Polymeric Foam Layer with Shaped Surfaces and Closed Cells
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Solution Overview
Problem
Existing methods for creating shaped polymeric foams often result in damaged cell structures or require complex processes, and there is a need for alternative foams with controlled surface exposure of internal cells and customizable features.
Innovation Solution
A method involving a rotating tool roll and extrusion die with a die lip to form a gap, where polymers with foaming agents, gases, or microspheres are introduced to create polymeric foam layers with controlled cell exposure and customizable features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If foam is made by injection molding or cutting large blocks, then shaped surfaces can be obtained, but the cell structure is damaged or the process becomes complex
Solution Approach 1:
The desired foam shape is prepared in advance in the tooling cavity before the foaming process occurs. The mold cavity is pre-formed with the exact final shape, and foam is then molded directly into this prepared cavity, eliminating the need for subsequent cutting or shaping operations that would damage the cell structure.
Solution Approach 2:
The invention replaces mechanical cutting and shaping operations with a direct molding process. Instead of cutting foam blocks or using convoluted cutting methods, the foam is molded directly into the desired shape through injection molding, substituting mechanical post-processing with a forming process that preserves cell integrity.
2Shape
If foam is embossed to create three-dimensional features, then shaped surfaces are obtained, but the cells are permanently damaged
Solution Approach 1:
The three-dimensional surface features are prepared in advance in the tooling cavity rather than being imposed on already-formed foam. The mold cavity contains the exact final shape with surface features, and foam is molded directly into this pre-prepared cavity, eliminating the need for subsequent embossing that would crush and damage the cell structure.
3Shape
If profile extrusion is used to create continuous shaped foam, then contoured shapes are obtained, but the process is limited to continuous production
Solution Approach 1:
The injection molding process is highly versatile and can produce a wide variety of foam shapes, sizes, and configurations in a single process. The mold cavity can be designed to create any desired shape including complex three-dimensional features, allowing the same basic process to serve multiple production needs without requiring specialized continuous extrusion equipment.
4Ease of manufacture
If conventional foam making methods are used, then production is simplified, but surface cell exposure cannot be controlled
Solution Approach 1:
The mold cavity is designed with specific local characteristics that control cell exposure at different locations on the foam surface. By varying the cavity design in different regions, the process can control whether cells are exposed or closed at specific areas, enabling precise control over surface cell exposure while maintaining the simplicity of the injection molding process.
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 method produces polymeric foam layers with controlled surface cell exposure and customizable features, suitable for applications like vibration damping and polishing, while maintaining structural integrity.
Implementation Method 1
The resulting foam has a glass transition temperature, Tg, in a range from -125°C to 150°C
Implementation Method 2
introducing a polymer comprising a gas onto a portion of the major circumferential surface of the tool roll... a gas is injected into the polymer... wherein the polymer foams to provide the polymeric foam layer
Data Source
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AI summary
Polymeric foam layer having a thickness up to 25,700 micrometers, having first and second opposed major surfaces, and comprising foam features extending from or into the first major surface by at least 100 micrometers, and having a Tg in a range from -125°C to 150°C, wherein the first and second opposed major surfaces are free of exposed internal porous cells (i.e., less than 10 percent of the surface area of each of the first and second major surface has any exposed porous cells) and wherein at least 40 percent by area of each major surface has an as-cured surface; and methods of making the same. Exemplary uses of polymeric foam layers described herein including a finishing pad for silicon wafers and vibration damping.