Knowledge of Barrier Films：the Introduction and Application of Asymmetric Films

From the cold-chain steaks on supermarket shelves that stay fresh for up to 15 days, to the IV bags in medicine cabinets that ensure stable drug efficacy, to the vacuum packaging in electronics factories that protect chips from moisture—these seemingly unrelated scenarios all rely on the same "invisible guardian": barrier film. Like a sophisticated "shield," barrier film effectively blocks oxygen, moisture, solvents, odors, and other substances, locking in product freshness, ensuring safety, and extending its lifespan. It has become an indispensable core material in fields such as food packaging, pharmaceutical packaging, electronic packaging, and chemical storage and transportation.

What is barrier film:

Simply terms, barrier film is a type of film material with special barrier properties that effectively blocks the penetration of gases, liquids, light, and other substances. Its core function is to protect the quality of the packaged goods, extend shelf life, and maintain product performance stability.

Key characteristic of barrier films:

The substances it targets can be divided into three main categories:

Gaseous substances:

The most typical examples are oxygen and carbon dioxide. Oxygen can cause oxidation and spoilage in food, render pharmaceuticals ineffective, and rust in electronic components. Carbon dioxide can affect the taste of carbonated beverages and the preservation of fresh produce. Barrier films can control the permeation of these gases to maintain the desired internal environment for the product.

Liquid/vaporous moisture:

This refers to water vapor. A humid environment can cause food to mold, pharmaceuticals to clump due to moisture absorption, and electronic components to short-circuit. Barrier films can significantly reduce water vapor transmission rates, keeping products dry and stable. For example, the barrier film in pharmaceutical blister packaging prevents tablets from absorbing moisture and deteriorating during their shelf life.

Other harmful substances:

including odor (such as environmental odor outside the packaging invading food), ultraviolet rays (some products are sensitive to ultraviolet rays and easily decompose and become ineffective), microorganisms (preventing the invasion of bacteria, mold, etc. through dense structure), and chemical solvents, grease, etc. in some special scenarios.

Other characteristic:

In addition to barrier properties, it also has flexibility, puncture resistance, heat sealing and other characteristics. For example, in food packaging, good flexibility can adapt to various shapes of food packaging, and puncture resistance can prevent sharp food from puncturing the packaging.

The application of barrier films：

Food packaging industry:

High-barrier cling film (oxygen and water barrier) and barrier film for retort bags (high-temperature barrier). These films prevent oxidation, mildew, and water loss, extending shelf life. Applications include cold chain fresh produce (steak, salmon); high-temperature sterilized foods (canned food, retorted meat); snack foods (potato chips, nuts); and liquid foods (chilled milk, juice).

Electronics industry:

Electronic components and other products are extremely sensitive to moisture and oxygen. Barrier films can effectively prevent electronic products from being damaged by moisture, such as chips, semiconductors, lithium batteries, and display screens.

Pharmaceutical and Medical Industry:

The pharmaceutical sector places extremely high demands on the safety and stability of barrier films. They must comply with standards such as GMP (Good Manufacturing Practice) and prevent the volatilization or degradation of active pharmaceutical ingredients. For example, barrier films for infusion bags must not only block water and oxygen but also exhibit excellent drug compatibility (no chemical reaction with the drug solution) to prevent ingredient migration. Sterile protective clothing must not only block bacteria and bodily fluids but also maintain breathability for enhanced wearer comfort.

Industrial packaging:

Barrier films used in the industrial sector must withstand harsh environments such as solvents, high temperatures, and mechanical shock. For example, for industrial product packaging (solvents, coatings), barrier films are used to create liner bags to block organic solvent penetration, preventing packaging corrosion and solvent volatilization.

Iteration and update of barrier film processing technology

As the core functional material of modern packaging, the development of barrier film has always revolved around the three major goals of "higher barrier efficiency, better overall performance, and lower cost and energy consumption."

In the early days, the mainstream process for producing basic barrier films involved melt-extruding a single material, such as PE or PP, through a single extruder, followed by cooling and shaping. This offered advantages in terms of low cost and high efficiency, but also significant performance shortcomings. To address the limitations of a single material, a "glue coating + hot pressing" process was adopted to combine multiple films. While this achieved complementary performance, it relied on solvent-based adhesives, which posed the risk of VOC (volatile organic compound) residues. Furthermore, the multiple steps (glue coating, drying, and lamination) resulted in low efficiency and high costs.

Driven by both consumer and industrial upgrades, the market demand for barrier films has evolved beyond simple barriers. This shift in demand is not only driving the evolution of barrier films from single-function to multifunctional composites, but also forcing breakthroughs in production equipment toward higher layer counts, more precise structures, and higher-efficiency production capacity. Currently, the barrier film industry is exploring the use of multiple extruders to simultaneously melt different substrates, such as PE (polythene), PA (polyamide), and EVOH (Ethylene-Vinyl Alcohol Copolymer: one of the most powerful barrier polymers currently available). This is then combined through a co-extrusion die to achieve melt-layered lamination, resulting in a one-step molding process without the need for adhesives. PE/PA co-extruded barrier films are a prime example. Their structural design of "PE (water barrier/heat seal) + PA (oxygen barrier/puncture resistance)" strikes an optimal balance between cost and performance, making them a prime example of cost-effective barrier solutions.

Industry Case Study:

PLASTAR is a company integrating R&D, production, and sales. Its barrier film equipment product line includes 5-11-layer co-extrusion blown film machines. These machines can co-extrude polyethylene and barrier materials to produce high-quality films with barrier properties exceeding those of standard substrate films. These films are particularly suitable for vacuum fresh-keeping food packaging and pharmaceutical packaging. The seven-layer asymmetric barrier film co-extrusion blown film machine is a breakthrough in the industry, achieving multiple advantages, including improved barrier performance and production savings.

Asymmetric Seven-Layer Barrier Film Co-extrusion Blowing Machine

Traditional barrier film blowing machines often utilize a "symmetrical structure" (e.g., 3-layer or 5-layer symmetrical) or a single functional layer design, resulting in significant bottlenecks in barrier efficiency, material cost, and application adaptability. The seven-layer asymmetric barrier film blowing machine, by combining "upgraded layer count and innovative asymmetric structure," elevates the balance of barrier film performance, cost, and flexibility to a new level. Its core advantages can be analyzed in depth from the following dimensions.

Core Advantages: Asymmetric Structure + Seven-Layer Design Breaks Through Barrier Performance Ceilings

The core breakthrough of the seven-layer asymmetric design lies in eliminating the waste of materials through symmetrical stacking. Instead, each layer precisely fulfills its dedicated functions: barrier, support, sealing, and environmental resistance. This design is particularly effective for applications requiring barrier properties (such as fresh produce preservation and pharmaceutical packaging), delivering performance advantages far exceeding those of traditional equipment.

1. Doubled Barrier Efficiency: High-barrier Materials "Precisely Used"

   The seven-layer asymmetric structure can be customized according to requirements. Two of the layers can be made of PA and EVOH, maximizing the film's barrier layer placement and thickness. For example, a design consisting of "PE (sealant layer) / TIE layer / PA (barrier layer 1) / TIE layer / EVOH (high-barrier core layer) / TIE layer / PE (puncture-resistant outer layer)" is possible.

2. Stronger Resistance to Environmental Interference: Asymmetric Layer Synergy Addresses Single-Performance Shortcomings

   Traditional low-layer barrier films often face a conflict between barrier and mechanical properties. For example, to improve puncture resistance, thickening the PE layer is necessary, but this dilutes the barrier material content; to enhance the barrier, adding a PA layer increases film brittleness. The seven-layer asymmetric structure perfectly addresses this issue through "functional layering."

Cost Advantage: "Precise Material Solution + Efficient Production" reduces costs without sacrificing performance.

For manufacturers, cost reduction is a key priority. The seven-layer asymmetric barrier film blowing machine doesn't simply increase costs with more layers. Instead, it achieves lower costs per unit area through "material optimization + process upgrades."

1. Optimizing the use of high-barrier materials.

   EVOH (ethylene-vinyl alcohol copolymer) is one of the most powerful barrier materials currently available, but its price is 5-8 times that of standard PE. To maintain barrier properties, a traditional five-layer symmetrical film must increase the EVOH content to 25%-30%. However, a seven-layer asymmetric structure optimizes the EVOH content by combining a "core layer focused + auxiliary layer" approach with a PA barrier layer, achieving superior barrier performance and reducing raw material costs per ton by 15%-20%.

2. Improved Production Efficiency and Reduced Energy Consumption.

   Seven-layer asymmetric barrier film blown film machines are typically equipped with “a high-speed co-extrusion system (seven precision extruders)”, “an IBC system（internal cooling system）”，“an Haul-off rotary device”, and “an automatic air ring system”. These intelligent systems not only significantly improves cooling efficiency and increases production, but also better control to control film width and thickness, enhancing product quality.

Process and Quality Advantages: Stable and Controllable, Meeting High-End Marketing

The core competitiveness of this seven-layer asymmetric barrier film blowing machine lies in its process stability and product consistency, making it particularly suitable for high-end markets with stringent quality requirements (such as export food packaging and medical-grade packaging).

1. Improved film thickness uniformity, with a tolerance within ±3%.

   The seven-layer machine is equipped with “an automatic air ring system”and “a thickness gauge system”. These systems measure the thickness of film bubble thickness in real time, maintaining an overall thickness tolerance within ±3%—critical for pharmaceutical packaging (e.g., infusion bags requiring precise volume) and electronic packaging (e.g., chip film requiring uniform protection).

2. Consistent product specifications and quality, improving yield rates.

   PLASTAR's "automatic dosing system" automatically adjusts the traction speed and screw speed, intelligently controlling and setting the feed rate to effectively ensure the specifications and quality of each unit of film. Material monitoring and intelligent feeding not only enable timely changes in product specifications but also reduce material waste.

Barrier Film Industry Outlook

From daily food preservation to precision electronic protection, barrier films are no longer just simple "packaging barriers". In the future, with the widespread adoption of environmentally friendly and biodegradable materials, the addition of intelligent monitoring capabilities, and the development of ultra-high-barrier and extreme-temperature-resistant specialty films for new energy, aerospace, and other fields, barrier films will more precisely meet the needs of diverse industries—from keeping steaks fresher longer in supermarkets to providing reliable protection for chips and hydrogen energy equipment. This evolution from general-purpose packaging to high-end customization will ultimately enable barrier films to serve as "invisible guardians" in a wider range of industrial scenarios, continuously contributing to product safety and industrial upgrading.