Reinforced Polymer Coating

Abstract

A coating is made by mixing an amine-terminated polymer precursor; an aromatic polyisocyanate polymer precursor; and nanotubes in the head of a spray gun and spraying the mixture onto a substrate.

Claims

1. A method of making a coating, comprising the steps of providing a mixture comprising an amine-terminated polymer precursor; an aromatic polyisocyanate polymer precursor; and nanotubes in the head of a spray gun; and spraying the mixture onto a substrate.

2. The method of claim 1, wherein the aromatic polyisocyanate polymer precursor comprises isotoluene diisocyanate.

3. The method of claim 1, wherein the aromatic polyisocyanate polymer precursor comprises methylene diphenyl diisocyanate.

4. The method of claim 3, wherein the aromatic polyisocyanate polymer precursor comprises methylene diphenyl 4,4-diisocyanate.

5. The method of claim 1, wherein the amine-terminated polymer precursor comprises a primary amine.

6. The method of claim 1, wherein the nanotubes are inorganic nanotubes, preferably phyllosilicate nanotubes.

7. The method of claim 6, wherein the nanotubes are at least one of halloysite, sepiolite, or palygorskite nanotubes.

8. The method of claim 7, wherein the nanotubes are natural halloysite nanotubes.

9. The method of claim 7, wherein the nanotubes are modified halloysite nanotubes.

10. The method of claim 8, wherein the halloysite is present in the metahydrate form.

11. The method of claim 8, wherein the halloysite is present in the Endellite form.

12. The method of claim 8, wherein the halloysite nanotubes have an average length of at least 7.5 m.

13. The method of claim 8, wherein the halloysite nanotubes have an aspect ratio of at least 75.

14. The method of claim 1, wherein the nanotubes are negatively charged at the external surface of the tube and positively charged at the internal surface of the tube.

15. The method of claim 1, further comprising the step, before the step of providing the mixture in the head of the spray gun, of dispersing the nanotubes in the amine-terminated polymer precursor to create a dispersion.

16. The method of claim 1, wherein the mixture is heated to a temperature in the range 60-90 C.

17. The method of claim 1, wherein the ratio of unreacted amine groups in the amine-terminated polymer precursor to unreacted polyisocyanate groups in the aromatic polyisocyanate polymer precursor lies in the range 2:1 to 1:2.

18. The method of claim 1, wherein the aromatic polyisocyanate polymer precursor comprises polyol monomers and/or polyurethane.

19. A coating comprising a polyurea matrix having halloysite nanotubes embedded therein, the halloysite nanotubes having an aspect ratio of at least 75.

20. A coating comprising a polyurea matrix having halloysite nanotubes embedded therein, the halloysite nanotubes having a mean average length of at least 7.5 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The invention will now be described by way of example with reference to the following figures in which:

[0045] FIG. 1 shows a graph of differential scanning calorimetry data obtained from different samples;

[0046] FIG. 2 shows a graph of thermogravimetric data obtained from different samples;

[0047] FIG. 3 shows a scanning electron micrograph of the surface of Example 2;

[0048] FIG. 4A shows a scanning electron micrograph of thin and long halloysite nanotubes with aspect ratio more than 50, the halloysite being available as Ultrahallopure from I-Minerals Inc.;

[0049] FIG. 4B shows a scanning electron micrograph of thin and long halloysite nanotubes with aspect ratio more than 50, the halloysite being available as patch halloysite from Western Australia.

[0050] FIG. 4C shows a scanning electron micrographs of thin and long halloysite nanotubes with aspect ratio more than 50, the halloysite being available as patch halloysite from Western Australia.

[0051] FIG. 4D shows a scanning electron micrographs of thin and long halloysite nanotubes with aspect ratio more than 50, the halloysite being available as patch halloysite from Western Australia.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0052] Reinforced polyurea samples were prepared as follows: [0053] a. Halloysite nanotubes were mechanically mixed with a polyetheramine-based polymer precursor mixture (Component B) for four hours; [0054] b. The polyetheramine-based polymer precursor mixture, including the dispersed nanotubes is fed to a spray system (Graco H-XP3), along with a diisocyanate-based mixture (Component A). Component A and Component B are fed into the spray system in a 1:1 ratio by weight; [0055] c. The two components are made to travel along 15 m of reactor-heated hose (or 122 m of reactor-heated hose, in the case of Examples 5 and 6) and are mixed in the head of a hot gun located at the outlet of the hose. The mixture is brought to a temperature in the range 65-75 C. and is sprayed onto a substrate at a pressure in the range 17-21 MPa. The gelling time of the mixture is around 15 seconds.

[0056] The properties of the halloysite nanotubes are set out in Tables 1 and 2, while the properties and composition of Components A and B are set out in Tables 3 and 4 (Table 4 shows the preferred composition for Components A and B).

Examples

[0057] Example 1 contained 2.5 wt % halloysite nanotubes from Applied Minerals Inc.

[0058] Example 2 contained 5 wt % halloysite nanotubes from Applied Minerals Inc.

[0059] Example 3 contained 7.5 wt % halloysite nanotubes from Applied Minerals Inc.

[0060] Example 4 contained 10 wt % halloysite nanotubes from Applied Minerals Inc.

[0061] Example 5 contained 5 wt % patch halloysite nanotubes from Western Australia

[0062] Example 6 contained 5 wt % Ultra Hallopure halloysite nanotubes from I-Minerals.

[0063] Comparative Example 1 contained no halloysite nanotubes.

Tensile Strength and Tear Strength Testing

[0064] Dog bone-shaped samples for tensile strength and tear strength testing were prepared using metallic cutters, using a pneumatic cut machine based on ISO 37 for tensile testing and one based on ASTM 624 C for tear strength testing.

[0065] Tensile strength and tear strength tests were performed on 10 samples for each composition and test type, using an Instron 5596 universal testing machine.

[0066] The results are given in Table 5.

Hardness Testing

[0067] The shore A hardness of polyurea samples containing with different percentages of halloysite nanotubes was evaluated using a digital hardness shore A durometer in line with ASTM D2240. 10 measurements were carried out on each sheet, to obtain the average hardness.

[0068] The results are given in Table 5.

Thermal Properties

[0069] The thermal properties of polyurea nanocomposite samples containing different percentages of halloysite nanotubes were evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

[0070] Differential scanning calorimetry was carried out using a DSC-7 calorimeter from Perkin Elmer, Inc. fitted with a refrigerated cooler. The samples were heated from 20 C. to 360 C. at a rate of 10 C./min under a nitrogen flow of 20 mL/min. Each sample weighed between 6.1 and 6.7 mg, and was put in an aluminium crucible and closed by pressing an aluminium cap.

[0071] The results are shown in FIG. 1, from which it can been seen that the thermograms for Examples 1-4 and Comparative Example 1 all have a distinctive peak at about 330 C. This indicates that the presence of halloysite nanotubes would not be expected to have a significant effect on the heat flow in polyurea samples during manufacturing.

[0072] Thermogravimetric analysis was carried out by heating the samples from 25 C. to 700 C. at a rate of 10 C./min under a nitrogen atmosphere followed by heating the samples from 700 C. to 900 C. at a rate of 10 C./min under an oxygen atmosphere.

[0073] The results are shown in FIG. 2, from which it can be seen that there is good overlap between the curves obtained from Examples 2 and 3 and Comparative Example 1 (the additional peak observed at about 700 C. in the derivative mass curves for Examples 2 and 3 is due to the char residue from the halloysite nanotubes). This shows that the presence of halloysite nanotubes does not affect the thermal stability or decomposition temperature of polyurea samples.

Scanning Electron Microscopy

[0074] FIG. 3 shows that the halloysite nanotubes are dispersed within the polyurea matrix, rather than being present in clumps.

TABLE-US-00001 TABLE 1 Average Average Surface Average inner external Average area length diameter diameter lumen space Aspect Density Nanofiller (m.sup.2/g) (nm) (nm) (nm) volume (%) ratio (g/cm.sup.3) Halloysite 65 500 20 50 22 9 2.53 nanotubes (Examples 1-4)

TABLE-US-00002 TABLE 2 Range of Range of Range of Surface Range of Inner External Range of Range of area length diameter diameter lumen space aspect Density Nanofiller (m.sup.2/g) (nm) (nm) (nm) volume (%) ratio (g/cm.sup.3) Halloysite 40-80 500-30,000 5-20 20-200 15-40 >15 2.53 nanotubes (Examples 5 and 6)

TABLE-US-00003 TABLE 3 Properties and composition of Components A and B (Examples 1-4 and Comparative Example 1) Name of product Component A Component B Chemical 4,4 Methylene Diphenyl Jeffamine D2000 ingredients Diisocyanate, 20-30 wt % Polyetheramine, 50-60 wt % Toluene Diisocyanate - Jeffamine T5000 Polytetramethylene Etl Polyetheramine, 3-10 wt % Glycol, (PTMEG) Diethyltoluenediamine, 50-70 wt % 20-30 wt % Propylene carbonate, Carbon black N550, 5-9 wt % 01-1 wt % Viscosity 1.800 0.1 0.225 0.025 (Pa .Math. s)

TABLE-US-00004 TABLE 4 Properties and composition of Components A and B (Examples 5 and 6). Name of product Component A Component B Chemical MDI (methylene diphenyl Jeffamine D2000 ingredients diisocyanate) prepolymer, Polyetheramine, 65 wt % 32 wt % with NCO of 18.7 Jeffamine T5000 TDI (toluene diisocyanate) Polyetheramine, 5 wt % prepolymer, 63 wt % with Jeffamine D-230 NCO of 15.5 Polytheramine, 6 wt % Propylene carbonate, Ethacure 100 19 wt % 5 wt % Tegoamin BDE, 1 wt % Tinuvin 1130, 2 wt % Tinuvin 292, 2 wt % Carbon black N550, 01-1 phr Viscosity 1.800 0.1 0.225 0.025 (Pa .Math. s)

TABLE-US-00005 TABLE 5 Tensile Hardness Modulus Modulus Modulus Tear strength Maximum (Shore at 0.7 at 1.4 at 2.1 Strength (MPa) Elongation % A) (MPa) (MPa) (MPa) (N/mm) Comparative 9 1 384 26 92 2 5 0.5 7 0.5 8 0.5 72 4 Example 1 Example 2 21 2 478 25 99 2 9 1 12 2 15 2 120 5 Example 5 27 5 520 32 99 2 9 1 12 2 15 2 135 8 Example 6 30 2 504 25 99 2 10 1 14 2 16 2 130 7 % increase of 143 24 9 69 76 88 67 Example 2 relative to Comparative Example 1 % increase of 200 35 8 80 71 88 88 Example 5 relative to Comparative Example 1 % increase of 233 31 8 100 100 100 81 Example 6 relative to Comparative Example 1