CHEMICAL ENGINEERING TRANSACTIONS VOL. 71, 2018 A publication of The Italian Association of Chemical Engineering Online at www.aidic.it/cet Guest Editors: Xiantang Zhang, Songrong Qian, Jianmin Xu Copyright © 2018, AIDIC Servizi S.r.l. ISBN 978-88-95608-68-6; ISSN 2283-9216 Preparation, Properties and Application of Polyaniline Nanocomposites Xin Li Department of Materials Engineering,Inner Mongolia Vocational College of Chemical Engineering, Inner Mongolia 010010,China xinli29001@126.com Based on the design of polyaniline structure, two different types of magnetic nanoparticles/polyaniline composites with electromagnetic absorption properties are prepared using the mechanical blending method based on protonic acid doping. Different sizes of FePt/PANI and Fe3O4/PANI composites with hollow structure are prepared by hard template method and mechanical blending method. The impact of the thickness of different shells on the absorbing property of composites is studied by adjusting the mass ratio of aniline/polystyrene. The research shows that the microspheres prepared with hollow structure have a fine morphology and uniform size and the average size is 1μm and 2μm respectively. With the increase of doping concentration, the minimum reflection loss peak shifts toward the low frequency and the corresponding matching thickness gradually becomes thicker. In addition, the loss mechanisms such as dielectric relaxation polarization, eddy current loss and interference cancellation play a major role in the electromagnetic wave absorption process of EG/PANI/Fe3O4 composites. 1. Introduction In the preparation process of conductive PANI, it is necessary to make a reasonable selection of dopants according to the preparation process. In the application of conductive polymers, the amount of material loss is relatively large, and part of electromagnetic energy loss is large. Polyaniline is an absorbing material that can absorb electromagnetic waves. The preparation process of polyaniline nanocomposites is simple and it has high application value in the preparation of conductive PANI. In practical application, the chemical synthesis method is often used for the monomer polymerization of aniline to form PANI. This paper mainly studies the preparation experiment and material processing manufacturing technique of polyaniline nanocomposites and analyzes the material properties and the application of electromagnetic wave absorption. 2. Literature review A conductive polymer is a polymer that exhibits semiconductor or even conductor properties by chemical or electrochemical doping of a polymer backbone having a conjugated double bond (Riaz, 2016). It not only breaks the traditional concept that polymer materials can only act as insulators, but also makes important contributions to the improvement of low-dimensional solid-state electronics. This laid the foundation for molecular electronics (Liu et al., 2016). Polyaniline is considered to be the most promising conductive polymer for practical applications (Pan et al., 2016). The button type secondary battery was prepared using polyaniline as an electrode material. Polyaniline has become a research hotspot in the field of conductive polymers. The history of polyaniline has been reviewed. The research is roughly divided into three phases: the debate about the nature of polyaniline, the development of organic semiconductors, and the hotspots of conductive polymer research (Ji et al., 2015). Polyaniline is a kind of polymer compound which has special electrical and optical properties. After doping, it has electrical and electrochemical properties (Luo et al., 2016). After certain treatment, various equipments and materials with special functions can be produced. The electrical activity of polyaniline originates from the P-electron conjugated structure in the molecular chain. With the expansion of the P-electron system in the DOI: 10.3303/CET1871149 Please cite this article as: Li X., 2018, Preparation, properties and application of polyaniline nanocomposites, Chemical Engineering Transactions, 71, 889-894 DOI:10.3303/CET1871149 889 molecular chain, the P-bonded state and the P*-inverse-bonded state form a valence band and a conduction band, respectively. This non-localized P-electron conjugated structure is doped to form P-type and N-type conductive states. Compared with the doping mechanism of other conductive polymers to generate cationic vacancies under the action of oxidant, the number of electrons in the doping process of polyaniline does not change. The doped protonic acid is decomposed to produce H+ and the counter anion enters the backbone. This combines with the N atoms in the amine and imine groups to form a pole and a dipole delocalized into the P bond of the entire molecular chain. As a result, polyaniline exhibits higher conductivity. This unique doping mechanism makes the doping and dedoping of polyaniline completely reversible. The degree of doping is affected by factors such as pH and potential, and is manifested as a corresponding change in the appearance color. Polyaniline is therefore electrochemically active and electrochromic. High quality polyaniline was synthesized by electrochemical method. Electrochemical preparation of polyaniline has been studied (Svenonius et al., 2016). Chemical oxidative polymerization and electrochemical polymerization are the most commonly used methods for polyaniline synthesis. In addition, there are vacuum evaporation, plasma polymerization, and photopolymerization (Zou et al., 2017). The researchers studied the temperature dependence of room temperature conductivity and conductivity of LGS-PANI at different LGS levels (Guan et al., 2018). LGS-PANI may have the following structure: When the content is 11.4wt%, LGS is the template and the stretching chain structure is formed. When the LGS content is 48.2wt%, a double-stranded ordered structure is formed. When the LGS content is 69.5wt%, the proportion of LGS single-chain disordered packing increases. When the LGS content is high, it also contains the hydrogen bond between LGS and PANI (Franco-Orozco et al., 2017). The aqueous solution of PAN/PANMPS can be stably placed for more than two months under normal environmental conditions (Silvagomes et al., 2016). When (Anmol)⁄(AMPSmol=0.3:1), PAN/PAMPS has a PAMPS-doped PANI of a double-stranded coil structure and is deposited into a granular form. SEM analysis by scanning electron microscopy showed that the particle morphology formed by the deposition was well dispersed in the linear polymer matrix. The room temperature conductivity of PANI/PAMPS solid membrane and PANI/PAMPS solution was studied separately. The thermostability of PANI/PAMPS was studied using a thermogravimetric analyzer (Shima et al., 2017). In summary, considering the conductivity, particle size and uniformity, dispersibility, conductivity stability and thermal stability of polyaniline composites, a suitable nanocomposite is selected as the conductive filler. Polyaniline is facilitated by the conversion of functional material phase structural materials, which has a new definition of the range of applications of polyaniline materials. 3. Method 3.1 Experimental The reagents and instruments used in the test are shown in Tables 1 and 2 below. Table 1: practical use of test sites Reagent name Reagent purity Manufacturer H2PtCl·6H2O Analytically pure Tianjin Guangfu Fine Chemical Research Institute FeCl3·6H2O Analytically pure Yantai Shuang Shuang Chemical Industry Co., Ltd. FeSO4·7H2O Analytically pure Baiyin Chemical Reagent Factory NaOH Analytically pure Tianjin Da Mao Chemical Reagent Factory Anhydrous ethanol Analytically pure Tianjin Fuyu Fine Chemical Co., Ltd. Azo two isobutadiene Analytically pure Tianjin Da Mao Chemical Reagent Factory aniline Analytically pure Tianjin Da Mao Chemical Reagent Factory toluene Analytically pure Tianjin Da Mao Chemical Reagent Factory hydrochloric acid Analytically pure BaiyinLiangyou Chemical Reagent Co., Ltd. Fourier transform infrared spectrometer (FT-IR) is used to test the functional group contained in the sample. In the infrared absorption spectrum, the wave number (cm-1) is usually used as the abscissa and the transmittance (%) as the ordinate; test method: a small amount of powder sample and a certain amount of KBr are taken for the tablet ting after mixing and grinding uniformly, and then it is placed in an infrared spectrometer for testing. The phase and crystallinity of the sample are characterized by X-ray diffractometer (XRD). Test method: the powder sample to be tested is placed in the sample tank for tableting and then it is placed in CuKα (the tube voltage and tube current are 40 kV and 150 mA respectively; the generator power is 890 3000 W; the scanning range is 10° to 90°; and the scanning step is 100/min) as the radiation source of the X- ray diffractometer for the testing. The transmission electron microscopy (TEM) is used to analyze the structure and particle size of the sample. Test method: a small amount of the powder sample to be tested is taken for the ultrasonic dispersion in absolute ethanol. Then, one or two drops of the dispersed solution is dropped on 300 mesh copper net and it is dried at 40 °C in a vacuum oven. Finally, it is put in the transmission electron microscope for observation and analysis. The surface morphology of the sample is analyzed by scanning electron microscopy (SEM). Test method: a certain amount of powder sample to be tested with uniform dispersion is directly adhered to the conductive paste and the surface is gilt to enable it to be conductive. Finally, it is placed in a scanning electron microscope for observation and analysis. Table 2: list of experimental apparatus and specifications Instrument name Instrument model Manufacturer Thermal type constant temperature heating magnetic stirrer DF-101S Zhengzhou Ya Rong Instrument Co., Ltd. Electronic balance FA2104N Shanghai Precision Science Instrument Co., Ltd Ultrasonic cleaner KQ5200B Kunshan Ultrasonic Instrument Co., Ltd. Centrifuge TGL-16G Shanghai Anting Scientific Instrument Factory Digital display intelligent temperature control magnetic stirrer SZCL-A Zhengzhou the Great Wall science and Trade Co., Ltd Rotary evaporator RE52-99 Shanghai Ya Rong biochemical instrument factory Vacuum drying oven DZF-6050 Shanghai Jinghong Experimental Equipment Co., Ltd Quartz automatic double water distiller 1810-B Jiangsu Jintan Zheng Ji Instrument Co., Ltd. Refrigerator BCD-181MLC Hefei MeiLing Limited by Share Ltd 3.2 Polyaniline Nanocomposites In recent years, magnetic nanoparticles/conductive polymer composites have been widely used in the field of electromagnetic wave absorption in military and civilian applications. Among conductive polymers, PANI is a good electrical loss type of absorbing material because of its low cost, simple preparation, low density and good environmental stability, which has received extensive attention. However, it is difficult for pure PANI to meet the requirements of absorbing bandwidth and performance of absorbing materials. Considering the electromagnetic matching requirement for good absorbing materials, many researchers combine magnetic nanoparticles with PANI to obtain the absorbing agent with good performance. For this reason, the alloys represented by Fe, Co, and Ni and their oxides have received extensive attention. Among magnetic materials, magnetic FePt nanoparticles have good chemical stability, which are an excellent magnetic loss type of absorbing material. The Fe3O4 nanoparticles have also received wide attention because of the simple preparation method, low cost and less magnetic loss. Li et al. prepared PANI/Mn0.8Zn0.2Fe2O4 nanocomposites by in-situ polymerization method and studied their absorbing properties in the range of 2 to 18 GHz. The results showes that its RLmin reached -20.6 dB at 14.4 GHz and its bandwidth of RL < -10 dB was up to 5.6 GHz. The bandwidth -5 Db