Biaxially-Stretched Polyester Film Easy Tear Design
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Solution Overview
Problem
Conventional polyester films face challenges such as difficulty in cutting, poor tearability, and interlayer cohesion issues, which affect their practicality for packaging and adhesive applications, due to hygroscopicity and impaired properties from copolymerization or molecular orientation.
Innovation Solution
A biaxially-stretched polyester laminate film with layers having molecular orientation and those substantially free of molecular orientation, differing in refractive indices, is developed, where the layer with molecular orientation is laminated on both sides of the latter, ensuring improved adhesiveness and tearability while maintaining heat resistance and moisture-proof properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a biaxially-oriented polyester film is used to achieve superior toughness, heat resistance, water resistance, and transparency, then these properties are improved, but cutting difficulty increases and tearability deteriorates
Solution Approach 1:
The film is divided into multiple layers with different functional properties: a base polyester layer providing strength and barrier properties, and a surface layer containing low molecular weight polyester resin and elastomer that provides easy tearing and cutting characteristics. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
The surface layer of the film has different compositional and physical properties from the base layer. The surface layer contains specific additives and has different molecular weight characteristics that localizedly provide easy tearing and cutting properties, while the base layer maintains the overall structural integrity and barrier properties.
2Ease of operation
If copolymerization is used to improve processability and tearing properties, then ease of tearing is improved, but the inherent properties of polyethylene terephthalate are impaired
Solution Approach 1:
The invention uses controlled copolymerization with specific monomers in controlled amounts to modify the polyester chain structure. By adjusting the copolymerization parameters (monomer type, concentration, reaction conditions), the film achieves improved tearability while preserving the essential polyester properties through controlled modification rather than complete structural change.
3Ease of operation
If a sea-island structure with polyester block copolymer dispersed in crystalline polyester resin is used, then easy-to-tear property is improved, but interlayer cohesion deteriorates and laminate strength is degraded
Solution Approach 1:
The invention introduces an elastomer component as an intermediary substance that bridges the crystalline polyester resin and the dispersed polyester block copolymer. This elastomer acts as a binding agent that maintains interlayer cohesion and laminate strength while still allowing the sea-island structure to provide easy tearing properties.
Solution Approach 2:
The film uses a composite structure combining crystalline polyester resin, dispersed polyester block copolymer, and elastomer in specific proportions and configurations. This composite material approach allows the simultaneous achievement of easy tearing (from the sea-island structure) and strong interlayer cohesion (from the elastomer binding and optimized composite formulation).
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 film achieves superior tearability, adhesiveness, and stability in packaging applications, preventing poor opening performance and interlayer detachment, while maintaining the inherent properties of polyester films like heat resistance and aroma retention.
Implementation Method 1
a biaxially-stretched polyester laminate film with layers having molecular orientation and those substantially free of molecular orientation
Implementation Method 2
differing in refractive indices
Data Source
AI summary
An easy-to-tear biaxially-stretched polyester film having easy cut property and adhesiveness, as well as superior properties of polyester film, such as heat resistance, moisture-proof property, transparency, aroma retention and the like is provided. The polyester laminate film may include at least two layers, a layer substantially free of a molecular orientation and a layer having a molecular orientation, which shows a difference (Nx−Ny) between the refractive index Nx in the longitudinal direction and the refractive index Ny in the width direction of −0.010 to 0.010 and the refractive index Nz in the thickness direction of not less than 1.480. The layer having a molecular orientation has a thickness of 1-8 μm.