Polyethylene Siloxane Foam for RF Cable Insulation
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Solution Overview
Problem
Current RF cable insulations face challenges in reducing energy dissipation factor (DF) due to low porosity and the use of environmentally harmful blowing agents, which also increase production costs and impurities in foams.
Innovation Solution
A foam is developed using a polymeric matrix of polyethylene grafted polymerized siloxane with carbon dioxide as the blowing agent, achieving high porosity and minimizing impurities through a process involving grafting, blending, and high-pressure molding to form a closed-cell foam with porosity greater than 75%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional blowing agents are used to form foam, then foaming capability is improved, but impurities and environmental harm increase
Solution Approach 1:
The patent changes the physical state parameters of carbon dioxide from gaseous to supercritical state by controlling temperature and pressure during the foaming process. This parameter change allows CO2 to act as an effective blowing agent without the harmful effects of traditional chemical blowing agents, eliminating impurities and environmental harm while maintaining foaming capability
Solution Approach 2:
The patent uses carbon dioxide, a cheap and readily available substance, as a replaceable blowing agent that can be easily introduced and removed from the system. The CO2 serves its purpose during foaming and then dissipates, leaving no harmful residues or impurities in the final foam product
2Productivity
If nucleating agents are used to expedite bubble formation, then foaming speed is improved, but production costs and impurities increase
Solution Approach 1:
The patent enables the polyethylene grafted polymerized siloxane material to self-nucleate bubbles without requiring external nucleating agents. The grafted siloxane structure provides inherent nucleation sites that facilitate bubble formation and growth during CO2 foaming, achieving fast foaming speed while eliminating the need for additional chemical additives that would increase costs and impurities
3Loss of energy
If porosity of insulation is increased to reduce dissipation factor, then energy loss is reduced, but structural integrity may be compromised
Solution Approach 1:
The patent creates a composite foam structure by grafting polymerized siloxane onto polyethylene chains. This composite structure forms a network of cross-linked regions within the foam matrix that provide structural reinforcement. The siloxane grafts create a three-dimensional network that maintains mechanical strength even at high porosity levels (greater than 75%), allowing the foam to achieve low dissipation factor while retaining sufficient structural integrity for cable insulation applications
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 foam exhibits improved porosity and smaller cell size, reducing energy dissipation and minimizing environmental impact while reducing production costs by eliminating the need for harmful blowing agents and nucleating agents.
Implementation Method 1
a plurality of cells formed in the polymeric matrix and containing a blowing agent comprising carbon dioxide
Implementation Method 2
molding the blended intermediate to form a molded intermediate; and foaming the molded intermediate using high-pressure CO2
Data Source
AI summary
In one aspect there is provided a foam comprising: a polymeric matrix comprising polyethylene grafted polymerized siloxane, and a plurality of cells formed in the polymeric matrix and containing a blowing agent comprising carbon dioxide. In another aspect there is provided a method of making a foam comprising: grafting polymerized siloxane to polyethylene to form a grafted intermediate; molding the grafted intermediate to form a molded intermediate; and foaming the molded intermediate using high-pressure CO2 to form the foam, wherein the foam has a porosity greater than 75％.