KR102295504B1 - Polymer composite containing carbon nanorod, and Preparation method thereof - Google Patents

Abstract

The present invention relates to a polymer composite including carbon nanorods and a method for manufacturing the same, wherein the polymer composite can exhibit excellent wear resistance and friction performance by including carbon nanorods in a polymer matrix, and due to the appropriate structure of the carbon nanorods By forming a three-dimensional structure within the polymer matrix, it is possible to effectively dissipate the load and heat generated at the interface.

Description

Polymer composite containing carbon nanorod, and preparation method thereof

The present invention relates to a polymer composite including carbon nanorods and a method for manufacturing the same.

Due to their excellent mechanical and chemical properties, composite materials have been widely used in a variety of applications. Among them, polymer-based composite materials have attracted much attention due to their tunability, ease of manufacture, low friction, and excellent self-lubricating properties. Therefore, polymer-based composites are considered promising candidates for tribological applications requiring high mechanical strength and wear resistance, and are generally composed of polymer matrices and inorganic fillers. Selection of the appropriate polymer matrix and inorganic filler is important for optimizing the mechanical and tribological properties of the polymeric system composite.

Various polymers such as epoxy-based resins, polyimides, poly(etheretherketone) (PEEK), poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) have been used to develop polymer-based composites. has been used Fluoropolymers exhibit excellent mechanical and chemical stability and abrasion resistance, so they can withstand harsh wear conditions. Many studies have focused on PTFE-based composites due to their low coefficient of friction and good wear resistance. However, the poor solubility of PTFE in various solvents and the high cost have limited the application of PTFE-based composites.

In order to solve the above problems, there is a need for research on a polymer composite material that can be manufactured at low cost while having better solubility and easy processability.

J. Am. Chem. Soc. 2014, 136, 13925-13931

An object of the present invention is to provide a polymer composite material having improved friction performance by controlling the chain structure of a polymer including carbon nanorods in a polymer matrix, and a method for manufacturing the same.

The present invention is from the group consisting of polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE). A polymer matrix comprising at least one selected; and

Provided is a polymer composite comprising carbon nanorods dispersed in a polymer matrix

In addition, the present invention comprises the steps of preparing a polymer-carbon nanorod composite by mixing a polymer and carbon nanorods; and

It provides a method for producing a polymer composite, comprising the step of preparing the polymer composite by applying pressure to the polymer-carbon nanorod composite.

The polymer composite according to the present invention can exhibit excellent wear resistance and friction performance by including carbon nanorods in the polymer matrix, and forms a three-dimensional structure in the polymer matrix due to the appropriate structure of the carbon nanorods, which occurs at the load and interface It can dissipate heat effectively.

1 is a schematic image of a method for manufacturing a polymer composite according to the present invention.
2 is an image taken with a scanning electron microscope (SEM) of the polymer composite material prepared in Example: a is a carbon nanorod, b is a PVDF/CNR composite before hot pressing, c and d are a PVDF film of a comparative example, e and f is an image of the polymer composite of Example 3.
3 is a Fourier transform infrared spectroscopy (FT-IR) graph of the polymer composite prepared in Example.
4 is a graph showing the results of differential scanning calorimetry (DSC) of the polymer composite prepared in Example: a represents the melting temperature of the polymer composite, and b represents the recrystallization temperature of the polymer composite.
5 is a graph of X-ray diffraction (XRD) results of the polymer composite prepared in Example.
6 is a graph showing the results of X-ray photoelectron spectroscopy (XRD) of the polymer composite prepared in Example.
7 is a graph showing the result of thermogravimetric analysis (TGA) of the polymer composite prepared in Example.
8 is a graph showing the coefficient of friction of the polymer composite material prepared in Example: a is the friction coefficient of each type of polymer composite according to the operating time, b is the friction coefficient of the polymer composite according to the operating time according to the carbon nanorod content indicates
9 is a graph showing a specific wear rate of the polymer composite prepared in one embodiment.
10 is an image taken with a scanning electron microscope (SEM) after the abrasion test of the polymer composite material prepared in Example.

Since the present invention can have various changes and can have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description.

However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

The present invention relates to a polymer composite material including carbon nanorods and a method for manufacturing the same, wherein the carbon nanorods improve the abrasion resistance of the polymer composite material by changing the surface properties, thereby saving maintenance costs, and within the polymer matrix of the polymer composite material By controlling the content of carbon nanorods, it is possible to exhibit proper wear resistance and friction performance, and to effectively disperse heat and load generated at the interface.

Hereinafter, the present invention will be described in detail.

The present invention relates to the group consisting of polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE). A polymer matrix comprising at least one selected from; and

Provided is a polymer composite including carbon nanorods dispersed in a polymer matrix.

The polymer matrix is a group consisting of polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE). It may be at least one selected from, specifically, the polymer matrix is polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly (ether) ether ketone) (PEEK) or poly(tetrafluoroethylene) (PTFE), and more specifically, polyvinylidene fluoride (PVDF).

In addition, in the polymer matrix, a band of the α-phase may be observed at any one or more positions ^{of 975 cm -1} , 854 cm ^-1 , 796 cm ^-1 , 763 cm ^-1 and 614 cm ^{-1 in the crystal phase.} Specifically, in the polymer matrix, the β-phase strength may decrease while the α-phase strength may increase in the crystalline phase. This can improve the friction performance of the polymer composite by reducing the secondary interaction between the polymer matrix and the carbon nanorods by increasing the crystalline phase of the α phase of the polymer matrix.

The polymer composite according to the present invention may contain 1 wt% to 20 wt% of carbon nanorods. Specifically, the carbon nanorods are 1% to 15% by weight, 1% to 10% by weight, 5% to 20% by weight, 5% to 15% by weight or 5% to 10% by weight. may include

As an example, the carbon nanorods may have an average diameter of 200 nm to 900 nm, and an average length of 3 μm to 15 μm. Specifically, the carbon nanorods have an average diameter of 200 nm to 800 nm, 200 nm to 600 nm, 300 nm to 900 nm or 300 nm to 700 nm, 400 nm to 900 nm, 400 nm to 700 nm or 400 nm to 600 nm, and an average length of 3 μm to 15 μm, 3 μm to 13 μm, 3 μm to 10 μm, 5 μm to 15 μm, 5 μm to 13 μm, or 5 μm to 10 μm.

By including the carbon or rod as described above in the polymer matrix, the polymer composite material according to the present invention can exhibit excellent friction performance and wear resistance.

The polymer composite material according to the present invention has a structure in which carbon nanorods are dispersed inside a polymer matrix, and only the polymer matrix exists on the surface of the polymer composite material, and the carbon nanorods may be included only in the polymer matrix. Specifically, from the surface of the polymer composite material to several tens of nanometers may be formed of only the polymer matrix. For example, a thickness of 10 nm to 100 nm from the surface of the polymer composite may be formed of only the polymer matrix.

In addition, the thickness of the polymer composite material may be 1 mm to 100 mm. Specifically, the thickness of the polymer composite may be 1 mm to 80 mm, 1 mm to 60 mm, 1 mm to 20 mm, 1 mm to 10 mm, or 1 mm to 5 mm.

As an example, the polymer composite material according to the present invention may have a coefficient of friction of 0.01 to 0.4 after 240 minutes when the reciprocating mode friction test is performed. Specifically, the friction coefficient may be 0.01 to 0.4, 0.01 to 0.35, 0.01 to 0.3, 0.01 to 0.2, or 0.01 to 0.1.

In addition, the wear rate of a polymeric composite material according to the present invention may be 1X10 ^-5 mm ³ / N · m to about ^{7X10 -5 mm 3 / N · m} . Specifically, the wear rate of the polymer composite material is 1X10 ^-5 mm ³ / N · m to about ^{6X10 -5 mm 3 / N · m} , 1X10 -5 mm 3 / N · m to about 4X10 ^-5 mm ³ / N · m or 2X10 ^-5 mm ³ /N·m to 5X10 ^-5 mm ³ /N·m.

In addition, mixing a polymer and carbon nanorods to prepare a polymer-carbon nanorod composite; and

It provides a method for producing a polymer composite, comprising the step of preparing the polymer composite by applying pressure to the polymer-carbon nanorod composite.

As shown in FIG. 1, in the method for manufacturing a polymer composite according to the present invention, nanofibers are prepared by electrospinning an aqueous solution containing polyacrylonitrile on a substrate, and the result of thermally decomposing the prepared nanofibers is used in a mortar. Grind to prepare carbon nanorod powder. Then, the polymer and the carbon nanorods prepared above are mixed in a certain ratio and the mixed solution dissolved therein is stirred for 24 hours and centrifuged to prepare a precipitated precipitate. The obtained precipitate is placed in a stainless steel mold and then hot pressed at high temperature and high pressure to prepare a polymer composite.

As an example, the method for manufacturing a polymer composite according to the present invention comprises the steps of: preparing carbon nanorods through electrospinning; preparing a polymer-carbon nanorod composite by mixing a polymer and carbon nanorods; and applying pressure to the polymer-carbon nanorod composite to prepare a polymer composite.

In the manufacturing of the carbon nanorods, an aqueous solution is prepared by stirring polyacrylonitrile with a solvent, and the aqueous solution is electrospun on a substrate of ITO or FTO to prepare nanofibers. The nanofibers may be stabilized at 200° C. to 400° C. for 30 minutes to 2 hours and then thermally decomposed at a temperature of 700° C. or higher or 800° C. or higher for 30 minutes to 2 hours.

As another example, the step of preparing a polymer-carbon nanorod composite by mixing the polymer and carbon nanorods is to prepare a mixed solution in which the polymer and carbon nanorods are mixed, centrifuge the mixed solution and in a vacuum oven Residual solvent can be removed by drying. Specifically, the mixed solution may be centrifuged to obtain a precipitate and then dried in an oven to remove the residual solvent. The precipitate from which the residual solvent has been removed may be used by pulverizing it into a powder as a polymer-carbon nanorod composite. The polymer-carbon nanorod composite prepared as described above may have a form in which a spherical polymer is attached to the surface of the carbon nanorod.

The polymer is selected from the group consisting of polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly(ether ether ketone) (PEEK) and poly(tetrafluoroethylene) (PTFE). It may include one or more selected. Specifically, the polymer matrix is polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVDF), epoxy resin, polyimide, polyaryl ether ketone (PAEK), poly(ether ether ketone) (PEEK) or poly (tetrafluoroethylene) (PTFE), and more specifically, polyvinylidene fluoride (PVDF).

In addition, in the mixed solution, the carbon nanorods may be mixed in an amount of 1 wt% to 20 wt%. Specifically, the carbon nanorods may be mixed at 1 wt% to 15 wt%, 1 wt% to 10 wt%, 5 wt% to 20 wt%, 5 wt% to 15 wt%, or 5 wt% to 10 wt% can By mixing the carbon nanorods in the same amount as described above, the coefficient of friction and the wear resistance of the polymer composite according to the present invention can be improved.

For example, the carbon nanorods may have an average diameter of 200 nm to 900 nm, and an average length of 3 μm to 15 μm. Specifically, the carbon nanorods have an average diameter of 200 nm to 800 nm, 200 nm to 600 nm, 300 nm to 900 nm or 300 nm to 700 nm, 400 nm to 900 nm, 400 nm to 700 nm or 400 nm to 600 nm, and an average length of 3 μm to 15 μm, 3 μm to 13 μm, 3 μm to 10 μm, 5 μm to 15 μm, 5 μm to 13 μm, or 5 μm to 10 μm.

As an example, the step of preparing the polymer composite by applying pressure to the polymer-carbon nanorod composite is putting the polymer-carbon nanorod composite in powder form into a mold and at a temperature of 150° C. to 250° C., a pressure of 10 to 30 bar. It is possible to prepare a polymer composite material by hot pressing. Specifically, a polymer-carbon nanorod composite in powder form is placed in a mold and 10 to 25 bar, 10 to 20 bar, or 15 to 25 bar at a temperature of 150°C to 220°C, 150°C to 200°C, or 170°C to 220°C. A polymer composite can be prepared by hot pressing with a pressure of By hot pressing under the above conditions, the polymer composite material in the present invention may have a form in which carbon nanorods are encapsulated in a polymer matrix.

Hereinafter, the present invention will be described in more detail through Examples and the like according to the present invention, but the scope of the present invention is not limited by the Examples presented below.

manufacturing example

First, 1 g of polyacrylonitrile (Polyacrylonitrile, PAN) was completely dissolved in 10 mL of dimethylformamide (DMF) by stirring at 50° C. for 6 hours. When it became clear and homogeneous, the solution was cooled to room temperature. The solution cooled to room temperature was taken with a 12 mL syringe and injected through a stainless steel needle connected to a high voltage DC power supply. The applied voltage and injection rate were electrospun polyacrylonitrile nanofibers on the FTO glass substrate under the conditions of 15 kV and 0.5 mL/h, respectively. After the electrospun polyacrylonitrile nanofibers were peeled off from the FTO glass, they were stabilized at 280°C for 1 hour and then pyrolyzed at 800°C for 1 hour. The resultant was grinded with a mortar to prepare carbon nanorods (CNR) in a uniform powder form.

Example 1

Then, 0.4 g of polyvinylidene fluoride (PVDF) powder was stirred at room temperature and dissolved in 10 mL of dimethylformamide (DMF). 0.04 g of the carbon nanorod (CNR) powder prepared in Preparation Example was added to a polyvinylidene fluoride (PVDF) solution. For uniform mixing, the prepared solution was sonicated for 30 minutes and then stirred for 24 hours. Then, the resulting mixture was added to 100 mL of ethanol to precipitate. PVDF powder was added to the precipitated solution to bring the total weight of PVDF/CNR compound to 4.0 g. A PVDF/CNR composite was obtained by centrifugation and drying the product in a vacuum oven to remove residual solvent. The agglomerated PVDF/CNR mass was ground into a fine powder using a mortar. The pulverized PVDF/CNR powder was put into a square stainless steel mold and then hot-pressed at 190° C. and 20 bar for 2 hours to prepare a polymer (PVDF/CNR) composite having 1 wt% carbon nanorods.

Example 2

A polymer composite having a CNR loading of 5 wt% was prepared in the same manner as in Example 1, except that 0.2 g of the carbon nanorod (CNR) powder prepared in Preparation Example was added to the polyvinylidene fluoride solution.

Example 3

A polymer composite having 10 wt% CNR loading was prepared in the same manner as in Example 1, except that 0.4 g of the carbon nanorod (CNR) powder prepared in Preparation Example was added to the polyvinylidene fluoride solution.

Example 4

A polymer composite having 15 wt% CNR loading was prepared in the same manner as in Example 1, except that 0.6 g of the carbon nanorod (CNR) powder prepared in Preparation Example was added to the polyvinylidene fluoride solution.

Example 5

A polymer composite having 20 wt% CNR loading was prepared in the same manner as in Example 1, except that 0.8 g of the carbon nanorod (CNR) powder prepared in Preparation Example was added to the polyvinylidene fluoride solution.

Comparative Example 1

4.0 g of polyvinylidene fluoride (PVDF) powder was put into a square stainless steel mold and then hot-pressed at 190° C. and 20 bar for 2 hours to prepare a pure PVDF film.

Experimental Example 1

In order to confirm the shape of the polymer composite material according to the present invention, the carbon nanorods prepared in Preparation Example, the polymer composite material prepared in Example 3, and the PVDF film prepared in Comparative Example were examined with a scanning electron microscope (SEM). was photographed, and the results are shown in FIG. 2 .

Figure 2 (a) is an image taken with a scanning electron microscope of the carbon nanorods prepared in Preparation Example, Figure 2 (b) is a PVDF / CNR composite before hot pressing in Example 3 taken with a scanning electron microscope It is an image, and (c) and (d) of FIG. 2 are images taken with a scanning electron microscope of the PVDF film prepared in Comparative Example, and FIGS. (e) and (f) are the polymer composites prepared in Example 3 This is an image taken with a scanning electron microscope.

Referring to FIG. 2 , the average diameter of the carbon nanorods (CNR) was about 500 nm, and the length was observed to be 5 to 10 μm. Before pressing, micro-sized polyvinylidene fluoride (PVDF) spheres were physically attached to the surface of the carbon nanorods. After pressing at 190 °C and 20 bar for 2 hours, the surface of the PVDF spheres became smooth as shown in Figs. 2(c) and (d). The pure PVDF film showed a crack-free structure and homogeneous morphology. (e) and (f) of Figure 2, in order to confirm the distribution of carbon nanorods, the polymer composite of Example 3 was cut vertically and then observed using a scanning electron microscope (SEM), looking at this, carbon nanorods were well dispersed in the PVDF matrix, and the surface was encapsulated by the PVDF matrix. The dispersed carbon nanorods acted as a framework for firmly holding the PVDF matrix, improving the wear resistance of the composite. Moreover, the 2D structure of carbon nanorods can effectively transfer friction-induced heat generated in friction measurements. High interfacial temperatures can negatively affect the mechanical strength and hardness of polymer-based composites.

Experimental Example 2

In order to confirm the physical and chemical properties of the polymer composite according to the present invention, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) for the polymer composites prepared in Examples 1 to 5 and PVDF films of Comparative Examples ), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) experiments were performed, and the results are shown in FIGS. 3 to 7 and Table 1 .

Sample Atomic contribution of element (%) Total C1s F1s O1s comparative example 74.88 14.56 10.56 100 Example 5 74.32 16.3 9.38 100

3 is a graph showing the results of Fourier transform infrared spectroscopy analysis of the polymer composite material prepared in Examples 1 to 5 and the PVDF film prepared in Comparative Examples. Referring to FIG. 3 , the interaction between the PVDF matrix of the polymer composite and the carbon nanorod filler can be seen. Specifically, the pure PVDF film exhibited three different crystalline phases (α, β and γ) depending on the chain structure with trans and gauche linkages. The α-phase of PVDF has a zero-sum dipole moment due to the symmetric and non-polar configuration of the chain structure. In contrast, the β and γ-phases of PVDF exhibit strong dipole moments due to the asymmetric arrangement of molecules. The α-phase of PVDF is suitable for tribological applications because it reduces the dipole-dipole moment induced between the PVDF chains where friction does not occur during the friction process. In the pure PVDF film, a strong band was observed at ^{840 cm −1} corresponding to the polar β-phase formed during the mechanical deformation and thermal annealing process. In the case of the polymer composite (PVDF/CNR), the strength of the β-phase gradually decreased, while the strength of the α-phase increased rapidly as the content of carbon nanorods (CNR) increased. This indicates that the carbon nanorods are well dispersed in the PVDF matrix and entangled with the PVDF chains. Through this, in the polymer composite according to the present invention, carbon nanorods affect the chain structure of PVDF, and the arrangement of PVDF chains is changed due to incorporation of carbon nanorods, and secondary interactions between them are reduced, so that the polymer composite material is It can be seen that the friction performance is improved.

4 is a differential scanning calorimetry (DSC) result graph of the polymer composite material prepared in Examples 1 to 5 and the PVDF film prepared in Comparative Example, (a) is the melting point of the polymer composite material and the PVDF film, (b) shows the recrystallization temperature of the polymer composite and PVDF film. Referring to FIG. 4 , all samples _{exhibited different melting temperatures (T m} ). Pure PVDF showed a melting temperature of 162 °C, and in the case of the polymer composite, as the carbon nanorod content increased, the melting temperature of the composite material gradually decreased. In addition, referring to (b) of FIG. 4 , in the case of the polymer composite, the recrystallization temperature increased as the carbon nanorod content increased. As confirmed by Fourier transform infrared spectroscopy (FT-IR) analysis, the configuration of the PVDF chain structure was changed from β-phase to α-phase due to the interaction between PVDF polymer chains and carbon nanorods. Due to the non-polar configuration of the PVDF chain and the stopping effect of the inorganic filler (carbon nanorods), the degree of chain packing of the PVDF matrix decreased, and thus the crystallinity of the polymer composite according to the present invention was reduced.

5 is a graph showing the results of X-ray diffraction (XRD) analysis of the carbon nanorods prepared in Preparation Examples, the polymer composite materials prepared in Examples 1 to 5, and the PVDF films prepared in Comparative Examples. Referring to FIG. 5 , the crystal properties of the pure PVDF film, carbon nanorods (CNR) and polymer composite (PVDF/CNR) can be seen. Carbon nanorods showed broad peaks at 25.0° and 44.1° with 2θ values corresponding to the (002) and (101) planes. The pure PVDF film showed strong crystalline peaks at 18.5° and 20.3° with 2θ values corresponding to the (020) and (110) planes. All polymer composites showed broad amorphous peaks, indicating that the PVDF chains were amorphous. However, the broad peak of carbon nanorods at 25.0° could hardly be observed in the XRD pattern of the PVDF/CNR composite even at high loading (ie, Example 5). In addition, the (020) and (110) peaks of the PVDF matrix show negligible shifts, suggesting a negligible interaction between the carbon nanorods and the PVDF matrix. The above results are inconsistent with scanning electron microscopy images, Fourier transform infrared spectroscopy, and differential scanning calorimetry (DSC) results. This negligible change seems to be observed because the penetration depth of the X-ray beam used for XRD measurements is not sufficient. Therefore, XRD measurement can only analyze the surface properties of the polymer composite sample, not the bulk properties. Through the pressing process, the PVDF matrix is mainly present on the surface of the polymer composite, whereas the carbon nanorods penetrate deeply into the polymer composite and become highly entangled PVDF. It can be seen that the chain is encapsulated.

6 is a graph showing the results of X-ray photoelectron spectroscopy (XPS) analysis of the polymer composite material prepared in Example 5 and the PVDF film prepared in Comparative Example, and Table 1 is a table showing the results. Referring to FIG. 6 and Table 1, the surface properties of the pure PVDF film and the polymer composite can be seen through XPS analysis. The C1s XPS spectrum of the pure PVDF film and the polymer composite (composite with high CNR content, CNR 20) did not show a significant difference. The atomic contribution of carbon (Cls) in the polymer composite of Example 5 was similar to that of the pure PVDF film. XPS analysis could hardly detect the presence of carbon nanorods. This was due to the short penetration depth (<10 nm) of the spectrometer. The XPS results are consistent with the XRD analysis, and it can be seen that the PVDF polymer chains are mainly present on the surface of the polymer composite and the carbon nanorods are encapsulated.

7 is a graph showing the results of thermogravimetric analysis (TGA) of the polymer composites prepared in Examples 1 to 5 and the PVDF films prepared in Comparative Examples. Referring to FIG. 7 , the thermal stability of the pure PVDF film and the polymer composite can be confirmed through thermogravimetric analysis (TGA). Specifically, the pure PVDF film exhibited primary pyrolysis accompanied by a mass loss of 65% at about 460 °C. In the case of the polymer composite, as the content of the carbon nanorods increased, the weight loss at the decomposition temperature of the polymer composite gradually decreased due to the high melting point (3550° C.) of the carbon nanorods. In addition, the uniformly dispersed carbon nanorods reduced heat due to friction by thermal diffusion due to the 2D structure. If carbon nanorods are not included, frictional heat is trapped on the PVDF surface due to the low thermal conductivity of PVDF. An increase in frictional sliding temperature can deteriorate mechanical properties such as hardness and shear strength of polymer composites.

Through this, it can be seen that the polymer composite material according to the present invention improves the mechanical properties of the polymer composite material by heat diffusion by including carbon nanorods.

Experimental Example 3

In order to confirm the frictional properties, abrasion resistance, long-term stability, etc. of the polymer composite material according to the present invention, a frictional property test was conducted on the polymer composite materials of Examples 1 to 5 and the PVDF films of Comparative Examples, and the results are shown in FIGS. 8 to 10 and Table 2.

Initial friction coefficient 60 min friction coefficient Final friction coefficient Wear rate
(10 ^-5 mm ³ /N m) comparative example 0.33 0.45 0.43 8.43 Example 1 0.16 0.44 0.47 3.50 Example 2 0.10 0.2 0.25 3.30 Example 3 0.07 0.04 0.03 3.70 Example 4 0.14 0.45 0.39 10.08 Example 5 0.20 0.43 0.39 11.93

The friction performance of the polymer composite according to the present invention was evaluated by performing a reciprocating mode wear test, and the mechanical properties and durability of the polymer composite were evaluated by the coefficient of friction.

Specifically, the friction coefficient and wear rate of the polymer composite were measured using STM-MTT (Hanmi Industry Ltd., Korea). Measurements were performed at 35° C. using the Reci Pro mode method. All applied normal forces were 3N in all experiments. The stroke distance of each cycle is 20 mm and the cycle frequency is 0.5 Hz. The total friction distances of the friction coefficient and wear rate tests were 300 and 900 m, respectively.

Figure 8 (a) is a graph showing the friction coefficient of the polymer composite of Examples 1 to 5 and the PVDF film of the comparative example according to the operating time, (b) alc Table 2 of Figure 8 is the carbon nanorod content by operating time It is a graph showing the coefficient of friction of the polymer composite according to With the exception of Example 1, the initial coefficient of friction of the polymer composite decreased with increasing operating time. As in Example 1, the friction coefficient of the polymer composite having the lowest carbon nanorod load increased as the operating time increased, and the friction performance of Example 1 was found to be similar to that of the pure PVDF film. In the polymer composite according to the present invention, the inclusion of 1 wt% of carbon nanorods was not sufficient to maintain a low coefficient of friction during the friction test. As the content of carbon nanorods increased, the friction coefficient of the polymer composite material decreased first and then increased rapidly. The polymer composite including the carbon nanorods in the content of 10 wt% showed the lowest coefficient of friction (ie, the initial coefficient of friction of 0.07 and the final coefficient of friction of 0.03). It can be seen that the incorporation of carbon nanorods is an efficient approach to improve the friction performance of PVDF-based composite materials.

As shown in FIG. 8 , the friction coefficient of the polymer composite decreases as the content of carbon nanorods increases may be due to three main reasons. First, as confirmed by Fourier transform infrared spectroscopy (FT-IR) analysis and differential scanning calorimetry (DSC) results, the fraction of the non-polar α-phase of the PVDF matrix increased with the increase of the carbon nanorod content, which resulted in The structural arrangement of the polymer composite is altered, resulting in a decrease in the dipole moment between the PVDF chains, which affects the interfacial adhesion. Second, compared with the soft PVDF matrix, the rigid carbon nanorods reduced the actual contact area of the composite with the opposite sliding body. A small contact area narrows the furrows and reduces the adhesion between the sliding bodies. Third, excellent lubrication properties were exhibited by pulverizing carbon nanorods into fine graphitic carbon particles during the friction process. With repetition of the reciprocating mode friction test, the graphite carbon particles compressed and formed a thin lubricating layer at the interface, reducing the frictional resistance and wear rate of the composite. However, when the content of the carbon nanorods exceeds 15 wt%, the friction coefficient of the polymer composite material rapidly increased, and recovered similarly to the low content condition. At high load, the aggregated carbon nanorods were peeled off the surface of the polymer composite, causing additional friction between the surfaces. As can be seen from (a) of Figure 8, the friction coefficient of the polymer composite (CNR 15wt%) of Example 4 slowly increased for 1 hour due to the separation of the carbon nanorods and the decrease in the stress concentration with time.

The long-term stability of the friction properties of the polymer composites of the present invention was evaluated by performing their reciprocating mode wear tests for 240 minutes. As can be seen from (b) of Figure 8, in the case of a polymer composite having a carbon nanorod content of 10 wt% or less, the friction coefficient after 60 minutes (red line) is lower than the friction coefficient after 240 minutes (blue line) appear. The friction coefficient after 240 minutes of the polymer composite containing a high content (10wt% or more) of carbon nanorods was higher than that of the polymer composite after 60 minutes. The friction coefficient of the polymer composite containing 5 wt% or less of carbon nanorods increased over time. Some PVDF fragments aggregated and increased the frictional resistance of the composite material. On the other hand, in the case of including more than 10 wt% of carbon nanorods, the friction coefficient of the polymer composite decreases with time, indicating that the carbon nanorods exhibit excellent lubricating properties.

9 is a graph showing the specific wear rate of the polymer composite material prepared in Examples 1 to 5 and the specific wear rate of the PVDF film of Comparative Example according to the carbon nanorod content. Referring to FIG. 9 and Table 2, the wear rate showed a similar trend to that shown by the coefficient of friction. The specific wear rate of the pure PVDF film is 8.43 × 10 ^-5 mm ³ /N m, and the specific wear rate in the case of including 1 wt% carbon nanorods (Example 1) is 3.50 × 10 ^-5 mm ³ /N m decreased. It was confirmed that even a small amount of carbon nanorods could effectively increase the wear resistance of the composite material. The polymer composite containing up to 10 wt % of carbon nanorods ^{showed a wear rate of 3.3 × 10 -5} mm ³ /N·m to 3.70 × 10 ^-5 mm ³ /N·m, showing almost the same wear rate, and a very low value. had The high abrasion resistance of the polymer composite comes from the reduced coefficient of friction and lubricating properties of the carbon nanorods. In addition, the 2D structure of the carbon nanorods promoted the release of friction-induced heat at the interface. When carbon nanorods were not included, the mechanical properties and wear resistance of the polymer composite were deteriorated due to the high sliding temperature. The fibrous structure of the carbon nanorods supported the applied load instead of the soft PVDF polymer, and the applied force was dispersed in the hard carbon nanorods. Due to this, the wear rate of the polymer composite was reduced. The well-dispersed carbon nanorods acted as a physical cross-linking network, and most of the applied load was transferred to the carbon nanorods. However, at a carbon nanorod content higher than 15 wt%, the specific abrasion rate of the polymer composite increased rapidly and was higher than that of the pure PVDF film. In the case of including excessive carbon nanorods, the carbon nanorods and PVDF agglomerated with each other to form a lump, and were peeled off from the polymer composite in the process of measuring the friction properties. These PVDF/CNR lumps increased the wear rate as well as the coefficient of friction of the composite.

10 is an image taken with a scanning electron microscope (SEM) of the surface of the polymer composite prepared in Examples 1 to 5 and the PVDF film prepared in Comparative Example after the abrasion test. Referring to FIG. 10 , vertical furrows were observed in all samples due to repeated strokes of the corresponding samples. Polymer composites having 1 to 10 wt% of carbon nanorods (Examples 1 to 3) exhibited a relatively smooth and uniform surface compared to the pure PVDF film. This is consistent with the friction coefficient and wear rate results. However, the polymer composites of Examples 4 (CNR 15) and Example 5 (CNR 20) had rough and inhomogeneous surfaces and micron-sized aggregated fragments were observed. Because the mechanical strength of the carbon nanorods was higher than that of the PVDF matrix, the applied stress was concentrated at the carbon nanorods-matrix interface, so that aggregated fragments were observed. The microcracks propagate along the agglomerate mass and cause large volume loss in the polymer composite, increasing the wear rate of the polymer composite.

Claims (5)

a polymer matrix that is polyvinylidene fluoride (PVDF); and
A polymer composite comprising carbon nanorods dispersed in a polymer matrix:
The carbon nanorods are made of only a polymer matrix having a thickness of 10 nm to 100 nm from the surface of the polymer composite,
Carbon nanorods are contained in an amount of 5% to 15% by weight based on the total amount of the polymer composite,
The average diameter of the carbon nanorods is 400 nm to 600 nm,
The average length of the carbon nanorods is 4 μm to 11 μm. manufacturing carbon nanorods through electrospinning;
preparing a polymer-carbon nanorod composite by mixing a polymer and carbon nanorods; and
Comprising the step of preparing a polymer composite by applying pressure and temperature to the polymer-carbon nanorod composite,
In the step of preparing the carbon nanorods,
Electrospinning is an applied voltage of 12 kV to 17 kV, and
It is carried out at an injection rate of 0.3 mL / h to 0.7 mL / h,
In the step of preparing the polymer composite,
a temperature of 180° C. to 200° C., and
The method for producing a polymer composite according to claim 1, characterized in that the pressure and temperature are applied at a pressure of 18 bar to 22 bar for 2 hours.
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