KR101443714B1 - Graphene oxide / Iron oxide / Chitosan Nanocomposite - Google Patents

Abstract

The present invention relates to a graphene oxide, an iron oxide, and a chitosan nanocomposite and, more specifically, to improve physical properties such as tensile strength, Young′s modulus, storage elasticity, etc as a synergy effect by comprising graphene oxide and iron oxide in a chitosan polymeric material. According to the present invention, by adding graphene oxide and iron oxide, physical properties such as tensile strength, Young′s modulus, and storage elasticity may be effectively improved and the chitosan polymeric material may be used in various fields. Also, since the nanocomposite of the present invention may be manufactured through a simple solution mixing evaporation method, thereby producing in large quantities at a low cost and with little manpower.

Description

Oxide graphene, iron oxide, and chitosan nanocomposite {Graphene oxide / Iron oxide / Chitosan Nanocomposite}

TECHNICAL FIELD The present invention relates to graphene oxide, iron oxide and chitosan nanocomposite materials, and more specifically, by containing graphene oxide and iron oxide in a chitosan polymer material, it is possible to improve physical properties such as tensile strength, Young's modulus and storage elasticity Lt; / RTI >

Chitosan is a linear and partially acetylated (1-4) -2-amino-2-deoxy-β-D-glucan polymer obtained from chitin, the second most abundant natural polymer on the planet. There have been many studies for use in various fields such as membranes, artificial skin, bone substitutes, and water treatment. Chitosan has several useful properties including biocompatibility, biodegradability and solubility in aqueous media. However, despite these various advantages and unique characteristics, the application range was limited due to the low mechanical and electrical properties. Therefore, there is a need to improve the physical and mechanical properties of such chitosan. For this purpose, a method of forming an organic-inorganic composite material by adding filler materials such as clay, hydroxyapatite, metal nanoparticles, carbon nanotubes, etc. has been studied.

Graphene, a monolayer of graphite, has an ideal 2D structure as a monolayer of carbon atoms packed with honeycomb crystal faces. Previously, Geim, Rao, and Stankovich have explored the appeal of this graphene in materials research. Due to its excellent mechanical, electrical and thermal properties as well as sp2 mixed carbon networks, graphene is seen as a new alternative for developing new functional materials. Although complete graphene does not exist naturally, bulk and solutions of various functionalized graphene materials, including oxidized graphene, can now be produced. The large surface area of graphene oxide (GO) has a number of functional groups such as -OH, -COOH, -O-, and C = O, making the GO hydrophilic and well dispersed in water as well as organic solvents . This feature facilitates the fabrication of graphene base materials using solutions. Previous studies have shown that GO can be dispersed throughout the polymer matrix, making GO-based nanocomposites with excellent mechanical and thermal properties. Since the GO is produced from low cost graphite, the GO / synthetic polymer composites have been studied with a great advantage over CNT in terms of cost.

There have been various attempts to improve the biocompatibility and other properties of nanocomposites by incorporating metal oxide nanoparticles into the nanocomposites. Fe ₃ O ₄ can be used to facilitate delivery and recovery of biomolecules for biological detection due to its inherent magnetic force. In addition, nanoparticles have a unique ability to promote rapid electron transfer between an electrode and an enzyme active site, and can be applied as a biosensor. There have been attempts to improve the electrical properties of chitosan by dispersing superparamagnetic Fe ₃ O ₄ nanoparticles in order to apply it as a biosensor. Adsorption of Fe ₃ O ₄ and chitosan has been reported to be caused by an electrostatic attraction mechanism, making chitosan an effective dispersant for the preparation of magnetic suspensions stabilized by electrostatic repulsion.

GO-IONP (iron oxide nanoparticle) composite was synthesized for various purposes. Yang et al. Studied the use of GO-IONP as a drug carrier. Chen et al. Recently demonstrated that magnetic GO-IONP nanocomposites can be used as a T2-weighted magnetic resonance (MR) contrast enhancer for in vitro cell markers.

The present inventors have made efforts to improve the properties of the chitosan polymer material and to make it possible to use it in a variety of fields, and have considered the application of the above-described Fe ₃ O ₄ and GO to the chitosan polymer. Fe ₃ O ₄ and GO were expected to be well dispersed in chitosan. Due to the easy adsorption of Fe ₃ O ₄ by GO, the porous support-forming properties of chitosan as well as mechanical and electrical properties of GO and Fe ₃ O ₄ It was expected that it would be possible to combine characteristics. And that this would significantly improve existing technologies for biosensing or bioenergy applications.

As a result of various studies, it has been confirmed that a new Fe ₃ O ₄ / GO / chitosan nanocomposite material having improved properties compared with conventional chitosan polymer-related materials can be produced by a simple solution evaporation method, . It was also shown for the first time that Fe ₃ O ₄ and GO on the chitosan polymer matrix show a synergistic effect with each other.

Venkatesan, J., & Kim, S. (2010) Chitosan Composites for bone tissue engineering. Marine Drugs, 8, 2252-2266. Li, D., Muller, M. B., Gilje, S., Kaner, R. B., Wallace, G. G. (2008) Processable aqueous dispersions of graphene nanosheets. Nature Nanotechnology, 3, 101-105.

The main object of the present invention is to provide a novel chitosan polymer composite material having improved properties.

Another object of the present invention is to provide a method for producing the chitosan polymer composite material.

According to one aspect of the present invention, there is provided a composite material of oxidized graphene, iron oxide, and chitosan polymer characterized by containing iron oxide and graphene oxide in a chitosan polymer.

According to the present invention, the physical properties of the chitosan polymer material can be effectively improved by containing oxidized graphene and iron oxide. This is because the graphene oxide and iron oxide can be present in a very well dispersed state on the chitosan polymer matrix and can enhance the hydrogen bonding action of each other. That is, oxidized graphene and iron oxide cause synergistic effects in improving the physical properties of the chitosan polymer material.

According to the present invention, it is possible to contain 0.1 to 2% by weight of iron oxide and 0.5 to 2% by weight of graphene oxide based on the weight of the chitosan polymer, preferably 0.3 to 0.7% by weight of iron oxide The graphene oxide is preferably added in an amount of 0.8 to 1.2% by weight. This is based on the analysis results of the characteristics of composite materials prepared from various iron oxide and graphene grains. When 0.5 wt% iron oxide and 1 wt% graphene oxide are contained, .

According to another aspect of the present invention, there is provided a method for improving the mechanical properties of a polymer molding by adding iron oxide and graphene oxide to a chitosan polymer.

According to the present invention, it is preferable to add 0.1 to 2% by weight of iron oxide based on the weight of the chitosan polymer and add 0.5 to 2% by weight of the graphene oxide.

According to another aspect of the present invention, there is provided a method for preparing a chitosan polymer, comprising the steps of: preparing a mixed solution by adding an iron oxide suspension and a graphene oxide suspension to a chitosan polymer solution; And drying the mixed solution in a predetermined shape to produce a molded product. The present invention also provides a method for producing a composite material of oxidized graphene, iron oxide and chitosan.

According to the present invention, it is preferable to add the iron oxide suspension and the oxidized graphene suspension so that the amount of iron oxide is 0.1 to 2 wt% and the amount of graphene oxide is 0.5 to 2 wt% based on the weight of the chitosan polymer.

In the present invention, the chitosan polymer preferably has a molecular weight of 100,000 to 1,000,000 g / mol.

In the present invention, iron oxide preferably has a particle size of 100 nm or less, more preferably 50 nm or less.

In the present invention, the graphene oxide preferably has a particle size of 50 탆 or less, more preferably 20 탆 or less.

According to the present invention, physical properties such as tensile strength, Young's modulus and storage elastic modulus of chitosan polymer material can be effectively improved by adding oxidized graphene and iron oxide, and thus chitosan polymer material can be advantageously used in various fields There will be. In addition, the composite material of the present invention can be produced by a simple solution mixed evaporation method, so that it can be mass produced with a low cost and manpower.

1 is a graph showing the stress-strain curve (a), the tensile strength (b), and the elastic modulus (c) of each nanocomposite film. 'P' is CS film, 'q' is (1%) GO / CS film, 'r' is (0.5%) Fe ₃ O ₄ / ) Fe ₃ O ₄ / (1%) GO / CS nanocomposite material film.
2 is a graph showing the water contact angle of each nanocomposite material film.
3 is a graph showing an XRD pattern of each nanocomposite film.
4 is a graph showing the FTIR spectrum of each nanocomposite film.
5 is a FESEM image and a TEM image of each nanocomposite film, wherein 'a' is the surface of the CS film, 'b' is the FESEM image of the cross section of the Fe ₃ O ₄ / GO / 'Is a TEM image of Fe ₃ O ₄ / GO / CS film.
6 is a TGA, DTG and DSC graph of each nanocomposite film.

Hereinafter, the present invention will be described in more detail with reference to Examples. These embodiments are only for illustrating the present invention, and thus the scope of the present invention is not construed as being limited by these embodiments.

Example 1.

(Average molecular weight = 350000 gmol ^-1 , 90% deacetylation level), potassium permanganate (for analysis), sodium nitrate and graphite (hereinafter referred to as "CS" Average particle size < 20 占 퐉) was purchased from Sigma Aldrich (Korea). Hydrogen peroxide was supplied from Daejung Chemicals and metals, Korea, and hydrochloric acid was purchased from Fluka. Sulfuric acid (98%) was purchased from Junsei Chemical (japan) and magnetite (Fe ₃ O ₄ ) nano powder (<50 nm particle size (TEM) Aldrich (Korea). Acetic acid was used with water as a solvent for CS. Water was distilled and ion exchange water was used.

Oxidized graphene synthesis

Oxidized graphene (hereinafter referred to as "GO") was synthesized by using a modified Hummers method (Hummers et al. 1958; Ramanathan et al. 2008) using natural graphite pieces (average particle size <20 μm).

In an ice water bath, 2 g of graphite and 1 g of NaNO ₃ were dissolved in 46 ml of concentrated H ₂ SO ₄ , stirred for about 15 minutes, and 6 g of KMnO ₄ was added in small portions with gentle stirring as possible to adjust the reaction temperature below 20 ° C . The suspension was stirred for 2 hours and maintained at 35 DEG C for 30 minutes, and then 92 mL of distilled water was slowly poured into the suspension. At this time, the temperature rapidly increases but does not exceed 98 캜. After 15 minutes, the suspension was diluted with about 280 mL of warm distilled water and 20 mL of 30% H ₂ O ₂ was added to remove residual KMnO ₄ and MnO ₂ . It turns bright yellow at this time. The suspension was filtered and washed with warm 5% aqueous HCl solution and distilled water, respectively, until the sulfate was removed and the pH of the filtrate was about 7. The GO sample was dried at 50 캜 under vacuum until it became a constant weight and then ground to a suitable particle size.

Fe ₃ O ₄ / GO / CS Nanocomposite Film Production

FIG. 1 shows a method for producing a nanocomposite material (Fe ₃ O ₄ / GO / CS) film of the present invention. Simple solution mixing - evaporation method was used.

2% (w / v) CS solution was prepared by dissolving CS in a 2% (v / v) acetic acid aqueous solution and then filtered to remove solid impurities. The iron oxide suspension (Fe ₃ O ₄ ) was swollen in 40 ml of distilled water and ultrasonicated for 15 minutes. Then, the iron oxide suspension was added to the CS solution so that the final iron oxide concentration was 0.5 to 2.0% by weight based on the CS weight, And the mixture was stirred for 5 hours. The GO suspension was then added to the mixed solution at various concentrations (e.g., 1 wt% based on the weight of CS) and the stirring speed was maintained at 350 rpm for 1 hour. The final CS concentration of the mixed solution was adjusted to 1% (w / v) by evaporating the water. After the solution was degassed in a vacuum for 30 minutes, the prepared Fe ₃ O ₄ / GO / CS solution was poured into a Teflon mold and dried at 70 ° C. for 8 hours to remove the solvent. The dried membrane was immersed in a 2 wt% NaOH aqueous solution for 1 hour to remove the acid, washed with water until neutral, and dried at 70 ° C for 6 hours. The obtained nanocomposite film was peeled off from the glass plate and stored at room temperature. The average thickness of the film is 0.04 mm.

Experimental Example 1

Wide-angle XRD patterns of the Fe ₃ O ₄ / GO / CS nanocomposite films prepared in Example 1 were investigated using a Rigaku Rotaflex (RU-200B) X-ray diffractometer using Ni filter and CuKα radiation. The tube current and the voltage were set to 300 mA and 40 kV, respectively, and data were collected from 0 to 80 ° C. 2θ intervals. The tensile properties of nanocomposite films were measured at room temperature using Instron 8871, a general test device. The surface morphology of nanocomposite films was analyzed by FE-SEM (LEO SUPRA 55, Carl Zeiss, Germany). The thermal stability of the film was measured at 30 to 900 ° C while heating at 10 ° C / min in a nitrogen atmosphere using a TA instrument (SDT Q600). Dynamic mechanical analysis (DMA) of nanocomposite materials was performed at a frequency of 1 Hz and at a heating rate of 2 ° C / min using a dynamic mechanical analyzer (DMA, Q800, TA) using a tension membrane clamp . The Raman analysis of the nanocomposite material was performed using a Jasco Raman spectrometer equipped with a CCD detector at a wavelength of 532 nm in a range of 100 to 2000 cm ^-1 , and the sample was cut into a 5 × 10 × 0.04 mm strip. The water contact angle of the samples was investigated using an FTA (FIRST TEN ANGSTROMS) 4000.

Fe ₃ O ₄ / Tensile Strength of GO / CS Nanocomposite Films

The mechanical properties of composite films were analyzed using a test instrument (Instron 8871), and tensile strength and modulus were measured. Fe ₃ O ₄ and GO were investigated for various tensile properties at room temperature. B of Figure 1 is CS, (1%) GO / CS, (0.5%) Fe 3 O 4 / (1%) GO / CS , and _{(1%) Fe 3 O 4} / (1%) GO / CS nanocomposite Comparing the tensile strength of the material. (0.5%) Fe ₃ O ₄ / (1%) Tensile strength of GO / CS composite (1%) GO / CS, (1%) Fe ₃ O ₄ / Respectively, by 10%, 14% and 28%, respectively. The tensile strength was determined as the maximum stress in the stress-strain curve as shown in Fig. 1 (a). The elastic modulus was determined by measuring the slope of the linear region of the stress-strain curve. As with the tensile strength results, the modulus of elasticity was also improved as Fe ₃ O ₄ was applied (c in FIG. 1). In _{particular, (0.5%) Fe 3 O} 4 / (1%) GO / CS composite material (1%) GO / CS, (1%) Fe 3 O 4 / (1%) GO / CS and compared to the CS material 22%, 5% and 74%, respectively. The initial stress increased almost linearly with the strain, and the nonlinear phenomenon before the maximum stress appeared in all of the nanocomposites.

GO / CS tensile strength and elastic modulus of the composite was found to be improved by the addition of _{Fe 3 O 4, (0.5%} ) Fe 3 O 4 / (1%) GO / CS nanocomposite is GO / CS composite The elastic tensile properties were 3% higher than the material. These results show that the optimum tensile strength is obtained by applying 1.5% nanopiller (Fe ₃ O ₄ and GO).

Hydrophilic properties of nanocomposite films

The hydrophilicity of the nanocomposite film was analyzed by measuring the contact angle of various nanocomposite films using FST (FIRST TEN ANGSTROMS) -4000. If the material has a high hydrophilicity, it exhibits a low water contact angle value (Park et al., 2008; Konyushenko et al., 2006). _{(1%) Fe 3 O 4} / (1%) GO / CS, CS, (1%) GO / CS , and (1%) Fe ₃ O contact angle of ₄ / CS film is 81 °, 80 °, respectively, 78 ° And 72 °, respectively. (1%) Fe ₃ O ₄ / CS nanocomposite film showed the highest hydrophilicity among the test films (see FIG. 2). (1%) The contact angle of GO / CS nanocomposite film was lower than that of CS film. This is probably due to the presence of multiple hydrophilic functional groups in the GO. Hydrophilicity can be controlled by adjusting the amount of Fe ₃ O _{4 on} the GO surface of the nanocomposite film.

XRD pattern of nanocomposite film

XRD patterns of graphite and GO are shown in Fig. The interlayer space of GO increased from 0.335 nm to 0.796 nm as compared with graphite, because the interlayer van der Waals action was weakened. It is therefore relatively easy to peel the GO into a single layer or a small number of layers by ultrasonically treating the GO.

FIG. 3 shows XRD patterns of CS, GO, Fe ₃ O ₄ , GO / CS, Fe ₃ O ₄ / CS and Fe ₃ O ₄ / GO / XRD patterns were collected at 5 ° to 80 ° (2θ). A strong peak of 2? = 11.11 corresponding to a space of 7.96 A in the XRD pattern of the pure GO was observed. The pure CS did not show any clear peak in XRD due to its amorphous structure. When GO was applied to the CS matrix, the strong peak of the GO disappears at 11.11 ° (7.96 Å), while the other diffraction peaks are similar to those of the pure GO and the 2θ results remain unchanged. The disappearance of the crystal peaks in nanocomposite films indicates that the GO is dispersed within the CS matrix. The XRD patterns of Fe ₃ O ₄ nanoparticles exhibited characteristic peaks (2θ = 30.1 °, 35.5 °, 43.1 °, 53.4 °, 57.0 ° and 62.6 °) consistent with those in the JCPDS database (PDF No. 65-3107) . The pattern of the Fe ₃ O ₄ / GO / CS composite material showed a peak according to the spinel structure of pure Fe ₃ O ₄ particles. In CS, one major peak was observed at 2θ = 20 ° (maximum intensity) corresponding to the characteristic peak of the CS chain aligned via intermolecular interactions (Yamaguchi et al., 2001). Ogawa et al. Proposed three forms of amorphous, hydrated, and anhydrous crystalline CS with characteristic peaks in the 10-20 ° range (Ogawa et al., 1984). The broad peak around 2? = 14.2 ° corresponds to the anhydrous crystalline structure of CS (Wang, Shen, Zhang & Tong, 2005). This crystal type peak appeared more clearly after incorporating Fe ₃ O ₄ and GO in CS. The peak of this angle, which is a wide peak, is presumably due to the presence of a polymorph, such as a hydrated crystal structure, which shows a peak at 2? = 11.7 °. These results indicate that the crystallinity or dense arrangement in the main chain is increased compared to pure CS (Tang et al., 2008).

Fe ₃ O ₄ / FT-IR spectroscopy of GO / CS nanocomposite films

Several studies have confirmed that the oxygen atom of GO is present in the form of -COOH, -C = O, -OH and -COC groups. The hydrophilic oxidative functional groups on the surface or corners of the GO sheet play a crucial role in improving the fusion between the GO and the polymer matrix. As in Figure ^{4, 1061.46cm -1, 1396.46cm -1,} 1729.51cm -1, CO (ν (epoxy or alkoxy)) of the peak of each 3396.69cm ^-1 carboxylic acid and the carbonyl portion, OH (ν (carboxyl ), C = O and OH (broad coupling ν (hydroxyl)). On the other hand, the spectra also showed a C = C-group adsorption peak at 1622.67 cm &lt; ^-1 &gt; corresponding to the sp2 characteristic of graphite. Spectroscopy of oxidized graphene indicates that graphite has been successfully oxidized to oxidized graphene. A large number of oxygen functional groups present in this graphene oxide make the GO sheet strong hydrophilic to improve solubility in water.

The synergy effect of the CS material characteristics due to the addition of the Fe ₃ O ₄ nanoparticles and the oxidized graphene was observed through FTIR experiments, and the results are shown in FIG. FTIR spectra of Fe ₃ O ₄ -CS nanocomposite material, CS and Fe ₃ O ₄ nanoparticles are shown in FIG. The peak near 3420 cm ^-1 is due to the -OH group. In Fe ₃ O ₄ -CS and Fe ₃ O ₄ nanoparticles, the peak at 592 cm ^-1 is due to the Fe-O group (d and a in FIG. 4). Of CS spectroscopy (Fig. 4 b) in, characteristic absorption bands are amide I (C = O stretching), 1588.49cm ^{-1 -1} is shown in 1654.20cm amide II (NH mixed type), and the peak of the 1420.66cm ^-1 CS stretching of the first alcohol group in CS. Fe ₃ O ₄ -CS nanocomposite spectroscopy of the material (Fig. 4 d) from the, as compared with the CS spectral amide I peak of 1654.20cm ^-1, amide II of 1588.49cm ^-1 of the peak and the first alcohol group -CO 1420.66 cm &lt; ^-1 &gt; peaks of stretching vibration were shifted to 1648.38, 1562.73 and 1411.41 cm &lt; ^{-1 &} gt ;, respectively. The movement of these peaks means that CS is covered with magnetic Fe ₃ O ₄ nanoparticles. E in Fig. 4 is Fe ₃ O ₄ / GO / amide I (1654.20cm ^-1) and amide II (1588.49cm ^-1) in the CS with a higher frequency of 1656.15cm 1562.43cm ^-1 and ^- indicates that the move to the ^first . On the other hand, the -OH group band of 3393.10 cm ^-1 in CS also shifted to high frequency. These results suggest that the use of Fe ₃ O ₄ and GO enhances the hydrogen bonding between CS and filler.

Shape analysis

FESEM photographs of the CS film and the fracture surface of the Fe ₃ O ₄ / GO / CS film after the tensile test are shown in FIG. As shown in FIG. 5 (a), the pure CS film was found to have a soft and smooth fracture. In particular, the fracture image of the Fe ₃ O ₄ / GO / CS film was observed to accumulate as the GO was added to the CS film (Fig. 5 (b) and (c)). These results are consistent with recent research reports (Dikin et al. 2007). A uniform distribution of Fe ₃ O ₄ and GO and a broken GO end were observed at the fracture surface. The breakdown of most GOs instead of escaping from the matrix implies strong interfacial adhesion between the GO and CS matrices. Good dispersion and interfacial adhesion are very important factors in making reinforced nanocomposites. TEM images of oxidized graphene have been reported in previous papers (Yadav et al. 2013). This image has a thick, twisty black line, which means that the GO sheet is uniformly distributed on the nanocomposite film without agglomeration.

Thermogravimetry

The integral procedural decomposition temperature (IPDT) measures the area under the curve and describes the overall shape of the curve in the singular. The IPDT proposed by Doyle (Doyle 1961) relates to the volatile part of a polymeric material and is used to determine the intrinsic thermal stability of a polymeric material (Vyazovkin and Sbirrazzuoli 2006). In this experiment, IPDT was calculated as follows.

IPDT (占 폚) = A ^* K ^* (Tf - Ti) + Ti

A ^* = S1 + S2 / S1 + S2 + S3

K ^* = S1 + S2 / S1

Where A ^* is the area ratio of the total experimental curve defined by the total TGA thermogram, Ti is the start experimental temperature and Tf is the final test temperature. S1, S2 and S3 for calculating A ^* and K ^* are provided in Yadav's study (Yadav et al. 2012). Through the thermogravimetric analysis (TGA), it was confirmed that the original graphite was very stable and there was no loss of weight even when heated to 900 ° C. According to these results, GO is more thermally unstable than graphite and undergoes three stages of decomposition. GO has a weight loss of 15% at 176.67 캜. The reduction in weight appears to be due to pyrolysis of the adsorbed water and functional groups containing oxygen such as carboxyl, hydroxyl, epoxy, nitrogen dioxide and ketone. The weight loss rate of the GO increases with increasing temperature from 176.67 ℃ to 250 ℃ and then decreases until it reaches a maximum of about 57.5% by weight at about 587.60 ℃, indicating that structural defects of the GO are present due to strong acid oxidation it means. Comparing the graphite and GO lattice (f and e in FIG. 6), the graphite and GO IPDTs are 91826.36 and 812.27, respectively, which means that graphite is thermally more stable than GO. The thermogravimetric results (TGA, DTG, DSC curve) of CS, (1%) Fe ₃ O ₄ / CS, (1%) GO / CS and (1%) Fe ₃ O ₄ / Respectively. The weight loss of 12 wt% at about 100 캜 appears to be due to the loss of adsorbed water from about 50 캜. The polymer decomposition temperature (PDT) was 189.3 ° C. The weight loss rate increased with increasing temperature from 150 ℃ to 300 ℃ and then decreased until it reached maximum value of 73.50wt% at 900 ℃. (1%) Fe ₃ O ₄ / (1%) The decomposition of the GO / CS nanocomposite film occurred at about 127.6 - 132.5 ℃ and 132.5 - 530 ℃. The Tmax value of this nanocomposite film is 276.4 占 폚. (1%) Fe ₃ O ₄ / (1%) The IPDT and FDT of GO / CS nanocomposite films were 954.5 ° C and 850 ° C, respectively. (1%) GO / CS nanocomposite films are more thermally stable than CS and (1%) Fe ₃ O ₄ / CS. (1%) GO / CS with _{(1%) Fe 3 O 4} / (1%) when comparing the laceration GO / CS, (1%) Fe 3 O 4 / (1%) GO / CS of the FDT and IPDT (1%) Fe ₃ O ₄ / (1%) means that GO / CS is (1%) thermally less stable than GO / CS.

Dynamic Mechanical Analysis (DMA)

As a result of analysis of the storage elasticity (E ') deviation of GO / CS and Fe ₃ O ₄ / GO / CS nanocomposite films, it was found that Fe ₃ O ₄ / GO / E ', which means that the interaction between the CS matrix, GO and Fe ₃ O ₄ is strong. In addition, the storage modulus (E ') was found to be more pronounced at higher temperatures.

Retention ratio = storage elastic modulus at 200 占 폚 / storage elastic modulus at 50 占 폚

The retention rate (Han et al. 2011) indicates the mechanical properties of the material with temperature. According to the analysis results, Fe ₃ O ₄ / GO / CS retention rate nanocomposite film is depends on the Fe ₃ O ₄ content. The retention ratios of GO / CS and Fe ₃ O ₄ / GO / CS calculated using the above equation were 0.548 and 0.505, respectively. Finally, it was confirmed that the Fe ₃ O ₄ / GO / CS nanocomposite film had improved mechanical properties at high temperatures.

The glass transition temperature (Tg) of the sample may be provided from the tan? Curve. The Tg of GO / CS and Fe ₃ O ₄ / GO / CS nanocomposites were determined to be 267 and 264 ° C, respectively. The addition of Fe ₃ O ₄ showed that the Tg of the nanocomposite moved to a lower temperature and the tensile modulus increased. This result shows that the higher the modulus of elasticity of the polymer, the higher the Tg It is different from the general phenomenon. This phenomenon is called antiplasticization phenomenon. According to the reported report (Jackson & Caldwell, 2003 A.), semi-digestion is defined as a decrease in Tg with increasing mechanical stiffness and embrittlement as a specific substance is added to the polymer. The tensile results show that addition of Fe ₃ O ₄ induces embrittlement of the matrix (maximum elongation tends to decrease). These results are consistent with previous studies (Sun, Zhang, Moon & Wong, 2004) using nano-sized silica, silver, and aluminum suggesting that semi-digestion induces polymer embrittlement. The mechanism of semi-digestion is probably a combination of several factors: filling the free volume of the polymer molecule, the interaction between the polar group of the polymer and the polar group of the antiplasticizer, the rigid small Physical curing behavior with respect to the presence of the molecule and hence its location limitation, noncooperative chain transfer of molecules (Jackson & Caldwell, 2003 B). Since the most flexible part of the tightly condensed polymer is a polar group (e. G., An amino group), the interaction of these groups with a hard and polar semi-plasticizer molecule will reduce flexibility. It can be concluded that the mechanism by which the free volume of the polymer matrix is filled and the physical stiffness due to the presence of hard Fe ₃ O ₄ nanoparticles is the only cause of semi-digestion in this system. Similar researchers (Ghosh et al., 2007) reported that low Tg was observed in ultra-thin polymer films with nano-sized materials called nanoconfinement of polymer properties.

The tan δ peak height was higher in GO / CS nanocomposites than in Fe ₃ O ₄ / GO / CS samples. The magnitude of the tan delta peak is associated with loss of vibrational energy that reflects the toughness and stiffness of the material at the damping or relaxation temperature of the capacity. These results further confirm the results of thermal experiments.

Raman spectroscopy

Raman spectroscopy can provide important information regarding the graphite structure, particularly whether carbon-based nanoparticles are amorphous or disordered carbon. In addition, structural change of graphite after oxidation can be confirmed by Raman spectroscopy. In this experiment, the original graphite has three characteristic peaks at 1363.52 (D-band, CC), 1583.25 (G-band, C = C) and 2732.47 cm- ¹ (2D-band). The Raman spectra of GO showed two major peaks at 1618.88 cm ^-1 and 1371.93 cm ^-1 , corresponding to the well known G band and D band, respectively. The D band is due to the defect and disordered state of the graphene oxide, while the G band is related to the hexagonal-plugging structure of graphite (Mao et al. 2012). The degree of defect can be determined by judging the intensity of the D band and the G band based on the ID / IG ratio. In this experiment, the ID / IG ratio was 0.146, indicating that the graphite is close to a defect free structure. Comparing the ID / IG ratio of the native graphite to the oxidized graphene, the oxidized graphene was found to have a higher ID / IG ratio of 0.867, indicating that there is a defect. The ID / IG ratios of GO, GO / CS and Fe ₃ O ₄ / GO / CS nanocomposites were 0.867, 0.897 and 0.894, respectively. Fe ₃ O ₄ / GO / CS has a higher ID / IG ratio than GO and GO / CS, indicating that the structure of the Fe ₃ O ₄ / GO / CS nanocomposite is the intended carbon nanosheet . Further, GO / CS and Fe ₃ O ₄ / GO / CS decreased the intensity of the two peaks in the nanocomposite material, which is less dense than the GO / CS and Fe ₃ O ₄ / GO / CS nanocomposite is oxidized graphene It is because.

Claims (6)

An oxide graphene, iron oxide and chitosan polymer composite material characterized in that the chitosan polymer contains 0.1 to 2% by weight of iron oxide and 0.5 to 2% by weight of oxidized graphene based on the weight of the chitosan polymer. delete A method for improving the mechanical properties of a polymeric molded article by adding the chitosan polymer to the chitosan polymer in an amount of 0.1 to 2 wt% based on the weight of the chitosan polymer and adding the graphene oxide in an amount of 0.5 to 2 wt%. delete Preparing a mixed solution by adding an iron oxide suspension and a graphene oxide suspension to the chitosan polymer solution so that the amount of iron oxide is 0.1 to 2 wt% and the amount of graphene oxide is 0.5 to 2 wt% based on the weight of the chitosan polymer; And
And drying the mixed solution in a predetermined shape to produce a molded product.
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