Cellular Wood-Plastic Composite Die System for Uniform Cell Formation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for extruding cellular wood-polymer composites face challenges in creating sufficient pressure for uniform cell formation in large profiles and achieving a cohesive structure, as they often result in low-density foams and inadequate adhesion of polymer streams due to filler addition.
Innovation Solution
A die system comprising an adapter, transition, flow restriction, compression, and shaping die plates that control extrudate flow to increase pressure and maintain melt pressure, ensuring uniform cell structure and cohesive bonding of cellulosic fibers and thermoplastic materials, while allowing for low-temperature processing to prevent premature cell development.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the extrudate flow is restricted to increase pressure for cell formation in large profiles, then the cell structure becomes more uniform, but the polymer streams become too widely spaced to adhere sufficiently
Solution Approach 1:
A foaming agent is introduced as an intermediary substance within the polymer-filler mixture. When the extrudate flows through the restricted die channels, the foaming agent generates gas bubbles that expand the material, allowing the divided polymer streams to remain connected through a cellular matrix. This mediator enables both flow restriction for pressure buildup and maintains cohesive structure despite the divided flow paths.
Solution Approach 2:
The patent changes the physical state parameters of the extrudate by introducing a foaming agent that transforms the material from a dense polymer-filler mixture to a cellular foam structure. This parameter change allows the material to expand after extrusion, filling the spaces between divided streams and creating adhesion without requiring the polymer streams to be in direct contact throughout the die structure.
2Manufacturing precision
If multiple channels are used to divide the flow and increase pressure, then cell formation is improved, but the device complexity increases
Solution Approach 1:
The die structure is segmented into multiple channels that divide the extrudate flow. Each channel acts as an independent pathway for the polymer-filler-foaming agent mixture. This segmentation creates the necessary flow restriction in each channel to build pressure for uniform cell formation, while the modular channel design makes the complex structure manufacturable and maintainable.
3Adaptability or versatility
If wood and other fillers are added to the polymer, then the composite material properties are improved, but the polymer streams do not adhere sufficiently without additional compression
Solution Approach 1:
The foaming agent serves as a mediator between the polymer and filler components. As the mixture flows through the restricted die channels, the generated gas bubbles create a cellular structure that binds the polymer-filler composite together. This intermediary mechanism provides adhesion without requiring additional compression, as the expanding foam matrix holds all components together during and after extrusion.
4Manufacturing precision
If the extrudate flow restriction is increased to produce pressure for foaming, then the density reduction is achieved, but the profile expansion after extrusion cannot be controlled
Solution Approach 1:
The die structure is designed with predetermined channel dimensions and configurations that control the degree of flow restriction before extrusion. The channel size, length, and arrangement are calculated in advance to generate the specific pressure needed for the desired density reduction while limiting post-extrusion expansion. This preliminary design of the flow path ensures both density control and shape stability.
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 solution enables the production of cellular composites with a uniform cell structure, reduced density, and improved mechanical properties, such as flexural modulus and thermal expansion, while maintaining the shape without post-extrusion expansion, and allowing for the use of various cellulosic materials like sawdust and newspapers.
Implementation Method 1
Development of pressure in the extrusion process is a result of restriction of the flow of the extrudate
Implementation Method 2
Extrusion of cellular, i.e., foamed, wood plastic composites depends on the formation of gas bubbles or cells within the composite matrix
Data Source
AI summary
The present invention is directed to a device for the production of a cellular wood plastic composite material comprised of an orifice that conducts the composite material from the adapter of the extruder to the transition die plate in such a manner that a uniform flow of material reaches the transition die plate; a transition die plate that further directs the flow of material to a flow restriction die plate in a manner ensuring that equal amounts of material are delivered to all areas of the flow restriction die plate; a flow restriction die plate that provides sufficient resistance to material flow to increase the melt pressure of the portion of the material that is upstream in relation to the flow restriction die plate and controls the temperature increase caused by this restriction by dividing the flow into numerous suitably sized and shaped streams; a compression die plate that fuses the separate streams issuing from the flow restriction die plate into a single stream of material and maintains the melt pressure at a level which will prevent premature development of cells in the material; a shaping die plate that is designed to shape the material in such a way that the fully expanded material will approximate the shape of the desired profile and to control the rate of cell development and expansion so that large numbers of uniform cells are produced.