Oriented Multilayer Barrier Film Resolving EVOH Stiffness Trade-off
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Solution Overview
Problem
Conventional multilayer barrier films face challenges in achieving both improved mechanical and barrier properties, particularly in food packaging, where ethylene-vinyl alcohol copolymer (EVOH) used as a barrier layer compromises processability and stretchability, and maintaining isotropic mechanical properties while reducing material usage and costs.
Innovation Solution
An oriented multilayer barrier polymer film structure comprising a polar barrier layer, an amphiphilic tie layer, and a multimodal polyethylene layer, which is mono-axially oriented, allowing for better adhesion and processability while maintaining high barrier and mechanical properties, and enabling thinner films with improved recyclability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVOH is used as a barrier layer to achieve low oxygen transmission rate, then barrier properties are improved, but mechanical properties and processability deteriorate
Solution Approach 1:
The film is divided into multiple functional layers: a polyethylene base layer providing mechanical strength and processability, and a separate EVOH barrier layer providing oxygen barrier properties. This segmentation allows each layer to optimize its specific function without compromising the other, resolving the contradiction between barrier performance and mechanical properties.
Solution Approach 2:
The invention uses a composite structure combining polyethylene and EVOH layers. The polyethylene provides ductility, processability, and mechanical strength, while the EVOH layer contributes oxygen barrier properties. The composite material approach allows the final film to exhibit both good mechanical properties and low oxygen transmission rate simultaneously.
2Reliability
If barrier layer thickness is increased to improve oxygen barrier properties, then barrier performance is improved, but material costs and film thickness increase
Solution Approach 1:
The EVOH barrier layer is applied locally only where oxygen barrier properties are needed, rather than increasing the thickness of the entire film structure. This localized application of the barrier material provides effective oxygen protection while minimizing overall material consumption and maintaining cost-effectiveness.
3Strength
If monoaxial stretching is applied to improve stiffness and impact behaviour, then mechanical properties in machine direction are improved, but mechanical properties in transverse direction deteriorate
Solution Approach 1:
The invention optimizes the stretching parameters (temperature, draw ratio, stretching speed) to achieve the desired balance between stiffness improvement and isotropic property maintenance. By carefully controlling these parameters, the film develops enhanced mechanical properties while minimizing anisotropic effects.
Data Source
AI summary
The invention described relates to oriented multilayer barrier films, especially films having a low oxygen transmission rate and isotropic mechanical properties. The films of the invention include a barrier layer embedded in nonpolar polyethylene layer linked by an adhesive tie layer and are produced using mono-axial orientation processes.These films possess improved barrier properties in the sense of lower oxygen permeability when compared to conventional barrier layer containing polymer films and improved mechanical properties.