What Makes Microporous Membranes Waterproof and Breathable?

Microporous membranes are thin polymer films with billions of interconnected pores. Typical pore sizes range from 0.1–0.5 μm, which is much smaller than liquid water droplets (tens of microns) but still large enough to permit the diffusion of water vapor molecules (~0.0004 μm). This scale difference explains how microporous membranes prevent liquid penetration while enabling vapor transfer.

Because of this unique structure, microporous membranes are widely used in hygiene, medical, protective clothing, functional apparel, agriculture, and construction.

What is a Microporous Membrane?

Microporous membranes are usually made from polypropylene (PP) or polyethylene (PE). They are produced through stretching or phase separation, resulting in a stable porous network.

Performance is evaluated with different methods depending on application:

• Air permeability: ISO 5636-5 (Gurley, often applied to thin films) and ISO 9237 (mainly for textiles).
• Moisture vapor transmission (MVTR): ASTM E96 or JIS L1099, widely used in apparel and textiles.
• Medical & protective resistance: ASTM F1670/F1671 and EN 14126, focusing on synthetic blood, viral, and infective agent penetration.

Not every test applies to every product; the method is chosen according to the intended application.

Waterproof and Breathable Performance

Waterproofness and breathability are validated by internationally recognized methods:

• Waterproofness: Hydrostatic pressure (EN 20811, AATCC 127). Typical PP/PE microporous membranes achieve 800–1500 mm H₂O.
• Breathability: Vapor transmission (ASTM E96, JIS L1099). Depending on thickness and lamination, MVTR values often fall in the 1000–5000 g/m²·24h range.

Our membranes can be adjusted in GSM, thickness, and structure to match different waterproof-breathable performance requirements.

Applications Across Industries

Hygiene Products

In baby diapers and adult incontinence pads, microporous membranes allow moisture vapor to escape while blocking liquid. This helps reduce skin irritation and maintain dryness over long wear periods.

Medical Protection

When laminated with nonwoven substrates and tested under proper conditions, selected membranes can comply with ASTM F1671 (viral penetration resistance) and AAMI Level 4 fluid barrier requirements. These applications include isolation gowns, surgical drapes, and medical coveralls.

Industrial & Protective Clothing

Microporous membranes are used in CE-certified Type 5B/6B garments to provide particle and limited chemical splash resistance. While they improve comfort compared with non-breathable films, heat build-up during extended use is still a consideration—making MVTR values an important design factor.

Functional Apparel

In outdoor and sportswear, microporous membranes deliver waterproofness and breathability in jackets, raincoats, and performance wear. The balance between hydrostatic head and MVTR is adjusted according to garment needs.

Construction Wraps

Microporous membranes used as house wraps prevent external rainwater intrusion while allowing interior humidity to escape. This helps reduce condensation and mold risk, protecting structural integrity.

Agricultural Fabric

Microporous films are applied in crop protection covers where moisture control and limited ventilation are required. In agriculture, adoption depends on cost, durability, and weather resistance as much as on breathability itself.

Sustainable Options for Modern Fabrics

We provide several sustainable microporous membrane solutions:

• GRS-certified recycled PET membranes, available for apparel and outdoor textiles.
• Solvent-free and PFC-free processing to reduce environmental impact.
• Biodegradable grades under development for specific disposable applications. These remain niche solutions today, but offer an option where end-of-life reduction is critical.

Certifications & Testing Standards

Our microporous membranes are produced under strict quality control. Certifications cover hygiene, medical, industrial, sustainability, and facility compliance.

For the full list of certifications, please visit our Certification Page.

Looking for Certified Microporous Membrane Solutions?

We supply PP/PE microporous membranes and laminated fabrics, customizable in GSM, width, and lamination structure. Our materials are applied across hygiene, medical, protective clothing, apparel, construction, and agriculture. If you need breathable, waterproof, and certified materials, Kae Hwa can deliver the right solution.

Contact us today to discuss your requirements.

FAQ

Q1: Are microporous membranes the same as breathable films?

A1: Microporous membranes are one of the most widely used breathable film types. Their micropore structure allows water vapor to pass while blocking liquid water.

Q2: Can microporous membranes block viruses?

A2: Certain laminated grades have been tested to comply with ASTM F1671 and AAMI Level 4 standards. These results apply to specific product constructions, not all microporous membranes.

Q3: Are microporous membranes sustainable?

A3: Options such as GRS-certified recycled PET and biodegradable membranes are available for selected applications. Suitability depends on performance and customer requirements.