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As global demand for recycled plastics continues to grow, recycling companies are under increasing pressure to produce cleaner, higher-quality recycled materials. Whether processing PET bottles, PP/PE films, or rigid plastic waste, one challenge remains consistent: efficiently separating contaminants from valuable recyclable plastics.
One of the most important machines that solves this problem is the Sink Float Separation Tank, also known as a float sink tank or density separation tank.
In modern plastic recycling lines, this equipment plays a critical role in improving material purity, reducing contamination, and increasing the value of recycled plastic flakes and pellets.
At Chenxing Machinery, we specialize in manufacturing high-performance plastic recycling machinery, including advanced sink float separation systems designed for industrial recycling applications worldwide.
A sink float separation tank is a water-based separation machine used in plastic recycling lines. It separates materials according to their density differences.
The principle is simple but highly effective:
Materials lighter than water float
Materials heavier than water sink
Since water has a density of approximately 1 g/cm³, plastics and contaminants react differently when entering the tank.
For example:
| Material | Density | Result |
|---|---|---|
| PP Film | ~0.90–0.93 g/cm³ | Floats |
| PE Film | ~0.91–0.96 g/cm³ | Floats |
| PET Flakes | ~1.34–1.39 g/cm³ | Sinks |
| Dirt/Glass/Metal | Higher than 1 g/cm³ | Sinks |
This makes the sink float tank one of the most efficient methods for separating mixed plastic materials and removing impurities.
Plastic waste streams are rarely clean. Recyclers often deal with:
Labels
Bottle caps
Dirt
Sand
Metal particles
Stones
Adhesives
Mixed plastic materials
Without proper separation, these contaminants can:
Lower recycled plastic quality
Damage downstream equipment
Increase production costs
Reduce pelletizing efficiency
Affect final product consistency
A sink float separation tank helps recycling plants produce cleaner plastic flakes and improve the efficiency of the entire recycling process.
The process begins when shredded plastic material enters the water-filled tank.
Inside the machine:
Rotating drums push materials into the water.
Floating plastics move across the tank surface.
Heavy contaminants sink to the bottom.
Screw conveyors discharge sunk impurities automatically.
Clean recyclable plastics continue to washing, drying, or pelletizing systems.
The longer the material remains submerged, the better the separation and cleaning performance.
This is why industrial recycling systems often use tanks ranging from 4 to 6 meters in length.
In PET bottle recycling:
PET flakes sink
PP/PE bottle caps float
PVC labels float
This separation stage is critical for producing high-purity PET flakes suitable for:
RPET sheet production
Fiber manufacturing
Food-grade recycling applications
PET pelletizing systems
In PP/PE film recycling systems:
Lightweight films float
Heavy contaminants sink
This allows recyclers to efficiently remove:
Sand
Glass
Stones
Metal debris
before drying and granulation.
Effective density separation improves recycled material quality significantly.
Extended soaking time allows better contaminant removal.
Removing heavy contaminants early protects crushers, pelletizers, and extruders.
Modern systems use screw conveyors and rotating drums for continuous industrial production.
High-quality tanks use Type 304 stainless steel interiors to resist rust and corrosion.
Cleaner material reduces downstream processing losses and maintenance expenses.
When choosing a sink float separation tank, recycling companies should evaluate:
304 stainless steel interiors offer superior durability and corrosion resistance.
Longer tanks improve soaking and separation performance.
Reliable motors ensure continuous operation under heavy industrial loads.
Efficient screw conveyor systems improve contaminant removal.
The tank should match the throughput of the entire recycling line.
As an experienced plastic recycling equipment manufacturer, Chenxing Machinery provides customized sink float separation tanks for various recycling applications.
Our systems feature:
Heavy-duty industrial construction
Type 304 stainless steel interiors
High-efficiency rotating drum systems
Stable screw conveyor discharge
Customizable dimensions
Integration with complete recycling lines
Our equipment is widely used in:
PET bottle washing lines
PP/PE film recycling plants
Hard plastic recycling systems
Industrial plastic waste processing facilities
As recycling standards become stricter worldwide, sink float separation technology continues evolving toward:
Higher automation
Lower water consumption
Smart monitoring systems
Energy-efficient operation
Improved contamination removal accuracy
Advanced recycling facilities increasingly rely on optimized separation systems to produce premium recycled plastic materials for global markets.
A sink float separation tank is much more than a washing unit — it is one of the most critical machines for improving recycled plastic quality and operational efficiency.
Whether recycling PET bottles or PP/PE films, proper density separation directly impacts:
Product purity
Production efficiency
Equipment lifespan
Recycling profitability
For recycling companies seeking cleaner recycled plastics and more reliable production systems, investing in a high-quality sink float separation tank is an essential step.
