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What are the materials of the packaging bag?

    There are many kinds of food packaging bags used for food packaging. They have their own unique properties and characteristics. Today we will discuss some common food packaging bag knowledge for your reference.



    The first type: HDPE/high-density polyethylene/low-pressure polyethylene/low-pressure film. 

    This is the most common material, which is the kind of shopping bag that we often see in supermarkets. It is made of our HDPE bag. Yes, this material can be individually bagged. It is a relatively common and cheap material in the market-PO bag. This kind of material is relatively brittle and harder, has a low expansion rate, and has a crisper sound when rubbed.



    The second type: LDPE/low-density polyethylene/high-pressure polyethylene/high-pressure film. 

    Transparent texture, softer, good toughness, good transparency, smooth hand feeling, the thicker and harder the material, the greater the expansion rate. This material can also be made into a bag separately, which is a relatively common and cheap material like PO bags.



    The third type: OPP/Oriented polypropylene.

   OPP/Oriented polypropylene is the most brittle and most transparent material. 

    The tension is not enough. It can be said that there is no tension at all. It is the most vulnerable to the mouth and the printing is the easiest to discolor, which is very bad For printing, it needs to be printed and left for a period of time to cut the bag.



    The fourth type: CPP/cast polypropylene/non-stretched polypropylene.

    This material has high transparency, higher hardness than PE film, and clearer, long as the base film of composite materials. It is often combined with other films to form a bag, which is a good composite film. CPP also has a cooking grade material that can be used for food that needs to be steamed.



    The fifth type: PET/polyethylene terephthalate.

    This material is also very transparent, its strength and toughness are better than polystyrene and polyvinyl chloride, it is not easy to break, and the surface is smooth and shiny. It is also one of the common composite materials.



    Sixth: PA/Nylon.

    This material is often used as a composite material for cooking/poaching bags, with good toughness and softness.



    Seventh: Aluminum Foil/AL Aluminum foil. 

    This is an extremely thin sheet formed by rolling high-purity aluminum several times. It is an excellent heat conductor and light-shielding body. Good mechanical strength, light weight, no thermal adhesion, metallic luster, good light-shielding, strong reflection to light, not easy to be corroded, good barrier properties, moisture-proof and waterproof, strong air tightness, and fragrance retention . It has metallic luster, high gas barrier, low adhesion viscosity, and it is easy to transfer the aluminum coating after composite processing.


    Food packaging bags generally refer to sheet plastics with a thickness of less than 0.25mm as films, and flexible packaging made of plastic films is widely used in the food industry. There are various types of food packaging bags. They are transparent, flexible, have good water resistance, moisture resistance and gas barrier properties, have good mechanical strength, stable chemical properties, grease resistance, easy to beautiful printing, and can be heat-sealed to make bags. Moreover, the commonly used food flexible packaging is usually composed of two or more layers of different films, which can generally be divided into outer layer, middle layer and inner layer according to the position.


    What are the requirements for the performance of each layer of the commonly used food flexible packaging film?
First of all, the outer film is generally printable, scratch-resistant, and medium-resistant. Commonly used materials include OPA, PET, OPP, and coated films.


    The middle layer film generally has the functions of blocking, shading, and physical protection. Commonly used materials include BOPA, PVDC, EVOH, PVA, PEN, MXD6, VMPET, AL, etc.


    Then there is the inner film, which generally has the functions of barrier, sealing, and anti-medium. Commonly used materials are CPP, PE, etc. In addition, some materials have the common function of the outer layer and the middle layer. For example, BOPA can be used as the outer layer to imprint, but also can be used as the middle layer to play a certain barrier and physical protection.


    What are the requirements for the characteristics of commonly used food flexible packaging films?
Generally speaking, the outer layer material should have scratch resistance, puncture resistance, UV resistance, light resistance, oil resistance, organic resistance, heat and cold resistance, stress cracking resistance, printability, thermal stability, low odor, low odor, non-toxic, gloss , Transparency, shading and other performances;


    The material of the intermediate layer should generally have impact resistance, compression resistance, puncture resistance, moisture resistance, gas resistance, fragrance retention, light resistance, oil resistance, organic resistance, heat and cold resistance, stress cracking resistance, double-sided composite strength, low odor, low odor, Non-toxic, transparent, light-proof and other properties;
Then there is the inner layer material. In addition to some common properties with the outer middle layer, it also has its own unique properties. It must have fragrance retention, low adsorption and anti-seepage properties.


    Now the development trend of food packaging bags is:

    1. Food packaging bags made of environmentally friendly materials.

    2. In order to reduce costs and save resources, food packaging bags are becoming thinner.

    3. Food packaging bags are developing towards special functionalization. High-barrier composite materials will continue to increase market capacity. The high-barrier film, which has the advantages of simple processing, strong oxygen and water vapor barrier properties, and improved shelf life, will be the mainstream of supermarket food soft packaging in the future.

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