Multilayer Film With High Loss Modulus Layers
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Solution Overview
Problem
Multilayer thermoplastic protective films often experience separation between layers during use, leading to undesirable aesthetic and mechanical changes, and lack sufficient transparency, low haze, and toughness for specific applications.
Innovation Solution
A multilayer film structure comprising a thermoplastic first layer with a high loss modulus, a thermoplastic elastomer and polyamide resin second layer with reduced crystallinity, and a third thermoplastic layer with high loss modulus, where the second layer is sandwiched between the first and third layers, enhancing interlayer adhesion and mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermoplastic protective films are used, then ease of manufacture is maintained, but interlayer separation occurs during use leading to undesirable aesthetic and mechanical changes
Solution Approach 1:
The patent employs a multilayer composite film structure where alternating layers of aromatic polyester (high loss modulus) and elastomer/polyamide blend (low loss modulus) are coextruded. This composite structure resolves the contradiction by using the elastomer layer to enhance interlayer adhesion and prevent separation, while maintaining manufacturing feasibility through standard coextrusion processes.
Solution Approach 2:
The patent applies different material properties to different layers: aromatic polyester layers provide structural integrity and optical clarity, while the elastomer/polyamide layers provide flexibility and adhesion. This local differentiation of material qualities allows the film to simultaneously achieve reliable interlayer bonding and maintain ease of manufacture through specialized coextrusion.
2Strength
If thermoplastic films are made more transparent and tougher, then optical clarity and mechanical strength improve, but haze increases
Solution Approach 1:
The patent uses a composite structure where aromatic polyester layers provide optical clarity and toughness, while the elastomer/polyamide layers provide flexibility without compromising transparency. The specific combination and thickness ratios of these layers enable the film to achieve high toughness and low haze simultaneously.
Solution Approach 2:
The patent optimizes parameters such as loss modulus values, layer thicknesses, and material compositions to achieve the desired balance between transparency, toughness, and haze. By controlling the loss modulus of each layer (aromatic polyester: ≥70 MPa, elastomer layer: ≤60 MPa) and adjusting the ratio of crystalline to amorphous regions, the film achieves enhanced optical clarity without sacrificing mechanical strength.
3Reliability
If multilayer films are designed with specific layer compositions, then transparency and toughness improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent uses a multilayer composite structure with alternating aromatic polyester and elastomer/polyamide layers. The elastomer layer acts as an adhesive barrier that prevents delamination, while the aromatic polyester layers provide structural stability. This composite design achieves reliable interlayer bonding with standard coextrusion precision requirements.
Solution Approach 2:
The patent specifies loss modulus parameters (aromatic polyester: ≥70 MPa, elastomer layer: ≤60 MPa) and layer composition ratios that can be achieved through conventional coextrusion technology. By optimizing these parameters, the film achieves resistance to interlayer delamination without requiring excessive manufacturing precision, as the elastomer layer's lower loss modulus naturally promotes layer bonding.
Data Source
AI summary
A multilayer film comprises first, second, and third layers. The first layer comprises at least one aromatic polyester, and has a loss modulus at 1 hertz and 25° C. of at least 70 megapascals. The second layer is thermoplastic and has a loss modulus at 1 hertz and 25° C. of less than or equal to 60 megapascals and comprises a thermoplastic elastomer and a polyamide. The third layer contacts the second layer opposite the first layer and has a loss modulus at 1 hertz and 25° C. of at least 70 megapascals. The second layer is sandwiched between the first and third layers. A method of making the multilayer film by coextrusion is also disclosed.