TECHNICAL FIELD

The present disclosure relates to polymers, and in particular to nanometer sized particles of boron or metallic nano-particles in polymer mixtures or polymer coatings.

BACKGROUND

Sealants are used in various industries, such as the automotive and appliance industries, in order to fill the gaps between joining parts, inhibit fluid leakage, seal the air/water/temperature in the interior of white goods and prevent damage caused by exterior forces, such as friction and/or wind. For example, an automotive sealant can be used as a windshield seal, hood seal, door mounted seal, trunk seal, and so on, and an appliance sealant can be used to seal opening of dishwashers, dryers, washing machines, refrigerators, and the like. Durability, strength, and resistance against environmental factors are important characteristics, as well as resistance to deformation, high UV durability, lower prices, resistance to microorganisms, and aesthetics.

Sealants can be prone to temperature changes and mechanical effects depending on their application. Particularly, the automotive sealants may be exposed to extreme temperature conditions as well as mechanical vibration resulting in cracking and deformation or color fading. The physical damage on sealants during their use or storage not only degrades the performance of the sealant itself but also negatively affects the automobile functionality.

Thus, there is still a need in the art for a readily available and enhanced polymer or polymer coating to provide durability, strength, and stain resistance as well as photocatalytic properties, and an efficient process for preparing such a polymer or polymer coating, particularly one that can be photocatalytically active within the visible light range.

BRIEF DESCRIPTION The present disclosure provides a novel and high performance polymer (or polymer coating) composed of nanometer- sized particles of boron or metallic nano-particles, which is referred to hereinafter as“nano-boron”. The nano-boron polymer of the present disclosure eliminates or reduces the above-mentioned shortcomings of prior synthetic rubber sealants (e.g., Thermo Plastic Elastomers, such as Ethylene Propylene Diene Terpolymer (EPDM)) and provides a stronger and enhanced photocatalytic activity or property, which enables improved durability and stain resistance for a synthetic sealant as well as potential self healing ability in the presence of additional capsulated agents.

In one embodiment, a nano-boron polymer composite is comprised of a vulcanized synthetic rubber formed from mixing and heating: between 25 - 45 wt% of an elastomer; between 20 - 40 wt% of carbon black; between 1 - 30 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 2 - 4 wt% of an activator; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or metallic nano-particles.

In another embodiment, a nano-boron polymer composite is comprised of a vulcanized synthetic rubber formed from mixing and heating: a polymer mixture at about 75 degrees Celsius, the polymer mixture including: between 25 - 45 wt% of ethylene propylene diene monomer (EPDM); between 1 - 30 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or metallic nano-particles, wherein the nano-boron particles or metallic nano-particles have a particle size of about 50 nm. The polymer mixture is mixed with between 20 - 40 wt% of carbon black at about 80 degrees Celsius, and with between 2 - 4 wt% of an activator at about 90 degrees Celsius.

In yet another embodiment, a synthetic rubber sealant including a nano-boron polymer composite as described above is disclosed.

Also described herein is a process for preparing a nano-boron polymer of the present disclosure. In one embodiment, a process for preparing a nano-boron polymer composite is comprised of mixing a polymer mixture at a first temperature, the polymer mixture including: between 25 - 45 wt% of an elastomer; between 1 - 30 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or nano-boron compound particles. The process further includes adding and mixing between 20 - 40 wt% of carbon black to the polymer mixture at a second temperature higher than the first temperature, and adding and mixing between 2 - 4 wt% of an activator to the polymer mixture and carbon black at a third temperature higher than the second temperature.

Beneficially, the nano-boron polymer and process for preparing the polymer as disclosed herein have resulted in a stronger and more durable enhancing photocatalytic activity through boron serving as a p-type dopant. With the addition of nano-boron as a dopant photocatalyst, the nano-boron containing polymer composite further helps remove stain formation. Hence, photocatalytic activity enhancement through nano-boron addition is advantageous against both stain formation and bacteria growth. Furthermore, we have observed that the addition of nanoboron resulted in deeper black color after exposure to UV light as compared to the baseline sealant. There is also a potential to enhance self healing ability (such as repair of micro-cracks in the presence of nanoboron) when the appropriate capsules are added into the polymer matrix in the presence or absence of the nanoboron particles.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings. Unless noted, the drawings may not be drawn to scale.

FIG. 1 illustrates a process for preparing a nano-boron polymer in accordance with an embodiment of the present disclosure.

FIG. 2 shows a graph of results from tearing tests on nano-boron polymer examples in accordance with an embodiment of the present disclosure.

FIGS. 3 and 4 show graphs of results from plastic deformation tests on nano-boron polymer examples in accordance with an embodiment of the present disclosure. FIGS. 5 and 6 show graphs of results from friction tests on nano-boron coating examples in accordance with embodiments of the present disclosure.

FIG. 7 shows a graph of results from a wearing test on nano-boron coating examples in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION

Nano-Boron Polymer Composites

In accordance with an embodiment as described herein, a nano-boron polymer composite is comprised of a vulcanized synthetic rubber formed from mixing and heating: between 25 - 45 wt% of an elastomer; between 20 - 40 wt% of carbon black; between 1 - 30 wt% of silica preferably 1 - 10 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 2 - 4 wt% of an activator; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or nano-boron compound particles.

In accordance with further embodiments, the nano-boron polymer composite as described above may have any one of the following components or elements, which may be alternatives that can be combined in various applicable and functional combinations: the elastomer is ethylene propylene diene monomer (EPDM); the activator is selected from the group consisting of zinc oxide, stearic acid, and a combination thereof; the accelerator is comprised of sulfur; the synthetic rubber is formed from mixing and heating between 0.1 - 1 wt% of nano-boron particles or nano-boron compound particles; the synthetic rubber is formed from mixing and heating between 0.1 - 0.5 wt% of nano-boron particles or nano-boron compound particles; the nano-boron particles or metallic nano-particles have an average particle size between about 50 nm and about 100 nm; the elastomer, silica, whitening, paraffinic processing oil, accelerator, and nano-boron particles or metallic nano-particles are heated at 75 degrees Celsius; the carbon black is heated at 80 degrees Celsius; the activator is heated at 90 degrees Celsius; the nano-boron compound includes a boron oxide; and any applicable combination thereof. Table 1 below shows weight percentage ranges for the components of the nano-boron polymer composite in accordance with an embodiment of the present invention.

According to another embodiment as described in the present disclosure, a nano-boron polymer composite is comprised of: a nano-boron polymer composite is comprised of a vulcanized synthetic rubber formed from mixing and heating: a polymer mixture at about 75 degrees Celsius, the polymer mixture including: between 25 - 45 wt% of ethylene propylene diene monomer (EPDM); between 1 - 30 wt% of silica, preferably 1 - 10 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or metallic nano-particles, wherein the nano-boron particles or nano-boron compound particles have a particle size of about 50 nm. The polymer mixture is mixed with between 20 - 40 wt% of carbon black at about 80 degrees Celsius, and with between 2 - 4 wt% of an activator at about 90 degrees Celsius. Synthetic Rubber Sealants

Another embodiment as described in the present disclosure pertains to a synthetic rubber sealant comprised of a nano-boron polymer composite, according to any one of the descriptions above.

In accordance with further embodiments, the synthetic rubber sealant as described above, may be formed as a sealant for an automobile part or an appliance part.

General Preparation Process

Referring now to FIG. 1, a method 100 for preparing a nano-boron polymer as described herein is provided in accordance with embodiments of the present disclosure. Method 100 includes at step 102, mixing a polymer mixture at a first temperature, the polymer mixture including: between 25 - 45 wt% of an elastomer; between 1 - 30 wt% of silica, preferably 1 - 10 wt% of silica; between 7 - 10 wt% of whitening; between 10 - 13 wt% of paraffinic processing oil; between 1 - 3 wt% of an accelerator; and between 0.1 - 10 wt% of nano-boron particles or nano-boron compound particles. Method 100 further includes at step 104, adding and mixing between 20 - 40 wt% of carbon black to the polymer mixture at a second temperature higher than the first temperature. Method 100 further includes at step 106, adding and mixing between 2 - 4 wt% of an activator to the polymer mixture and carbon black at a third temperature higher than the second temperature. Step 108 illustrates the formation of a nano-boron polymer from the mixing and heating of the reactants. The plurality of nano-boron particles may be substantially pure boron or a combination of substantially pure boron and boron compounds.

In accordance with further embodiments, the methods of preparing a nano-boron polymer composite as described above may include any one of the following, which may be alternatives that can be combined in various applicable and functional combinations: the elastomer is ethylene propylene diene monomer (EPDM); the accelerator is comprised of sulfur; the activator is selected from the group consisting of zinc oxide, stearic acid, and a combination thereof; between 0.1 - 1 wt% of nano-boron particles or metallic nano-particles are included in the polymer mixture; between 0.1 - 0.5 wt% of nano-boron particles or nano- boron compound particles are included in the polymer mixture; the nano-boron particles or metallic nano-particles have an average particle size between about 50 nm and about 100 nm; the first temperature is about 75 degrees Celsius, the second temperature is about 80 degrees Celsius, and the third temperature is about 90 degrees Celsius; further comprising mixing and heating the polymer mixture, carbon black, and activator at a fourth temperature higher than the third temperature; the fourth temperature is about 105 degrees Celsius; and any applicable combination thereof.

Advantageously, the nano-boron polymers of the present disclosure and methods for forming the nano-boron polymers eliminate or reduce the above-mentioned shortcomings of prior synthetic rubber sealants and provides a stronger polymer with enhanced photocatalytic activity or property, which enables improved durability and stain resistance for a synthetic sealant.

Examples

Example 1: Preparation of nano-boron polymer composites

Nanometer- sized particles of boron (nano-boron) with 99% purity, bulk density of 1.73 g/cm3, melting point of 2400 degrees Celsius, hardness of 9.5 (Mohs hardness scale), and average particle size of 50 nm were obtained from NaBond Technologies Corporation, China.

Five different polymer composite mixtures were prepared, with each mixture prepared to have a total weight of 1,350 grams. Different quantities of nano-boron were added to four polymer mixtures to provide different nano-boron wt% concentrations. Table 2 below lists the components of the prepared polymer mixtures. Table 2

In order to homogeneously disperse the nano-boron particles and other components, the sample mixtures were continuously stirred and heated. The polymer mixture including nano boron particles, EPDM, silica, whitening, paraffinic processing oil, and accelerator, as noted above in Table 2 for mixtures 1 - 5, were mixed at 75 degrees Celsius for 30 seconds in a rubber mixer. Then, carbon black was added and mixed with the polymer mixture at 80 degrees Celsius for 50 seconds in the rubber mixer. Then, activators were added and mixed with the polymer mixture at 90 degrees Celsius for 30 seconds in the rubber mixer. The rubber mixer was cleaned for 20 seconds to make sure that all the mixing components are completely removed homogeneously from the mixer, and then the entire mixture was mixed again for 10 seconds. The mixture was then rolled in a rolling machine and finally pressed in a press machine to produce sample sheets.

Prepared polymer sample sheets were tested for tearing resistance and plastic deformation.

Example 2: Resistance to Tearing

Prepared polymer sample sheets 01 - 05 were formed from mixtures 1 - 5 (Example 1), respectively, and were tested for tearing resistance. These samples were pressed for 7 minutes at 195 degrees Celsius in the press machine. The tearing tests were done three times, and the average maximum force applied prior to tearing and standard deviations for the measurements are shown in Table 3 below.

Table 3: Tearing Test

FIG. 2 compares resistance to tearing of the polymer samples Sample 01 - Sample 05 formed from the mixtures in Example 1. The equation of the trend line was calculated to be y = 0.4463x + 6.381. The slope is positive, and thus an increase in the maximum force for tearing is observed as the mass of nano-boron is increased in the otherwise common mixture. The correlation coefficient was found as R = 0.95277, and thus the relationship between the maximum force for tearing and the mass of nano-boron is almost linear. Accordingly, it can be observed that a greater force is required to tear the test sample when there is more nano boron in the mixture. Example 3: Plastic Deformation

The test specimens were pressed for 15 minutes at 195 degrees Celsius in the pressing machine. The prepared polymer samples were each tested three times for plastic deformation, and the percentage of deformation and standard deviations for the initial height and final height measurements are shown in Table 4 below. Table 4: Plastic Deformation

FIGS. 3 and 4 show graphs of results from plastic deformation tests on nano-boron polymer samples Sample 01 - Sample 05 from mixtures 1 - 5 of Example 1, respectively, in accordance with an embodiment of the present disclosure.

FIG. 3 shows a bar graph of the initial and final heights of disk samples, which were placed between two metal layers and compressed by 25% and left in a cabinet for 24 hours. The equation of the initial height graph was calculated to be y = - 0.0033x + 21.585. The slope is negative, which means a decreasing trend. The equation of the final height graph was calculated to be y = 0.0l07x + 21.288. The slope is positive, which means an increasing trend. Also both of the correlation coefficients, which are R ² = 0.0762 and R ² = 0.2599, respectively, show that the graphs are not linear. The final height of a sample, when there is nano-boron in the mixture, is higher than the final height of the original mixture.

FIG. 4 shows a bar graph of the percentage amount of plastic deformation from the deformation test. This graph shows the relationship between the plastic deformation and the mass of boron nanopowder. The equation of this graph is y = - 0.49x + 10.018 and has a negative slope which means a decreasing trend. The correlation coefficient of the graph, which is R ² = 0.598, shows that the relationship between the amount of plastic deformation and the mass of boron nanopowder is not linear. The lowest plastic deformation was obtained when there was 5.4 grams of boron nanopowder in the mixture. Also the mixtures including boron nanopowder have lower plastic deformations compared to the original mixture. Therefore, it can be observed that mixtures including nano-boron particles are more elastic than the original mixture.

Nanoboron Coatings

The addition of boron nanopowder and metallic nano-particles into a coating material for a polymer, such as a sealant, was also investigated. Three different coating materials were prepared. A first coating material was comprised of a standard coating material including a water based silicone material having a 30% solids content and a black color. A second coating material was comprised of 200 grams of the standard coating material and 1 gram of boron nanopowder. A third coating material was comprised of 200 grams of the standard coating material and 1 gram of boron oxide.

In one example, a primer was applied onto a polymeric surface to which the coating materials were to be applied to provide for adhesion between the polymeric surface and the coating material. After applying the primer, the polymeric surface was heated with a heat gun, for example, to about 90 degrees Celsius. The coating material was then applied using a sprayer and the sample heated to 125 degrees Celsius and cured for 2.5 minutes.

Static and dynamic friction tests were done on the coating materials noted above, the results of which are provided below in Table 5 and Table 6. FIGS. 5 and 6 show graphs based on the results in Table 5 and Table 6, respectively, from friction tests on nano-boron coating examples in accordance with embodiments of the present disclosure.

The weight used for these tests was 200 grams (which is the weight of the sledge). The sledge velocity was 300 mm/min. Surface temperature was 21.20DC. The test distance was 100 mm. The addition of boron nanopowder into the coating material generally increased the coefficient of static and dynamic friction. The highest values were obtained when there was boron nanopowder in the coating material. The lowest value was obtained when there was no other addition in the standard coating material.

For the three coating materials noted above, Table 5 includes average static friction coefficients, standard deviation of the static friction coefficients, average dynamic friction coefficients, and standard deviation of the dynamic friction coefficients. As the graph in FIG. 5 indicates, the addition of boron oxide and boron nanopowder in the coating material increased both coefficients of static and dynamic friction increased as compared to the standard coating material.

For coating materials having different amounts of nanoboron and metallic nano-particles Table 6 includes average static friction coefficients, standard deviation of the static friction coefficients, average dynamic friction coefficients, and standard deviation of the dynamic friction coefficients. As the graph in FIG. 6 indicates, as the mass percentage of the boron oxide in the coating material increased, both coefficients of static and dynamic friction increased as well.

Table 5: Static and Dynamic Friction

Table 6: Static and Dynamic Friction - Different Nanoboron Amounts

Wear tests to analyze the amount of abrasion were performed on the coating materials noted above, the results of which are provided below in Table 7. FIG. 7 shows a graph of wearing percentages based on the results in Table 7 from the wear tests on nano-boron coating examples in accordance with embodiments of the present disclosure.

Table 7: Wear Tests - Different Nanoboron Amounts

As the wear test results show, the amount of worn material decreases in both wet and dry wearing when boron oxide is added to the coating material.

The foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been disclosed with reference to embodiments, the words used herein are intended to be words of description and illustration, rather than words of limitation. While the present invention has been described with reference to particular materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein. For example, the various components or reactants that make up the nano-boron polymer or the various components that describe the polymer or preparation methods disclosed above can be alternatives which may be combined in various applicable and functioning combinations within the scope of the present invention. Rather, the present invention extends to all functionally equivalent structures, materials, and uses, such as are within the scope of the appended claims. Changes may be made, within the purview of the appended claims, as presently stated and as may be amended, without departing from the scope and spirit of the present invention. All terms used in this disclosure should be interpreted in the broadest possible manner consistent with the context.