Wisdom For Polyethylene vol.20
20. Drum Inner Liners
2025-12-04
Inner Liners for Chemical and Industrial Drums
On our website, we feature products related to the chemical and industrial sectors, where a variety of inner liners are used for the logistics of liquids, powders, and viscous materials.
These liners, commonly referred to as "inner bags," may also be called "liners," "inners," or "uchibukuro" in industry terminology.
Here, we revisit the basics and consider why inner liners are necessary.
These liners, commonly referred to as "inner bags," may also be called "liners," "inners," or "uchibukuro" in industry terminology.
Here, we revisit the basics and consider why inner liners are necessary.
Two Reasons Why Inner Liners Are Needed in the Chemical Industry
(1) To prevent interaction with the contents
Drums are usually made of steel, which can react with certain chemical substances.
For this reason, coated steel drums or stainless steel drums (SUS drums) are sometimes used.
However, when the contents are sensitive to oxygen or moisture, or when preventing fine particulate contamination is critical, the use of inner liners is essential.
Drums are usually made of steel, which can react with certain chemical substances.
For this reason, coated steel drums or stainless steel drums (SUS drums) are sometimes used.
However, when the contents are sensitive to oxygen or moisture, or when preventing fine particulate contamination is critical, the use of inner liners is essential.
(2) To simplify drum cleaning
Without inner liners, residues tend to adhere to the inner surface of the drum.
High-viscosity materials such as adhesives or pastes are especially difficult to clean and may require heat treatment.
However, environmental regulations increasingly limit such processes.
Without inner liners, residues tend to adhere to the inner surface of the drum.
High-viscosity materials such as adhesives or pastes are especially difficult to clean and may require heat treatment.
However, environmental regulations increasingly limit such processes.
In these cases, using an inner liner allows for easy replacement and facilitates reuse.
Types and Shapes of Inner Liners for Chemical and Industrial Use
(1) Basic Shapes
・Envelope-type polybag:
The most common shape, sealed either with a flat seal or a single-seal method.
Highly versatile and suitable for a wide range of applications.
The most common shape, sealed either with a flat seal or a single-seal method.
Highly versatile and suitable for a wide range of applications.
(2) Special Shapes
・Gusseted bag:
With gussets at both ends, forming a three-dimensional shape.
Suitable for large-volume storage, such as pallet covers or case liners.
With gussets at both ends, forming a three-dimensional shape.
Suitable for large-volume storage, such as pallet covers or case liners.
・Square-bottom bag:
With a square or rectangular bottom, designed to fit square containers.
With a square or rectangular bottom, designed to fit square containers.
・Drum liner (round-bottom bag):
Circular bottom, designed specifically for drums.
Available in open and closed types.
Circular bottom, designed specifically for drums.
Available in open and closed types.
(3) Inner Liners with Special Functions
・Double bag:
A two-layer structure, either by inserting one bag into another or sealing two tubes simultaneously.
Used to protect contents and prevent contamination.
A two-layer structure, either by inserting one bag into another or sealing two tubes simultaneously.
Used to protect contents and prevent contamination.
・Ball-seal / tied-bottom inner bag:
The bottom is gathered and sealed—ball-seal uses heat welding, tied-bottom uses PP strings.
Used to protect contents and prevent contamination.
The bottom is gathered and sealed—ball-seal uses heat welding, tied-bottom uses PP strings.
Used to protect contents and prevent contamination.
Type | Features | Main Applications |
Polybag (envelop type) | General-purpose, versatile | Packaging powders and liquids |
Gusseted bag | Three-dimensional with end gussets | Case or pallet covers |
Square-bottom bag | Fits square containers | Container liners |
Drum liner (round-bottom bag) | Circular bottom, ideal for drums | Transport of viscous materials and adhesives |
Double bag | Two-layer structure, prevents contamination | Content protection, contamination prevention |
Ball-seal / tied bottom inner bag | Bottom gathered and sealed (heat or string) | Content protection, contamination prevention |
Summary
The selection of inner liners largely depends on:
- The properties of the contents (reactivity, viscosity, purity requirements)
- The type of container used (drum, square container)
- The working environment (cleaning needs, disposable requirements)
Choosing the optimal liner is directly linked to quality assurance and operational efficiency.
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