What are the applications of PE Film Pelletizing Machine in plastic recycling?

Polyethylene (PE) film, specifically Low-Density Polyethylene (LDPE) and Linear Low-Density Polyethylene (LLDPE), accounts for nearly half of the global flexible packaging market. However, its characteristics—being lightweight, fluffy (low bulk density), and highly susceptible to contamination—present significant technical challenges during the recycling process. Traditional recycling equipment often faces issues such as feeding difficulties, high energy consumption, and poor degassing.

In the mainstream recycling solutions of 2025, the integrated configuration has become the standard configuration for Cutter Compactor PE film pelletizing lines, completely replacing the separated "crusher + force feeder" model.

In-depth Analysis of Working Principles and Advantages

The cutter compactor is positioned at the extruder inlet and is equipped with a high-speed rotating cutter disk at its base. As waste film (including washed material with relatively high moisture content) enters the chamber, the rotating blades perform a dual function: they shred the material while simultaneously utilizing the heat generated by high-speed friction to pre-heat and densify the feedstock.

Technical Comparison: Cutter Compactor vs. Traditional Feeding

The application of this technology allows PE film pelletizing lines to efficiently process industrial stretch film, bubble wrap, shopping bags, and washed agricultural mulch. It not only increases throughput but also ensures the homogeneity of the melt.

Precision Engineering of Extrusion Systems: L/D Ratio and Degassing

To address residual ink, moisture, and volatile impurities in waste film, the extruder's design parameters are of paramount importance. Based on current industry standards, the L/D (length-to-diameter) ratio of high-performance PE film pelletizers has evolved from the traditional 28:1 to 33:1 or even 36:1.

• 33:1 L/D Standard Model: Optimized for relatively clean Post-Industrial Waste (PIW), such as factory offcuts. The extended screw length provides ample plasticization time, ensuring the resulting pellets are free of fish eyes (gels).

• 36:1 L/D Enhanced Model: Engineered specifically for Post-Consumer Waste (PCW). The extended screw allows for a double-stage vacuum degassing system. The primary stage performs natural venting to remove significant amounts of water vapor, while the secondary stage utilizes high vacuum to forcibly extract ink volatiles and low-molecular-weight oligomers.

This sophisticated technical configuration ensures that even heavily printed film waste can be processed into high-quality, dense, and void-free pellets.

Melt Filtration and Pelletizing

Filtration System: To address common impurities in film such as paper labels, wood chips, and aluminum foil residues, a Back-flush Screen Changer or a Double-column large-area Screen Changer is critical for ensuring continuous production. These systems allow for screen replacement without downtime, eliminating the frequent production interruptions and material waste associated with conventional screen changes.

Pelletizing Process: Water-ring Pelletizing is the preferred method for PE film recycling. Compared to traditional strand pelletizing, water-ring pelletizing offers a higher degree of automation and eliminates the risk of strand breakage. Furthermore, it produces uniform, rounded pellets with superior flowability, which are ideal for subsequent blow molding or injection molding applications.

Deep Application Fields of PE Film Pelletizing Machines

1. Closed-Loop Recycling: Film-to-Film

This represents the highest tier of the circular economy and is technically the most demanding application field.

• Heavy-Duty Bags and Trash Liners: This is the largest market for recycled LDPE (rLDPE). Utilizing three-layer co-extrusion technology (ABA structure), recycled pellets are extensively used in the core layer (accounting for 50%–70% of the total thickness), while the inner and outer layers utilize virgin resin or high-grade recycled material to ensure surface gloss and mechanical strength.

• Industrial Shrink and Stretch Films: High-quality rLDPE pellets—typically sourced from clean waste processed through 36:1 L/D extruders—can be blended at a ratio of 10%–30% with virgin resin to manufacture new pallet stretch films. This reduces costs and assists enterprises in meeting mandatory recycled content requirements under the EU PPWR (Packaging and Packaging Waste Regulation).

• Agricultural Mulch Films: Despite high requirements for aging resistance, recycled pellets meticulously sorted and enhanced with UV stabilizers are widely used to produce new mulch and silage films, achieving an internal cycle for agricultural plastics.

2. Infrastructure and Construction: Preferred for Durable Products

• Piping Systems: HDPE and LDPE recycled pellets are ideal raw materials for manufacturing agricultural drip tapes, low-pressure water pipes, and cable conduits. The excellent corrosion resistance and flexibility of PE materials are fully utilized in these applications.

• Wood-Plastic Composites (WPC): A rapidly growing market. Recycled PE pellets act as the matrix resin, blended with wood or bamboo flour, then extruded into outdoor decking, railings, and landscaping profiles. The WPC industry is less sensitive to pellet color (typically dark shades), making it an excellent outlet for off-color or mixed PE film pellets.

• Waterproofing Membranes and Geomembranes: In construction waterproofing, recycled PE pellets are used in the core layer of waterproofing membranes to provide essential ductility and impermeability.

3. Consumer Goods and Injection Molding Applications

• Logistics Packaging: This includes injection-molded plastic pallets, crates, and trash bins. While these products primarily use HDPE, incorporating an appropriate amount of LDPE recycled pellets into the formulation acts as a toughening agent, enhancing impact resistance and preventing low-temperature brittle fracture.

• Modified Plastic Base Resin: High-purity recycled PE pellets are often procured by compounding plants as base resins for modified plastics (e.g., reinforced or flame-retardant modifications), which are then used in high-end sectors such as automotive interiors and home appliance housings.

Comparison Table of Recycled PE Pellet Grades and Typical Applications

2025 Market Trends and Economic Benefit Analysis

According to authoritative market analysis, the global recycled plastic granules market is projected to reach $34 billion in 2025 and grow to $47 billion by 2032, with a Compound Annual Growth Rate (CAGR) of approximately 4.7%. The core drivers propelling this growth include:

• Regulatory Drivers: The implementation of Extended Producer Responsibility (EPR) policies and mandatory recycled content targets in regions like the EU and California is compelling brand owners to procure Post-Consumer Recycled (PCR) materials in high volumes.

• Cost Advantages: Despite fluctuations in virgin resin prices, recycled pellets typically maintain a price point between 70%–85% of virgin resin costs, providing downstream manufacturers with significant margin for cost optimization.

• Corporate ESG Goals: Utilizing recycled materials is the most direct pathway for companies to reduce their carbon footprint. Every ton of PE plastic recycled reduces CO2 emissions by approximately 1.5 tons compared to the production of virgin resin.

Troubleshooting and Operational Maintenance Guide

To ensure the long-term stable operation of the pelletizing line and high granule quality, operators must master solutions for common issues. Below is a summary of troubleshooting strategies based on practical field experience.

4.1 Surface Roughness or Foaming (Porous Pellets)

• Root Cause: Excessive moisture in raw materials or ineffective degassing.

• Solutions:

  • Inspect the upstream drying system to ensure the moisture content of the material entering the cutter compactor is below 5%.

  • Clean the filters in the vacuum degassing chamber and ensure the vacuum level reaches -0.06 MPa or higher.

  • Slightly increase the temperature of the extruder's middle zones to reduce melt viscosity (facilitating gas escape) or reduce screw speed to increase degassing residence time.

4.2 Agglomeration or Clumping

• Root Cause: Insufficient cooling or mismatched pelletizing speed.

• Solutions:

  • Check the cooling water temperature; it is recommended to keep it below 40°C. If ambient temperatures are high, a chiller must be installed.

  • Adjust the ratio between cutter speed and die-face discharge speed. A cutter speed that is too slow causes oversized, clumping pellets, while a speed that is too fast may generate fines.

  • Verify that the centrifugal dryer fan is functioning correctly to ensure pellets are fully cooled and dried before entering the storage silo.

4.3 Unstable Throughput

• Root Cause: Inconsistent feeding in the cutter compactor or material "bridging."

• Solutions:

  • Enable the automatic load monitoring system: This regulates the conveyor feeding speed based on the amperage of the compactor's main motor. The system slows down feeding when current is high and accelerates when low, ensuring the extruder operates at "full load" without "overloading."

  • Inspect the cutter compactor blades for wear. Dull blades fail to effectively grab and densify lightweight film, leading to a significant drop in feeding efficiency.

4.4 Discoloration or Black Spots

• Root Cause: Localized overheating leading to material degradation (carbonization) or material stagnation in "dead zones."

• Solutions:

  • Perform regular screw cleaning. It is mandatory to use purging compounds to displace the PE melt within the barrel before every shutdown.

  • Calibrate temperature control instruments and thermocouples to prevent runaway heating zones from causing localized temperature spikes.

  • Optimize the screen-changing operation to prevent the introduction of external contaminants during the process.

Conclusion

PE film pelletizing systems represent the indispensable technical cornerstone for achieving a plastic circular economy. Driven by the technological advancements of 2025—particularly the adoption of integrated cutter compactors, high L/D ratio screw designs, and intelligent degassing systems—waste film recycling efficiency and the quality of recycled pellets have reached unprecedented levels. For recycling enterprises, selecting the appropriate equipment configuration delivers more than just increased throughput and reduced energy consumption; it is the strategic key to securing a lead in an increasingly standardized and premium-oriented recycled plastics market.