Why Is The Degassing System Important In The Plastic Pelletizing Process?

During the plastic recycling and pelletizing process, many clients tend to focus primarily on the extruder, filtration system, and pelletizing method, yet they often overlook a critical core component that determines pellet quality: the Degassing System.

In fact, for materials such as PE films, PP woven bags, PET bottle flakes, printed films, agricultural films, and waste plastics with high moisture content, the effectiveness of the degassing process directly impacts:

Pellet appearance
Melt stability
Product odor
The quality of downstream products
Extrusion efficiency
Equipment operational stability

Particularly when processing recycled plastics that are heavily contaminated, high in moisture, or contain inks and volatile substances, a highly efficient degassing system has become virtually a "standard feature" for any high-quality pelletizing line.

A degassing system is a critical functional module installed on a plastic pelletizing extruder. Its primary functions are to:

Vent moisture
Remove volatile gases
Eliminate inks and low-molecular-weight impurities
Reduce air content within the melt
Stabilize the plasticization process

During the plastic melting process, waste plastics often contain various internal contaminants, including:

Moisture/Water vapor
Oil residues
Adhesives
Printing inks
Volatile Organic Compounds (VOCs)
Residual cleaning agents
Trapped air

If these substances are not effectively and promptly vented, they will severely compromise the quality of the final pellets.

When moisture or gases trapped within the plastic melt cannot be expelled, the cooling and pelletizing stages often result in:

Pellets containing bubbles
Internal voids
Rough surface textures
Irregularly shaped pellets

These issues directly degrade the quality of the recycled material, negatively impacting its performance in subsequent downstream processes such as film blowing, injection molding, or fiber drawing.

This is particularly critical in the recycling and pelletizing of PE films; since agricultural films and packaging films often possess high moisture levels, the absence of effective degassing makes them highly susceptible to pellet foaming issues.

Waste plastics frequently retain residues such as:

Printing inks
Food residues
Cleaning agents
Organic contaminants

During the high-temperature plasticization process, these substances release odors. An efficient vacuum degassing system effectively extracts volatile gases, thereby:

Reducing odors in granules
Enhancing the market value of recycled materials
Expanding the application scope of finished products

Low-odor granules are particularly critical for the high-end film, injection molding, and packaging industries.

If a significant amount of gas is present within the polymer melt:

Melt pressure will fluctuate
Electrical current will be unstable
Extrusion will be uneven
Granule size will be inconsistent

Conversely, stable degassing serves to:

Improve melt homogeneity
Enhance extrusion stability
Maintain continuous production
Minimize the risk of downtime

This is especially crucial for large-scale, continuous recycling production lines.

If residual gas remains within recycled granules, downstream processing of finished products is prone to defects such as:

Silver streaks
Flow marks (gas marks)
Black spots
Surface pitting
Reduced mechanical strength

Particularly in demanding processes such as:

Film blowing
Injection molding
Wire drawing
Pipe extrusion

insufficient degassing can significantly compromise the quality of the finished product.

Releasing a portion of the gas through open vent ports.

Characteristics:

Simple structure
Low cost
Suitable for clean materials

However, its effectiveness is limited for plastics with high moisture content or heavy contamination.

Utilizing a vacuum system to forcibly extract volatile gases and moisture.

Advantages:

High degassing efficiency
Reduces pellet odor
Improves pellet density
Better suited for recycled plastics

Currently widely applied in:

PE film pelletizing
PP woven bag recycling
PET recycling
Industrial waste plastic recycling

High-end pelletizing lines typically employ:

A primary atmospheric vent
A secondary vacuum degassing unit

This configuration achieves a more thorough removal of volatile substances.

Particularly suitable for:

Heavily printed films
High-moisture agricultural films
Heavily contaminated industrial waste plastics

In the plastic pelletizing process, the degassing system is not merely an "auxiliary function," but a critical core technology that determines the quality of the pellets.

Especially within the waste plastic recycling industry—as market demands for the quality of recycled materials continue to rise—efficient degassing has become an essential standard for high-end pelletizing equipment. For companies seeking to enhance granule quality, minimize odors, improve production stability, and expand the scope of recycled material applications, selecting the appropriate degassing system will directly impact the economic viability and market competitiveness of their entire recycling project.

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