Polyethylene Multilayer Foam Sheets With Reduced Carbon Fallout
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Solution Overview
Problem
Existing polyethylene-based resin foam sheets face issues with conductivity due to the need for large amounts of conductive carbon, which can impair foamability and cushioning properties, and may cause carbon to fall off and contaminate surroundings or packaged objects.
Innovation Solution
A polyethylene-based resin multilayer foam sheet with a conductive layer containing a mixed resin of low-density polyethylenes and ethylene-based copolymers with a specific melting point difference and controlled conductive carbon content, laminated on one or both sides, is produced through coextrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large amount of conductive carbon is blended in the foam sheet to achieve conductivity, then the conductivity is improved, but the foamability and cushioning properties are impaired
Solution Approach 1:
The foam sheet is divided into multiple layers with different functions: non-conductive foam layers for cushioning and a conductive layer for static charge dissipation. This segmentation allows each layer to optimize its specific function without compromising the other, resolving the contradiction between conductivity and cushioning properties.
Solution Approach 2:
Conductive carbon is not uniformly distributed throughout the entire foam sheet but is concentrated in a specific conductive layer. This local quality approach ensures conductivity is provided where needed while maintaining cushioning properties in the foam layers, avoiding the impairment that occurs when carbon is dispersed throughout the entire structure.
2Reliability
If a large amount of conductive carbon is blended in the foam sheet to achieve conductivity, then the conductivity is improved, but the conductive carbon is more likely to fall off and contaminate surroundings
Solution Approach 1:
By segmenting the foam sheet into distinct layers with the conductive carbon confined to a specific conductive layer, the carbon is better contained and less likely to migrate or fall off. The layer structure provides physical containment that prevents carbon fallout while maintaining conductivity.
Solution Approach 2:
The conductive layer is formed as a composite material with conductive carbon blended in a polyethylene-based resin matrix. This composite structure provides both conductivity and structural integrity, holding the carbon particles in place and preventing them from falling off, while still achieving the required conductivity.
3Reliability
If conductive carbon is increased to achieve conductivity, then the conductivity is improved, but the foamability is hindered
Solution Approach 1:
The foam sheet is segmented into non-conductive foam layers and a conductive layer. The non-conductive foam layers contain no conductive carbon, allowing them to be easily foamed with good foamability. The conductive layer, which contains carbon, is applied as a separate layer, thus the carbon does not interfere with the foaming process of the foam layers.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The multilayer foam sheet achieves conductivity while minimizing conductive carbon fallout, ensuring effective static charge dissipation and preventing contamination, with enhanced cushioning and handleability.
Implementation Method 1
a difference TmB−TmC between a melting point TmB of the polyethylene (B) contained in the conductive layer and a melting point TmC of the ethylene-based copolymer (C) contained in the conductive layer is 30° C. or more and 80° C. or less
Implementation Method 2
conductive carbon blended in the mixed resin... enables to reduce the falling of the conductive carbon from the foam sheet, and a production method therefor... achieves conductivity while minimizing conductive carbon fallout, ensuring effective static charge dissipation
Data Source
AI summary
A polyethylene-based resin multilayer foam sheet may include a polyethylene-based resin foam layer containing a polyethylene-based resin (A) as a base resin, and a conductive layer laminated on at least one side of the foam layer. The conductive layer contains: a mixed resin of one or more polyethylenes (B) of low-density polyethylenes and/or linear low-density polyethylenes and an ethylene-based copolymer (C) having a structural unit derived from ethylene and a structural unit derived from a monomer having a polar group; and conductive carbon. The conductive carbon blended in the conductive layer may be in a range of from 3 to 15 wt. %. The difference, TmB−TmC, between the melting point TmB of the polyethylene (B) and the melting point TmC of the ethylene-based copolymer (C) each contained in the conductive layer may be in a range of from 30 to 80° C.