Coextrusion Die Segmentation for Microlayer Integrity
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Solution Overview
Problem
Existing coextrusion dies face challenges in combining microlayers with thicker layers due to interfacial flow instabilities, which disrupt the physical integrity and independent properties of the microlayers.
Innovation Solution
A coextrusion die design incorporating a microlayer assembly and distribution plates, where microlayers are deposited onto a forming stem in a predetermined order to form a unified mass, which then merges with thicker layers, minimizing interfacial flow instabilities and maintaining the integrity of the microlayers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If microlayers are combined with thicker layers in a coextrusion die, then the film gains improved mechanical properties such as flex cracking and puncture resistance, but interfacial flow instabilities occur that disrupt the physical integrity and independent properties of the microlayers
Solution Approach 1:
The die is segmented into separate functional zones: a microlayer assembly section with multiple thin layers (1-20 mils each) and a thicker layer section with fewer thick layers (20-100 mils each). This segmentation allows independent control of flow characteristics in each zone, preventing interfacial instability between dissimilar thicknesses while maintaining the composite structure needed for improved mechanical properties.
Solution Approach 2:
An intermediary flow control mechanism is introduced in the form of a die design that mediates between the microlayer assembly and thicker layers. The die structure acts as a buffer zone that equalizes flow rates and reduces shear rate differences between the microlayers and thicker layers, preventing interfacial flow instabilities while allowing both layers to maintain their integrity.
2Quantity of substance
If the number of layers in a multilayer film is increased to achieve microlayering, then the film thickness is reduced to 0.5-50 mils with improved mechanical properties, but the flow rate and mass flow rate increase causing interfacial flow instabilities when combined with thicker layers
Solution Approach 1:
The extrusion system is segmented into separate microlayer extrusion channels and thicker layer extrusion channels, each optimized for their specific flow requirements. The microlayer section handles high layer count with lower individual flow rates, while the thicker layer section handles lower layer count with higher flow rates, eliminating the conflict between total quantity and flow rate.
Solution Approach 2:
The die design implements parameter changes in the form of variable channel geometries and flow control mechanisms that adjust flow rates and shear rates for different layer types. By changing flow parameters locally rather than maintaining uniform parameters throughout, the system can accommodate both high-layer-count microlayers and thick layers without interfacial instability.
3Reliability
If thicker layers are used for heat-sealing and abuse-resistance functions, then the film gains superior performance in these functions, but the powerful sheer forces from higher mass flow rate disrupt the microlayers when combined in the same die
Solution Approach 1:
The die is divided into separate flow paths for microlayers and thicker layers, allowing independent optimization of shear forces in each path. The thicker layers can be extruded with higher shear forces appropriate for their heat-sealing function without imposing disruptive shear forces on the microlayers, as the segmentation isolates the two flow systems until they are gently merged in a controlled zone.
Solution Approach 2:
An intermediary merging zone is introduced where the microlayer assembly and thicker layers are combined. This intermediary zone acts as a buffer that equalizes shear rates and flow velocities before the layers are fully integrated, preventing the powerful shear forces from the thicker layers from disrupting the microlayer structure while still allowing the thicker layers to perform their heat-sealing and abuse-resistance functions.
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 die effectively combines microlayers with thicker layers, preserving the physical integrity and independent properties of the microlayers, enhancing the mechanical properties of the resulting film, such as flex cracking and puncture resistance.
Implementation Method 1
one or more distribution plates, each of the plates having a fluid inlet and a fluid outlet, the fluid outlet from each of the plates being in fluid communication with the primary fluid passage and structured to deliver a layer of fluid to the primary fluid passage
Implementation Method 2
a microlayer assembly, comprising (1) a microlayer fluid passage, and (2) a plurality of microlayer distribution plates, each of the microlayer plates having a fluid inlet and a fluid outlet, the fluid outlet from each of the microlayer plates being in fluid communication with the microlayer fluid passage and structured to deliver a microlayer of fluid to the microlayer fluid passage
Implementation Method 3
the microlayer fluid passage is in fluid communication with the primary fluid passage such that the microlayered fluid mass flows from the microlayer fluid passage and into the primary fluid passage
Implementation Method 4
wherein, the microlayer fluid passage is in fluid communication with the primary fluid passage such that the microlayered fluid mass flows from the microlayer fluid passage and into the primary fluid passage, thereby merging the microlayered fluid mass with the one or more layers of fluid from the one or more distribution plates
Data Source
AI summary
A die for coextruding a plurality of fluid layers includes one or more distribution plates for forming relatively thick layers, and a microlayer assembly for forming a plurality of microlayers. The die further includes internal fluid passages and/or forming surfaces to allow the microlayers to assemble into a microlayered fluid mass prior to merging with the relatively thick layers from the distribution plates.