Polyethylene Blend Drawtape for Seal Integrity and Load Capacity
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Solution Overview
Problem
Conventional drawtapes made from high density polyethylene (HDPE) are strong but form weak heat seals and cause discomfort due to low yield under heavy loads, necessitating a more ergonomic and economical solution that balances strength with seal integrity and user comfort.
Innovation Solution
A drawtape film composed of a polymeric blend with a minor component of linear low density polyethylene (LLDPE) between 5-50 wt% and a major component of medium density polyethylene (MDPE), high density polyethylene (HDPE), or their combinations, with specific melt indices and densities, enhancing elongation and load-carrying capacity while maintaining thermal bond integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If HDPE is used as the base material in drawtape films to provide load carrying strength, then tensile strength is improved, but heat seal strength with bag panels deteriorates
Solution Approach 1:
The patent uses a composite polyethylene material consisting of multiple layers with different densities (HDPE layer for strength, LDPE layer for sealability). This composite structure allows the drawtape to simultaneously achieve high tensile strength from the HDPE layer and good heat seal strength from the LDPE layer, resolving the contradiction between strength and sealability.
2Strength
If stronger polymers such as HDPE are used in drawtapes, then load carrying capacity is improved, but user comfort deteriorates due to low yield under heavy loads
Solution Approach 1:
The patent employs a composite structure where the LDPE layer provides elasticity and yield under load, while the HDPE layer provides tensile strength. This combination allows the drawtape to deform comfortably under heavy loads (improving user comfort) while maintaining sufficient strength to carry the load (improving load carrying capacity).
Solution Approach 2:
Different regions of the drawtape have different material properties: the HDPE layer provides localized strength where needed for load bearing, while the LDPE layer provides localized elasticity for user comfort. This local differentiation of material qualities resolves the contradiction between strength and comfort.
3Strength
If HDPE is used to provide greater tensile strength, then break resistance is improved, but seal weakness increases
Solution Approach 1:
The drawtape is segmented into multiple functional layers: an HDPE layer for break resistance and a separate LDPE layer for seal integrity. This segmentation allows each layer to be optimized for its specific function, with the HDPE layer providing break resistance and the LDPE layer providing seal integrity, thus resolving the contradiction between break resistance and seal integrity.
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 polymeric blend drawtape achieves significant elongation without failure, supports heavy loads, and maintains seal integrity, offering improved ergonomics and economic viability by balancing strength and comfort.
Implementation Method 1
sealed or attached at select locations to the panels of the bag proximate the top
Data Source
AI summary
Drawtape includes a film of a polymeric blend of a minor polymer component of linear low density polyethylene and a major polymer component of medium density polyethylene and/or high density polyethylene. The drawtape of the disclosed subject matter is capable of a strong seal with a commercial polymeric bag, and provides a high elongation prior to tape failure or seal failure. Drawtape bag and method of making the drawtape are also provided.