Túi hút chân không màng ghép PA / PE
Depending on the purpose of packaging, we can use single-layer plastic bags or laminated film packaging (multi-layer) to vacuum.
In theory, all types of plastic bags can be vacuumed, as long as they are thick enough to not tear under the strong suction of the vacuum. After the air is sucked out and sealed, the packaging must remain intact so that air does not re-enter the interior. For the purpose of vacuuming for family activities, most types of thick enough plastic bags can meet well.
However, in industrial production, the story is completely different. Vacuum bags for frozen foods require the ability to withstand low temperatures for a long time without drying out, a phenomenon that common plastic materials such as LDPE, HDPE or PP all face.
As for the purpose of packaging to minimize the volume and volume of packages such as pillowcases, comforters, mattresses, etc., The packaging used needs to be soft and flexible but still has to be strong enough to withstand extreme suction, compressing the product inside to the smallest possible size. High-thickness Low-density Polyethylene (LDPE) bags can meet these packaging requirements. When the vacuum cleaner sucks the air out of the package, it creates wrinkles and shrinks on the package. With stiffer materials such as Polypropylene (PP) or High-density Polyethylene (HDPE), these creases can form tearing folds that lead to packaging failure. Vacuum LDPE bags can also be added to the material tank when being produced, adding a toughness additive to the material tank, which improves packaging performance significantly.
Returning to the vacuum-sealed plastic bag for frozen food, manufacturers need to find a material that can withstand strong suction to completely remove the air inside, and can withstand freezing temperatures for a long time. There are many engineering plastics that can meet this requirement, but they have problems with heat sealing. And most importantly, they have not been proven to be safe and approved for food storage according to the standards issued in many countries. Using such packaging would be very unsafe, and the product contained inside would almost no longer have a chance to be exported.
And the main solution is a type of laminated film packaging made up of many layers of materials combined to create outstanding properties, with the innermost layer in direct contact with the product being food safe materials (LDPE). and outer layers are engineering plastics with outstanding properties.
There are many types of vacuum bags with different compositions such as PET/PE, PA/PE, PE/PA/EVOH, OPET/PP, OPA/PP, etc. There are also bags due to special requirements that are composed of 5, even 7 different layers of film. The selection of the right type of vacuum bag will be based on the needs and responsiveness of each type of material that makes them up. For example, bags made of PA/PE are safe to boil at 100°C, but cannot be sterilized at 121°C, but PA/PP or PET/PP bags can. This is because the melting point of PE is only 120°C and PP is up to 165°C.
There is one thing in common among all vacuum bags currently on the market, is that they can all be considered freezer safe, because this is the core purpose of this type of packaging.