Multilayer Film Inner Layer Modulus Contrast
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Solution Overview
Problem
Current multilayer films used in packaging struggle to enhance tear resistance, stiffness, and optical properties like gloss and haze without compromising dart impact resistance or increasing material thickness, particularly with a thin core layer made from different modulus materials.
Innovation Solution
A multilayer film configuration with a thin inner layer, comprising at least three layers where the inner layer has a thickness of 20% or less of the total film thickness, featuring a polymer component with a 2% secant modulus significantly higher or lower than the skin layer, measured according to ISO 527-3-95 standards, and characterized by specific melt index or melt flow rate properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the film thickness is increased to improve tear resistance and stiffness, then tear resistance and stiffness are improved, but material cost and weight increase
Solution Approach 1:
The patent applies local quality by creating a multilayer film structure where different layers have different mechanical properties. The skin layers provide tear resistance and stiffness, while the core layer provides ductility and impact absorption. This allows each layer to contribute its specific properties locally, achieving overall film performance without increasing total thickness.
Solution Approach 2:
The patent uses composite materials by combining polymers with different modulus values in a multilayer configuration. The skin layers use higher modulus polymers for stiffness and tear resistance, while the core layer uses lower modulus polymers for ductility. This composite structure achieves superior mechanical properties compared to single-layer films of equivalent or greater thickness.
2Strength
If the film thickness is increased to improve dart impact resistance, then dart impact resistance is improved, but material cost and weight increase
Solution Approach 1:
The core layer is specifically designed with lower modulus and higher ductility to absorb impact energy locally. This localized energy absorption mechanism protects the film from catastrophic failure during dart impact testing without requiring increased overall film thickness.
Solution Approach 2:
The multilayer composite structure combines materials with different mechanical responses to impact. The skin layers provide structural integrity while the core layer provides impact energy dissipation, achieving superior dart impact resistance at reduced thickness compared to homogeneous films.
3Strength
If the inner layer thickness is increased to improve tear resistance, then tear resistance is improved, but optical properties like gloss and haze deteriorate
Solution Approach 1:
The skin layers are optimized for optical properties with appropriate thickness and material selection to maintain gloss and clarity. The core layer thickness is controlled to provide sufficient tear resistance while minimizing negative impact on optical properties. This local optimization of each layer's thickness achieves the balance between mechanical and optical performance.
Data Source
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AI summary
The invention provides a film comprising at least three layers, and wherein at least one layer is a inner layer with a thickness of 20 percent or less of the total thickness of the film, and wherein said inner layer, or a polymer component used to form said inner layer has one of the following properties: A) a MD tensile, 2 percent secant modulus at least two times higher than the MD tensile, 2 percent secant modulus of a skin layer, or B) a MD tensile, 2 percent secant modulus at least five times lower than the MD tensile, 2 percent secant modulus of a skin layer, and where the inner layer, or at least one polymer component of the inner layer, has one of the following properties: C) a melt index, I2 (190°C/2.16kg) of less than, or equal to, 2 g/10 min, or D) a melt flow rate, MFR (230°C/2.16 kg) of less than, or equal to, 5g/10 min. The invention also provides for articles prepared from the inventive films and for methods of making the same.