Presse-film plastique : densité et taux de compression

Les systèmes de compression et de densification de films plastiques jouent un rôle crucial dans le recyclage moderne du plastique. En éliminant efficacement l'humidité et en compactant les films plastiques en vrac, ils préparent le matériau pour un traitement ultérieur et réduisent considérablement les coûts de stockage et de transport. Deux indicateurs de performance clés pour ces systèmes sont : densité comprimée et taux de compressionCet article explore la signification de ces termes, les valeurs typiques basées sur des recherches sectorielles et les facteurs qui les influencent.

Principaux points à retenir :

• Compressed Density: Typically ranges from 0.91 to 0.97 g/cm³ for common plastics like LDPE and HDPE, aligning with the intrinsic density of the material itself.
• Compression Ratio: Can reach up to 50:1, meaning the system can reduce the initial volume of loose plastic film by up to 50 times. Typical ranges are often between 20:1 and 50:1.
• Variability: Exact figures depend on the specific machine, the type of plastic being processed, and operating conditions. Always consult manufacturer specifications for precise data.

What is a Plastic Film Squeezer & Densifier System?

These systems are engineered to handle post-consumer or industrial plastic films (like shopping bags, packaging film, or agricultural film). The process generally involves two main steps:

1. Squeezing: A screw press or similar mechanism physically squeezes the plastic, removing significant amounts of residual moisture (often reducing humidity to less than 3%, according to manufacturers like Rumtoo Machine).
2. Densifying: The squeezed plastic is often heated and agglomerated or compacted into denser forms, such as small granules or chunks. This makes the material easier to handle, store, and feed into subsequent recycling machinery like pelletizers.

Compressed Density: Understanding the Output Material

Le densité comprimée refers to the density of the plastic material after it has been processed by the squeezer and densifier. Essentially, this is the density of the resulting granules or compacted material.

• Alignment with Intrinsic Density: Since the system primarily reshapes and compacts the plastic rather than fundamentally altering its chemical structure, the compressed density closely matches the intrinsic material density of the specific plastic type being processed.
• Common Plastic Densities: Research and industry data indicate the following typical density ranges for granules derived from common films:
  • LDPE (Low-Density Polyethylene): 0.91 – 0.94 g/cm³
  • LLDPE (Linear Low-Density Polyethylene): 0.918 – 0.940 g/cm³
  • PEHD (polyéthylène haute densité) : 0.94 – 0.97 g/cm³
  • PP (Polypropylène) : 0.90 – 0.91 g/cm³
• Material vs. Bulk Density: It’s important to distinguish compressed (material) density from bulk density. Bulk density considers the air spaces between granules when stored and is therefore lower (e.g., around 0.5-0.6 g/cm³ for PE granules). Compressed density refers to the density of the solid plastic material itself.

Table: Typical Material Densities of Processed Plastic Films

Type de plastique	Density Range (g/cm³)	Utilisations courantes
PEBD	0.91 – 0.94	Films, bags, packaging
PEBDL	0.918 – 0.940	Stretch films, liners
PEHD	0.94 – 0.97	Bottles, containers
PP	0.90 – 0.91	Woven bags, films, caps

Source: Compiled from industry data.

Compression Ratio: Measuring Volume Reduction

Le taux de compression quantifies how effectively the system reduces the volume of the input plastic material. It’s expressed as the ratio of the initial volume (loose film) to the final volume (densified material).

• Significant Volume Reduction: These systems are highly effective at compaction. Industry sources (like Rumtoo) suggest densifiers can achieve volume reduction ratios of up to 50:1.
• Typical Range: While the maximum can be high, a typical operational range is often cited as 20:1 to 50:1.
• Influencing Factors: The actual ratio achieved depends heavily on:
  • The initial state and bulk density of the plastic film (very loose films allow for higher compression).
  • The type of plastic material.
  • The specific design and operating parameters of the squeezer & densifier.
• Calculation Basis: The ratio reflects the change from a very low initial bulk density (loose films might be around 0.01-0.02 g/cm³) to the much higher final material density (around 0.90-0.97 g/cm³).

Why Do These Figures Matter?

Understanding compressed density and compression ratio helps in:

• Logistics Planning: Estimating storage space requirements and transportation efficiency.
• Process Optimization: Ensuring the densified material meets the requirements for downstream processes (e.g., extrusion).
• Equipment Selection: Choosing a machine with the appropriate capacity and performance for specific needs.

Conclusion and Recommendation

Plastic Film Squeezer & Densifier Systems offer significant advantages in recycling by reducing moisture and volume. Based on available research:

• Le densité comprimée of the output material typically falls between 0.91 and 0.97 g/cm³, depending on the plastic type (e.g., LDPE ~0.91-0.94 g/cm³, HDPE ~0.94-0.97 g/cm³).
• Le taux de compression generally ranges from 20:1 to 50:1, indicating substantial volume reduction.

While these ranges provide a good guideline, the performance of any specific system can vary. It is always recommended to consult the equipment manufacturer’s specifications and datasheets for precise density and compression ratio figures relevant to your specific application and materials