Characterization of membrane permeability and classification

Thin film of water vapor barrier property, under certain conditions, every square metre, every day, 24h) Through the gas quality, g) — — Moisture transmission shall be described. Thin film of water vapor through the volume is smaller, the higher barrier property; On the other hand, the amount of membrane, its barrier property. According to the membrane permeability, thin film will also be roughly divided into three categories. 1) high barrier property of soft film [ The thickness of 2. 54 um film in x: 23, 65% RH conditions, moisture permeability & lt; 2g/( m2 • 24h) ] 。 (2) the barrier property film [ The thickness of 2. 54 um film, under the condition of 23 ° C and 65% RH, moisture permeability of 2 ~ 20 g/( m2 • 24h) ] 。 (3) low barrier property ( The barrier property) Thin film [ The thickness of 2. Um film, 54 in 23 ° C and 65% RH condition, moisture permeability is greater than 20 g/( m2 • 24h) ] 。 In the national standard GB/T 5048 moisture-proof packaging, from a practical perspective, not an packaging film thickness, only consider film through humidity, ( 40±1) ° C, relative wet degree under the condition of 80% ~ 92%, the moisture transmission & lt; 15g/( m2 • 24h) Film is called 3 level moisture-proof packaging film; < 5g/( m2*24h) Film called a level 2 moisture-proof packaging film; < 2g/( m2 • 24h) The film called grade 1 moisture-proof packaging film; > 15g/( m2• 24h) Film is excluded outside the moisture-proof packaging film.