Resumo: Nanocompósitos Esfoliados de Poliestireno (PS) e Hidróxido Duplo Lamelar (HDL) composto por zinco, alumínio e dodecil sulfato de sódio, como ânion interlamelar, foram sintetizados via polimerização in situ. O efeito de diferentes composições de HDL (0,5, 1, 3 e 5% em massa) foi avaliado. Os nanocompósitos obtidos foram caracterizados através de ensaios de Difração de Raios X (DRX), Espectroscopia no Infravermelho por Transformada de Fourier (FTIR), Microscopia Eletrônica de Transmissão (MET) e Análise Termogravimétrica (TGA). Os resultados obtidos através das análises de DRX e MET mostraram que todos os nanocompósitos produzidos apresentaram morfologia esfoliada. Os resultados das TGA, quando se utilizam 50% de perda de peso como ponto para comparação, apresentaram ganhos significativos de estabilidade térmica para todas as composições dos nanocompósitos em comparação ao poliestireno puro. Este comportamento possibilita uma vasta gama de aplicação destes novos materiais em diversos campos da indústria e pesquisa. Palavras-chave: Nanocompósito, hidróxido duplo lamelar, poliestireno, polimerização in situ. Synthesis and Characterization of Exfoliated Polystyrene-Layered Double Hydroxide Nanocomposites Via In Situ PolymerizationAbstract: Exfoliated nanocomposites of polystyrene (PS) and layered double hydroxide (LDH) compound of zinc, aluminium and sodium dodecyl sulfate, as interlayer anion, have been synthesized via in situ polymerization. The effect from the LDH compositions (0.5, 1, 3, 5% weight) was studied. The nanocomposites were characterized by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and Thermogravimetric Analysis (TGA). The XRD and TEM results showed an exfoliated morphology for the nanocomposites in all compositions. With the 50% weight loss taken as a reference, the TGA results indicated significant improvement in thermal stability for all compositions of the nanocomposites, in comparison to pure polystyrene. This is promising for the application of these new materials in many fields of industry and research. Keywords: Nanocomposite, layered double hydroxide, polystyrene, in situ polymerization. IntroduçãoOs nanocompósitos podem ser definidos como materiais híbridos em que pelo menos um dos componentes tem dimensões nanométricas [1][2][3] . Nanocompósitos poliméricos apresentam recente desenvolvimento e têm como marco inicial a publicação de um trabalho na década de 80/90 pelo grupo de pesquisa da empresa Toyota, onde foi produzido um nanocompósito de nylon 6 e o argilomineral (montimorilonita). O novo nanocompósito produzido apresentou uma extraordinária melhora nas suas propriedades mecânicas, térmicas e físicas quando comparado ao polímero puro [4] . Entre os nanocompósitos poliméricos, muitos estudos mostram como a dispersão de compostos lamelares em uma matriz polimérica afeta as propriedades do material obtido, no entanto, na maioria dos trabalhos são utilizados argilominerais trocadores catiônicos naturais, como a mon...
Polystyrene (PS)/layered double hydroxide (LDH) nanocomposites were synthesized by in situ free radical bulk polymerization. LDH formed by magnesium and aluminum (Mg:Al—molar ratio of 2:1) was prepared by coprecipitation method and intercalated with sodium dodecyl sulfate (DDS). The nanocomposites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), and flammability test. The XRD and TEM demonstrated that synthesized nanocomposites in all compositions studied showed a high global dispersion of LDH in PS, suggesting exfoliation. The results of TGAs (when 50% mass loss was selected as a comparison point) and flammability tests for synthesized nanocomposites, presented a significant improvement in thermal stability and flammability property when compared with pure PS. This behavior and properties indicate application of the surfactant intercalated LDH reinforced PS in fields where thermal stability is an important characteristic. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers
Poly(methyl methacrylate) (PMMA)/layered double hydroxides (LDH) nanocomposites were synthesized by in situ bulk polymerization. The LDHs were synthesized by coprecipitation method. Eight LDHs having different compositions were produced, varying the divalent/trivalent cations (Zn/Al, Mg/Fe), the ratio between these cations (2: 1 and 4: 1) and the LDH intercalated anions (dodecyl sulfate and laurate). The LDH percentage (wt %) in the PMMA was fixed at 1%. The thermal properties of the nanocomposites were evaluated by thermal analysis (thermogravimetric-TGA and differential scanning calorimetry-DSC). Most of the nanocomposites presented higher thermal resistance than PMMA and the best results were presented by the following nanocomposites: PMMA/ (Zn/Al 2: 1 laurate) and PMMA/(Zn/Al 4: 1 laurate). The dynamic mechanical properties of the nanocomposites were investigated and compared to those obtained for PMMA. It was noticed that PMMA/(Mg/Fe 4: 1 laurate) nanocomposite presented an elastic modulus 2.2 times higher than PMMA at 40C. This investigation demonstrated that the addition of low concentrations of selected LDHs can enhance some desired properties of PMMA.
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