Multimodal Polyethylene Copolymer for Thin Film Impact Strength
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Solution Overview
Problem
Current multimodal polyethylene copolymers face challenges in achieving high impact strength and isotropic properties, especially when converted into thin films, as they often exhibit unbalanced tear behavior and require specific processing conditions to maintain mechanical properties.
Innovation Solution
A multimodal polyethylene copolymer is developed by copolymerizing ethylene with two alpha-olefin comonomers in multiple stages, achieving a density range of 906 to 925 kg/m³ and a melt flow rate of 10-200 g/10 min, which allows for improved processability and mechanical properties, including high dart drop impact strength and isotropic behavior, even at high draw down ratios.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional multimodal polyethylene copolymers are used to produce thin films, then film production is achieved, but impact strength and isotropic properties are insufficient
Solution Approach 1:
The polymer is divided into three distinct molecular weight modes (light, medium, heavy fractions) with different functional characteristics. The light fraction provides processability and drawability, the medium fraction contributes to isotropic properties and tear resistance, while the heavy fraction enhances impact strength. This segmentation allows each mode to optimize specific properties without compromising others.
Solution Approach 2:
The invention creates a composite polymer structure by combining multiple molecular weight modes in a single copolymer composition. Each mode acts as a functional component within the composite, where the light fraction provides processability, the medium fraction provides isotropic properties, and the heavy fraction provides impact strength, achieving superior overall performance.
2Length of moving object
If high draw down ratios are applied to produce thin films, then film thickness is reduced, but mechanical properties deteriorate
Solution Approach 1:
The polymer composition is designed to dynamically adapt to processing conditions through its multimodal structure. The light fraction enables high draw down ratios and thin film production by providing appropriate melt viscosity and flow characteristics, while the medium and heavy fractions maintain mechanical integrity during and after stretching, allowing the system to dynamically achieve both thinness and strength.
3Ease of manufacture
If specific processing conditions are used to maintain mechanical properties, then processability is improved, but device complexity increases
Solution Approach 1:
The multimodal polymer composition is designed to self-regulate and self-optimize during processing. The different molecular weight modes automatically contribute their specific properties (light fraction for flow, medium for isotropy, heavy for strength) without requiring complex external control systems or highly specialized equipment, allowing the material to serve its own processing needs.
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 resulting copolymer enables the production of thin films with enhanced mechanical properties, such as DDI20 of 400 g or more, and improved isotropy, while maintaining good processability and drawability, making it suitable for various film applications.
Implementation Method 1
A multimodal polyethylene copolymer is developed by copolymerizing ethylene with two alpha-olefin comonomers in multiple stages
Data Source
AI summary
The present invention is directed to a multimodal polyethylene copolymer comprising a first and a second copolymer of ethylene and at least two alpha-olefin comonomers. Such multimodal copolymers are highly suitable for conversion processes that require a high Draw Down Ratio, like the production of thin films. Such multimodal polyethylene copolymers provide a good impact strength in the sense of a high Dart drop impact strength (DDI) and good isotropy of the films produces thereof. The invention further presents final articles such as films made therefrom.