Pearly Lustre Film
Pearly lustre film, is made by bidirectional stretching after its raw material PP mixed together with adding modifiers such as CaCO3, pearlescent pigment (powder), rubber, etc. During the bidirectional stretching, the PP resin molecules are stretched, and CaCO3 particles are mechanically stretched away from each other, forming blisters. Therefore, the pearly lustre film is a microporous foam film with a density of about 0.75g/cm. PP molecules lose their heat sealing ability after biaxial orientation. However, as a modifier such as rubber, PP molecules still have certain heat sealing ability, though the heat sealing strength is very low. Pearly lustre film is easy to tear, often used in the packaging of ice cream and popsicles.
The standard of bidirectional tensile polypropylene pearly lustre film in China is BB/T 0002-1994, and its physical and mechanical properties are shown below in Table 2-3.
Table2-3 physical and mechanical properties of pearly lustre film
Item | index | ||
PLa Type | PLb Type | ||
Tensile strength(MPa) | vertical | ≥70 | |
horizontal | ≥130 | ||
Elongation at break（%） | vertical | 85~150 | |
horizontal | 20~50 | ||
thermal-shrinkage rate (%) | vertical | ≤5.0 | |
horizontal | ≤4.0 | ||
≤0.8 | |||
Heat sealing strength（N/15mm） | ≥1.8 | - | |
Wetting Tension（mN/m） | ≥38 | ||
≥70 | |||
Glossiness（%） | ≥45 | ≥60 | |
Density（g/cm³） | ≤0.75 | ||
Water vapor permeability【g/(m²·24h)】 | ≤15 | ||
