Co-Extruded Insulating Film Structure for Layer Adhesion
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Solution Overview
Problem
Existing insulating films for electrical devices face challenges in achieving good adhesion between layers without compromising thermal properties and flame retardance, while also providing a soft composition to prevent damage.
Innovation Solution
A multilayer film structure comprising a polypropylene composition, a polyolefin composition with a propylene-ethylene copolymer and an ethylene/C4-C10 alpha olefin copolymer, and a polyethylene composition, where the layers are co-extruded to enhance adhesion and maintain mechanical and electrical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a multilayer film with polypropylene outer layer and softer inner layer is employed to provide mechanical properties and prevent damage, then mechanical protection is improved, but adhesion between layers deteriorates
Solution Approach 1:
The patent applies local quality by creating a tie layer with specific composition (polyethylene and/or polypropylene) that differs from the outer and inner layers. This tie layer is positioned specifically at the interface between the polypropylene outer layer and the softer inner layer to provide localized adhesion enhancement without compromising the overall mechanical protection or softness of the film structure.
2Reliability
If adhesion between layers is improved by modifying the tie layer composition, then internal adhesion is improved, but thermal properties and flame retardance deteriorate
Solution Approach 1:
The patent applies parameter changes by carefully controlling the composition parameters of the tie layer, specifically limiting polyethylene content to 5-50 wt% and polypropylene content to 50-95 wt%, with the polypropylene having a melting point of 160-170°C. These parameter adjustments optimize the balance between adhesion (improved by softer polyethylene) and thermal properties/flame retardance (maintained by predominant polypropylene with high melting point).
Data Source
AI summary
A film that comprises: a) a first layer (A) comprising a polypropylene composition (PC1), b) a second layer (B) comprising a polyolefin composition (PC2) comprising: i) a propylene-ethylene copolymer (PP2) having a Tm of 130 to 150 °C; and ii) a first ethylene/C4-C10 alpha olefin copolymer (PE1) having a Tm of 30 to 60 °C, and c) a third layer (C) comprising a polyethylene composition (PC3), wherein layer (B) has a first surface and a second surface located opposite the first surface, a surface of layer (B) is in adherent contact with layer (A) and the opposite surface of layer (B) is in adherent contact with layer (C), resulting in a layer structure A-B-C having layer (B) disposed between layer (A) and layer (C).