Development and solutions for barrier properties of packaging materials

December 29, 2023


        With the development of the society develops and the improvement of people's quality of life, consumers are paying more and more attention to food safety. The ingredients in most food are easily contaminated by the environment or microorganisms, causing quality degradation and deterioration. Therefore, food packaging plays a vital role. So how to effectively improve the barrier properties of packaging?

        First of all, we need to understand which of the current packaging materials has better barrier properties.

I High barrier packaging film materials

        Currently, many of these packaging technologies use plastic film packaging materials. Although they are required to have a variety of properties, the most important is that they must have good barrier properties.

Plastic single film

        Now the types of plastic single films commonly used in flexible packaging include PVDC, EVOH, PA, PVA, inorganic oxide-plated films, etc. Among them, PVDC, EVOH, and PA are used in the largest amounts. These materials have high barrier properties.

Polyvinylidene chloride resin has the following varieties

        Extrusion-grade resin is easy to process when molten. Its latex can be used for coating polypropylene and polyethylene plastic films. It can be also be used for coating PET, PVC, PS and PE rigid containers to improve the barrier properties of the substrate.

Application of polyvinylidene chloride resin in barrier properties

        It is mainly used for gas barrier, oxygen barrier and water barrier properties. It is mainly used to make films and heat shrinkable films to package food such as meat or other foods, medicines, etc.


        Polyamide (PA) whose name is also called nylon, which has good transparency, easy molding, high strength and the ability to maintain high stiffness in a wide temperature range.

PA main performance

        1.It has good low temperature resistance and certain heat resistance.

        2.It has high gas barrier properties but poor moisture barrier properties.

        3. Non-toxic, odorless, good weather resistance but poor dyeability.

        4. Good chemical stability, resistant to solvents, oils and dilute acids.

        Nylon can be co-extruded with other materials such as polyolefin. At the same time, nylon is also used to compound with other films such as polyethylene films. In the laminated structure, nylon mainly provides high barrier properties, stiffness and tensile strength.

Aluminum or inorganic oxide film

        Aluminized film and inorganic oxide film coating, that is, a layer of aluminum or inorganic oxide (SiO, SiO2) with a thickness of 0.05 micron is vacuum-coated on a film such as polyolefin or polyester (PET). In particular, the inorganic oxide-plated film not only has high barrier properties, but can also be used to directly heat packaged food in a microwave oven.

        The vacuum aluminized film not only has the same mechanical properties as the base material, but also has the same high barrier properties as aluminum foil. For example, from the perspective of saving materials and energy, using vacuum-aluminized films on the surface instead of aluminum foil to make high-barrier packaging materials is the future development trend of high-barrier materials. At the same time, the cost is lower than other films. Therefore, vacuum aluminized films have replaced aluminum foil laminated films on many occasions.

        Commonly used evaporated film base materials include BOPA, PET and PP. In addition to being used in occasions requiring barrier properties, vacuum aluminized films are also used as decorative materials with their gorgeous appearance.

II. composite materials

        Laminated modification of plastic packaging films is the most effective method to improve the barrier properties of plastic packaging materials. The lamination of plastic packaging films can be either two-layer lamination or multi-layer lamination. The more layers they have, the better the barrier effect they own. If the compatibility of the two film materials is good, they can be laminated directly. But the two films with poor compatibility between the composite materials, an appropriate adhesive must be used. The most commonly used adhesive is polyurethane. Adhesives and bonding resins.

Lamination between general resins

        This type of composite structure includes LDPE/LDPE, LDPE/HDPE, LDPE/HDPE/LDPE, etc.

Lamination of general resin and medium barrier resin

        The outer layer of this laminated method is general resin, while the inner layer is medium barrier resin. Since the compatibility of the two resins is not very good, an adhesive layer is often added. Therefore, if an adhesive layer is included, the total number of layers is mostly three or five. The general resins in laminated materials are: LDPE, LLDPE, HDPE, PP and PVC, etc., while the medium barrier resins are: PA, PET and EVA, etc. Among them, general resins such as PE, PP, etc. also play the role of heat sealing layer in the bag making process of composite films.

Lamination of general resin and high barrier resin

        General resins are LDPE, HDPE, LLDPE, PP, etc., which are commonly used in the outer layer.

        High-barrier resins are EVOH and PVDC, which are often used in the middle layer to prevent the barrier properties from being affected by humidity. The inner layer is made of general resin, which plays the role of protection and heat sealing. Due to the poor compatibility between the two laminated materials, an adhesive layer is often added. they include HDPE/adhesive/EVOH/adhesive/HDPE, PP/adhesive/EVOH/adhesive/PP, etc.

Lamination of plastic films and aluminum foil

        This laminated method is a lamination between plastic film materials and metal foil materials. This kind of laminated packaging material has excellent barrier properties due to the high barrier properties of aluminum foil, and can be used for moisture-proof, fresh-keeping and fragrance-preserving applications with higher requirements. In packaging. Commonly used plastic materials in lamination include BOPP and BOPET.

        Adding inorganic fillers to polymers can not only improve the mechanical strength of the material, but also effectively improve the barrier properties of the material. Especially since the 20th century, the rapid development of nanotechnology has led to the emergence of various new nanofillers, opening up a new path for the preparation of high-barrier materials. The most widely studied and currently commercialized materials are lamination of nano-clay and polymers. Nano-clay is a silicate with a layered structure and no permeability. Because it has a high aspect ratio, adding a small amount of nano-clay to the polymer can make the diffusion path of gas molecules tortuous, thereby reducing the gas permeability of the material and improving the barrier properties.

        With the rapid development of science and technology, various high-barrier materials are emerging in endlessly, especially flexible packaging materials which provide guarantees for better extending the shelf life of food and improving food quality. However, as environmental pollution problems become increasingly serious, biodegradable polymers with good packaging properties, easy processing, and low prices are being continuously developed to replace the currently widely used synthetic plastics.

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