Multilayered packaging

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Multilayered packaging (commonly referred to as multilayer packaging) refers to composite materials made from two or more distinct layers. Each is selected for its specific protective or functional properties. Common forms include films, pouches, aseptic cartons, bottles, and tubes.^[1]

Each layer in a multilayer system has a different role. Layers may provide heat sealability, tensile strength, or enhanced gas and light barrier properties. Polyethylene (PE), polyethylene terephthalate (PET), polyamide (PA), ethylene vinyl alcohol (EVOH), aluminium foil, and paperboard are some of the most common materials used. Sustainability, reduced environmental impact, and extended shelf life are becoming increasingly critical in the development of multilayer packaging systems.^[2]

The development of multilayer packaging materials began in the mid-20th century to address the limitations of single-layer materials. They often did not meet performance requirements—particularly in protecting chemically-sensitive products.^[3]

Aseptic cartons by Tetra Pak in the early 1960s were one of the earliest examples of this technology. They used laminated layers of paperboard, polyethylene, and aluminum foil.^[3]

In the 1970s and 1980s, companies began using multilayer films to make vacuum-sealed pouches and heat-safe bags for ready-to-eat meals and foods that last a long time. Around the same time, they also made multilayer containers, like plastic bottles with special layers that keep out oxygen. These were used for sauces, spices, and medicines.^[4]

By the 1990s, multilayer packaging was common around the world. New advances in how the layers were joined, shaped, and glued together made this type of packaging stronger, cheaper, and more useful.^[4]

Multilayer packaging can look different depending on how it is used, what materials are combined, and how much protection is needed to keep food or medicine safe.^[5]

These sacks are made from several layers of strong kraft paper, with each layer having a different thickness. Multi-layer paper sacks are becoming more popular in industries like cement, medicine, and fertilizer. To protect what’s inside from moisture, the inner or outer layer is often coated with a thin layer of plastic (polyethylene; PE).^[6]

These packages are often used in the paint industry, in Tetra Paks for milk, fruit juice, and syrups, and in making medicines. Common layer combinations include:^[7]

• Paper with aluminum foil and low-density polyethylene (LDPE), a flexible type of plastic
• Aluminum foil with paper and LDPE
• PE, a common plastic, with aluminum foil and paper
• PET, a strong plastic often used in bottles, with aluminum foil and LDPE

Many plastic bottles and tubes are made with several layers of different plastics. For example, some use PET, EVOH, and PE. These are used for things like sauces, juices, and cosmetics. In this design, EVOH keeps out oxygen so the product stays fresh, while PE or polypropylene (PP) make the container strong and easy to seal.^[8]

These pouches are often used for ready-to-eat and sterilized foods. They are made with special layers, such as PA, EVOH, or thin silicon oxide (SiOx) coatings. These layers make the pouches tough so they don’t tear easily, and they also block gases like oxygen to help keep food fresh.^[9]

Food preservation is a complex process that relies heavily on advanced packaging technologies, which is why multilayered structures are an essential part of the food industry. These systems are engineered based on the specific properties of the product to enhance barrier properties against oxygen, moisture, and light, while preserving product integrity, shelf life, and storage stability.^[10] Multilayer systems are fine-tuned to match the physicochemical characteristics of the food product. For instance, EVOH-sensitive items because of its exceptionally low oxygen transmission rate (< 1 cm³.m^-2.day^-1.atm^-1 in dry conditions). In contrast, polyolefin layers are externally incorporated to enhance water vapor resistance and sealing efficacy. Paperboard or PET is often included to improve mechanical strength, printability, and stiffness.^[1]

Multilayer films used in modified atmosphere packaging (MAP) account for approximately 30% of the food packaging sector.^[11] MAP is a hermetically sealed multilayer material system that prolongs the shelf life of perishable goods by creating a modified gaseous environment. In this, the package is flushed with different mixtures of gases (N₂/CO₂/O₂) that slow microbial spoilage and oxidation.^[11][12] Moreover, sealing efficacy is crucial for maintaining product integrity and preventing degradation.^[13]

Multilayer food packaging is categorized into two primary types, flexible and rigid, according to material, physical form, and composition, with each kind optimized through specific production methods.^[13]

Multilayer packaging protects food by regulating the movement of gases, vapors, and contaminants via barrier layers. The protective mechanism is based on diffusion and solubility control, as stated by Fick's first law:^[14]

${\displaystyle F=-D{\frac {dC}{dx}}}$

Where F represents the flux (quantity of gas per unit area per unit time), D denotes the diffusion coefficient, and ${\displaystyle {\frac {dC}{dx}}}$ is the change in concentration over the thickness of the film. The total permeability P of a layer is the diffusion coefficient times the solubility:^[15]

${\displaystyle P=D\cdot S}$

In multilayer systems, the effective permeability can be determined using a series resistance model:^[16]

${\displaystyle {\frac {1}{P_{\text{total}}}}=\sum _{i=1}^{n}{\frac {l_{i}}{P_{i}}}}$

Where ${\textstyle l_{i}}$ and ${\textstyle P_{i}}$ are the thickness and permeability of each layer. High-barrier polymers like EVOH do not let much oxygen through because they are crystalline and polar. However, EVOH is sensitive to moisture; when the relative humidity is high, its barrier degrades as it plasticizes.^[17] To prevent water vapor from getting in, an additional layer of PE is added externally.^[18]

Aluminum foil or aluminum oxide (AlO_x) coatings are used for packaging that requires a high barrier. Gas transport in these inorganic layers follows the Knudsen diffusion coefficient Dc, which is governed by:^[19]

${\displaystyle D_{c}={\frac {d}{3}}{\sqrt {\frac {8RT}{\pi M}}}}$

Where d is the diameter of the pore, R is the gas constant, T is the temperature, and M is the gas's molecular weight. These layers protect effectively, but only if they are protected from pinholes or cracks.^[19]

Multilayer packaging in industrial production primarily uses three manufacturing techniques: coextrusion, lamination, and coating. Each method is used for its capacity to effectively join the material layers into a single cohesive structure, tailored for diverse packaging purposes.^[20][21]

This involves the simultaneous extrusion of numerous polymer melts via a specially designed die to create multilayer structures in a single, continuous process.^[22] This usually involves using a tie layer (e.g., maleic anhydride grafted polyolefin) within the molten polymers that interfacially reacts to provide appropriate adhesion.^[23] This approach enables precise control of layer thicknesses and uniform distribution of materials, which is important for obtaining consistent barrier performance and optical transparency.^[24] Coextruded films generally consist of three to nine layers, while combinations with over fifteen layers exist in specialized barrier packages.^[25]

Lamination is an approach to adhering prefabricated substrates, such as plastic sheets, aluminum foils, or paper layers, to form a multilayered structure.^[26] Adhesive and thermal bonding are the most common technologies used in industrial lamination. Adhesive lamination is widely used for its versatility in material selection and compatibility; it includes solvent-based, solventless, and water-based adhesive systems that are chosen based on packaging applications and regulatory requirements.^[27][25] Thermal lamination involves heating and pressurizing layers to fuse them without adhesives. It is often used for laminating polymer layers that are innately compatible, such as PE sheets.^[27]

This method is based on applying thin, functional coats to substrates to obtain resistance to moisture, oxygen, UV radiation, and microbial contamination. Vacuum metallization, plasma-enhanced chemical vapor deposition, and extrusion coating are three standard coating processes used in industry.^[28][29]

• Vacuum metallization adds extremely thin aluminum layers to polymer films, improving barrier characteristics without significantly increasing weight.^[30]
• Plasma-enhanced chemical vapor deposition processes deposit ultra-thin transparent oxide coatings, such as AlO_x or SiO_x, onto polymer films for better barrier protection while maintaining transparency. This is useful in food packaging applications that need product visibility with an enhanced gas barrier.^[24][28]
• Extrusion coating directly applies molten polymers onto substrates such as paperboard or films, which is extensively used in carton packaging and paper-based barrier systems.^[31]

Life Cycle Assessment studies on multilayer packaging demonstrate that its lightweight design and barrier characteristics lead to lower overall environmental impacts than monomaterial or alternatives.^[32] Cradle-to-gate studies indicate that multilayer films frequently surpass alternatives such as glass or paperboard laminates in terms of global warming potential and cumulative energy demand.^[32]

However, these functional and environmental advantages are counterbalanced by end-of-life complications. The diverse composition and strong interfacial adhesion of the layers make most traditional recycling methods ineffective.^[2] Because of this, multilayer packaging represents over 17% of plastic packaging waste generated in the EU annually.^[33] Mechanical separation of tightly bound layers like PE/EVOH or PET/Al is currently not possible at scale, and less than 5% of multilayer plastic waste is effectively recycled.^[34] Moreover, contamination from colorants, adhesives, and food leftovers restricts recyclability and diminishes output quality.^[29] Due to the lack of effective separation or recycling methods, the majority of post-consumer multilayer waste is disposed of in landfills or incinerated, hence compromising circularity objectives.^[35] From a circular economy standpoint, multilayer packaging performs poorly on criteria including recyclability rate, material recovery, and design for disassembly.^[2] Recent legislative frameworks, including the EU's 2025 Packaging Waste Regulation (PPWR), specify that multilayer packaging must be recyclable at scale by 2030.^[36]

Some recent advancements in multilayer recycling include:

• Solvent-based methods, like CreaSolv and NewCycling, are being developed to selectively extract suitable polymers from multilayer laminates while preserving their performance characteristics.^[13]
• Compatibilization techniques are found capable of improving the interfacial adhesion and processability of immiscible polymers in multilayer packaging waste streams.^[29]
• Biochemical techniques, such as enzymatic depolymerization, are reported to degrade PET. They can also be used for multilayers containing PET.^[37]

Multilayer biodegradable packaging systems are developing into advanced food packaging solutions that incorporate active functionalities such as antibacterial and antioxidant properties within layered biodegradable structures made for the controlled release.^[38][39] These systems mainly include a barrier layer with an active layer holding functional agents (e.g., tea polyphenols, curcumin, silver nanoparticles), and a control layer to maintain (regulate) the release rate of the active components into food products.^[28]

Methods include electrospinning, coextrusion, and layer-by-layer deposition are used to construct these systems with biodegradable biopolymers such as polylactic acid, chitosan, gelatin, and starch derivatives.^[28]

These materials enhance mechanical and barrier qualities while also mitigating sustainability issues by substituting petroleum-derived polymers. However, broad implementation requires progress in economic production, performance verification in a practical setting, and regulatory conformity.^[39]

• Food Packaging
• Plastics recycling
• Packaging waste
• Modified Atmospheric packaging
• Food waste
• Food preservation
• Food safety

• BGPLAST (19 February 2025). "Multilayer extrusion revolutionizing packaging and industrial applications".
• EXTRUSION-INFO. "Multilayer packaging: Innovative and sustainable".
• PLASTICSENGINEERING (17 June 2025). "EU's PPWR: Strategies for Compliance by 2030".
• INTERPACK. "Mono-material, a ray of hope".
• Devi, Gayathri. "Multi-Layered Plastics: Why should it be banned?". Citizen consumer and civic action group.