Polymeric Nanofoam Thermal Insulation via Nanoporous Cell Structure
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Solution Overview
Problem
Current thermally insulating polymeric foams with cell sizes above 100 micrometers require low thermal conductivity gases, and achieving high porosity and reduced thermal conductivity in nanoporous structures is challenging, while also being cost-effective and avoiding the use of nanofillers.
Innovation Solution
A polymeric nanofoam is developed using a miscible mixture of acrylonitrile copolymer and (meth)acrylic polymer, with a porosity of 0.50 or greater, and a narrow cell size distribution, achieved through melt-blending and expansion with carbon dioxide as a blowing agent without nano-sized nucleating additives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polymeric foam uses cell sizes of 100 micrometers or greater, then it is easier to manufacture, but thermal conductivity increases and insulation performance deteriorates
Solution Approach 1:
The patent applies parameter changes by reducing the cell size from conventional 100 micrometers or greater to nanoporous dimensions of 100 nanometers or less. This dramatic reduction in cell size parameter fundamentally changes the thermal transport mechanism, suppressing gas molecule movement and collisions, thereby reducing thermal conductivity by approximately two-thirds compared to conventional foams while maintaining manufacturability through the specific polymer blend composition.
2Loss of energy
If polymeric foam reduces cell size to 100 nm or less, then thermal insulation improves, but achieving high porosity becomes more difficult
Solution Approach 1:
The patent employs composite materials by creating a blend of two immiscible polymers: a styrenic polymer (polystyrene or styrene-acrylonitrile copolymer) and a (meth)acrylic polymer (poly(methyl methacrylate) or poly(ethyl methacrylate)). This composite polymer system, with specific weight ratios, enables simultaneous achievement of nanoporous cell structure and high porosity (50-90%) through controlled phase separation during foaming, overcoming the difficulty of achieving high porosity at such small cell dimensions.
3Ease of manufacture
If polymeric foam uses low-cost styrenic polymers, then manufacturing cost decreases, but achieving nanoporous structure with high porosity is challenging
Solution Approach 1:
The patent uses composite materials by combining low-cost styrenic polymers with (meth)acrylic polymers in specific ratios. This composite approach enables the economical styrenic polymer to achieve nanoporous structure formation (cell size ≤100 nm with porosity 50-90%) that would be difficult to obtain alone, while keeping overall material costs lower than using expensive polymers like poly(meth)acrylic alone, thus resolving the contradiction between cost and manufacturing precision.
4Device complexity
If polymeric foam avoids using nanofillers as nucleators, then cost and complexity decrease, but achieving narrow cell size distribution and high nucleation density is difficult
Solution Approach 1:
The patent applies self-service by designing a polymer blend system where the two immiscible polymers (styrenic and (meth)acrylic) automatically phase-separate during the foaming process, creating numerous nucleation sites without requiring any added nanofillers. The specific composition ratio (70-95 wt% styrenic, 5-30 wt% (meth)acrylic) enables self-organization into a nanoporous structure with narrow cell size distribution (Dv/Dn ≤ 2.5) and high nucleation density, simplifying the formulation while achieving precise structural control.
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 results in a highly porous polymeric nanofoam with improved thermal insulation properties and reduced thermal conductivity, achieved without the need for expensive polymers or nanofillers, demonstrating enhanced energy efficiency and cost-effectiveness.
Implementation Method 1
reducing the pressure on the foamable polymer mixture by at least 10 MegaPascals at a rate of at least 10 MegaPascals per second while the foamable polymer mixture is at a temperature at least 20 degrees Celsius below the glass transition temperature of the (meth)acrylic-free acrylonitrile-containing copolymer having the highest glass transition temperature to allow the foamable polymer mixture to expand into the polymeric foam
Implementation Method 2
The contribution of cell gas to thermal conductivity through polymeric foam decreases dramatically when the cell size of the foam is reduced below one micrometer. Therefore, polymeric foam having a nanoporous structure (that is, having an average cell size that is below one micron; 'nanofoam'), especially polymeric foam having an average cell size of 300 nm or less, and most preferably 100 nm or less is desirable as thermal insulation.
Data Source
AI summary
A polymeric nanofoam has a continuous polymer phase containing at least one (meth)acrylic-free acrylonitrile-containing copolymer and at least one (meth)acrylic polymer where the concentration of (meth)acrylic polymer is in a range of 5-90 weight-percent of the total continuous polymer phase while the amount of methacrylic copolymer is 50 weight-percent or less of the total continuous polymer phase; the polymeric foam having a porosity of at least 50%, an absence of nano-sized nucleating additives and at least one of the following: (a) a number average cell size of 500 nanometers or less; and (b) an effective nucleation site density of at least 1 x 1014 sites per cubic centimeter of prefoamed material. The total weight of copolymerized acrylonitrile is in a range of 3-28 weight-percent based on total continuous polymer phase weight. At least one (meth)acrylic-free acrylonitrile-containing copolymer has a higher glass transition temperature than all of the (meth)acrylic polymers.