Polymer-Encapsulated Carbon Nanotube: Process for Its Preparation and Use Thereof

Abstract

A process for preparing a polymer-encapsulated carbon nanotube material is described. The process comprises a suspension polymerization process involving a carbon nanotube material. The process can also involve a charge control agent. The polymer-encapsulated carbon nanotube material has particles size in the micron range. The material can be used in toner applications.

Claims

1. A process for preparing a toner material, wherein the process comprises a suspension polymerization process involving a carbon nanotube material and a charge control agent that is free of any chemical group which reacts with radicals, wherein the charge control agent is at a concentration of about 0.01 to 0.03 wt % relative to the suspension polymerization mixture.

2. (canceled)

3. (canceled)

4. The process according to claim 1, wherein the charge control agent is free of any carbonyl group or thiocarbonyl group.

5. The process according to claim 1, wherein the charge control agent is modified with boron.

6. (canceled)

7. A process for preparing a polymer-encapsulated carbon nanotube material, comprising: (a) preparing a first mixture or dispersed phase comprising monomers of at least one type, a cross-linker, an initiator and a charge control agent; (b) preparing a second mixture or continuous phase comprising a polymeric alcohol, a stabilizer and a carbon nanotube material; and (c) mixing the dispersed phase with the continuous phase to obtain a suspension polymerization mixture which leads to the polymer-encapsulated carbon nanotube material.

8. The process according to claim 7, wherein step (a) comprises a step of adding the charge control agent to a mixture comprising the monomers, the cross-linker and the initiator.

9. The process according to claim 7, wherein step (b) comprises heating to a temperature of about 50 to 90 C.

10. The process according to claim 7, wherein step (c) comprises adding the dispersed phase to the continuous phase, drop by drop, under stirring.

11. The process according to claim 7, wherein step (c) comprises heating to a temperature of 50 to 90 C. for about 5 to 9 hours.

12. The process according to claim 7, wherein step (c) further comprises, after step (c), a step of cooling to room temperature (d).

13. The process according to claim 7, wherein the charge control agent is free of any chemical group which reacts with radicals.

14. The process according to claim 7, wherein the charge control agent is free of any carbonyl group or thiocarbonyl group.

15. The process according to claim 7, wherein the charge control agent is modified with boron.

16. The process according to claim 7, wherein the charge control agent is at a concentration of about 0.01 to 0.03 wt % relative to the suspension polymerization mixture.

17. The process according to claim 7, wherein the monomers are styrene and butyl acrylate, the cross-linker is divinyl benzene (DVB), the initiator is Benzyl peroxide BP, the charge control agent is benzyltributylammonium-4-hydroxyl-naphtalene-1-sulfonate (MEP-51), the polymeric alcohol is poly vinyl alcohol (PVA), and the stabilizer is Sodium n-dodecyl sulfate (SDS).

18. A polymer-encapsulated carbon nanotube material obtained by a process which comprises: (a) preparing a first mixture or dispersed phase comprising monomers of at least one type, a cross-linker, an initiator and a charge control agent; (b) preparing a second mixture or continuous phase comprising a polymeric alcohol, a stabilizer and a carbon nanotube material; and (c) mixing the dispersed phase with the continuous phase to obtain the polymer-encapsulated carbon nanotube material.

19. The polymer-encapsulated carbon nanotube material according to claim 18, wherein the monomers are styrene and butyl acrylate, the cross-linker is DVB, the initiator is BPO, the charge control agent is MEP-51, the polymeric alcohol is PVA, and the stabilizer is SDS.

20. The polymer-encapsulated carbon nanotube material according to claim 18, having particles size in the range of the micron.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] Example embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which:

[0034] FIG. 1 illustrates the conversion of the monomers versus the charge control agent (MEC-88) concentration.

[0035] FIG. 2 illustrates the chemical structure of MEC-88.

[0036] FIG. 3 presents a scanning electron microscope (SEM) micrograph for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEC-88 concentration of 0.42 wt % (0.102 g; Sample 1, Table 14).

[0037] FIG. 4a, FIG. 4b and FIG. 4c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEC-88 concentration of 0.28 wt % (0.068 g; Sample 2, Table 14).

[0038] FIG. 5a, FIG. 5b and FIG. 5c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEC-88 concentration of 0.14 wt % (0.034 g; Sample 3, Table 14).

[0039] FIG. 6a, FIG. 6b and FIG. 6c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEC-88 concentration of 0.07 wt % (0.017 g; Sample 4, Table 14).

[0040] FIG. 7a, FIG. 7b and FIG. 7c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEC-88 concentration of 0.05 wt % (0.011 g; Sample 5, Table 14).

[0041] FIG. 8 illustrates the conversion of the monomers versus the charge control agent (MEP-51) concentration.

[0042] FIG. 9 illustrates the chemical structure of MEP-51.

[0043] FIG. 10 presents a scanning electron microscope (SEM) micrograph for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEP-51 concentration of 0.42 wt % (0.102 g; Sample SP-CNT-D-MEP-51-1, Table 15).

[0044] FIG. 11a, FIG. 11b and 11c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEP-51 concentration of 0.28 wt % (0.068 g; Sample SP-CNT-D-MEP-51-2, Table 15).

[0045] FIG. 12a, FIG. 12b and 12c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEP-51 concentration of 0.14 wt % (0.034 g; Sample SP-CNT-D-MEP-51-3, Table 15).

[0046] FIG. 13a, FIG. 13b and 13c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEP-51 concentration of 0.07 wt % (0.017 g; Sample SP-CNT-D-MEP-51-4, Table 15).

[0047] FIG. 14a, FIG. 14b and 14c present scanning electron microscope (SEM) micrographs for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at a MEP-51 concentration of 0.05 wt % (0.011 g; Sample SP-CNT-D-MEP-51-5, Table 15).

[0048] Other features of the present embodiments will be apparent from the accompanying drawings and from the detailed description that follows.

DETAILED DESCRIPTION

[0049] In order to provide a clear and consistent understanding of the terms used in the present specification, a number of definitions are provided below. Moreover, unless defined otherwise, all technical and scientific terms as used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure pertains.

[0050] The use of the word a or an when used in conjunction with the term comprising in the claims and/or the description may mean one, but it is also consistent with the meaning of one or more, at least one, and one or more than one. Similarly, the word another may mean at least a second or more.

[0051] As used herein, the words comprising (and any form of comprising, such as comprise and comprises), having (and any form of having, such as have and has), including (and any form of including, such as include and includes) or containing (and any form of containing, such as contain and contains), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0052] As used herein, the term about is used to indicate that a value includes an inherent variation of error for the device or the method being employed to determine the value.

[0053] As used herein, when referring to numerical values or percentages, the term about includes variations due to the methods used to determine the values or percentages, statistical variance and human error. Moreover, each numerical parameter in this application should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0054] This disclosure is drawn to a process for the preparation of a polymerized toner material. The process is based on suspension polymerization and involves use of carbon nanotube instead of carbon black. The polymer-encapsulated carbon nanotube material of this disclosure has particles with sizes in the micron range. Also, the size of the particles is uniform throughout the material. The particles have a core-shell structure with carbon nanotube attached to the core.

[0055] Monomers used in this disclosure are styrene and butyl-acrylate. As will be understood by a skilled person, other suitable monomers may also be used. Such monomers include for example p-chlorostyrene, vinyl naphthalene, vinyl esters such as vinyl acetate, vinyl propionate and vinyl benzoate. Prior to undertaking the polymerization process, the monomers were purified to remove any inhibitors.

[0056] The initiator used in this disclosure is benzyl peroxide. As will be understood by a skilled person, other suitable initiators may also be used. Such initiators include for example hydroquinone (HQ). The initiator was generally used as received.

[0057] Divinyl benzene was used as cross-linker. As will be understood by a skilled person, other suitable cross-linkers may also be used. Such cross-linkers include for example ethylene glycol methacrylate (EG).

[0058] Sodium n-dodecyl sulfate (SDS) was used as dispersant. As will be understood by a skilled person, other suitable dispersant may also be used. Such dispersants include for example sodium styrene sulfonate (NaSS).

[0059] Polyvinyl alcohol (PVA) was used as stabilizer. As will be understood by a skilled person, other suitable stabilizers may also be used. Such stabilizers include for example Polyethylene Glycol (PEG).

[0060] Details of each of the above chemicals used in this disclosure including their suppliers are provided in Table 2 below.

TABLE-US-00002 TABLE 2 Details of chemicals used in this disclosure Chemical name Purity Supplier Styrene (St) 99% Duksan Co. n-Butylacrylate (BuA) 99% Samchun Pure Chem. Co. Divinylbenzene (DVB) 80% Aldrich Polyvinyl alcohol (PVA) 87-89% Alfa Aesar hydrolyzed Sodium n-dodecyl sulfate International (SDS) Laboratory Benzyl peroxide (BP) 97% Alfa Aesar

[0061] Carbon nanotubes (CNTs) of four different types were investigated in this disclosure. The four CNT types are: CNT modified with NH.sub.2, CNT modified with boron, CNT unmodified long chain and CNT unmodified short chain. The properties of the CNTs used are listed in Tables 3-6 below.

TABLE-US-00003 TABLE 3 Properties of unmodified CNTs, grade KNT-M.sub.31 (herein after CNT-A) Method of Purity Unit Value measurement Averages nm 9.5 TEM diameter Average m 1.5 TEM length Carbon % 90 TGA purity Metal oxide % 10 TGA Amorphous * HRTEM carbon Surface area M.sup.2/g 250-300 BET * Pyrolytically deposited Carbon on the surface of the NC7000

TABLE-US-00004 TABLE 4 Properties of short multi-walled CNTs, grade KNT-s M31 (herein after CNT-B) Method of Purity Unit Value measurement Averages nm 3-10 TEM diameter Average m 0.5-2 TEM length Carbon % >95 TGA purity Metal oxide % Amorphous * HRTEM carbon Surface area M.sup.2/g >500 N/A

TABLE-US-00005 TABLE 5 Properties of CNTs modified with NH.sub.2, grade KNT-MNH.sub.13 (herein after CNT-C) Method of Purity Unit Value measurement Averages nm 13-18 TEM diameter Average m 1-12 TEM length Carbon % 99 TGA purity Metal oxide % Amorphous * HRTEM carbon Surface area M.sup.2/g N/A N/A

TABLE-US-00006 TABLE 6 Properties of CNTs modified with boron, grade KNT-MBO (herein after CNT-D) Method of Purity Unit Value measurement Averages nm 20-30 TEM diameter Average m N/A N/A length Carbon % N/A N/A purity Metal oxide % Amorphous * HRTEM carbon Surface area M.sup.2/g N/A N/A

[0062] Eight different types of charge control agent (CCA), obtained from Korea, were investigated in this disclosure. Their properties are outlined in Table 7 below. As will be understood by a skilled person, other suitable charge control agents may also be used. Such charge control agents include for example quaternary ammonium compound, or an amine and alkyl pyridinium compounds.

TABLE-US-00007 TABLE 7 Properties of the eight types of CCA used in this disclosure Chemical Charge No. name Chemical code Company C/g 1 CCA Nigrosine International Lab. 143-19-1 2 CCA MEC-105S Korea 20~30 3 CCA MEC-88 Korea 20~35 4 CCA MEC-84-E Korea 10~35 5 CCA MEC-84 Korea 10~35 6 CCA MEC-84-S Korea 10~35 7 CCA MEC-91 Korea 30~45 8 CCA MEP-51 Korea +30~+45

EXAMPLE 1

[0063] Polymerization of poly (styrene-butyl acrylate) in presence of CNT-D and a type of CCA, MEC-88, was performed as follows: purified monomers of styrene and butyl acrylate were mixed with DVB (as cross-linker) and BPO (as initiator) to form a dispersed phase. After that, MEC-88 was added to the dispersed phase and we waited until all solids were well dissolved. The continuous phase was prepared by dissolving PVA with molecular weight of 13,000 in distilled water and heated to 70 C., under gentle stirring. Then SDS (as suspension stabilizer) was added to dissolve PVA in water. The dispersion of CNT-D was performed by sonication under ice (to decrease the temperature generated by sonicator) for 10 minutes at an amplitude of 75% in the aforementioned continuous phase. The continuous phase containing well dispersed CNT-D was stirred by Ultura-Turax from IKA-T25 digital for 10 minutes at a speed of 7000 rpm. While the continuous phase was stifling, the dispersed phase (monomers+DVB+BPO) was added drop by drop to produce a suspension.

[0064] The mixture was then transferred to a reactor and degased under vacuum at 70 mbar for 10 minutes. After that, the mixture was again stirred using a mechanical stirrer (IKA Eurostar 100 control) at a speed of 180 rpm. Finally, the suspension was polymerized at 75 C. for 7 hours under slow purging of nitrogen gas for deoxygenation. The reaction was terminated by cooling to room temperature. The resulting latex was dispersed in distilled water and isolated by centrifugation. The supernatant was decanted and any remaining polymer was washed again, until the supernatant was clear. The product was then dried in a vacuum oven for 24 hours without any heating to remove the residual water. The recipes of all the experiments performed are shown in Table 8 below.

TABLE-US-00008 TABLE 8 Recipes for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at different concentrations of the CCA MEC-88 Monomers St BuA DVB BP PVA SDS CNT-D Tem Time MEC-88 H.sub.2O Sample code (g) (g) (g) (g) (g) (g) (g) ( C.) (hours) (g) (wt %) MEC:CNT.sub.D (mL) Sample 1 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.102 0.42 3:1 150 Sample 2 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.068 0.28 2:1 150 Sample 3 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.034 0.14 1:1 150 Sample 4 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.017 0.07 1:2 150 Sample 5 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.013 0.05 1:3 150

EXAMPLE 2

[0065] Polymerization of poly (styrene-butyl acrylate) in the presence of CNT-D and a type of cca, MEP-51, was performed as follows: purified monomers, DVB and BPO were prepared as described above in Example 1. However, contrary to the procedure in Example 1, MEP-51 was not added to the dispersed phase, due to the fact that MEP-51 does not dissolve in any of the monomers used. In this example, we tried to dissolve MEP-51 in a small amount of ethanol and then mixed it to the continuous phase that was prepared in same way as described above in Example 1 in relation to MEC-88. The remaining steps were the same as with MEC-88 in Example 1. Dissolving MEP-51 in ethanol then mixing it to the continuous phase allowed to reach complete dissolution of MEP-51. The recipes of the experiments performed are shown in Table 9 below.

TABLE-US-00009 TABLE 9 Recipes for suspension polymerization of styrene and butyl acrylate in presence of CNT-D at different concentrations of the CCA MEP-51 Monomers Sample St BuA DVB BP PVA SDS CNT-D Tem Time MEC-88 H.sub.2O code (g) (g) (g) (g) (g) (g) (g) ( C.) (hours) (g) (wt %) MEC:CNT.sub.D (mL) Sample 1 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.102 0.42 3:1 150 Sample 2 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.068 0.28 2:1 150 Sample 3 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.034 0.14 1:1 150 Sample 4 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.017 0.07 1:2 150 Sample 5 18.18 4.49 1.828 0.25 0.25 0.046 0.034 75 7 0.013 0.05 1:3 150

[0066] Characterizations of the polymerized particles were conducted by various techniques as follows: (i) Monomer conversion rate was determined gravimetrically. The sample was taken in a petri-dish and dried under the hood overnight. The conversion rate was calculated from the dried particles. (ii) Polymerized particles size was measured by Dynamic Light Scattering (DLS), Nano-ZS (Malvern Co., UK) with measurement range 0.3 nm-10 microns (diameter) was used. Light source HeNe laser 633 nm, Max 5 mV and minimum sample volume 12 L was used to measure the particles size of the prepared latex. Further, the samples were prepared in 0.01N NaCl solution according to the Malvan recommendation for latex standard. (iii) The morphology of the particles was assessed by Scanning Electron Microscopy (SEM). Scanning Electron Microscope (SEM NNL 200, FEI Company, Netherlands) was used to characterize the morphology of the polymerized latex. For this purpose a drop of dilute polymerized latex (1:5) with Millipore water was spread to dry over copper holder, and this drop was dried in air and metalized with 3 nm Pt.

[0067] Each of the four types of CNT outlined above in Tables 3-6 were investigated with the aim of determining the best one for achieving a good conversion rate and desirable particles size. The results obtained at various concentrations are listed in Tables 10-13 below.

TABLE-US-00010 TABLE 10 Effect of CNT-A concentration on suspension polymerization of St and BuA CNT concentration DLS measurements Conversion Samples (%) Z-Average PDI rate (%) Sample 1 0.065 228 0.3 76 Sample 2 0.125 1792 1.0 73 Sample 3 0.250 6621 0.4 70 Sample 4 0.500 625 0.6 9 Sample 5 0.750 1929 1.00 13 Sample 6 0.100 5749 0.84 10

TABLE-US-00011 TABLE 11 Effect of CNT-B concentration on suspension polymerization of St and BuA CNT concentration DLS measurements Conversion rate Samples (%) Z-Average PDI (m) (%) Sample 1 0.065 1955 1.00 78 Sample 2 0.125 2557 1.00 72 Sample 3 0.250 1779 1.00 59 Sample 4 0.500 172 0.11 47 Sample 5 0.750 279 0.265 59 Sample 6 0.100 372 0.303 33

TABLE-US-00012 TABLE 12 Effect of CNT-C concentration on suspension polymerization of St and BuA CNT concentration DLS measurements Conversion Samples (%) Z-Average PDI (m) rate (%) Sample 1 0.065 5216 0.176 75 Sample 2 0.125 782 0.617 73 Sample 3 0.250 151 0.255 75 Sample 4 0.500 195 0.159 58 Sample 5 0.750 1608 0.152 64 Sample 5 1.00 268 0.351 59

TABLE-US-00013 TABLE 13 Effect of CNT-D concentration on suspension polymerization of St and BuA CNT concentration DLS measurements Conversion rate Samples (%) Z-Average PDI (m) (%) Sample 1 0.065 4259 1.00 96 Sample 2 0.125 4031 1.00 94 Sample 3 0.250 6621 0.4 90 Sample 4 0.500 5715 0.35 96 Sample 5 0.750 1929 1.00 93 Sample 6 1.00 5890 0.367 90

[0068] From Tables 10 and 11 above, which relate to CNT unmodified, it can be seen that, the conversion rates of the polymerized particles were below 78%. This indicates that the retarding/inhibiting effects of the carbonyl group are still present when suspension polymerization occurs. From Tables 12 and 13 which relate to CNT modified with NH.sub.2 and boron, respectively, there are still some retarding/inhibiting effects, particularly for CNT modified with NH.sub.2, even though most carbonyl groups were replaced by NH.sub.2. It may not be possible to replace all the carbonyl groups by NH.sub.2. The best conversion rates were achieved with CNT modified with boron, CNT-D. As showed in Table 13, in each case the conversion rate was 90% or more. This suggests that there are almost no retarding/inhibiting effects when polymerization occurs.

[0069] Polymerization of monomers in the presence of CNT-D at a concentration of 0.25 wt % and CCA was performed with two types of CCA, namely, MEC-88 and MEP-51. It is known in the art that MEC-88 is a negative charged CCA type. It is also known that MEC-88 does dissolve well in styrene. Accordingly, in our experiments we dissolved MEC-88 in styrene before polymerization takes place. We investigated the effect of the concentration of MEC-88 on the conversion rate of the monomers as well as the polymerized particles size. The results are outlined in Table 14 below.

TABLE-US-00014 TABLE 14 Suspension polymerization of styrene and butyl acrylate in the presence of CNT-D at five different concentrations of MEC-88 DLS Measurement CCA CCA CNT-D CNT-D Conversion PDI Sample Code (g) wt % (g) wt % rate (%) Z-Average (m) Sample 1 0.102 0.42 0.034 0.14 12 4032 1.00 Sample 2 0.068 0.28 0.034 0.14 58 5882 0.16 Sample 3 0.034 0.14 0.034 0.14 68 5077 0.50 Sample 4 0.017 0.07 0.034 0.14 70 4576 1.00 Sample 5 0.011 0.05 0.034 0.14 75 6910 0.57

[0070] From the Table 14 above, it can be seen that the conversion rates at concentrations of MEC-88 between 0.05-0.42 wt %, are 75% or less. FIG. 1 shows the conversion versus the concentration of MEC-88. It can be seen that, the conversion rate decreases with the increase of MEC-88 concentrations. The maximum conversion rate (75%) was achieved with the minimum concentration of MEC-88 (0.05 wt %). By way of explanation, it is known in the art that most types of radical polymerization are adversely influenced by the presence of carbon black, such that the reaction may be retarded or completely inhibited when a strong radical scavenger is used. The functional groups on the surface of carbon black particles are mainly carbonyl groups. Such groups are likely to interact with the primary or propagating radicals. This leads to the retarding/inhibiting effects, as reported by Kiatkamjornwong et al. referred to above. This observation made by Kiatkamjornwong et al. can be related to the phenomenon observed in this disclosure in relation to the use of MEC-88. Indeed, the chemical structure of MEC-88 depicted in FIG. 2 includes a carbonyl group, which is responsible for the retarding/inhibiting effects. In other words it would not be easy to obtain a high conversion rate of monomers in the presence of MEC-88, since there are carbonyls groups that act as retarding/inhibiting effects.

[0071] The use of MEC-88 leads to the size of the polymerized particles in the micron range, as outlined in Table 14, DLS results (0.16-1 m). However, as can be seen on SEM micrographs shown in FIG. 3, FIG. 4a, FIG. 4b, FIG. 4c, FIG. 5a, FIG. 5b, FIG. 5c, FIG. 6a, FIG. 6b, FIG. 6c, FIG. 7a, FIG. 7b and FIG. 7c, the polymerized particles were not uniform. This is less desirable in toner materials.

[0072] After the relatively unsatisfied results obtained with MEC-88 to produce a material for toner application, we investigated another type of CCA, MEP-5. This CCA type principally is positively charge and its chemical structure depicted in FIG. 9 has no carbonyl group. These characteristics may allow us to solve the problem associated with the retarding/inhibiting effects mainly attributed to carbonyl groups. As indicated above, MEP-51 does not dissolve in either styrene or water. We tried to dissolve MEP-51 in ethanol in different amounts before mixing it with water (water is acting as the continuous phase that contains PVA, SDS, and dispersed CNT-D). However, we realized that when the amount of ethanol increased, the dispersion of CNT was affected. We thus tried to dissolve MEP-51 in small amount of ethanol (5 ml) to avoid any decrease in dispersion state of CNT. We then investigated the effect of MEP-51 concentration on the conversion rate. Also, particles size and particles morphology at various concentrations of MEP-51 were studied. The results are outlined in Table 15 below.

[0073] As indicated above, ethanol was used in our experiments to dissolve the CCA MEP-51. A skilled person will understand that other suitable solvent can be used for this purpose. This includes for example any C.sub.1-C.sub.6 alcohol. Other suitable solvent may be for example acetone and hexane.

TABLE-US-00015 TABLE 15 Recipes of suspension polymerization of styrene and butyl acrylate in the presence of CNT-D at five different concentrations of MEP-51 DLS Measurement CCA CCA CNT-D CNT-D Conversion PDI Sample Code con(g) wt % con(g) wt % rate (%) Z-Average (m) SP-CNT-D-MEP-51-1 0.102 0.42 0.034 0.14 28 2106 1.00 SP-CNT-D-MEP-51-2 0.068 0.28 0.034 0.14 91 6793 0.226 SP-CNT-D-MEP-51-3 0.034 0.14 0.034 0.14 90 5251 0.146 SP-CNT-D-MEP-51-4 0.017 0.07 0.034 0.14 93 5784 0.217 SP-CNT-D-MEP-51-5 0.011 0.05 0.034 0.14 97 5882 0.161

[0074] From the Table 15 and FIG. 8 it can be seen that the conversion rates were 90% or more for all the concentrations below 0.28 wt %. For the highest concentration of 0.42 wt %, the conversion rate was 28 wt %. Accordingly, the conversion rate is improved when MEP-51 is used instead of MEC-88.

[0075] Again referring to Kiatkamjornwong et al., in their work, the conversion rate of styrene and butyl acrylate were not more than 80% for all the cases when carbon black was used as pigment, and this conversion rate decreased with the increase of the carbon black concentration. In this disclosure, when we used CNT, and the conversion rate was 90% or more with MEC-51 as CCA. Accordingly, it is advantageous to use CNT as pigment instead of carbon black. This was not known in the art. Another advantage associated with the use of CNT is the particles size of toner materials obtained, in the micron range as shown in FIG. 10, FIG. 11a, FIG. 11b, FIG. 11c, FIG. 12a, FIG. 12b, FIG. 12c, FIG. 13a, FIG. 13b, FIG. 13c, FIG. 14a, FIG. 14b and FIG. 147c. Indeed, smaller particles sizes for toner materials, in the nanometer range, for example, are not desirable, since such particles are potentially harmful for the health. Accordingly, this disclosure provides for a new toner material that is potentially less harmful for the health.

[0076] Four points stem from FIG. 10, FIG. 11a, FIG. 11b, FIG. 11c, FIG. 12a, FIG. 12b, FIG. 12c, FIG. 13a, FIG. 13b, FIG. 13c, FIG. 14a, FIG. 14b and FIG. 14c. Firstly, for all the concentrations, the polymerized toner particles are in micron size. Secondly, the particles size obtained from SEM are quite in agreement with DLS measurement indicated in Table 15. Thirdly, uniformity of the particles decreases with the increase of MEP-51 concentrations. Fourthly, it can be seen that attachment of the CNTs on the core particles did occur.

[0077] The above four remarkable points prove that CNTs can act in same in the same way as carbon black, when used as pigment for toner materials. In other words, carbon nanotube can replace carbon black in the preparation of toner materials. The use of CNTs instead of carbon black presents some advantages. For example, a high conversion of the monomers, a particles size in the micron range thus avoiding any harmful effect that might be associated with a material with particles size in the nanometer range. Also, the size of the particles is more uniform throughout the material.

[0078] Although the present embodiments have been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader spirit and scope of the various embodiments.

[0079] This disclosure refers to a number of documents, the content of which is herein incorporated by reference in their entirety.

INDUSTRIAL APPLICABILITY

[0080] The polymer-encapsulated carbon nanotube material of this disclosure presents some advantages over a polymer-encapsulated carbon black material. The material of this disclosure has particles with size in the micron range, which is potentially less harmful for the health than a material having particles with size in the nanometer range. The material of this disclosure is used as toner material in various types of printing including computer printing. Also, the material of this disclosure is environmentally friendly, since a reduced amount thereof is required for printing. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense.