SELF-MINERALIZING MULTIFUNCTIONAL COATING COMPOSITION

Abstract

A coating composition includes alkaline mineral particles including an oxide of an alkaline earth metal and an amine-containing polymer. The amine-containing polymer is adsorbed on the alkaline mineral particles. Forming a coating composition includes at least partially coating alkaline mineral particles with an amine-containing polymer and dispersing the alkaline mineral particles in a liquid to yield the coating composition. The alkaline mineral particles include an oxide of an alkaline earth metal.

Claims

1. A coating composition comprising: alkaline mineral particles comprising an oxide of an alkaline earth metal; and an amine-containing polymer, wherein the amine-containing polymer is adsorbed on the alkaline mineral particles.

2. The coating composition of claim 1, wherein the alkaline mineral particles comprise one or more of MgO, CaO, CaSiO.sub.3, Ca.sub.2SiO.sub.4, and Mg.sub.2SiO.sub.4.

3. The coating composition of claim 2, wherein the alkaline mineral particles have a diameter in a range of about 1 nm to about 100 nm.

4. The coating composition of claim 1, wherein the amine-containing polymer comprises one or more of polyethylene terephthalate, poly(methyl methacrylate), poly(allyl amine), poly(vinyl amine), and poly(ethylene imine).

5. The coating composition of claim 1, further comprising water, alcohol, or both.

6. The coating composition of claim 5, further comprising one or more resin binders.

7. The coating composition of claim 6, wherein the one or more resin binders comprises an epoxy resin, an acrylic resin, or both.

8. The coating composition of claim 6, wherein the one or more resin binders comprise poly(methyl methacrylate), poly[(vinyl acetate)-co-(methy/ethyl/butyl acrylate)], or both.

9. The coating composition of claim 1, further comprising a silicone polymer.

10. The coating composition of claim 9, wherein the silicone polymer comprises a functionalized polysilsesquioxane.

11. The coating composition of claim 10, wherein the functionalized polysilsesquioxane comprises poly(dimethylsiloxane).

12. The coating composition of claim 1, further comprising one or more pigments.

13. A coating formed from the coating composition of claim 1.

14. The coating composition of claim 1, wherein the coating composition reflects solar radiation.

15. A method of storing carbon dioxide, the method comprising: contacting carbon dioxide with the coating composition of claim 1; capturing the carbon dioxide with the amine-containing polymer; transporting the carbon dioxide to the oxide of the alkaline earth metal; and forming an alkaline earth metal carbonate species.

16. A method of forming a coating composition, the method comprising: at least partially coating alkaline mineral particles with an amine-containing polymer, wherein the alkaline mineral particles comprise an oxide of an alkaline earth metal; and dispersing the alkaline mineral particles in a liquid to yield the coating composition.

17. The method of claim 16, wherein the coating composition further comprises one or both of a resin binder and a silicone polymer.

18. The method of claim 16, wherein the coating composition further comprises one or more pigments.

19. The method of claim 16, wherein the alkaline mineral particles comprise one or more of MgO, CaO, CaSiO.sub.3, Ca.sub.2SiO.sub.4, and Mg.sub.2SiO.sub.4.

20. The method of claim 16, wherein the amine-containing polymer comprises one or more of polyethylene terephthalate, poly(methyl methacrylate), poly(allyl amine), poly(vinyl amine), and poly(ethylene imine).

Description

BRIEF DESCRIPTION OF DRAWINGS

[0015] FIG. 1A depicts an example of a CO.sub.2-absorbent composite in the form of a coating.

[0016] FIG. 1B depicts amine polyethylene terephthalate (amine-PET).

DETAILED DESCRIPTION

[0017] This disclosure describes self-mineralizing multifunctional coating compositions and composites formed therefrom. The coating composition includes an amine-containing polymer and reflective particles of an alkaline mineral. The amine-containing polymer facilitates capture of carbon dioxide (CO.sub.2) at atmospheric concentrations by a composite formed from the coating composition. The captured CO.sub.2 diffuses through the composite and reacts with the alkaline mineral to yield a carbonate. The coatings provide CO.sub.2 capture and storage as well as solar reflectance. The composite can be in the form of a paint. When the paint is used to coat building materials in an urban setting, the paint promotes cooling of the building materials. This cooling can reduce energy consumption and mitigate urban heat island effects.

[0018] FIG. 1A shows a schematic of a composite 100 in the form of a coating. Composite 100 is formed from a composition that includes amine-containing polymer 102 and alkaline mineral particles 104. Amine-containing polymer 102 is adsorbed on alkaline mineral particles 104. The adsorption can include physical adsorption, chemical adsorption, or both. Examples of forces present in physical adsorption include electrostatic forces and van der Waals forces. One example of chemical adsorption is covalent bonding. The amine-containing polymer 102 facilitates the capture of CO.sub.2 and provides a percolating network for transporting the CO.sub.2 to the alkaline mineral particles 104. The thickness of the amine-containing polymer 102 on alkaline mineral particles 104 can be in a range of about 0.01 μm to about 1.0 μm.

[0019] The composite 100 can include additives 106. The additives 106 can include resin binders, silicone polymers, or both for additional strength or ductility. Suitable resin binders include epoxy resins or acrylic resins such as poly(methyl methacrylate) (PMMA) or poly[(vinyl acetate)-co-(methy/ethyl/butyl acrylate)]. Suitable silicone polymers include methyl/phenyl/methoxy/aminopropyl-functionalized polysiloxanes such as poly(dimethylsiloxane) (PDMS) or similarly functionalized polysilsesquioxanes.

[0020] The alkaline mineral particles 104 include an oxide of an alkaline earth metal that can store CO.sub.2 by reacting with CO.sub.2 to form a carbonate species. Suitable alkaline earth oxides include magnesium oxide (MgO), calcium oxide (CaO), calcium inosilicate (CaSiO.sub.3), calcium orthosilicate (Ca.sub.2SiO.sub.4), forsterite olivine (Mg.sub.2SiO.sub.4). The alkaline mineral particles 104 can be nanoparticles (e.g., with a diameter in a range of about 1 nm to about 100 nm).

[0021] The amine-containing polymer is configured to capture CO.sub.2 at atmospheric concentrations. Amine groups can be incorporated into a polymer through aminolysis or transesterification with an amine-containing reagent to yield the amine-containing polymer. The amine-containing polymer can include terminal amine groups. Polymers suitable for forming the amine-containing polymer include polyethylene terephthalate (PET), PMMA, poly(allyl amine) (PAA), poly(vinyl amine) (PVAm), poly(ethylene imine) (PEI). Amine-containing reagents suitable for the aminolysis or transesterification reaction include ethylene diamine, related ethylene amine oligomers (e.g., diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine), longer alkyl diamines (e.g., propanediamine, butanediamine, pentanediamine) and related alkyl amine oligomers. In some cases, multifunctional amine reagents are used to promote crosslinking of the amine-containing polymer. Suitable multifunctional reagents include tris(2-aminoethyl)amine, tris(3-aminoethyl)amine, low molecular weight branched PEI.

[0022] Amine-functionalized waste polyethylene terephthalate (PET) can be used as a precursor material for the amine-containing polymer. The PET can be functionalized with amines through a transesterification reaction. FIG. 1B depicts an example of an amine-containing polymer produced from polyethylene terephthalate (PET) and ethylene diamine. The amine groups of ethylene diamine are incorporated into PET through transesterification of ester bonds to yield amine-PET 110. The PET used for the synthesis of amine-PET 110 can be sourced from waste plastic. The transesterification process breaks down the waste plastic and converts it into a slurry. While PET is insoluble in most solvents, micronized PET particles with an amine-functionalized surface can be dispersed in water or alcohol as a slurry that can be used as a coating. Suitable alcohols include ethanol or propanol.

[0023] The composite 100 can include one or more pigments. The composite 100 can be a paint. Carbonation of alkaline mineral particles 104 by CO.sub.2 capture results in an increase in radiation reflectance of the composite 100. When the composite 100 is used as a paint on a structure, this increase in radiation reflectance decreases the energy consumption for cooling the structure.

[0024] The mechanical properties of the coating can be measured as a function of CO.sub.2 exposure time to determine how the mechanical properties change with increased carbonation. Elasticity and yield strength can be measured by tensile testing or dynamic mechanical analysis (DMA), and hardness can be measured by indentation measurements. Since the degree of carbonation can vary with depth into the sample, DMA can give an approximation of the average properties of the sample whereas indentation measurements can better determine the properties of the carbonated surface. Microindentation (e.g., Vickers hardness test) can be used to obtain values for the mechanical properties of the composite as a whole.

[0025] The morphology of the composite 100 can be examined by scanning electron microscopy (SEM). Fourier transform infrared spectroscopy (FTIR) can be used to measure chemical composition. An average composite thickness can be estimated based on the Brunauer-Emmett-Teller (BET) surface area and thermogravimetric analysis (TGA) measurements of the organic-inorganic mass ratio. The composite thickness and morphology can also be examined by cutting sample cross-sections of the composite and imaging them with SEM or atomic force microscopy (AFM). The crystal structure can be characterized by X-ray diffraction (XRD). A smaller size of the alkaline mineral particles 104 provides more surface area and accelerates CO.sub.2 absorption. Table 1 lists properties of MgO and its estimated maximum capacity for CO.sub.2 absorption.

TABLE-US-00001 TABLE 1 Properties of MgO and estimated capacity for CO.sub.2 absorption. Molecular Weight 40.3 g/mol Density 3.6 g/cm.sup.3 Max. CO.sub.2 capacity of mineral 1.09 g (CO.sub.2)/g (mineral) Max. CO.sub.2 capacity of paint 262 g (CO.sub.2)/m.sup.2 (0.2 mm thick coating)* 3,800 m.sup.2/metric ton CO.sub.2 *Calculated based on paint composed of 60 wt % mineral content, density of organic phase 1.2 g/cm.sup.3, and ignoring any CO.sub.2 held by organic amines

[0026] The speed of CO.sub.2 absorption and the capacity of the mineral powders or composite mixtures can be measured using a TGA instrument where CO.sub.2 concentration, water-vapor content, and temperature can be controlled and monitored in real-time. For measurements of absorption over longer periods of days or weeks, a system can be used in which a closed container is pressurized with CO.sub.2 gas and the pressure decrease is measured over time.

[0027] The absorption speed and diffusion depth of CO.sub.2 can be measured in a closed-chamber system using samples of the composite greater than 0.5 mm thick with only the top surface exposed to better mimic the performance of a paint coating. After CO.sub.2 exposure, the sample can be fractured or cut to expose a cross-section that can be characterized by SEM and energy-dispersive X-ray spectroscopy (EDX). Microscopy of a simple fractured sample can reveal qualitative aspects of particle packing, morphology change with CO.sub.2 absorption, and adhesion between inorganic and organic phases. Cutting and polishing the sample can reveal cross-sections of mineral particles, and the distribution of carbon in the section can be mapped by EDX. This analysis shows the depth of CO.sub.2 diffusion into the coating as well as into any individual mineral particle.

[0028] Combined AFM and infrared absorption spectroscopy (AFM-IR) can be used to analyze the organic-inorganic surface. AFM-IR uses a wavelength-tunable IR laser to simultaneously perform AFM imaging and mapping of IR absorption by photothermal expansion. AFM-IR can map the composition, mechanics, and morphology of the mineral-amine-polymer interface with sub-micron resolution.

[0029] Ab initio and density functional theory (DFT) calculations and molecular dynamics (MD) simulations can be used to analyze the coating in 3 ways. (1) The simulations can assist in screening candidate alkaline minerals and binders, at different molar ratios as applicable, by simulating their CO.sub.2 diffusion coefficient and computing their CO.sub.2 absorption capacity. (2) The calculations can be used to gain atomistic and molecular-level insight into the mechanisms underlying CO.sub.2 absorption as well as interactions between CO.sub.2 and the composite ingredients. This will be done by computing the coordination number, total energy, and residence time of CO.sub.2 and its interaction energy and radial distribution function with respect to the coating components. Simulations can be carried out at different temperatures and water contents in the binder to further analyze the influence of these factors on the kinetics of CO.sub.2. (3) The calculations can be used to test the influence of carbonation on the hardness and mechanical properties of the coating at the nanometer scale (e.g., on the order of a few million atoms).

[0030] The thermal emissivity of the disclosed coatings can be analyzed using the material's thermal properties, such as thermal conductivity, density, and specific heat. The optical characteristics of the material can be analyzed including chromatic coordinates and whiteness to understand their influence on the radiation absorption of the material. Reflective measurements within the range of solar radiation can be made to obtain the solar reflectance of the material. A solar simulation analysis and infrared thermography (IRT) can be performed to test the behavior of material surface in interaction with solar irradiance. The results can be validated using the findings from the physical test with a scaled demonstrator. Energy simulation with EnergyPlus™ can be used to assess the impacts of the disclosed coatings on the cooling- and total energy savings of a sample building. The results can help estimate the energy-related carbon avoidance to be achieved using the disclosed coatings.

[0031] Particular embodiments of the subject matter have been described. Other embodiments, alterations, and permutations of the described embodiments are within the scope of the following claims as will be apparent to those skilled in the art. While operations are depicted in the drawings or claims in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed (some operations may be considered optional), to achieve desirable results.

[0032] Accordingly, the previously described example embodiments do not define or constrain this disclosure. Other changes, substitutions, and alterations are al so possible without departing from the spirit and scope of this disclosure.