Moisture Resistant Paper: Properties, Applications, and Maintenance

What is Moisture Resistant Paper?

Moisture resistant paper is a specialized type of paper engineered to withstand exposure to water, humidity, and other moisture-rich environments without significant degradation. Unlike standard paper, which absorbs water readily (with a Cobb value of 20-30 g/m² for uncoated varieties), moisture resistant paper typically has a Cobb value of less than 5 g/m², indicating superior water repellency. This is achieved through various treatments and coatings, such as:

• Polymer coatings (e.g., polyethylene or polypropylene) with thicknesses ranging from 12-30 microns

• Silicone treatments that create hydrophobic surfaces with contact angles exceeding 90 degrees

• Internal sizing agents like alkyl ketene dimer (AKD) at concentrations of 0.1-0.5% by weight

Key Characteristics and Technical Data

Modern moisture resistant papers exhibit several scientifically measurable properties:

• Tensile Strength: Wet tensile strength retention of 50-80% compared to dry state (ASTM D829)

• Water Vapor Transmission Rate (WVTR): Typically 5-15 g/m²/day at 38°C/90% RH (ASTM E96)

• Surface Energy: Ranges from 30-45 mN/m for coated varieties versus 70+ mN/m for untreated paper

• Burst Strength: Maintains 200-400 kPa even after water exposure (TAPPI T403)

• Opacity: Generally 85-95% despite coatings (ISO 2471)

Applications of Moisture Resistant Paper

The unique properties of moisture resistant paper make it indispensable in numerous industries:

Food Packaging

In direct food contact applications, FDA-compliant versions with ≤0.1 mg/kg migration limits are used for:

• Fast food wrappers with 15-30 lb basis weight and grease resistance

• Frozen food packaging maintaining integrity at -18°C to 25°C

• Bakery papers with 210°C heat resistance

Medical and Pharmaceutical

Sterilization-compatible grades feature:

• Autoclavability at 121°C for 20 minutes

• Chemical resistance to 70% isopropyl alcohol

• Low linting properties (<0.5 mg/100 cm² per IEST-RP-CC003)

Industrial and Commercial

• Outdoor signage with 5+ years weather resistance

• Marine charts with 0.05% dimensional stability in salt spray

• Construction papers with MIL-P-3420D military specifications

Maintenance and Care Guidelines

Proper handling extends the functional lifespan of moisture resistant papers:

Storage Conditions

• Maintain relative humidity at 40-60% RH (per ISO 187)

• Store at 15-25°C away from heat sources

• Keep in original packaging until use to prevent UV degradation

Cleaning Procedures

For coated varieties:

• Use pH-neutral cleaners (6.5-7.5 pH range)

• Apply with soft microfiber cloths (≤100 GSM weight)

• Avoid abrasive cleaners exceeding 0.3 µm roughness

Printing Considerations

Long-term Preservation

For archival applications:

• Store in polypropylene sleeves with 3-5 mm air gaps

• Monitor with data loggers tracking ±1°C/±2% RH

• Inspect annually for signs of edge wicking or coating delamination