How to judge whether the moisture-proof performance of paper meets the requirements?

This problem is very important, and the moisture-proof performance directly determines the protective effect of packaging in humid environment. The core conclusion is that whether the paper meets the requirements can be determined by the combination of moisture-proof index detection, actual scene test and appearance process judgment.

1. Look at the core moisture-proof indicators first.

Water absorbency (Cobb value): This is a key indicator, which refers to the amount of water absorbed by paper per unit area in a specified time (g/m2). The lower the value, the better the moisture resistance. The suggested Cobb value for packaging in food and humid environment is ≤30g/㎡.

Surface treatment marks: The moisture resistance of paper marked with "film coating", "wax coating", "film coating" and "moisture-proof coating" is far better than that of untreated paper.

Material characteristics: the original wood pulp paper has better moisture resistance than recycled paper, and the thick paper absorbs water more slowly than the thin paper. Special moisture-proof paper (such as moisture-proof kraft paper) will clearly indicate the moisture-proof grade.

2. Simple and operable actual test

Drip test: Drop 1-2 drops of clear water on the paper surface to observe seepage velocity. Impermeability within 1 minute, water droplets remain intact, indicating that the foundation is moisture-proof; There is no obvious infiltration within 3 minutes, which can meet the needs of general humid environment.

Immersion test: immerse a corner of the paper in water and take it out for observation after 30 seconds. Only the surface is wet, non-layered and non-softening, indicating that the moisture resistance is good; If it absorbs water quickly and softens, it does not meet the requirements of moisture.

Simulated transportation test: wrap the paper around the sample and put it in an environment with humidity above 80% for 24 hours. After being taken out, the paper has no deformation and mildew, and the internal samples are dry, which shows that the moisture-proof performance is up to standard.

3. Pay attention to avoiding pits

Avoid confusing "waterproof" and "moisture-proof": most paper materials are moisture-proof (slow water absorption), not waterproof (no water absorption at all), which should be reasonably expected according to the scene.

Pay attention to environmental adaptation: in high humidity areas (such as rainy season in southern China) or cold chain transportation, paper with double moisture-proof treatment (such as film covering and moisture-proof coating) should be selected.

Check the test report: when purchasing in bulk, the supplier is required to provide Cobb value test report and moisture-proof performance certification to avoid verbal commitment.