A Comprehensive Guide to Thin-Film Manufacturing: Unlocking the Performance Secrets of Membrane Materials—From Basic Formation to High-End Customization

[Preface] 

Mobile phone screen protectors need high light transmittance and scratch resistance; food vacuum bags must provide oxygen-barrier properties and heat-sealability; lithium battery separators require precise pore control. —— At the heart of these performance differences lies the choice of thin-film manufacturing processes. 

Today, thin-film technology has entered... “ Material compatibility + Process combination + Performance customization ” From shopping-bag films priced at just a few cents to optical films costing thousands of yuan, the manufacturing process directly determines the product’s value. This article dissects mainstream manufacturing processes, analyzes their advantages, application scenarios, and potential upgrade paths, providing practitioners with a framework for making informed choices. 

I. Core Molding Process: Determines the Film’s… “ Innate genes ”

The core forming process determines the film’s thickness, mechanical properties, and basic shape. The industry’s mainstream processes fall into five major categories, covering all scenarios from general-purpose to high-end applications. 

(1) Blow Molding: Low-Cost, General-Purpose Film “ Main force ”

Blow molding (film blowing) is the most mature process and, with its cost-effectiveness, occupies half of the general-purpose film market. 

• Core principle ： PE 、 PP After the resin melts, it is extruded from the annular die into a tubular shape. “ Membrane vesicle ” The film is produced by inflating it with compressed air, shaping it with cooling rollers, and then drawing and slitting it. 
• Key indicators Blow ratio ( 1.5-4 倍, affecting width and toughness), cooling air velocity (determining crystallinity). 
• Strengths and Weaknesses Equipment investment is for the cast film process. 60% , can produce 5 Film with a width of over one meter; but with thickness deviation. ±5%-10% Generally transparent. 
• Typical applications ： LDPE Plastic wrap, LLDPE Express delivery bag, HDPE Agricultural film, supermarket tear-open food bags—immediately. PE Blown film product, cost per ton ≤1.2 Ten thousand yuan. 

(2) Cast Molding: High-Precision Films “ Standard configuration ”

When the demand shifts toward uniform thickness and smooth surfaces, cast film (cast molding) becomes the preferred method and is widely used in the packaging and electronics industries. 

• Core principle : Molten resin through T Extruded through a flat die and spread onto... 20-60℃ Rapid shaping on the chrome-plated cooling roller to prevent uneven crystallization. 
• Technical Highlights Cooling roller zone temperature control, thickness deviation ±2%-5% Its precision far exceeds that of blown film. 
• Compatible material ： CPP 、 PET 、 PA Wait, CPP Due to its excellent heat-sealing properties, cast film serves as the core inner layer in composite packaging. 
• Real-life case The inner layer of the composite film for instant noodle seasoning packets. CPP — produced via the casting process, with a smooth surface ensuring compatibility with the outer layer. PET The combined effect. 

(3) Biaxial Stretching: Performance Upgrade “ Key password ”

Biaxial stretching ( BOPP/BOPET/BOPA ) is synonymous with high-end membranes, achieving a leap in performance by physically stretching and reorganizing molecular arrangements. 

• Core principle After casting a thick-sheet base film, along the longitudinal direction ( MD )、horizontal ( TD ) Each stretch 2-5 Double, heat-setting to relieve internal stress. PP Longitudinal stretching temperature 120-140℃ ， PET For 80-110℃ 。
• Performance breakthrough Tensile strength improved 2-3 Twice, improved barrier properties 50%+ 。 BOPP Cigarette film light transmittance 92% Its fold resistance far exceeds that of the un-stretched material. PP 。
• Industry News ：2025 Yearly Lun New Materials 6.4 Meter wide BOPP The production line has been put into operation, and the independently developed bidirectional stretching process can produce... 3 μm The following ultra-thin capacitor film boasts internationally leading technology. 

(4) Calendering: For thick-film and functional films “ Dedicated process ”

Rolling and calendering produces thick films through mechanical rolling; fillers can be added or surface modifications can be performed, making this process irreplaceable in specialized applications. 

• Core principle The resin (or filler-containing mixture) that has been softened by heating is subjected to... 3-5 Rolled and pressed by the group's calendering rollers. 0.05-1mm Thick film, cooled and shaped then wound up. 
• Unique advantages Add fillers such as calcium carbonate to reduce costs, and directly emboss the surface to create a textured finish. PVC This process is used for both floor membranes and waterproofing membranes. 
• Technical upgrade Intelligent calendering equipment equipped with an online laser thickness measurement system, enabling sub-nanometer-level monitoring and precise control of thickness deviation. ≤±3% 。

(5) Solution Casting: For High-Precision Membranes “ Ultimate Solution ”

Solution casting (solvent method) is a reliable approach for producing ultra-thin and functional films, and it is indispensable in the fields of separation membranes and optical films. 

• Core principle Resin dissolves in DMF The solvent is dissolved to form a solution, which is then coated onto a substrate. After multiple drying stages to remove the solvent, the material is stretched and set into its final shape. 
• Technical Parameters : Can produce ≤1 μm Ultra-thin films—denseness is influenced by solution concentration and drying curves. The team led by Jin Xiaoyue at the Beijing Academy of Sciences has improved this process. Al₂O₃ Encapsulation film has ultra-high light transmittance. 93%。
• Limitations and Breakthroughs Traditional crafts face significant environmental pressures; currently, solvent recovery is being implemented (recovery rate: ...). ≥90% ) and achieve greening by replacing with water-based solvents. 

II. Functional Upgrade Process: Imparting Properties to the Film “ Next-day skills ”

The single-molding process struggles to meet complex requirements; auxiliary processes such as coating and composite methods are employed instead. “ Synergistic effect ” Endowing thin films with special functions is the core competitive edge of high-end products. 

(1) Coating Process: Precisely Enhancing Specific Performance 

Customization is achieved by coating the basement membrane surface with functional coatings; the mainstream approaches fall into two main categories: 

• Wet coating ： PVDC Coating liquids such as oxygen-barrier coatings and acrylate (anti-slip) coatings are applied via blade coating and then dried and cured, finding use in the oxygen-barrier layer of cling films and the anti-fingerprint layer of mobile phone films. 
• Vacuum coating Under vacuum conditions, aluminum... SiO₂ Wait for it to evaporate and deposit into a nanometer-thick layer, BOPP Aluminum-plated film with enhanced barrier properties 10 Double, used for tea and nut packaging. 

(2) Composite Process: Achieving Performance “1+1>2” 

Combining the advantages of different membranes through hybrid processes to create multifunctional integrated membranes is a core technology for food packaging and electronic encapsulation. 

• Co-extrusion composite Multiple dies simultaneously extrude different resins to form multilayer films, eliminating the need for adhesives. Guangdong Tian'an New Materials specializes in polyurethane films. “ Thermosetting +UV+EB Co-extrusion process, efficiency improved 30%。
• Dry method / Wet-laid lamination Adhesive bonding PET/AL/PP Laminate films, such as food cooking bags “PET/AL/CPP” Structure, PET Strong support, AL Oxygen barrier, CPP Heat sealing. 

(3) Stretching and shaping: Eliminate defects and enhance stability. 

Formed films with internal stress are prone to warping; stretch setting is used to address this. 1.1-1.3 Double-heat stretching enhances stability; this process is essential for ensuring that optical light-guiding films and lithium-battery separators remain deformation-free during use. 

III. The Core Logic Behind Process Selection: Precisely Matching Needs 

The selection of manufacturing processes should be based on a framework that considers three dimensions—materials, performance, and cost—to avoid blindly following trends. 

• Match by material Crystalline ( PE/PP ) Priority: blown film, cast film; non-crystalline ( PVC/CA ) Suitable for calendering and solution casting; high performance ( PET/PA ) Two-way stretching is required. 
• Sort by performance High-precision (optical film) solution casting selection / Biaxial stretching; for cost-effective (shopping bags), choose blown film; for high-barrier applications (food packaging), choose co-extrusion. / Coating. 
• Cost-optimized Cost-sensitive products can have fillers added during calendering and film blowing; high-end products strike a balance between investment and premium pricing, such as... BOPET The unit price of the membrane is standard. PET of the 2 Twice. 

IV. Conclusion: Process Innovation Will Lead the Future of the Thin-Film Industry 

The upgrading of thin-film processes has always been driven by downstream demand. Currently, the industry is exhibiting three major trends:智能化 (intelligentization) AI Optimize parameters to enhance consistency; greenify processes (replacing high-pollution techniques with water-based solvents); and achieve multifunctionality (coatings). + Combining integrated functionalities such as conductivity and antibacterial properties. 

For practitioners, understanding the relationship between craftsmanship and performance is both the foundation of product development and the key to seizing opportunities. —— The breakthroughs in new-energy capacitor films and flexible-screen encapsulation films are, at their core, the result of process innovation. 

What process challenges have you encountered in production? Which emerging technologies are you paying attention to? Feel free to share your thoughts in the comments section and let’s explore the potential of membrane materials together.