BOPE Film Composition for Tenter-Frame Stretchability
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Solution Overview
Problem
Conventional polyethylene films are difficult to stretch using the tenter frame process due to poor stretchability, limiting the production of biaxially oriented polyethylene (BOPE) films, especially when compared to polypropylene or PET.
Innovation Solution
Utilizing medium density polyethylene (MDPE) with a broad molecular weight distribution, specifically a density of 0.94 to 0.95 g/cm³, melt index of 0.2 to 5 g/10 min, and molecular weight distribution (Mw/Mn) of 10 to 50, in the tenter frame process to produce BOPE films through sequential machine and transverse direction stretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional polyethylene is used in the tenter frame process, then the process can be applied to PE films, but the stretchability is poor and biaxial orientation is difficult to achieve
Solution Approach 1:
The patent changes the molecular weight distribution parameter of polyethylene from conventional narrow distribution to very broad distribution (Mw/Mn ≥ 10), which fundamentally alters the material's stretchability and enables successful biaxial orientation in the tenter frame process
Solution Approach 2:
The patent creates a composite polymer system by blending different polyethylene components with varying molecular weights to achieve a very broad molecular weight distribution, combining the flow properties of low molecular weight components with the strength and stretchability of high molecular weight components
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 process enables the production of high-quality BOPE films with improved toughness, barrier, optics, and heat resistance, suitable for various packaging applications, including laminated structures that are more easily recyclable.
Implementation Method 1
stretching said base structure to a degree of from about 3:1 to about 10:1 in the machine direction and stretching said base structure to a degree of from about 3:1 to about 10:1 in the transverse direction
Data Source
AI summary
A Biaxially Oriented Polyethylene (BOPE) process uses a selected polyethylene having a medium density and a very broad molecular weight distribution. The use of this selected polyethylene facilitates stretching in the BOPE process in comparison to previously used polyethylene resins having a higher density and/or a narrower molecular weight distribution.