Production of Micrometer-sized composite Polymer ...

Production of Micrometer-sized Composite Polymer-magnetic Spheres Using as Precursor Metalurgical Wastes

Production of Micrometer-sized Composite Polymer-magnetic Spheres Using as Precursor Metallurgical Wastes Y.A. Perera-Mercado*, R. Betancourt-Galindo, E.M. Saucedo-Salazar, B.A. Puente-Urbina, D.I. Medellín-Banda, M.G. Neira-Velázquez, M.H. Gutierrez-Villarreal and S.P. García-Rodríguez Centro de Investigación en Química Aplicada (CIQA), Blvd. Enrique Reyna Hermosillo No. 140, Col. San José de los Cerritos, C.P. 25294, Saltillo, Coahuila, México

Summary Micrometer-sized composite polymer-magnetic spheres consisting of a magnetic-spherical core with a polystyrene shell were produced. The magnetic-spherical core was produced by plasma thermal conversion of waste powders precursor (iron oxide) generated during the conventional process of steel production. Precursor powders were projected into an Ar-He plasma plume using industrial thermal-spray equipment. The results are a total conversion of the precursor powders into magnetic-spherical particles with diameters in the micrometer size range. The surfaces of the magnetic-spheres were functionalized by a chemistry hydrolysis method using 3-aminopropyltrimethoxysilane (APTMS) and creating superficial amine structures that improved the adherence of the final polystyrene shells that was polymerized by adapting the miniemulsion process. The products at the different synthesis steps were characterized by diverse techniques, such as: X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), Fourier Transformed Infrared spectroscopy (FTIR) and the magnetic properties were investigated with a vibrating sample magnetometer.

Keywords: Polystyrene, Core-shells, Magnetic-spheres, Ar-He Plasma, Composite, Hybrid materials

1. Introduction The design and synthesis of hybrid materials with controlled shapes and desired morphology have stimulated great research interest because of their novel properties and final potential applications. In recent years, extensive studies have been carried out on the preparation of composite materials by different synthesis routes with the ability to combine the properties of each component; hence there are a very wide range of disciplines contributing to the developments in this kind of materials and technology worldwide. On this way, the preparation and characterization of nano- and microspheres composites have received high

scientific attention because of their wide potential of application1-7. For example, organic/inorganic composites combine the advantages of the inorganic material like stiffness, magnetism and thermal stability, because the polymer components normally show ﬂexibility, ductility and processability. So, many recent efforts have been focused on the integration of inorganic particles inside of polymer microspheres to form core-shells structures8 that make possible explore their novel collective mechanical, thermal, optical, magnetic, and electronic properties9,10 thereby converting them in ideal candidates for applications ranging from drug delivery, catalysis carriers, bioseparation and diagnostic contrast agents11.

*E-mail: [email protected]; Tel. +52 (844) 4389830. Ext.1410 This paper was presented at: 2nd International Congress on Advanced Materials (AM2013) in Zhenjiang, China. 16-19 May 2013.

Smithers Rapra Technology, 2014

©

Polymers & Polymer Composites, Vol. 22, No. 4, 2014

Specifically, the magnetic-polymer hybrid particles with core-shells structured show a unique magnetic responsively, low cytotoxicity, and chemically liable surface12. These magnetic particles, especially with a core of magnetite (Fe3O4) and/or maghemite (γ-Fe2O3) phases have attracted increasing interest because of their outstanding properties including soft magnetism for their saturation magnetizations (Ms) and lower coercitive force13, superparamagnetism and low toxicity. It is worth to notice that the Fe3O4 has been considered an ideal material for biological and biomedical magnetic applications such as targeted for antitumor therapy, hyperthermia treatment of cancers, enzymatic assays, and activity agent for medical diagnostics because of its good hydrophilic, biocompatible, nontoxicity properties, and high chemical stability14. Various approaches have been explored for synthesis of high-quality magnetic iron oxide particles15-20.

387

Y.A. Perera-Mercado, R. Betancourt-Galindo, E.M. Saucedo-Salazar, B.A. Puente-Urbina, D.I. Medellín-Banda, M.G. Neira-Velázquez, M.H. Gutierrez-Villarreal and S.P. García-Rodríguez

On the other hand, the preparation of materials with core-shell structures on nanometer and/or micrometer scales includes diverse process of polymerization; for example, the copolymerization of hydrophobic monomer core-hydrophilic shells. But the compatibility between the inorganic-core and the organic-shell represent important challenges. On this way, a lot of work has been done to fabricate magnetic composite particles by encapsulating magnetite particles using an interlayer over the magnetite particles, these inorganic coatings are commonly silica, titanium dioxide and others, produced through a sol-gel approach21-24. These kinds of interlayer improved the organicinorganic interaction generating more stable composite systems. Finally, to prepare hybrid magnetic spheres, the most common way is the dispersion of the spherical magnetic particles into the liquid phase of a polymerizable formulation to encapsulate the magnetic spheres generating the magnetic hybrid particles25. Thereby, diverse routes can be used, for instance, surfactant directed chemical oxidation polymerization, miniemulsion polymerization, suspension polymerization, and copolymerization of monomers (one of them is the functional monomer) where is commonly used to introduce a reactive functional groups into the composite spheres; Finally, it is important mention that polystyrene and poly-(methyl methacrylate) (PMMA) are the most frequently polymer materials used for hybrid magnetic supports26-27.

known as “iron flakes” and its chemical composition is shown in the Table 1. The rich-Fe precursor was transformed by Ar-He plasma projection process, using plasma thermal sprayed equipment Plasmadyne (Praxair) SG100. Argon and Helium gases were used to generate the plasma flame. The Plasma parameters used for the projection were: Ar:He (rate 1:1) with a gas feeding flows of 6 L/min at an electric current of 1000 A. Finally, the recollected material consisted in perfect magnetic-spheres.

2.2 Functionalization of Magnetic Spheres To assure the interaction between the magnetic core (sphere) and the polymeric shell was necessary to modify the surface of the magnetic-spheres with 3-aminopropyltrimethoxysilane (APTMS). So, the surfaces of the magnetic-spheres are functionalized by an hydrolysis chemical method to form superficial films with terminal amine groups that work as anchors between the magnetic core and the polymeric shell. The functionalized process consisted in the mixing of 0.5 g magnetic-spheres particles with octane used as solvent and then, adding the APTMS as modifier agent in a relation of octane:APTMS equal to 0.5:1. The mixture solution is maintained at temperatures between 50-60 ºC for 5 h. The functionalized surface magnetic-spheres also help to obtain

a good dispersion of them during next step of polymerization process.

2.3 Polymeric Encapsulation A micellar solution was prepared in a weight rate of surfactant/water (CTAB/ H2O) of 0.5/99.5%. Subsequently, 0.05 g of magnetic particles previously functionalized were added into 6 g of styrene as monomer, 0.11 g of hexadecane and 0.017 g of initiator soluble in the oleic phase (AIBN). The dispersion was sonificated for 15 min to get a homogenous solution. A blend was then prepared from a micellar solution along with the solution of magnetic particles, which was sonificated for 2 min to get a stable miniemulsion, followed by the addition of 0.5 g of methacrylic acid at 80 °C to starting the polymerization reaction process. The general procedure for the generation of the micrometer-sized polymeric magnetic-spheres is shown in Figure 1.

2.4 Characterization Techniques Morphologies and sizes of the particles generated in each step (original precursor material, spheroidization, functionalization and encapsulation) were evaluated using a field emission scanning electron microscope (FE-SEM) JEOL 7401-F, operating at low voltage (2kV) and 8 mm as work distance. Additional, X-Ray Energy Dispersive

Figure 1. Diagram of preparation of polystyrene-Fe3O4 magnetic-spheres composite

2. Experimental PROCEDURE 2.1 Preparation of Magneticspheres (Core) The precursor used to produce the magnetic-spheres was for first time an industrial waste generated by the Mexican steel industry; this material is

388

Table 1. Chemical composition of the waste Fe-rich precursor Oxide % wt.

SiO2 7.37

Al2O3 0.1

CaO

MgO

MnO

FeO

1.2

0.07

1.8

89.25

Na2O 0.06

K2O 0.07

ZnO 0.06



Spectrometer (EDS) associate with FE-SEM equipment was used for the qualitative chemical analysis of the magnetic-spheres. X-ray diffraction patterns of the rich-Fe precursor and the magnetic-spheres obtained after their plasma spheroidization were obtained to determine the phase transformation carried out during the projection process. Samples were characterized at room temperature using a Siemens Diffractometer. Diffraction parameters were: 2q ranging from 10° to 90° and a Cu-Kα (λ = 1.5418 Å) radiation was used in all experiments at 35 kW and 25 mA. Magnetization curves were carried out on a Quantum Desing PPMS using a DC magnetization with fields up 1 T at 300 K. Both materials, the precursor waste and the magneticspheres produced by Ar:He plasma were analyzed also by this characterization technique. Finally, FTIR analyses were carried out on a Nicolet Magna 5500 Spectrometer. The samples are prepared using a mixture of the magnetic-spheres and KBr.

3. RESULTS AND DISCUSSION 3.1 Preparation of Magneticspheres (Core) Figure 2a shows the scanning electronic microscopy (SEM) micrograph from the precursor used in this work before its plasma conversion into magneticspheres (Figure 2b). The Fe-rich precursor is formed by particles with angular surfaces and different sizes. In Figure 2b it can be observed that the produced spherical particles have a wide distribution of sizes and all of them are in the micrometer range. Figure 2c shows the qualitative EDS analysis of the magnetic-spheres indicating that iron (Fe) is the major component of this new material; also secondary elements such as silicon (Si) and manganese (Mn) were identified, which coincides with the chemical composition of the precursor (Table 1). A SEM image associated with the EDS analysis shows a detail of the magnetic-spheres produced by plasma

Ar-He where is possible observed that mostly magnetic-spheres have a dendritic surface morphology. On the other hand, the precursor and also magnetic-spheres were analyzed by X-ray diffraction (DRX). The XRD spectrum (Figure 3a) shows an evident transformation of crystalline phases during the plasma projection process. The original precursor material shows a mixture of wüstite (FeO) and magnetite (Fe3O4) phases and after the spheroidization by Ar:He plasma projection a new mixture of phases can be identified as magnetite (Fe3O4) and maghemite (γ-Fe2O3). M o r e o v e r, F i g u re 3 b s h o w magnetization curves of the original precursor material and the magnetic spheres. The magnetization data for the magnetic-spheres suggests a ferromagnetic behavior at room temperature with not hysteresis and a saturation magnetization of 83 emu/g at 10 kOe, this lower saturation

Figure 2. (a) Mexican Industrial waste precursor Fe-rich known as “iron flakes”, (b) Magnetic-spheres generated, (c) EDS analysis and SEM micrograph (detail) from a magnetic spherical micro-particle analyzed

Figure 3. (a) XRD spectra from the magnetic-spheres generated by the plasma thermal spray technology, (b) Magnetization curves as-synthesized magnetic Fe3O4 spheres and precursor


389


magnetization values in comparison to the reported for the bulk magnetite (92 emu/g) could be attributed to the presence of the maghemite phase that is mixed with the magnetite phase inside of the magnetic-spheres; in general terms the magnetic-spheres show the behavior that is described by soft magnetic materials. The original precursor shows a normal hysteresis magnetization curve with a saturation magnetization of 20 emu/g at 10 kOe; it is due to the mixed phases inside of the original precursor, mostly wüstite (FeO) that is a non-magnetic phase that decreases the magnetic properties of the spherical material produced.

3.2 Functionalization of Magnetic Spheres The surfaces of the magnetic-spheres are functionalized by a chemistry hydrolysis method forming superficial

films with amines on the surface terminal section. The functionalized process used in this research was reported in the experimental section. This methodology step allows forming chemical bonds between the two different materials (ceramic and polymer) and increasing the compatibility of the systems. Modified magnetic-spheres and non-modified magnetic-spheres were characterized using FTIR analysis. The spectra of both systems are shown in Figure 4. Magnetic-spheres FTIR spectra shows (Figure 4a) the presence of a large band around 3500-3300 cm-1 assignable to the Fe-OH and a deformation vibration of the –OH bond at 1620 cm-1. After the superficial modification of the magnetic-spheres, the FTIR spectra (Figure 4b) indicates the presence of the covalent bonding of the silane monomer on the magnetic-

Figure 4. FTIR spectrals. (a) Magnetic-spheres, (b) Functionalized magnetic-spheres

spheres surface though the new band at 1050 cm-1 that is attributed to Si-O-Si stretching vibrations and more specifically in this case, for the Si-O-Fe covalent bonds. On the other hand, the absorption band at 3416 cm-1 is characteristic for the free NH2- terminal groups, the band being covered with the stretching vibration band of the -OH group. The band NH2 scissoring appeared at 1610 cm-1. The absorption band at 1332 cm-1 has been associated with the C-N bond and the band at 1223 cm-1 is attributed to SiCH2 bond. The vibrations associated for each analyzed material are given in Table 2. Figure 5 shows a FE-SEM micrograph where is possible observe the functionalized magnetic-spheres. A group of agglomerated magneticspherical particles are identified (Figure 5a). The Figure 5b shows a detail of the binder functionalized bridge between two magnetic-spheres. It is possible to observe that the magnetic-spheres dendritic surfaces are covered with this new material changing the roughness of the spherical material and also creating a fresh surface which will improve the dispersion into polymer matrix and also the adherence between the shell-polymer and the core-ceramic magnetic-spheres.

3.3 Polymeric Encapsulation

Table 2. FTIR signal associated to the chemical bonding vibrations Wavelength (cm-1)

Magnetic-spheres

Magnetic-spheres Functionalized

1050

Si-O-Fe

Si-O-Fe and Si-O-Si

28,29

1220

-

Si-CH2

28,29,30

C-N

28

-OH and NH2

28,30

-CH2

28,29

1335-1370

-

1620

-OH

3416

-

3024-2933

-

3500-3300

Fe-OH and -OH

390

NH2-

Fe-OH and -OH

Ref.

30 28,30

Figure 6 shows the FE-SEM micrographs of the prepared polystyrene micrometer-sized magnetic-spheres by adapting a miniemulsion polymerization process. Figures 6a and 6b indicate that the miniemulsion process can be applied for cover magnetic particles with variable diameters of particles into the micrometer range. No-agglomerate core-shell particles were obtained in different micrometer sizes because the magnetic-spheres particle sizes produced previously by Ar:He plasma conversion of waste precursor are heterogeneous.



Figure 5. FE-SEM micrographs from the magnetic-spheres after functionalized with APTMS

Finally, the polymeric magneticspherical particles show a smooth surface of adherent polystyrene on the magnetic-spheres core. This novel procedure brought about a new generation of hybrid polymer/ceramic magnetic-spheres with different particle sizes.

4. CONCLUSIONS Composite polystyrene/ceramic magnetic spheres particles type core-shells with diameters into the micrometer-sized range were produced. The composite polymer/ ceramic magnetic spheres with ferromagnetic behavior were synthesized from magnetic-spheres with different particle diameters that were obtained through the Ar-He plasma transformation of an industrial waste which is generated by the Mexican Metallurgical Industry. The functionalization of the magneticspheres helped with the dispersion of the magnetic-spheres during the encapsulation process with polystyrene

Figure 6. FE-SEM micrographics of micrometer-sized polystyrene-Fe3O4 spheres composite

and also improved its adhesion to the magnetic-spheres cores. The adapted miniemulsion procedure was an efficient methodology to get the coreshells structures of this new composite material. Finally, the composite materials produced with this novel procedure can be used to produce a hybrid polymer-ceramic magneticspherical material for diverse industrial and researching applications.

REFERENCES 1.

Siegel R.W., Chem. Eng. News, 77 (23) (1999) 25.

2.

Bigi A., Boanini E., Walsh D. and Mann S. Angew., Chem. Int. Ed., 41 (2002) 2163.

3.

Yang D., Qi L.M. and Ma J.M., Adv. Mater., 14 (2002) 1543.

4.

Lizama B., Lopez-Castanares R., Vilchis V., and Vázquez F., Mater. Res. Innovat., 5 (2001) 63.

5.

Gao Y., Choudhury N.R., Dutta N., Matisons J., Reading M. and Delmotte L., Chem. Mater., 13 (2001) 3644.


6.

Antonietti M. and Goltner C., Angew. Chem. Int. Ed., 36 (1997) 910.

7.

Winiarz J.G., Zhang L.M., Lai M., Friend C.S. and Prasad P.N.J., Am. Chem. Soc., 121 (1999) 5287.

8.

Monteiro O.C., Esteves, A.C.C. and Trindade T., Chem. Mater., 14 (2002) 2900.

9.

Chan Y.N., Craig G.S.W., Schrock R.R. and Cohen R.E., Chem. Mater., 4 (1992) 885.

10. Forster S. and Antonietti M., Adv. Mater., 10 (1998) 195. 11. Yin D., Yong H., Leyang Z., Ying Ch. and Xiqun J., Biomacromolecules, 7 (2006) 17661772. 12. Shouhu X., Yi-Xiang J.W., Ken Cham-Fai L. and Kangying S., J. Phys. Chem. C, 112 (2008) 1880418809. 13. Lijun Z., Hongjie Zh., Yan X., Shuyan S., Shiyong Y., Weidong Sh., Xianmin G., Jianhui Y., Yongqian L., and Feng C., Chem. Mater., 20(1) (2008) 198-204. 14. Peng H., Lingjie Y., Ahui Z., Chenyi G., and Fangli Y.J., Phys. Chem. C, 113 (2009) 900-906.

391


15. Duan H.W., Kuang M., Wang X.X., Wang Y.A., Mao H. and Nie S.M., J. Phys. Chem. C, 112 (2008) 8127. 16. Sun S.H. and Zeng H.J., Am. Chem. Soc., 124 (2002) 8204. 17. Zhu Y.F., Zhao W.R., Chen H.R. and Shi J.L., J. Phys. Chem., 111 (2007) 5281. 18. Shultz M.D., Reveles J.U., Khanna S.N. and Carpenter E.E., J. Am. Chem. Soc., 129 (2007) 2482.

21. Deng J., Ding X., Zhang W., Peng Y., Wang J., Long X., Li P. and Chan A.S.C., Polymer, 43 (2002) 2179. 22. Xu X., Friedman G., Humfeld K., Majetich S. and Asher, S., Adv. Mater., 13 (2001) 1681. 23. Vestal C.R. and Zhang Z.J., J. Am. Chem. Soc., 124 (2002) 14312. 24. Deng Y., Yang W., Wang C. and Fu S., Adv. Mater., 15 (2003) 1729.

19. Hong R., Fischer N.O., Emrick T. and Rotello V.M., Chem. Mater., 17 (2005) 4617.

25. Weijun L. and Zhicheng Zh., Polymer Composite, 31 (2010) 1846.

20. Ge J.P., Hu Y.X., Biasini M., Beyermann W.P., Yin and Y.D. Angew., Chem., Int. Ed., 46 (2007) 4342.

26. Chen A.Z., Kang Y.Q., Pu X.M., Yin G.F., Li Y. and Hu J.Y., J. Colloid. Interface. Sci., 330 (2009) 317.

392

27. Mahdavian A.R. and Sehri Y., Eur. Polym. J., 44 (2008) 2482. 28. Durdureanu-Angheluta A., Ardeleanu R., Pinteala M., Harabagiu V., Chiriac H. and Simionescu B.C., Digest Journal of Nanomaterial and Biostructures, 3(1) (2008) 33-40. 29. Zhang K., Wu W., Guo K., Chen J.-F. and Zhang P.-Y., Colloids and surface A: Physicochem. Eng. Aspects, 349 (2009) 110-116. 30. Medhat I., Abdallah N. and DiaaEldin K., Indian Journal of Pure & Applied Physic, 43 (2005) 911-917.
