Most liner specification is about moisture. For powders and fine granulate it is about electrostatic charge, and that is a different conversation with higher stakes.
Where the charge comes from
Triboelectric charging: when dissimilar materials separate after contact, electrons transfer. Powder flowing against a polyethylene liner does this continuously, and polyethylene is an excellent insulator, so the charge accumulates rather than dissipating.
Discharge a container by tipping it and the accumulated charge finds the nearest path to ground, which may be an operator, a frame member, or the air.
The three problems, in ascending order of seriousness
- Cling. Powder adheres to the liner and will not discharge cleanly, leaving residual product and a slow, frustrating emptying process.
- Dust clouds. Charged particles repel each other and stay airborne, which is a housekeeping and respiratory issue.
- Ignition. For combustible dusts with low minimum ignition energy, an electrostatic discharge can be sufficient. This is a process safety matter and is outside what a packaging supplier should be adjudicating.
Liner types
| Type | Mechanism | Typical surface resistivity | Suited to |
|---|---|---|---|
| Standard PE | None | 10¹⁴ – 10¹⁶ Ω/sq | Pellets, non-dusty granulate |
| Antistatic (topical) | Hygroscopic additive migrates to surface | 10¹⁰ – 10¹² Ω/sq | General dust control |
| Permanent antistatic | Additive integral to the film | 10⁹ – 10¹¹ Ω/sq | Low-humidity environments |
| Static dissipative | Conductive network, controlled drain | 10⁶ – 10⁹ Ω/sq | Sensitive electronics feedstock |
| Conductive / FIBC Type C | Grounded conductive threads | < 10⁶ Ω/sq | Combustible dust, with grounding |
The humidity dependency nobody mentions
Topical antistatic additives work by attracting a microscopic moisture layer to the film surface, which provides a conductive path. In dry conditions — winter heating, desert climates, dehumidified rooms — that moisture layer does not form and the additive stops working.
A topical antistatic liner that performed perfectly in July can behave like plain polyethylene in January.
If your facility runs below about 30% relative humidity, specify permanent antistatic or dissipative film rather than topical.
Grounding is not the liner's job
This is the point we make most firmly. A conductive liner only works as part of a grounded system: the liner bonded to a grounding point, the pallet or frame bonded, and the whole path verified. An ungrounded conductive liner can be worse than an insulating one, because it accumulates charge across a conductive surface and discharges all of it at once.
If your material is a combustible dust, the liner specification follows from a hazard assessment done by someone qualified to do it. We supply what the assessment specifies; we do not perform the assessment, and we are suspicious of any packaging supplier who offers to.
The corrugated side
The board itself is mildly conductive and generally helps rather than hurts. The practical corrugated consideration for powders is the octabin geometry: eight sides rather than four means no 90-degree corners for powder to bridge in, which reduces both residual material and the amount of agitation needed to discharge — and agitation is what generates charge in the first place.
A sensible default
For non-combustible powders in a normally humid facility: an octabin with a permanent antistatic liner and a bottom discharge spout. It controls cling, reduces dust, empties cleanly, and does not depend on seasonal humidity to work.
Our pieces are written by the people who do the work rather than by a content agency, which is why they contain more numbers and fewer adjectives than is fashionable. If a figure here does not match your experience, we would genuinely like to hear about it — two of our published coefficients have changed that way.