What Is Micro-porous Film?
Direct Answer
Micro-porous film is a plastic film with microscopic pores that allow vapor passage while blocking liquid, the core technology behind breathable backsheets.
Key Takeaways
- Micro-porous film is a plastic film with microscopic pores that allow vapor passage while blocking liquid, the core technology behind breathable backsheets.
- How it works: Calcium carbonate particles are mixed into the polymer; when the film is stretched, the polymer separates around the particles leaving microscopic pores.
- Most breathable diaper backsheets use stretched calcium-carbonate micro-porous films
- Myth: Micro-porous films are fragile. They are engineered for production and wear strength
How Micro-porous Film Works
Calcium carbonate particles are mixed into the polymer; when the film is stretched, the polymer separates around the particles leaving microscopic pores. Pore size is controlled so water vapor (0.0004 microns) passes freely but liquid droplets (over 100 microns) cannot. This is the standard breathable-backsheet technology in modern diapers.
Examples and Applications
- Most breathable diaper backsheets use stretched calcium-carbonate micro-porous films
- Pore density per cm2 is a key quality metric (pore density test)
Micro-porous Film vs. Related Terms
| Term | What it is | Key difference |
|---|---|---|
| Cast PE film | Micro-porous Film | Cast film is solid (non-breathable); micro-porous film is stretched to create vapor-passing pores |
Limitations and Common Misconceptions
- Myth: Micro-porous films are fragile. They are engineered for production and wear strength
- Myth: All films with holes leak. Pores are vapor-scale, far smaller than liquid droplets
How are micro-pores created in film?
Calcium carbonate fillers cause the polymer to separate into micro-pores when the film is stretched.
Why don't micro-porous films leak?
The pores are about 0.0004 microns — large enough for vapor, far too small for liquid droplets.
References
- Pampers Official - What's in a Pampers diaper (component materials) — 品牌官方 (accessed 2026-08-02)
- JP CIA (industry) - Baby diaper material: key components and their functions — 行业媒体 (accessed 2026-08-02)