High barrier vacuum packaging film material

In recent years, high barrier film materials have been widely used in the market for product packaging such as food, pharmaceuticals, chemicals, electronic device packaging, and fuel cell membranes due to their excellent barrier properties, low cost, easy use, good transparency, strong printing adaptability, and good mechanical properties, and have developed rapidly.
Excellent barrier properties are important characteristics of high barrier film materials, including good gas barrier, moisture barrier, oil barrier, fragrance retention, etc. Early barrier film materials were represented by films such as ethylene vinyl alcohol copolymer (EVOH), polyamide (PA), polyvinylidene chloride (PVDC), polyvinyl alcohol (PVA), etc. With the strong demand for products in food and beverage, medical, chemical and other fields, the requirements for packaging barrier properties are becoming increasingly strict. Various high-performance high barrier film materials have been developed, including multi-layer polymer composite films, vacuum evaporation composite films, polymer/layered nano composite films, etc. This article summarizes and shares the barrier properties, production technology and application development of various high barrier film materials.

1. Multi layer polymer composite film

Due to the advantages and disadvantages of various polymers in terms of performance, a single polymer film material is difficult to meet the multifunctional requirements of many products. Therefore, multi-layer film composite technology is used to composite two or more single polymer films to form a multi-layer polymer composite film, so that the performance advantages of various polymers complement each other. This not only improves the barrier performance of the film material, but also enhances other properties such as heat sealing, heat resistance, mechanical properties, and UV resistance. The current research and development of multilayer film composite technologies mainly include co extrusion composite, coating composite, self-assembly composite, etc.

1.1 Co extruded composite film
Co extruded composite film is a multi-layer composite film produced by heating and melting various polymers using multiple extruders and co extruding them through a multi-channel composite head. Co extrusion composite technology is mainly used for thermoplastic polymer composites with compatibility, without the use of solvents, with low environmental pollution, fewer production processes, and low production costs. It is widely used in film production enterprises.
At present, new research progress has been made in co extruded composite film materials. Wang Ruobing et al. [1] used four polymers, polyethylene (PE), polypropylene (PP), nylon 6 (PA), and ethylene vinyl alcohol copolymer (EVOH), as raw materials for melt co extrusion to prepare five layer composite film materials. EVOH and PA6 are the barrier layers of the composite film, and PE is the heat sealing layer of the composite film. Five layer co extruded composite film has high barrier properties and good mechanical properties, making it an ideal high barrier packaging material. Liang Xiaohong et al. [2] modified EVOH by blending it with PE and PA to prepare PE/PA/EVOH/PA high-strength and high barrier composite film, which has excellent comprehensive performance and good application prospects.

1.2 Coating composite film
Coating composite film is a multi-layer composite film formed by dissolving barrier polymers in a solvent to form a coating liquid, applying the coating liquid onto the surface of a base film using a coating equipment, and drying and curing it. Coating composite technology can be used for polymers that are difficult to process separately into films, such as PVDC, PVA, etc. The process is simple, the production cost is low, and the barrier performance is good, but there may be residual organic solvents, causing environmental pollution.
At present, there have been many new advances in the research of coating composite films. Sang Lijun et al. [3] coated 2-4um PVDC composite films on PP, PE, CPP (cast polypropylene), PET (polyester) films, which significantly reduced their breathability and moisture permeability, and applied them to the manufacture of pharmaceutical composite packaging bags. Shuxin et al. [4] used biaxially oriented PP, biaxially oriented PET, biaxially oriented PA or PE films as base films. After corona treatment, modified acrylic polymer BARILAYER high barrier coating liquid was applied to the corona surface of the base film. After 5-6 hours of indoor drying and curing at 40-50 ℃, the coating surface was printed and then compounded with a layer of polyolefin film to obtain a new type of high oxygen resistant plastic flexible packaging film. The product raw materials are easy to obtain, the price is low, the barrier performance is better than PVDC, and it is not affected by relative humidity. BARILAYER is biodegradable, and combustion only produces CO2 and H2O, which is environmentally innovative.

1.3 Layer by Layer self-assembly composite film
Layer by layer self-assembled composite film is a multi-layer composite film formed by alternating deposition of specific polymers, quantum dots, nanoparticles, biomolecules, etc. under complementary interactions (electrostatic interactions, hydrogen bonding, coordination bonding, covalent bonding, etc.). By changing the sedimentation cycle PH、 Under conditions such as temperature, molecular weight, and ionic strength, high-performance composite film materials can be obtained, which are widely used in flame retardancy, antibacterial, gas barrier, and other applications.
New research progress has also been made in the current layer by layer self-assembly of composite films. Polyacrylic acid (PAA) and polyethylene oxide (PEO) are self-assembled layer by layer through hydrogen bonding to prepare tough gas barrier composite films. When the pH is adjusted to 3, PAA/PEO bilayer self-assembly of 20 layers forms a high barrier composite film, which is coated on a 1.58mm thick natural rubber sheet. The oxygen permeability of the natural rubber sheet is reduced by 89.6%, and the oxygen barrier properties are excellent. The hydrogen bonding strength is weaker than that of ion bonding. The resulting high barrier composite film has certain toughness and is suitable for high strain applications. Layer by layer self-assembly deposition of polyetherimide PEI, PAA, and PEO is carried out to form a PEI/PAA/PEO/PAA composite film through the combination of PEI/PAA ion bonding and PAA/PEO hydrogen bonding. When the pH is adjusted to 3, 20 layers of PEI/PAA/PEO/PAA four molecular layer self-assembly are formed to form a high barrier toughness composite film, which is coated on a 1mm thick polyurethane rubber sheet, reducing the oxygen permeability of the polyurethane rubber sheet by 93.3%. It is suitable for gas barrier of inflatable products such as tires.

1.4 Other composite films
In addition to the above-mentioned multi-layer film composite technology, innovative methods such as layer by layer casting composite, chemical grafting composite, and blend extrusion composite were also used to prepare multi-layer polymer composite films with excellent barrier properties.
A three-layer degradable left-handed polylactic acid (PLLA)/polyvinyl alcohol (PVA)/left-handed polylactic acid (PLLA) composite film was prepared by layer by layer casting method, with the middle layer PVA as the barrier layer and the hydrophobic PLLA on both sides as the protective layer. The PVA barrier layer significantly improves the barrier properties of PLLA. When the PVA content accounts for 20% of the composite film, the oxygen barrier properties are 272 times higher than those of PLLA single film, and the mechanical properties are also improved. PLLA/PVA/PLLA composite films have stronger practical applicability and fully comply with the development trend of environmentally friendly composite films.
Chitosan CS was grafted onto an oxidized cellulose OC matrix, and the chemical grafting process changed the microstructure of the matrix. The OC/CS composite film combines the performance advantages of both polymers, with excellent water and oxygen resistance, antibacterial properties, high transparency, and good mechanical properties. It is a safe, biodegradable, and high-performance packaging material.
Ethylhexyl acrylate EHA film was prepared by blending and extruding EVOH with PA6, and then compounded with PE film to obtain EHA/PE composite film. Research has shown that EHA film has high oxygen resistance, and the water and oxygen resistance of EHA/PE composite film is superior to PA film, EVOH film, and PA6/PE composite film, making it suitable for refrigerated preservation packaging.

2. Vacuum evaporation composite film
By using vacuum coating technology, metals (such as aluminum Al) or inorganic oxides (such as silicon oxide SiO2, aluminum oxide Al2O3, titanium oxide TiO2) are evaporated on the surface of plastic films to prepare vacuum aluminum plated films or vacuum evaporated ceramic films. These films have excellent barrier properties, high production efficiency, low cost, and easy use, and are widely used in food packaging and even electronic product packaging fields. Ceramic films have high light transmittance and are environmentally friendly, making them a current research hotspot for high barrier films.
The use of plasma enhanced chemical vapor deposition method to evaporate SiOx layer on the surface of polycaprolactone (PCL) film substrate can improve the barrier performance of the film without being affected by temperature and humidity, while meeting the requirements for developing environmentally friendly materials.
A new PLLA/SiOx/PVA composite film was prepared by depositing SiOx layer on the surface of PLLA film using plasma chemical vapor deposition method, and coating PVA layer on the SiOx layer using solution coating method. Its barrier performance is similar to PA/PE composite film, and its flexibility is also improved. In addition, its biodegradable environmental protection advantage can replace PA/PE composite film in the field of food packaging, and its prospects are very promising.
Zhu Lin et al. [13] used radio frequency magnetron co sputtering to evaporate TiNx/CFy thin films on the surface of PP substrate films. When the volume fraction of TiNx was 0.28, the composite film had the best barrier and flexibility properties, solving the cracking problem of traditional ceramic films.

3. Polymer/layered inorganic nanocomposite film
Polymer/layered inorganic nanocomposite film is formed by dispersing layered inorganic fillers that can form nanoscale structural micro areas into polymers to form nanocomposite films. The nano layer structure of the filler can block gas infiltration, improve material airtightness, and significantly enhance the polymer's barrier properties. At present, layered nanofillers such as montmorillonite (MMT), layered double hydroxides (LDHs), and graphene (GNSs) have become a research frontier and hotspot with their unique structures and excellent properties.
Using the principle of entropy increase, self-assembled highly ordered organic/inorganic nanocomposite films were prepared. Using an inkjet printer, a 0.1-0.2% volume fraction of polyvinylpyrrolidone (PVP) aqueous solution was printed as a polymer film layer, and a 0.2wt% volume fraction of MMT dispersion was printed as a nano layer. The polymer layer and nano layer were self-assembled by ion bonding to form a PVP/MMT bilayer film layer. After printing 5 layers of PVP/MMT bilayer film layers on a PET substrate, the oxygen barrier performance was better than that of high barrier metal PET, and it had high transparency, safety, and environmental protection. It has broad application prospects in the field of food packaging.
Graphene oxide nanoribbons (GONRs) were prepared by oxidative decompression of multi walled carbon nanotubes, followed by chemical modification of GONRs with isophorone diisocyanate (IPDI) to obtain functional graphene oxide nanoribbons (IP GONRs). Functional graphene oxide nanoribbons (IP GONRs)/thermoplastic polyurethane (TPU) composite films were prepared on a coating machine using solution forming method. When the content of IP GONRs is 3.0wt%, the oxygen permeability of TPU decreases by 67%, and the barrier performance is significantly improved, which has potential applications in the fields of food packaging and lightweight gas storage.
A flexible and transparent polyvinyl alcohol (PVA)/hydrotalcite (LDH) composite self-supporting film was prepared using a simple filtration method. The excellent two-dimensional ordered structure of the composite film effectively suppressed oxygen diffusion and improved the film's oxygen barrier performance. It has good prospects in the fields of electronic device packaging and raw material battery separators with extremely high barrier requirements.

summarize
Currently, driven by strong market demand for food, pharmaceuticals, and chemical products, packaging film materials continue to develop rapidly. Products have higher requirements for film materials, requiring the development of multifunctional film materials such as high barrier, freshness, heat resistance, and antibacterial properties. Among them, high barrier film materials are developing rapidly. As resources become increasingly scarce and people's environmental awareness increases, the development of environmentally friendly high barrier membrane materials has also become a hot topic. In the next few years, we should continue to focus on the research and development of high barrier membrane materials, shorten the gap with foreign high barrier membrane technology, and meet the growing market development needs.

The contribution of high barrier film packaging bags in food and drug packaging is mainly reflected in the following aspects:
Extended shelf life: High barrier film can effectively prevent the penetration of oxygen and other gases, thereby inhibiting the growth of microorganisms, ensuring the safety and hygiene of packaging contents, and effectively extending the shelf life of food and drugs.
Maintain freshness: The excellent antioxidant properties of high barrier film can prevent the contents from oxidizing and deteriorating due to oxygen permeation, maintaining the freshness and nutritional value of food and drugs.
Preventing fragrance loss: High barrier film has excellent fragrance and solvent barrier properties, effectively preventing the loss of fragrance and solvent components in the contents, and improving storage stability.
Preventing mold growth: The strong water vapor barrier performance of high barrier film can prevent the content from mold growth caused by water vapor penetration, further ensuring the quality and safety of food and drugs.
Improving packaging performance: Among many high barrier materials, polyvinylidene chloride (PVDC) and ethylene vinyl alcohol copolymer (EVOH) are two common types, which have excellent barrier properties against oxygen and water vapor. PVDC has very low oxygen and water permeability due to its high density and the presence of hydrophobic groups, and has excellent gas barrier properties.
Meeting specific needs: High barrier films have a wide range of applications in the food packaging field, such as cling film, vacuum packaging, and pharmaceutical blister packaging, to meet specific needs.