Multilayered packaging

Multilayer packages are a type of composite structure composed of two or more distinct material layers. The layers work together to achieve the specific protection and mechanical properties. Many industries — such as food and beverages, pharmaceuticals, cosmetics, and industrial goods — use this type of packaging. Films, pouches, aseptic cartons, bottles and tubes are all examples of its applications ^[1].

Multilayered beverage cartons

Each layer has a different role in a multilayer system: one may provide heat sealability, another tensile strength, while others enhance gas and light barrier properties. Polyethylene (PE), polyethylene terephthalate (PET), polyamide (PA), ethylene vinyl alcohol (EVOH), aluminum foil, and paperboard are some of the most common materials. Over time, sustainability, reduced environmental impact and extended shelf life have become increasingly critical in the development of multilayer packaging systems ^[2].

History

Early adoption of aseptic cartons in Europe, 1960s

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

One of the earliest commercial examples was the introduction of aseptic cartons by Tetra Pak in the early 1960s, using laminated layers of paperboard, polyethylene, and aluminum foil ^[3].

During the 1970s and 1980s, multilayer films became widely used as vacuum-sealed pouches and retort bags for ready-to-eat meals and shelf-stable goods. At the same time, multilayer containers — including plastic bottles with oxygen barriers — were created to package sauces, spices, and medicines ^[4].

By the 1990s, multilayer technologies had become essential to worldwide packaging systems. Advancements in tie-layer chemistry, extrusion dies, and lamination adhesives are improving functional diversification and cost effectiveness ^[4].

Types

Multilayer packaging systems can take various forms depending on the intended use, material combinations, and required barrier properties.^[5]

Multiwall paper sacks

These are made of multiple layers of extensible kraft paper of varying grammages. They are gaining popularity in the cement industry, pharmaceutical, and fertilizer industry, where the inner or outer layer are often coated with polyethylene (PE) to protect the contents from moisture ^[6].

Laminated-cartons

These are commonly used in the paint industry, in Tetra Paks containing milk, fruit juice, syrups, and the pharmaceutical industry. Typical layer combinations include ^[7]:

• Paper/foil/LDPE
• Aluminium foil/paper/LDPE
• PE/aluminium foil/paper
• PET/aluminium foil/LDPE

Plastic bottles and tubes

Multilayer plastic containers (e.g., PET/EVOH/PE) are widely used for packaging sauces, juices, and cosmetics. EVOH is an oxygen barrier, while PE or polypropylene (PP) ensures sealability and mechanical durability ^[8].

High-barrier flexible pouches

These are commonly used for ready-to-eat and sterilized food products. They frequently combine PA, EVOH, or SiOx coatings to ensure puncture resistance and superior gas barriers ^[9].

Multilayer food packaging

Multilayer food package having 6 layers with functional barriers to the environment

See also: Food packaging

Food preservation is a complex mechanism that relies heavily on advanced packaging technologies, which is why the multilayer structure 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, 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, ethylene vinyl alcohol (EVOH) is widely used for oxygen-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].

Diffusion-controlled barrier performance of multilayer systems

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 li and Pi 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 AlOx 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].

Manufacturing methods

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].

Co-extrusion for multilayer films

Coextrusion

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

Lamination process for a multilayer laminates

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].

Coating

This method is based on applying thin, functional coats to substrates to obtain features such as 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 AlOx or SiOx, onto polymer films for better barrier protection while maintaining transparency. This is useful in food packaging applications that need product visibility with 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].

End-of-life management

End-of-life of multilayer packages

See also: Plastic recycling, Packaging waste

Multilayer packaging has notable environmental benefits during the usage phase, mainly due to its lightweight design and superior barrier characteristics. Which decreases food spoilage and has lower emissions. This overall improves the sustainability of the food system ^[32].

Life Cycle Assessment studies consistently demonstrate that these attributes lead to lower overall environmental impacts than monomaterial or alternatives ^[33]. Especially, 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 ^[33].

However, these functional and environmental advantages are counterbalanced by end-of-life complications. The diverse composition and strong interfacial adhesion of the layers, essential for their performance, make most traditional recycling methods ineffective ^[2]. Because of this, multilayer packaging represents over 17% of plastic packaging waste generated in the EU annually ^[34]. 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 ^[35]. 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 ^[36]. 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 and Packaging Waste Regulation (PPWR), specify that multilayer packaging must be recyclable at a scale by 2030 ^[37].

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 ^[38].

Smart and biodegradable multilayer system

See also: Active packaging, Sustainable packaging

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 ^[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 PLA, 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].

See also

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