The Mystery Behind the Metallocene Content in Thin Films: A Comprehensive Analysis of Varying Film Composition Ratios and the Logic Behind Them

Preface 

Metallocene polyethylene mPE ) is the thin film “ Performance Enhancer “—— A small addition can significantly enhance puncture resistance. 30% , Reduced heat-sealing temperature 15℃ , it can also reduce production thickness. But practitioners often feel puzzled: the metallocene additive content in food packaging films reaches 30% , ordinary agricultural film only requires 5% , the content also varies across different layers of the same composite film. 10  Percentage points. 

This difference is “ Performance requirements, processing costs, and process compatibility ”  The balanced outcome. This article starts by examining the core role of metallocenes, breaks down the content standards for six major categories of films, and delves deep into the technical logic, helping you master the key insights. “ How much to add, and why add it ”  The underlying pattern. 

1. First, let’s understand: Why can metallocenes alter film performance? 

Metallocene polymers, with their narrow molecular weight distribution and uniformly short-branched molecular structure, provide three key advantages to the film—these serve as the foundation for determining its composition. 

1. A Leap in Mechanical Performance : Break elongation rate compared to the traditional PE High 50% , highly resistant to impact 40% , outstanding puncture resistance; 
2. Thermal Sealing Performance Optimization : Initial heat-sealing temperature as low as 90℃ (Traditional PE Required 110℃+ ), the heat-sealing strength increases 25% , suitable for high-speed packaging; 
3. Optical Performance Improvement : Low haze 30% , Transmittance increases 5%-8% , meeting high transparency requirements. 

But metallocene prices are higher than those of conventional ones. LLDPE High 20%-30% During processing, the melt viscosity fluctuates significantly, placing high demands on equipment. Therefore, setting the content precisely is crucial. “ Achieve the target performance with the minimum addition amount. ”。

II. Standards for Metallocene Content in Six Major Film Types and Their Underlying Causes Broken Down 

According to functional positioning, the metallocene content is divided into three gradients: high, medium, and low. 

(1) High-Content Tier 20%-35% ): Prioritizing Ultimate Performance 

Suitable for scenarios with stringent requirements for strength, heat sealing performance, and transparency: 

1. Food Preservation Composite Film (Heat-Sealing Layer) 

• Typical Content ： 25%-35% (As for VMCPP Thin-film heat-sealing layer); 
• Example : Steam-and-cook bag heat-seal layer 30% Metallocene + 70% LDPE ）、Frozen food film（ 28% Metallocene + 72% LLDPE ); 
• Core Cause ： 
  • Low-temperature heat sealing 90-100℃ ) Avoid compromising the flavor of the food, 30% Content exceeds heat-sealing strength 35N/15mm (Traditional PE Only 20N/15mm ); 
  • -40℃ Below 25%+ Content prevents cracking, maintaining elongation at break 600%+ ；
  • High purity compliance FDA Standards: Too high a content increases costs, while too low a content fails to meet the requirements. 

2. Tear-resistant substrate composite film (surface layer) 

• Typical Content : Surface layer 25%-30% , Mid-level 15%-25% ；
• Example : Three-layer co-extruded film (top layer 30% Metallocene + 70% EVA , Mid-level 20% Metallocene + 1% Hydrotalcite + 79% EVA ); 
• Core Cause ： 
  • The surface needs to be puncture-resistant, 30% The tear resistance reaches a high level 80kN/m , the middle layer focuses on buffering, 20%+ Just use the masterbatch for foaming; 
  • Top layer maintains high performance with elevated content, while the middle layer reduces content to control costs—better than using a full-layer approach. 30% Province 15% Raw material costs; 
  • After adding functional masterbatch to the middle layer, the proportion of metallocene is reduced to prevent the melt from becoming too viscous. 

(II) Medium-Content Tier 8%-20% ): Balancing Performance and Cost 

Suitable for scenarios that demand performance but are cost-sensitive: 

1. High-end agricultural greenhouse film 

• Typical Content ： 12%–18% ；
• Example ： PO Anti-fogging greenhouse film 15% Metallocene + 65% LLDPE + 20% Functional masterbatch); 
• Core Cause ： 
  • 15% Content transmittance exceeds 90% (Than pure LLDPE High 5% ), enhancing crop photosynthesis; 
  • Cooperation 0.4%-0.8% Light stabilizer, 12%+ The content extends lifespan from 1  The year extends to 2  Year; 
  • Agricultural film is used extensively—per liter 1% Content ton cost increases 200  Yuan, 18% To balance the critical point. 

2. Heavy-duty packaging film (fertilizer) /  Feed bag) 

• Typical Content ： 10%-15% ；
• Example ： 25kg Feed bag 12% Metallocene + 88% HDPE ); 
• Core Cause ： 
  • 12% The content boasts puncture resistance that reaches 1800gf (Traditional HDPE Only 1000gf ), preventing tampering and puncture; 
  • 15% The content can adjust the thickness from 80μm Reduced to 60μm , Ton-membrane multi-production 3000  A bag to offset the price premium; 
  • Improve HDPE Fluidity prevents crystal spots from appearing on the blown film. 

3. Transparency PP Modified Membrane 

• Typical Content ： 14%-18% (Metallocene Polypropylene mPP ); 
• Example : Transparency PP Woven bag film 16% mPP + 83% PP + 0.25% Nucleating agent); 
• Core Cause ： 
  • 16% The impact strength of the content ranges from 15 kJ/m² Rise to 41.14 kJ/m² , resolve PP Brittle fracture; 
  • In synergy with a nucleating agent, the light transmittance reaches 90.6% (Pure PP Only 75% ); 
  • 18%+ The content will cause the tensile strength to decrease from 35 MPa Drop to 31MPa , affecting performance. 

(III) Low-Content Tier 3%-10% ): Cost first, performance second 

Suitable for common functional scenarios, addressing the shortcomings of base resins: 

1. Common agricultural plastic film 

• Typical Content ： 3%-8% ；
• Example : Spring-Planted Mulch Film 5% Metallocene + 95% LLDPE ); 
• Core Cause ： 
  • 5% The content achieves puncture resistance strength of 1200gf , meeting basic needs for warmth and moisture retention; 
  • Dosage per mu 5kg , each time it drops 1% Reduce per-acre cost of content 1.2  Yuan, 3%-8% Balancing performance with farmers' affordability; 
  • Biodegradable mulch film controls content to prevent interference with degradation efficiency. 

2. Daily-use packaging film (shopping bags) /  Courier bag) 

• Typical Content ： 4%-10% ；
• Example : Supermarket shopping bags 8% Metallocene + 92% LDPE ）、Courier bag inner layer（ 6% Metallocene + 94% LLDPE ); 
• Core Cause ： 
  • 8% The content achieves a tensile elongation rate of 550% , with load capacity exceeding 5kg (Traditional LDPE Only 3kg ); 
  • Minor additions for improvement LDPE Melt strength reduces the film-breakage rate during blown film production; 
  • Daily-use films have low added value, 10%+ High content leads to high prices, reducing competitiveness. 

3. Factors Influencing Metallocene Content 4 A key variable 

In addition to functional requirements, the following variables also have their optimal content adjusted: 

(1) Processing Method: Blow Molding vs Casting 

• Blow molding : Content is lower than that of cast products 5%-8% , due to high content (> 25% ) It can easily lead to membrane vesicle instability and uneven thickness, requiring careful control. 20% Inside; 
• Casting : Affordable 35% High content, fast cooling (faster than blown film) 30% ), stabilizing the melt viscosity. 

(2) Raw Material Composition: Single Resin vs Blending 

• With LDPE Blending: Reduced Content 5%-10% ， LDPE Improved machinability, 20% Metallocene + 80% LDPE ≈ 25% Metallocene + 75% LLDPE ；
• Blended with functional masterbatch: Add 5% After the masterbatch is produced, metallocene is 25% Drop to 20% Still maintains strength; 
• Synergistic with nucleating agents: 0.25% Nucleating agent + 14% mPP Transparency ≈16% mPP Use separately. 

(3) Equipment Conditions: Screw L/D Ratio and Cooling System 

• Length-to-diameter ratio 25:1–32:1 : Content can be enhanced 3%-5% , sufficient shear improves melt stability; 
• Double-layer air ring cooling: Content can be enhanced 5% , rapid heat dissipation prevents uneven crystallization—single-layer air rings must be precisely controlled. 20% Inside. 

(4) Product Thickness: Ultra-Thin Film vs Thick Film 

• Ultra-thin film (< 20μm ): Content Enhancement 5%-10% , after thinning, high-strength reinforcement is required (such as 20μm Membrane 28% vs 45 μm Membrane 20% ); 
• Thick film (> 100μm ): Content decreases 3%-5% , it has sufficient inherent strength, but the high content increases processing difficulty. 

4. Set with Metallocene Content 3 Great实战 Techniques 

(1) Determine the benchmark content based on core needs 

1.  Clearly define key metrics: 

• Heat-sealing Priority (Food Packaging): Heat-Seal Strength ≥30 N/15 mm , Benchmark 25%；
• Strength First (Heavy Packaging): Puncture-Resistant ≥1500gf , Benchmark 12%；
• Transparency First (Greenhouse Film): Light Transmittance ≥88% , Benchmark 10%；

2. Minor requirement adjustment: Add if low-temperature resistance is needed. 3%-5% 。

(II) Reducing Content Through Blend Optimization 

1.  General formula: 

• High cost performance: 15% Metallocene + 65% LLDPE + 20% LDPE (Province 15% Cost); 
• High transparency: 12% Metallocene + 85% LLDPE + 0.3% Nucleating agent (abbreviated as 8% Cost); 

2. Error avoidance: Versus HDPE The blending content does not exceed 15% , anti-layering. 

(III) Integration with Equipment and Process Adjustments 

1.  Old equipment (length-to-diameter ratio < 25:1 ): Content decreases 5% , using “ Low -  High -  China ”  Temperature process reduces melt fluctuations; 

2.  New equipment (double-layer air ring): Enhanced content 3%-5% , Blow-up Ratio 1.8–3.5 Membrane bubble stability maintained. 

V. Common Misconceptions Alert: Avoid These Content-Setting Methods

• Blindly chasing high prices : Regular shopping bag plus 20% Metallocene, ton cost increases 4000  Yuan, 10% Already sufficient; 
• Ignoring blending : Using high concentrations alone increases costs but improves processing stability; 
• Don't look at the device : Forcing outdated equipment to work 30% , leading to excessive screw torque, film breakage, and reduced efficiency 50%；
• Uneven layering : The composite membrane with uniform layer composition consumes more material compared to the layered design. 10% Ingredients. 

Conclusion 

The setting of the metallocene content in the thin film is “ Performance, Cost, Process ”  Precise matching —— High content delivers ultimate performance, medium content strikes a balance, and low content controls costs. From food packaging 30% To agricultural film 5% , each proportion reflects a deep understanding of function. 

In the future, low-content, high-performance metallocene materials will become the trend. Mastering the logic behind content levels will not only help optimize formulations but also give you a competitive edge in cost management. What challenges have you encountered when setting content levels? Feel free to share your thoughts in the comments!