PET films
BOPET film is made by bidirectional stretch after PET resin T - die extrusion. With good performance of transparency, gloss and heat resistance, BOPET films are often used as the printing layer of retort pouch. PET film’s Detailed performances are as below:
(1) BOPET film’s strength of extension is the best compared with any other films. A very thin PET product can meet the needs of strong rigidity and high stiffness, 12 micron PET film have been widely used.
（2）BOPET film has good transparency - the transmittance is above 90%; good gloss and printing adaptability, which is especially suitable for reverse printing.
（3）The applicable temperature range of BOPET film is at -70 ~ 150℃, it can maintain excellent physical and mechanical properties over a wide temperature range. It also has good dimensional stability (when it’s at 170 ~ 180℃, its shrinkage is less than 1% ~ 20%). What’s more, its performance will not be affected even if it’s heated under a high temperature for a long time, suitable for a majority of product packaging.
（4）Excellent moisture and water resistance. After soaking for 24h, PET film’s water - absorbency is less than 0.2% ~ 0.4%. There are very few change in size and mechanical properties caused by moisture absorption.
（5）Water vapor permeability and oxygen permeability are rather low. When it’s 100 micron thick, the water vapor permeability is 5.5g/(m²·24h), and the oxygen permeability is 19ml （m²·24h·0.1MPa). With extremely high barrier to air and odour, PET is one of the incense preservation materials.
（6）With good performance of oil and drug resistance, and not easy to dissolve, PET also has good resistance to acid and alkaline corrosion, can withstand the erosion of organic solvents, grease, yet these performances are easy to be deteriorated when it’s in contact with strong alkaline.
（7）When BOPET is laminated as the middle layer, since the both sides of BOPET need adhesive for bonding, Surface tension on non-corona treated surfaces is also important (National standard requires ≥40mN/m, and enterprise standard is usually ≥42mN/m).
The quality standard of BOPET film for packaging in China is GB/T 16958-1997, and the physical and mechanical properties required are shown in Table 2-7.
Table 2-7 physical and mechanical properties of BOPET films
Items | category | |||
Superior product | First-class product | Qualified product | ||
tensile strength（MPa） | vertical | ≥190 | ≥180 | ≥170 |
horizontal | ≥200 | ≥185 | ≥170 | |
elongation at break（%） | vertical | ≥100 | ≥90 | ≥80 |
horizontal | ≥100 | ≥90 | ≥80 | |
Heat shrinkage rate（%）（150℃，30min） | vertical | ≤2.0 | ≤2.0 | ≤3.0 |
horizontal | ≤1.5 | ≤1.5 | ≤2.0 | |
haze（%） | ≤3.0 | ≤3.5 | ≤4.5 | |
gloss（%） | ≥90 | ≥85 | ≥80 | |
friction coefficient（motionless/motional） | ≤0.55/0.65 | |||
Wetting tension （mN/m） | non-corona treated | ≥40 | ||
corona treated | ≥50 | |||
