Porous polymer composite for daytime radiative cooling and method of making a porous polymer composite

Patent metadata

Field	Value
Publication number	US-12516233-B2
Application number	US-202217854786-A
Country	US
Kind code	B2
Filing date	Jun 30, 2022
Priority date	Jul 9, 2021
Publication date	Jan 6, 2026
Grant date	Jan 6, 2026

Abstract

A porous polymer composite for daytime radiative cooling includes a porous polymer matrix comprising a thermoplastic polymer and including a plurality of pores, and selectively emitting particles dispersed in the porous polymer matrix. When exposed to solar radiation, the porous polymer composite comprises an infrared emissivity of at least about 80% in a wavelength range of 8-13 μm and/or a solar reflectivity of at least about 80% in a wavelength range of 0.3-2 μm.

First claim

The invention claimed is:

1 . A porous polymer composite for daytime radiative cooling, the porous polymer composite comprising:
a porous polymer matrix comprising a thermoplastic polymer and including a plurality of pores; and selectively emitting particles dispersed in the porous polymer matrix, wherein, when exposed to solar radiation, the porous polymer composite comprises an infrared emissivity of at least about 80% in a wavelength range of 8-13 μm and/or a solar reflectivity of at least about 80% in a wavelength range of 0.3-2 μm.

2 . The porous polymer composite of claim 1 , wherein a weight ratio of the selectively emitting particles to the thermoplastic polymer is at least about 1:5.

3 . The porous polymer composite of claim 1 , wherein the pores have a range of sizes from about 10 nm to about 5 microns.

4 . The porous polymer composite of claim 1 , wherein the thermoplastic polymer comprises polyethylene and/or wherein the selectively emitting particles comprise silicon oxide.

5 . The porous polymer composite of claim 1 , wherein the selectively emitting particles comprise a gradient in concentration in the porous polymer matrix.

6 . The porous polymer composite of claim 1 not including a reflective metal layer.

7 . The porous polymer composite of claim 1 , wherein a solar-facing surface of the porous polymer composite includes a pattern of raised features.

8 . The porous polymer composite of claim 7 , wherein the solar-facing surface has a water contact angle of greater than 150°.

9 . The porous polymer composite of claim 1 , further comprising photocatalytic particles embedded in or coated on a surface of the porous polymer matrix to impart antibacterial properties.

10 . A cooling system comprising:
the porous polymer composite of claim 1 disposed on a solar-facing surface to be cooled.

11 . The cooling system of claim 10 , wherein the solar-facing surface is part of a building, roof, vehicle, tent, or apparel item.

12 . A method of making the porous polymer composite for daytime radiative cooling of claim 1 , the method comprising:
mixing together a thermoplastic polymer, selectively emitting particles, and a polymer solvent to form a first polymer mixture; forming the first polymer mixture into a predetermined shape at a temperature sufficient to obtain a homogeneous solution of the thermoplastic polymer and the polymer solvent, with the selectively emitting particles distributed therein; cooling the predetermined shape, thereby inducing phase separation of the homogeneous solution into a liquid phase comprising the polymer solvent and a solid phase comprising the thermoplastic polymer and the selectively emitting particles; and extracting the liquid phase from the predetermined shape, thereby forming a porous polymer composite comprising a porous polymer matrix with the selectively emitting particles dispersed therein, the porous polymer matrix comprising the thermoplastic polymer and including a plurality of pores.

13 . The method of claim 12 , wherein the temperature sufficient to obtain the homogeneous solution is at least about 110° C.

14 . The method of claim 12 , wherein a ratio of weight of the thermoplastic polymer to volume of the polymer solvent is in a range from about 1:2 to about 1:6, the weight being measured in grams and the volume being measured in milliliters.

15 . The method of claim 12 , wherein the thermoplastic polymer comprises polyethylene, and/or wherein the selectively emitting particles comprise silicon oxide.

16 . The method of claim 12 , wherein the forming comprises molding, extrusion, spinning, and/or 3D printing.

17 . The method of claim 16 , wherein the forming comprises compression molding using a molding apparatus, and further comprising:
placing a metal mesh between a surface of the first polymer mixture and a heated platen of the molding apparatus; and pressing the heated platen against the metal mesh, thereby pressing the metal mesh into the surface and imprinting a pattern of raised features.

18 . The method of claim 12 , wherein a second polymer mixture comprising a different amount of the selectively emitting particles than the first polymer mixture is employed during the forming so as to obtain a gradient in concentration of the selectively emitting particles in the predetermined shape.

19 . The method of claim 12 , further comprising incorporating photocatalytic particles into or onto a surface of the predetermined shape.

20 . The method of claim 12 , wherein the predetermined shape comprises a film, a fiber or an arbitrary 3D shape.

Assignees

• Univ Illinois

Inventors

• Cai Lili
• Zhou Kai
• Yan Xiao
• Miljkovic Nenad

Classifications

• C08J2207/00

  Foams characterised by their intended use · CPC title

• B29K2509/00

  Use of inorganic materials not provided for in groups {B29K2503/00 - B29K2507/00,} as filler · CPC title

• B29K2023/06

  PE, i.e. polyethylene · CPC title

• C08J2423/06

  Polyethene · CPC title

• B29K2995/0012

  having particular thermal properties · CPC title