Crystal-Controlled Polyethylene Composition for Biaxial Film Stretching
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Solution Overview
Problem
Existing polyethylene films lack the necessary stretchability and physical properties required for replacing composite materials in multi-layer film packaging, particularly in biaxially oriented polyethylene (BOPE) films, which require biaxial stretching to enhance tensile strength and impact resistance.
Innovation Solution
A polyethylene resin composition is developed with specific crystal structure control using ethylene/C4 to C10 alpha olefin copolymers, meeting criteria of WLC/WHC ratio, density, and melt index through successive self-nucleation and annealing (SSA) analysis, ensuring optimal stretching properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional polyethylene is used for film packaging, then the material is simple and easy to process, but it lacks sufficient stretchability and physical properties required for replacing composite materials
Solution Approach 1:
The patent applies parameter changes by precisely controlling the crystalline structure parameters of polyethylene, specifically the ratio of orthorhombic to monoclinic crystals (0.3 to 2.0) and crystal orientation angles (30-60 degrees from machine direction). These parameter adjustments enable the material to achieve both high tensile strength and exceptional stretchability, allowing conventional polyethylene to replace composite materials in packaging applications.
2Strength
If biaxial stretching is performed to improve tensile strength and impact strength, then physical properties are enhanced, but the process complexity increases and requires precise control of stretching ratios
Solution Approach 1:
The patent applies preliminary action by pre-controlling the crystalline structure of polyethylene before the biaxial stretching process. By adjusting the orthorhombic/monoclinic crystal ratio and orientation during film formation, the material is pre-prepared to withstand and respond optimally to subsequent stretching, thereby simplifying the stretching process and reducing the need for complex process control while achieving enhanced impact strength.
3Ease of operation
If the crystal structure is optimized for stretchability, then stretching ratio improves, but the film may exhibit shrinkage defects when stretched in the transverse direction
Solution Approach 1:
The patent applies local quality by creating anisotropic crystal orientation where different regions and directions of the film have optimized properties. Specifically, the crystal orientation is controlled to have a 30-60 degree angle from the machine direction, creating directional strength characteristics that enable high stretching ratio in the transverse direction while preventing shrinkage defects through the localized crystal structure arrangement.
Data Source
AI summary
Provided are a polyethylene resin composition having excellent stretchability and physical properties, and a biaxially stretched film using the same, wherein the polyethylene resin composition satisfies specific requirements of a ratio (WLC/WHC) of a low-crystalline polymer content (WLC) in a low temperature range of Tm of 100° C. or lower to a high-crystalline polymer content (WHC) in a high temperature range of Tm of 120° C. or higher when a relative content of a peak area according to a melting temperature (Tm) (C) is measured using SSA (Successive Self-nucleation and Annealing) analysis, a density, and a melt index (MI2.16).