's characteristics and application objectives.
Single-layer systems
Single-layer systems represent the simplest configuration from a plant and operational standpoint. They consist of a single extruder that feeds an annular die, which forms the film bubble. In traditional flexible packaging, this solution is often associated with high-volume production and relatively homogeneous materials.
When using recycled materials, a single-layer system directly exposes all the material's critical issues. Since there are no "compensation" layers, any defect in the granule—rheological variability, the presence of contaminants, thermal instability—is immediately reflected in the bubble behavior and film quality. This makes single-layer systems particularly sensitive to the use of recycled materials, especially when the material quality is not high or consistent.
However, this very direct exposure can also represent an advantage in terms of control.
The single-layer system allows for immediate reading of the material's behavior and can be used as an industrial test bed for the qualification of recyclates. In applications where performance requirements are not extremely stringent, the single-layer remains an industrially viable solution, provided the process is expertly managed and the material is properly selected.Double-layer systems
The introduction of a second layer significantly expands the film's design possibilities. Double-layer systems allow for the combination of materials with different functions, creating a more balanced structure from a mechanical and functional standpoint. In the context of recycled materials, the double layer often represents the first layer of complexity capable of absorbing some of the critical issues inherent in recycled materials.
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