COMPOSITION COMPRISING A SLURRY OF CAPSULES AND METHODS THEREOF

Abstract

There is provided a composition comprising a slurry of capsules, the capsules having shells comprising silica and said shells encapsulating phase change materials (PCM); and a cementitious binder. There is also provided a method for preparing said composition.

Claims

1. A composition comprising: a slurry of capsules, the capsules having shells comprising silica and said shells encapsulating phase change materials (PCM); and a cementitious binder.

2. The composition of claim 1, wherein the slurry has a pH of no less than 5.

3. The composition of claim 1, wherein the slurry comprises multivalent metal ions.

4. The composition of claim 3, wherein the multivalent metal ions comprise calcium ions.

5. The composition of claim 1, wherein the composition further comprises diatomite.

6. The composition of claim 1, wherein the composition further comprises one or more of latex, an organic polymer, filler, or graphite.

7. The composition of claim 5, wherein the composition comprises diatomite and filler at a ratio of from 1:3 to 1:1.

8. The composition of claim 6, wherein the latex when present is present at an amount of from 0.5 wt % to 10 wt % based on the dry weight of the composition, the filler when present is present at an amount of from 5 wt % to 55 wt % based on the dry weight of the composition, and the organic polymer when present is present at an amount of from 0.05 wt % to 0.5 wt %.

9. The composition of claim 1, wherein the capsules are present at an amount of from 2.5 wt % to 50 wt % based on the dry weight of the composition.

10. The composition of claim 1, wherein the cementitious binder is present at an amount of from 20 wt % to 60 wt % based on the dry weight of the composition.

11. The composition of claim 5, wherein the diatomite is present at an amount of from 5 wt % to 20 wt % based on the dry weight of the composition.

12. The composition of claim 1, wherein the total water content of the composition is from 5 wt % to 50 wt %.

13. The composition of claim 1 comprising: from 10 wt % to 30 wt % of capsules based on the dry weight of the composition; from 30 wt % to 50 wt % of cement based on the dry weight of the composition; from 10 wt % to 50 wt % of sand and/or calcium carbonate based on the dry weight of the composition; from 5 wt % to 20 wt % of diatomite based on the dry weight of the composition; from 1 wt % to 5 wt % of latex based on the dry weight of the composition; from 0.05 wt % to 0.5 wt % of cellulose based on the dry weight of the composition; from 5 wt % to 50 wt % total water content of the composition; and optionally from 0.1 wt % to 2 wt % of performance enhancing additives based on the dry weight of the composition.

14. A method of preparing the composition of claim 1, the method comprising: providing a slurry of capsules, the capsules having shells comprising silica and said shells encapsulating phase change materials (PCM); and mixing the slurry of capsules with a cementitious binder.

15. The method of preparing the composition of claim 14, wherein providing the slurry of capsules comprises: adding a silica precursor to emulsified droplets of PCM in the presence of salt and alcohol to enhance silica growth around the emulsified droplets, thereby forming the slurry of capsules having shells comprising silica and encapsulating PCM.

16. The method of preparing the composition of claim 15, wherein the salt comprises a multivalent metal salt, the silica precursor comprises an alkoxy silane and the alcohol is selected from the group consisting of: methanol, ethanol, propanol, isopropanol and combinations thereof.

17. The method of preparing the composition of claim 15, further comprising adding a pH adjusting agent to the slurry of capsules to obtain a pH of no less than 5.

18. The method of preparing the composition of claim 17, wherein the pH adjusting agent comprises an alkaline pH adjusting agent.

19. The method of preparing the composition of claim 15, further comprising mixing one or more of a filler, diatomite, latex and organic polymer with the slurry of capsules.

20. The method of preparing the composition of claim 15, wherein the method comprises: adding cement, sand and/or calcium carbonate, diatomite, latex and cellulose to the slurry of capsules; and optionally adding additional water to the mixture of cement, sand and/or calcium carbonate, diatomite, latex, cellulose and capsules, wherein the final composition comprises from 10 wt % to 30 wt % of capsules based on the dry weight of the composition, from 30 wt % to 50 wt % of cement based on the dry weight of the composition, from 10 wt % to 50 wt % of sand and/or calcium carbonate based on the dry weight of the composition, from 5 wt % to 20 wt % of diatomite based on the dry weight of the composition, from 1 wt % to 5 wt % of latex based on the dry weight of the composition, from 0.05 wt % to 0.5 wt % of cellulose based on the dry weight of the composition, and from 5 wt % to 50 wt % total water content of the composition.

Description

BRIEF DESCRIPTION OF FIGURES

[0117] FIG. 1 is a schematic diagram 100 for illustrating a method of emulsifying PCM particles to obtain PCM oil/water emulsion (O/W emulsion) with micron sized droplets in accordance with various embodiments disclosed herein. PCM particles 102 are dispersed in a continuous water phase (e.g., water/ethanol (EtOH) 104) in the presence of oil (e.g., surfactant 106) to obtain PCM O/W emulsion with micron sized droplets 108.

[0118] FIG. 2 shows an optical microscope image of PCM oil/water emulsion (O/W emulsion) with micron sized droplets. The image is taken at 4× magnification. PCM used is paraffin mixtures (e.g., Pluss OM-28P obtained from Pluss Advanced Technologies Pvt. Ltd). The o/w emulsion is OM28P in EtOH/water solution.

[0119] FIG. 3 is a schematic diagram 300 for illustrating a method of forming a silica shell over emulsified PCM micron sized droplets to obtain silica-based PCM microcapsules in accordance with various embodiments disclosed herein. The pH of the PCM O/W emulsion is adjusted, and a silica precursor/solution (sol) (e.g., tetraethyl orthosilicate (TEOS)) 302 is introduced slowly to the emulsion and allowed to undergo hydrolysis and condensation reaction on the surface of the emulsified micron sized droplets to form a silica shell 304 over the PCM 306.

[0120] FIG. 4 is a schematic diagram of a silica-based PCM microcapsule in accordance with various embodiments disclosed herein. The silica-based PCM microcapsule 400 comprises a robust silica shell 402 encapsulating a PCM 404.

[0121] FIG. 5 shows images of silica-based PCM microcapsules in accordance with various embodiments disclosed herein that are prepared from different PCMs with low water solubility, showing that the microencapsulating process is highly compatible with PCMs with low water solubility. PCMs are prepared in EtOH/H.sub.2O (1:3) mixture. PCM A: Paraffin mixture OM-28P; PCM B: Fatty acid mixture OM-29; PCM C: Fatty acid ester mixture CM29; and PCM D: Fatty acid ester mixture SL28.

[0122] FIG. 6 shows SEM images of silica-based PCM microcapsules with smooth surfaces. The top image is taken at 1,000× magnification, with the scale bar representing 10 μm. The bottom image is taken at 2,000× magnification, with the scale bar representing 10 μm.

[0123] FIG. 7 shows a SEM image of silica-based PCM microcapsules with rough surfaces. The SEM image is taken at 200× magnification, with the scale bar representing 100 μm.

[0124] FIG. 8 shows images of a scale up of PCM encapsulation in accordance with various embodiments disclosed herein.

[0125] FIG. 9 shows results obtained from compatibility test performed with cementitious materials. Part (a) shows a sample prepared by mixing 70 wt % cement (binder) with 30 wt % silica-based PCM capsules. Part (b) shows a sample prepared by mixing 70 wt % cement (binder) with 30 wt % commercial polymer encapsulated PCM capsules.

[0126] FIG. 10 shows images of initial skim coat formulation prepared by direct mixing of PCM capsule powder. The top 2 images are captured before outdoor exposure tests and the bottom 2 images are captured after 2 weeks of outdoor exposure tests. Images on the left show samples prepared from PCM capsule powder+cement+water. Images on the right show samples prepared from PCM capsule powder+cement+water+graphite.

[0127] FIG. 11 shows an image of skim coat sample prepared from a mixture of sieved PCM capsule powder with cement. As shown, the skim coat does not have good adhesion strength. There is loss of adhesion and the skim coat could be peeled off easily from substrates without additives.

[0128] FIG. 12 shows an optical microscope image of diatomite powder in water, with the scale bar representing 10 μm. The image is taken at 40× magnification. Porous structure can be observed for diatomite powder in water.

[0129] FIG. 13 shows a differential scanning calorimetry (DSC) graph of a skim coat sample prepared with ball milling process.

[0130] Part A of FIG. 14 shows an image of a skim coat sample prepared by incorporating PCM capsules using ball milling procedure. Part B of FIG. 14 shows an image of a skim coat sample prepared by incorporating PCM capsules using PCM slurry procedure.

[0131] FIG. 15 shows an image of a skim coat sample prepared by adding graphite to the formulation. No obvious change was observed with addition of 1 wt % or 2 wt % graphite.

[0132] FIG. 16 shows images of skim coat samples formulated by adding ammonia, cellulose and latex powder. The skim coat samples were observed to harden quickly and remained crack-free.

[0133] FIG. 17 shows images of skim coat samples prepared from 2 controls. Control 1 contains fillers and additives while control 2 contains 40 wt % cement and 60 wt % sand.

[0134] FIG. 18 shows images of skim coat samples prepared from different PCM capsules content (i.e. 5 wt %, 8 wt % and 10 wt %) respectively.

[0135] FIG. 19 shows images of skim coat samples prepared from different PCM capsules content (i.e. 20 wt %, 30 wt % and 40 wt %) respectively.

[0136] FIG. 20 is a graph showing the thermal conductivity of skim coats containing different PCM content (i.e. 5 wt % PCM, 8 wt % PCM, 20 wt % PCM, 30 wt % PCM and pure PCM (100 wt %)). The controls used are Control 1 (containing fillers and additives) and Control 2 (containing cement and sand).

[0137] FIG. 21 is a graph showing the specific heat capacity (by volume) of skim coats containing different PCM content (i.e. 5 wt % PCM, 8 wt % PCM, 20 wt % PCM and 30 wt % PCM). The controls used are Control 1 (containing fillers and additives) and Control 2 (containing cement and sand).

[0138] FIG. 22 is a schematic diagram for illustrating an experimental set up in a laboratory for measuring back surface temperature. A sample 2200 is positioned approximately 35 cm below an infrared (IR) lamp 2202. The temperature of the back surface of sample 2200 is measured (and displayed on temperature sensor/display 2204) by attaching the temperature sensor/display directly to said surface.

[0139] FIG. 23 is a graph showing the temperature change over time (or thermal regulation effect) of skim coats containing different PCM content (i.e. 5 wt % PCM, 20 wt % PCM and 30 wt % PCM). The controls used are Control 1 (containing fillers and additives) and Control 2 (containing cement and sand).

[0140] FIG. 24 is a schematic diagram for illustrating an experimental set up in a laboratory for measuring air temperature in mini house testing or cool roof house thermal testing. The mini house comprises two compartments 2400 and 2402. The roof 2404 of compartment 2400 is uncoated (i.e. used as a control) while the roof 2406 of compartment 2402 is coated with a thermoshield (i.e. 20 wt % PCM skim coat with a 6 mm thickness). The temperature of air in the interior of compartment 2400 is measured with a temperature sensor 2408. The temperature of air in the interior of compartment 2402 is measured with a temperature sensor 2410 by attaching the temperature sensor directly to the back surface of the roof (i.e. interior).

[0141] FIG. 25 is a graph showing the back surface temperature change over time results obtained from the mini house testing or cool roof house thermal testing as illustrated in FIG. 24.

[0142] FIG. 26 is a schematic diagram 2600 for illustrating total solar reflectance (TSR) of PCM skim coats prepared in accordance with various embodiments disclosed herein. At step 2602, a robust silica shell 2610 encapsulates a PCM 2608 to form a silica-based PCM microcapsule 2612, which is formulated into a PCM skim coat 2614 at step 2604. Heat (for e.g., exterior heat) is absorbed by the PCM skim coat which leads to lower interior temperature and cooler interior air. At step 2606, the PCM skim coat is further coated with double layer cool coatings 2616 having a thickness of about 100 μm and applied on a drywall 2618.

[0143] FIG. 27 shows an image of PCM skim coat that is not coated with cool coatings (on the left) and an image of PCM skim coat further coated with cool coatings (on the right).

[0144] FIG. 28 is a graph showing the total solar reflectance (TSR) in % of PCM skim coats containing different PCM content (i.e. 5 wt % PCM, 10 wt % PCM, 20 wt % PCM and 30 wt % PCM) that are not coated with cool coatings. The controls used are two Control 2 (containing cement and sand), one coated with cool coating and one not coated with cool coating.

[0145] FIG. 29 is a graph comparing the back surface temperature difference of PCM skim coats containing different PCM content (i.e. 8 wt % PCM and 30 wt % PCM) that are not coated with cool paint with those that are coated with cool paint. The control used is Control 1 (containing fillers and additives) not coated with cool paint.

[0146] FIG. 30 shows images of further tests and work to be performed such as outdoor exposure tests and scaling up for large scale field studies.

EXAMPLES

[0147] Example embodiments of the disclosure will be better understood and readily apparent to one of ordinary skill in the art from the following discussions and if applicable, in conjunction with the figures. It should be appreciated that other modifications related to structural, physical and chemical changes may be made without deviating from the scope of the invention. Example embodiments are not necessarily mutually exclusive as some may be combined with one or more embodiments to form new exemplary embodiments. The example embodiments should not be construed as limiting the scope of the disclosure.

Example 1: Preparation of Silica-based Phase Change Material Microcapsules

Microencapsulation Technology

[0148] Silica-based phase change material (PCM) microcapsules were prepared using microencapsulation technology which comprises 2 steps.

[0149] Firstly, as shown in FIG. 1, phase change material (PCM) particles 102 are dispersed in a continuous water phase (e.g., water/ethanol (EtOH) 104) in the presence of oil (e.g., surfactant 106) to obtain PCM oil/water emulsion (O/W emulsion) with micron sized droplets 108. A SEM image of the PCM O/W emulsion showing droplets in micron size is provided in FIG. 2. The surfactant 106 is added to aid in emulsifying PCM particles 102 in water/EtOH 104. The PCM O/W emulsion may also be prepared with a hotplate 110 for temperature control (e.g., heating to an appropriate temperature) and/or mixing (e.g., mechanical stirring).

[0150] Next, as shown in FIG. 3, the pH of the PCM O/W emulsion is adjusted, and a silica precursor/solution (sol) 302 is introduced slowly to the emulsion and allowed to undergo hydrolysis and condensation reaction on the surface of the emulsified micron sized droplets to form a silica shell 304 over the PCM 306. In this example, tetraethyl orthosilicate (TEOS) was used as the silica precursor/sol.

[0151] The synthesized silica-based PCM microcapsule 400 comprises a robust silica shell 402 encapsulating a PCM 404 (FIG. 4). The core-shell PCM-silica microcapsules are produced in slurry format, which can be used for the preparation of skim coat formulations later.

[0152] The present microencapsulation technology has the following advantages: [0153] Simple process, low toxicity, easy to scale up [0154] Sustainable products—no polymer used [0155] Better compatibility with inorganic cementitious building materials [0156] Robust silica shell

Highly Compatible Process

[0157] Process is compatible with different PCMs with low water solubility (FIG. 5) [0158] Surface morphology of capsules may change with different PCMs used [0159] Cycling performance can be conducted to check the stability of the microcapsules with different PCMs [0160] Good capsule: [0161] no change in appearance of capsules, no oil leak observed after over 2000 cycles [0162] Bad capsule: [0163] PCM melted, oily slurry formed

[0164] FIG. 6 shows SEM images of silica-based PCM microcapsules with smooth surfaces. FIG. 7 shows a SEM image of silica-based PCM microcapsules with rough surfaces.

Example 2: Preliminary Studies

[0165] Prior to producing a skim-coat formulation, the following background work was performed.

[0166] The encapsulation process of different phase change materials (PCMs), namely CrodaTherm™ 29 (CM29) (i.e. fatty acid ester mixtures) obtained from Croda International Plc, savE® OM29 (i.e. fatty acid mixtures) obtained from Pluss Advanced Technologies Pvt. Ltd, OM28p (i.e. paraffin mixtures) obtained from Pluss Advanced Technologies Pvt. Ltd and SL28 (i.e. fatty acid ester mixtures) was tested and confirmed in the lab. CM29 and OM28p were proved to be compatible with encapsulation process. The produce capsules performed well in the cycling performance test.

[0167] The reaction parameters were optimized and the reaction time was reduced from 72 hours (hr) to 24 hours (hr) to facilitate the scale-up.

[0168] 50 litres (L) scale up of CM29 encapsulation was successfully conducted (FIG. 8). 200 L scale up is currently on-going. The scale up was conducted in a coated metal drum with a hotplate at the bottom to control the temperature. A mixer was used to generate stable emulsion and the reactants were added manually. There were some deviations in the scale up operation. For example, the pH of reaction is around 1-2, which is lower than the pH described in the operation procedure earlier provided. Based on analysis, those PCM capsules performed well in the cycling performance tests. They are therefore suitable to be used in skim coat applications. The finished product comprises PCM capsule slurry with 40-45 wt % capsule content. The stable capsules can hold the PCM without leak for over 2,000 heating/cooling cycles.

Example 3: Initial Evaluation—Compatibility

[0169] Compatibility test was performed with cementitious materials by mixing 70 wt % cement (binder) respectively with (a) 30 wt % silica-based PCM capsules; and (b) 30 wt % commercial polymer encapsulated PCM capsules. The commercial PCM is a research sample supplied by Croda International Plc.

[0170] The results from the compatibility tests are shown in FIG. 9. Cracks were observed on the sample prepared from commercial polymer encapsulated PCM capsules (FIG. 9b). On the other hand, the sample prepared from silica-based PCM capsules was relatively free of cracks (FIG. 9a).

Example 4: Skim Coat Formulation Development

Direct Mixing of PCM Capsule Powder

[0171] Initially, it was found that if PCM capsule powder is directly used in skim coat, the poor dispersing of PCM in cement matrix will result in weak adhesion between capsule aggregates and matrix. The situation became even worse after outdoor weathering (FIG. 10).

Use of Sieved PCM Capsule Powder or PCM Slurry

[0172] Also, it was found that the skim coat could be easily peeled off from the substrate due to low adhesion strength when sieved PCM capsule powder or the PCM slurry was used to prepare the skim coat (FIG. 11).

Use of Metakaolin, Diatomite and Calcium Carbonate

[0173] Even though it was believed that Metakaolin can be used to partially replace cement, no obvious improvement was found with the use of Metakaolin in our cases. The formulation was checked/tested with different silicon hydrophobic powder content but it did not show any visible positive effect on the skim coat samples. Diatomite and Calcium carbonate were tested as the filler together with the sand. It was found that diatomite alone can form stable solid bulk material with PCM. Without being bound by theory, it is believed that its porous structure (FIG. 12) can absorb the PCM and prevent PCM leaking at elevated temperature. Therefore, a portion of diatomite is used in the skim coat formulation. Similar experiments were conducted using calcium carbonate. It was found that calcium carbonate does not have this stabilization effect on PCM oil.

Use of Redispersible Latex Powder

[0174] It was found that the use of redispersible latex powder can improve adhesion strength of the skim coat. A ladder test was conducted. It was found that 2% of latex powder can provide sufficient adhesion to the substrate. For the sample above 2% dosage, no substantial effect was observed.

Use of PCM Capsule Slurry or Ball Milling Device for Incorporation

[0175] After confirming the effect of additives, different ways to incorporate PCM capsules in the skim coat were attempted, including the use of PCM capsule slurry and the use of ball milling device to incorporate PCM capsule powder. The experiment showed that the use of ball milling device can improve the mixing of PCM with cement, increase overall density and therefore improve the mechanical strength of skim coats. However, it was found that the melting-solidification process of the PCM was somehow affected after the ball milling process, according to the differential scanning calorimetry (DSC) curve (FIG. 13). For the PCM slurry, the mechanical strength of the skim coat is lower than the control sample but it is much better than the initial skim coat samples.

[0176] It was also noted that cracks can be observed on sample obtained from ball milling procedure (FIG. 14A) as well as on sample obtained from PCM slurry procedure (FIG. 14B) if additives are not added properly. The steps involved in preparing a skim coat via ball milling procedure are described as follows. [0177] 1. Dry PCM capsules powder and diatomite are mixed in a dish and ball-milled. [0178] 2. The resulting ball-milled mixture is sieve and added to cement and remaining components of the skimcoat. [0179] 3. Add water till it becomes a viscous and cream-like mixture. [0180] 4. The mixture is then applied on a board evenly and allow it to dry over few days to obtain a skim coat.

Use of Graphite

[0181] With 1% or 2% graphite, it was noticed that no obvious change was observed (FIG. 15).

Use of pH Adjusting Agent (e.g., Ammonia) and Cellulose

[0182] It was found that capsule slurry is the possible finished product form and removal of ‘wash to neutral pH’ step from PCM capsule manufacturing process was requested in order to reduce cost. The effect of the acid residue on skim coat was then investigated. The skim coats with different PCM capsule content (10%-30%) were found to be weak and full of cracks, when the ‘unwashed’ PCM capsule slurry from an earlier study with a low pH was used, even with the addition of additives. It is believed that the acid can react with the alkaline in the cement, so the pH of slurry was adjusted to 6-7 with a pH adjusting agent (ammonia solution). No crack was found in the skim coat when the pH adjusted slurry was used. When attempts were made to prepare more samples for testing, it was found that sometimes, the cracks developed within a couple of hours during the drying process.

[0183] It is believed that cellulose derivatives with hydroxy functional groups can be used in plaster formulations to improve water retention, increase setting time and therefore prevent cracking. It can also allow hydration reaction occurring completely for fast hardness/strength development. Therefore, the new formulation was developed with the addition of hydroxyethyl cellulose (MW 90000).

Use of Ammonia, Cellulose and Latex Powder

[0184] FIG. 16 shows images of skim coat samples prepared by adding ammonia, cellulose and latex powder. The skim coat samples were observed to harden quickly and remained crack-free.

Example 5: Stages of Skim Coat Formulation Development

Stage: Initial Input from an Earlier Investigation

[0185] Skim Coat Formulation: [0186] Cement sand=40:60; add water to adjust to suitable viscosity

[0187] Remarks: [0188] Suitable for blank sample preparation; low binding power with PCM; soft and powdery after curing

Stage: Use of Dry PCM Capsule (Powder Form) in Formulation

[0189] Remarks: [0190] Issue: cannot distribute well in the skim coat, low strength and stability after exposure [0191] Solution 1: sieve to control particle size—still soft skim coat, low density [0192] Solution 2: switch to slurry form PCM and use ball milling method to incorporate PCM capsule powder—slurry form PCM—mid density, sometimes cracked; Ball milling skim coat—high density, but thermal property affected, sometimes cracked

Stage: Materials to Improve Strength, Stability and Consider

[0193] Skim Coat Formulation: [0194] Materials checked: Metakaolin (improve strength); Diatomite (fine powder, porous structure); Calcium carbonate (fine powder)

[0195] Remarks: [0196] Metakaolin tested at different ratios, no significant improvement observed [0197] Diatomite/Calcium carbonate/sand—Diatomite can stabilize PCM oil when mixing together, also fine particle size can improve skim coat strength [0198] Use a combination of diatomite and sand (1:2.4) to get both benefits

Stage: Materials That Can Improve Fire Resistance

[0199] Skim Coat Formulation: [0200] Expandable graphite

[0201] Remarks: [0202] Mixing with skim coat, no adversary effect on properties (strength, adhesion) observed.

Stage: Materials That Improve Substrate Adhesion and Provides Workability

[0203] Skim Coat Formulation: [0204] Redispersible latex powder

[0205] Remarks: [0206] Poor adhesion observed with PCM in the skim coat. [0207] Tested at different concentrations: 0.5%; 1%; 2% [0208] ˜2% is good concentration that improves adhesion to substrates

Stage: Materials That Neutralize Excessive Acid

[0209] Skim Coat Formulation: [0210] Ammonia solution

[0211] Remarks: [0212] pH of the slurry is not controlled well. A sample prepared earlier has a pH of 1 [0213] Low pH slurry affects the cement strength and results in cracks [0214] Adjust slurry pH to 6-7 before mixing with cement

Stage: Materials That Can Increase Water Retention Time and Minimize the Cracking

[0215] Skim Coat Formulation: [0216] Hydroxyethyl cellulose (MW 90000)

[0217] Remarks: [0218] Cracks were found to develop within a couple of hours after drying. [0219] Cellulose can improve water retention in cement; increase drying time to allow hydration reaction occurred completely for fast hardness/strength development; reduce the cracks formulation during drying [0220] 0.25% to cement tested—hard skim coat without cracks obtained

Example 6: Skim Coat Formulations

[0221] Skim coats in accordance with various embodiments disclosed herein were prepared with different concentrations of PCM (5 wt %-40 wt %). Two controls were used; control 1 contains fillers and additives while control 2 contains 40 wt % cement and 60 wt % sand (see FIG. 17). The concentration of PCM used was 5 wt %, 8 wt %, 10 wt %, 20 wt %, 30 wt % and 40 wt % respectively (see FIG. 18 and FIG. 19). The contents of the skim coat formulations are presented in Table 1 below.

TABLE-US-00001 TABLE 1 Skim coat with PCM capsules formulation Skim Coat Formulations Con- Con- PCM capsule wt % trol trol 40% 30% 20% 10% 8% 5% 1 2 PCM 105.9 79.5 53.0 27.7 21.4 15.0 0 0 capsule slurry (g) Containing: 40.0 30.0 20.0 10.0 8.0 5.0 0 0 PCM (g) Water in 65.9 49.5 33.0 17.7 13.4 10.0 0 0 PCM slurry (g) Cement (g) 40.0 40.0 40.0 40.0 40.0 40.0 40 40 Sand (g) 10 20.0 26.8 34.3 35.0 38.0 41 60 Diatomite 7.6 8.0 11.1 13.7 15.0 15.0 17 0 (g) Latex 2 2.0 2.0 2.1 2.0 2.0 2 0 Powder (g) Hydroxy- 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0 ethyl Cellulose (g) Water (g) 13 16.5 26.4 34 40 40 34 34 for workability Total water 78.9 66 59.4 51.7 53.4 50 34 34 (g) in paste Coverage 1.3 1.35 — — 1.6 1.5 1.7 1.9 (g paste/ cm.sup.3)

[0222] A unique skim coat formulation that is defect free and workable and meets the following requirements was successfully developed.

Requirements of Skim Coat

[0223] Appearance [0224] Tensile adhesion strength (14 days) [0225] Compressive strength (28 days) [0226] Accelerated weathering tests [0227] To ensure compliance with the standard specifications required for building works in Singapore, a skim coat is required to display sufficient tensile adhesion strength (14 days), compressive strength (28 days) and withstand accelerated weathering testing.

Additional Tests for Skim Coat with PCM

[0228] Temperature regulation effect [0229] Thermal conductivity [0230] Heat capacity

Example 7: Performance of Skim Coats

[0231] In this example, the performance (in terms of thermal conductivity, specific heat capacity (by volume), thermal regulation effect, mini house tests, total solar reflectance etc.) of the skim coats prepared in accordance with various embodiments disclosed herein was investigated. The results are provided as follows.

Thermal Conductivity

[0232] As shown in FIG. 20, the thermal conductivity of the skim coats decreases with increasing PCM content. A higher PCM content present in the skim coats imparts lower thermal conductivity and provides better insulation.

Specific Heat Capacity (By Volume)

[0233] As shown in FIG. 21, the heat capacity of the skim coats increases with increasing PCM content. A higher PCM content present in the skim coats imparts larger heat capacity and provides better thermal control.

Thermal Regulation Effect of PCM Skim Coats

[0234] Thermal regulation effect of PCM skim coats was investigated by measuring back surface temperature in a laboratory set up as shown in FIG. 22.

[0235] As shown in FIG. 23, the temperature change observed for 20% PCM skim coat (6 mm thickness) is ˜4° C.-5° C. lower and the temperature change observed for 30% PCM skim coat (6 mm thickness) is ˜6° C.-7° C. lower as compared to the controls. The thickness of the samples was measured at several points on the substrate and the measurements recorded were uniform at 6 mm.

[0236] The results show that PCM absorb the heat, imparts lower thermal conductivity and provides better insulation to the skim coats.

Mini House Tests/Cool Roof House Thermal Tests

[0237] Mini house tests or cool roof house thermal tests were carried out to measure air temperature in a laboratory set up as shown in FIG. 24.

[0238] The results obtained are provided in FIG. 25. As compared to a control, the back surface temperature observed for PCM skim coat prepared from cement and 20 wt % PCM having a thickness of 6 mm is ˜4° C. lower over a time period of more than 2 hours. It is therefore shown that heat (for e.g., exterior heat) is absorbed by the PCM skim coat which leads to lower interior temperature and cooler interior air (see step 2604 of FIG. 26).

Total Solar Reflectance of Skim Coat

[0239] PCM skim coats were coated with cool coatings and their total solar reflectance were compared with PCM skim coats that were not coated with cool coatings (FIG. 26 and FIG. 27).

[0240] It was observed from FIG. 28 that the skim coat with PCM shows high TSR even without being coated with commercial cool coatings.

Thermal Regulation Effect of PCM Skim Coat With/Without Cool Coatings

[0241] Experiments were conducted to compare the back surface temperature difference of PCM skim coats containing different PCM content (i.e. 8 wt % PCM and 30 wt % PCM) that are not coated with cool paint with those that are coated with cool paint (FIG. 29).

[0242] A 2° C. difference of back surface temperature was observed between PCM skim coat having 8 wt % PCM that is coated with cool paint and PCM skim coat having 8 wt % PCM that is not coated with cool paint due to differences in their TSR. Similar back surface temperature was observed for PCM skim coat having 30 wt % PCM that is coated with cool paint and PCM skim coat having 30 wt % PCM that is not coated with cool paint as their TSR are similar. [0243] Advantageously, various embodiments of the method disclosed herein provides a highly compatible process for PCM encapsulation. [0244] Embodiments of the method disclosed herein are scalable and allows silica based PCM capsules to be produced at a low cost with good cycling performance. [0245] PCM skim coat formulations were developed with good thermal regulation effect. [0246] Interestingly, the skim coat with PCM shows high TSR even without being coated by cool coatings.

Example 8: Further Tests and Work

[0247] The skim coat formulations and skim coats prepared in accordance with various embodiments disclosed herein were subjected to the following tests: [0248] Compressive strength and flexural strength [0249] Outdoor exposure test to check the performance in actual conditions [0250] Scale up PCM skim coat for additional tests (to comply with standard specifications required for building works in Singapore) and perform large scale field studies (FIG. 30)

Example 9: Production of Robust Capsules Encapsulating CrodaTherm 29

[0251] Procedure for lab scale production of capsules encapsulating CrodaTherm 29 is described below.

[0252] The composition can be proportionately increased for scaling up to 50 kg. It will be appreciated that stirring speed will be different (slower) at larger reactors. Normally, stirring speed is adjusted to obtain the PCM droplet size in the range of 3-10 micrometers (monitored by sampling and checking under a microscope). [0253] 1. Triton X-100 (13.71 g) is added in a vial, followed by calcium chloride (0.33 g) and CrodaTherm 29 (76.41 g). [0254] 2. The above mixture is dissolved in ethanol/DI water in the ratio of 1:3 (150 ml:450 ml). [0255] 3. The mixture is stirred with overhead stirrer (slowly increased to 1000 rpm) and heated at 40° C. for at least 60 minutes. [0256] 4. 4.0 M HCl solution was used to adjust the pH to about 4. [0257] 5. The emulsion was stirred until droplet size reaches about 5-20 um (about 1.5 hrs). [0258] 6. TEOS (51.75 ml) was infused using syringe pump at 0.1 ml/min. [0259] 7. The reaction was left to stirred for 1 day (˜700 rpm) and monitored using microscope. [0260] 8. Upon completion of reaction, the suspension was filtered and washed with DI water and collected.
CrodaTherm 29 (CM29) may also be replaced by other phase change materials such as OM29 (i.e. fatty acid mixtures), OM28p (i.e. paraffin mixtures) and SL28 (i.e. fatty acid ester mixtures).

APPLICATIONS

[0261] Various embodiments of the present disclosure provide a strategy to formulate PCM slurry directly into a skim/plaster coat with appropriate additives.

[0262] Various embodiments of the composition and method disclosed herein allow for good adhesion to substrate with optimum temperature effects for e.g. a good balance between the temperature control and coating properties.

[0263] Various embodiments of the composition and method disclosed herein allow for commercially available additives to be added to give defect free surface of the coating.

[0264] Various embodiments of the composition and method disclosed herein allow for the provision of a coating that withstands weathering effects in Singapore.

[0265] Various embodiments of the composition and method disclosed allow for different PCM capsules with different phase transition temperature can be incorporated into the formulation.

[0266] Various embodiments of the composition and method disclosed herein may be used for other type of coatings other than skim coat for building energy efficiency and saving strategies. For example, the embodiments of the composition and method disclosed herein be applicable for recast cement panels or boards, precast light weight concrete panel (wet area and dry areas—hollow core and solid), food delivery insulation box, insulation board/foam/foam board, and/or refrigerator/food vending machine.

[0267] It will be appreciated by a person skilled in the art that other variations and/or modifications may be made to the embodiments disclosed herein without departing from the spirit or scope of the disclosure as broadly described. For example, in the description herein, features of different exemplary embodiments may be mixed, combined, interchanged, incorporated, adopted, modified, included etc. or the like across different exemplary embodiments. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.