A PE PP plastic film pelletizing line converts washed film flakes, bags, woven material and suitable production scrap into uniform recycled pellets. Because flexible plastics have low bulk density and can contain residual moisture, ink or contamination, reliable pellet production depends on more than the extruder alone. Feeding, densification, melt filtration, vacuum degassing and pellet cutting must work as one coordinated system.
Sanxing Machine designs film recycling pelletizing lines according to the polymer, material condition, target output and final pellet application. This guide explains the main process stages and the questions that should be answered before selecting a line.
Suitable input materials
A correctly configured system can process a range of flexible PE and PP materials, including:
- Washed LDPE and LLDPE film flakes
- Packaging, stretch and shrink film
- PE shopping bags and suitable post-consumer film
- PP woven bags, raffia and jumbo-bag material
- Clean industrial film scrap and edge trim
- Agglomerated or squeezed polyolefin material
The feedstock should be identified before equipment selection. PE and PP can require different temperature settings and filtration strategies, while printed film, high moisture, paper, aluminum or incompatible polymers can affect pellet quality. Food-contact suitability should never be assumed from the pelletizing step alone.
How a film pelletizing line works
1. Feeding and material preparation
Loose film is difficult to meter directly into an extruder because it bridges easily and changes in bulk density. Depending on the material, the line may use a belt feeder, force feeder, cutter compactor, agglomerator or squeezing system. Stable preparation improves extruder loading and reduces output fluctuation.
2. Cutting, compacting and densification
A cutter compactor reduces film size, mixes the material and increases bulk density before extrusion. Friction can also help remove part of the residual moisture. For washed film, a squeezing dryer may perform mechanical dewatering and compaction before the pelletizing line.
3. Controlled extrusion
The prepared material enters the screw and barrel, where it is conveyed, heated and melted. Screw geometry, length-to-diameter ratio, motor power and temperature control are selected according to the polymer and required output. Stable feeding is essential because inconsistent loading can produce unstable pressure and pellet quality.
4. Vacuum degassing
Moisture, printing ink and volatile residues can generate gas during melting. Vacuum degassing helps remove these volatiles and can reduce bubbles or surface defects. Heavily printed or damp materials may need stronger drying, multiple venting zones or a different extrusion arrangement.
5. Melt filtration
Filters remove solid contamination before pellet cutting. Screen changer selection depends on contamination level, production continuity and the required pellet cleanliness. Cleaner industrial scrap may use a simpler filtration system, while post-consumer film usually needs more robust continuous filtration.
6. Pellet cutting and cooling
The filtered melt is converted into pellets using a cutting system selected for the polymer and production goal. Common options include water-ring, strand and underwater pelletizing. Pellets are cooled, separated from water, dried and conveyed to collection or storage.
Single-stage or two-stage extrusion?
A single-stage extruder can be suitable for relatively clean, dry and consistent material. A two-stage or cascade system offers additional degassing and filtration flexibility for washed or printed post-consumer film. However, the correct choice should be based on feedstock tests, quality targets, energy considerations and maintenance expectations—not on the assumption that more equipment is always better.
What affects capacity and pellet quality?
Nominal throughput is only one part of line selection. Actual performance is influenced by:
- Polymer type, melt flow and material mixture
- Bulk density after washing or squeezing
- Residual moisture and printing ink
- Contamination level and required filtration fineness
- Frequency of screen changing
- Feeding stability and motor loading
- Pelletizing method and cooling-water condition
- Operator settings and preventive maintenance
Target pellet properties should be discussed in advance. Color, odor, melt flow, moisture, black specks and mechanical performance are affected by the input material and the complete recycling process.
Connecting washing and pelletizing
For post-consumer flexible plastics, the best results come from treating washing and pelletizing as one production system. The plastic washing line determines cleanliness, moisture and particle size; the pelletizing line determines melt homogenization, filtration and final pellet form.
Sanxing can plan the material transfer between washing, squeezing, storage and extrusion. Buffering and controlled feeding are especially important when the washing section and pelletizing section have different operating cycles.
Utility and layout planning
A complete proposal should identify installed power, typical operating load, cooling-water demand, compressed air, floor space, lifting access and maintenance clearance. Workshop layout should allow safe material flow and enough space for screen changing, screw removal and routine cleaning.
Electrical standards and control components can be selected for the destination market. Final utility consumption depends on the confirmed machine size, feedstock and operating conditions.
Questions to answer before ordering
- Is the input PE, PP or a controlled mixture?
- Is it clean factory scrap or washed post-consumer film?
- What are the residual moisture and contamination levels?
- What capacity and pellet specification are required?
- What will the recycled pellets be used to manufacture?
- Which pellet cutting method is preferred?
- What power, water, compressed air and workshop space are available?
Frequently asked questions
Can wet washed film be fed directly into the extruder?
Residual moisture must be controlled. Washed film commonly passes through mechanical squeezing and, when necessary, additional drying before extrusion.
Which pelletizing method is best for PE and PP film?
Water-ring pelletizing is widely used for many PE and PP film applications, while strand or underwater systems may suit other materials and output requirements. Selection depends on melt behavior and project goals.
How often must the melt filter be changed?
Filter service frequency depends on contamination and filtration fineness. A representative material sample helps determine a practical filtration solution.
How do I receive a configuration proposal?
Send material photos, moisture information, target capacity and pellet application to Lisa through the contact page. Sanxing will prepare a suitable equipment and layout recommendation.
Operating control and routine maintenance
A pelletizing line performs best when operators track material condition and machine data together. Useful records include feed rate, extruder current, zone temperatures, melt pressure before and after filtration, vacuum level, screen-change frequency, pellet appearance and finished-batch weight. A sudden pressure increase can indicate filter loading, while unstable current may point to irregular feeding or changing bulk density.
Preventive maintenance should cover cutter-compactor knives, feeder components, screw and barrel wear, heaters, temperature sensors, vacuum pipes, screen changers and pelletizer blades. Cooling-water quality and flow also affect pellet cutting and drying. Cleaning procedures should be defined when changing colors or polymers to reduce cross-contamination between production batches.
Recyclers should retain a sample from each batch and compare color, odor, contamination, moisture and melt behavior with the agreed internal standard. This simple traceability practice helps link pellet variation back to a particular incoming material lot or operating condition. It also supports more consistent communication with downstream customers and provides useful evidence when the process needs adjustment.