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Journal ArticleDOI

Propriedades mecânicas de nanocompósitos de polipropileno e montmorilonita organofílica

01 Jun 2006-Polimeros-ciencia E Tecnologia (Associação Brasileira de Polímeros)-Vol. 16, Iss: 2, pp 136-140

AbstractNanocomposites of polypropylene and commercial montmorillonite organophilic Cloisite 20A containing 2.5%, 5%, 7.5% and 10% of clay with polypropylene-graft-maleic anhydride as coupling agent were prepared through the melt intercalation by twin-screw extruder. The materials were characterized by x-ray diffraction, tensile and impact properties according to ASTM D638 and D256 test methods, respectively. The x-ray diffraction results showed exfoliated or intercalated structures for different concentrations of the clay. The tensile modulus improved with the increase of the amount of the clay while the impact strength showed unsatisfactory results.

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Journal ArticleDOI
Abstract: The development of nanocomposite materials with polymeric matrices, especially those using layered silicates, provides an alternative to composites with conventional fillers. One of the controversial aspects in the scientific literature about polypropylene-montmorillonite nanocomposites (PP/OMMT) regards its thermal stability compared to the PP matrix. The aim of this work is to evaluate the influence of the presence of montmorillonite clay in the degradation of composites, showing the limitations of thermogravimetric analysis (TGA) and emphasizing the importance of complementary analyzes such as differential scanning calorimetry (DSC) and oxidation induction time (OIT). The TGA results showed that the higher the organoclay content, the higher the temperature at which the release of volatiles takes place. However, the OIT results indicated a lower temperature for the onset of exothermic reactions for these materials and consequently the stability of the material is reduced. The use of DSC method simulating conditions of TGA, called oxidation induction temperature or dynamic OIT, was used to evaluate the stability of the composites explaining the divergence between the TGA and OIT results. The thermal analysis results were correlated to organoclay morphology, as evaluated by WAXS. It was concluded that the clay contributed to the beginning of exothermic oxidation reactions and to the kinetics decrease of volatile release and its formation.

45 citations


Journal ArticleDOI
Abstract: An evaluation was made of the degradation of polypropylene (PP) and montmorillonite (MMT) nanocomposites. The nanocomposites were compatibilized with polypropylene grafted with maleic anhydride (PP-g-MA) and with acrylic acid (PP-g-AA). The concentration of MMT varied from 1 to 5% (w/w). Nanocomposites were processed in a twin screw extruder up to five times. X-ray diffraction showed a decrease in the refraction angle with reprocessing steps and for PP-g-MA based nanocomposites, indicating an increase in the interplanar distance due to clay intercalation and exfoliation. Infrared analysis showed an increase in the concentration of carbonyl and unsaturated groups with the increase in the number of reprocessing cycles, and reduction as the MMT concentration increased. Colorimetry assays indicated a decrease in the luminosity and degree of redness due to the oxidation of the iron ions present in MMT to Fe 2 O 3 . The intensity of the yellow color of the b * coordinate was augmented with the number of reprocessing cycles but decreased with MMT concentration, confirming the FTIR analysis. Rheological measurements showed no crossing point between storage ( G ′) and loss ( G ″) moduli versus frequency, which is characteristic of a percolated nanocomposite networks. Within a range of frequencies, complex viscosity decreased with the number of reprocessing cycles, but the presence of montmorillonite was found to be responsible for lower differences between viscosity of nanocomposites reprocessed one and five times.

40 citations


Journal ArticleDOI
Abstract: The aim of this work is to study the interactions of different nanoparticles modified with (3-aminopropyl)triethoxysilane (APTES) and to relate them with the morphology and the final properties of the PHBV nanocomposites The compounds were prepared by melt processing in a twin screw extruder with 3 mass% of nanoparticles and the resulting nanocomposites were physically and mechanically characterized to evaluate the effect of the different reactive groups available for interactions within the polymer matrix The nanocomposites prepared with either the unmodified montmorillonite (Mt) or the modified (m-Mt) form presented similar or improved thermal and mechanical properties of the matrix, while those prepared with organically modified halloysite (m-Hal) presented a general decrease in the properties compared to neat PHBV The differences between the properties can be attributed to the different interactions of the clay minerals with the modifier and with the polymer In the m-Hal the amino groups are located at the edges and freely react with the carbonyl groups of the PHBV decreasing its molecular weight In the m-Mt, these groups are confined to the clay mineral interlayer and thus the interactions with the polymer are nondestructive

35 citations


Journal ArticleDOI
Abstract: The aim of this work was to evaluate the physical properties of bionanocomposites based on chitosan (Ch) reinforced with different commercial nanoclays and further incorporated with rosemary essential oil (REO). Cloisite®Na+, Cloisite®Ca++ and Cloisite®20 were evaluated through mechanical and X-ray diffraction (XRD) analyses. Incorporation of montmorillonites (MMT´s) improved the mechanical properties, with natural MMT’s providing greater reinforcement. Cloisite®Na+ was chosen to be casted incorporated with different concentrations of REO (0; 0.5; 1; 2%), due to its higher hydrophilic character. Rosemary essential oil reduced the tensile strength (33% at 2% of REO) and films turned opaque, more saturated in colour, and UV light block was improved (between 25–75% at 400 nm for 0.5–2% of REO). Superficial hydrophilicity and water solubility increased with the addition of REO while swelling index decreased. Bionanocomposites showed greater potential than pure chitosan for being used as packaging for food industry.

30 citations


Journal ArticleDOI
Abstract: Uma argila bentonita policationica nacional foi utilizada para a producao de uma argila organofilica, obtida a partir da sintese com o sal de amonio quaternario, cloreto de cetiltrimetilamonio. A argila tratada com o sal orgânico (BENT-org) e a nao tratada (BENT) foram caracterizadas por espectroscopia de absorcao no infravermelho (FTIR) e difratometria de raios X (DRX). Posteriormente, as argilas foram misturadas com o polipropileno (PP) pelo metodo de intercalacao por fusao em uma extrusora dupla-rosca co-rotativa. Os compositos foram caracterizados pelas tecnicas de DRX, calorimetria diferencial de varredura (DSC) e analise termogravimetrica (TGA). Os resultados de FTIR e DRX mostraram a presenca dos grupos caracteristicos do sal de amonio e a intercalacao deste entre as camadas do argilomineral. As analises de DRX dos compositos com 3 e 5% em massa de BENT-org evidenciaram a presenca de picos deslocados para regioes de baixo ângulo, sugerindo a intercalacao das cadeias do polimero entre as camadas da argila. Os resultados de DSC indicaram que a argila pode ter atuado como agente nucleante devido ao aumento na Tcc (temperatura de cristalizacao no resfriamento) dos compositos. De acordo com os resultados de TG, constatou-se que a incorporacao da argila ao PP melhorou a estabilidade termica do polimero nos compositos com 5% em massa de BENT e 3 e 5% em massa de BENT-org.

21 citations


References
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Journal ArticleDOI
Abstract: This review aims at reporting on very recent developments in syntheses, properties and (future) applications of polymer-layered silicate nanocomposites. This new type of materials, based on smectite clays usually rendered hydrophobic through ionic exchange of the sodium interlayer cation with an onium cation, may be prepared via various synthetic routes comprising exfoliation adsorption, in situ intercalative polymerization and melt intercalation. The whole range of polymer matrices is covered, i.e. thermoplastics, thermosets and elastomers. Two types of structure may be obtained, namely intercalated nanocomposites where the polymer chains are sandwiched in between silicate layers and exfoliated nanocomposites where the separated, individual silicate layers are more or less uniformly dispersed in the polymer matrix. This new family of materials exhibits enhanced properties at very low filler level, usually inferior to 5 wt.%, such as increased Young’s modulus and storage modulus, increase in thermal stability and gas barrier properties and good flame retardancy.

5,682 citations


Journal ArticleDOI
Abstract: An overview of polymer–clay hybrid nanocomposites is provided with emphasis placed on the use of alkylammonium exchanged smectite clays as the reinforcement phase in selected polymer matrices. A few weight percent loading of organoclay in nylon 6 boosts the heat distortion temperature by 80°C, making possible structural applications under conditions where the pristine polymer would normally fail. A similar loading of clay nanolayers in elastomeric epoxy and polyurethane matrices dramatically improves both the toughness and the tensile properties of these thermoset systems. Glassy epoxy nanocomposites exhibit substantial improvement in yield strength and modulus under compressive stress–strain conditions. The latest development in polypropylene hybrids have yielded nanocomposites with improved storage moduli. Polyimide hybrids in thin-film form display a 10-fold decrease in permeability toward water vapor at 2 wt.% clay loading. In situ and melt intercalation processing methods are effective in producing reinforced polystyrene hybrids. Nitrile rubber hybrids show improved storage moduli and reduced permeabilities even toward gases as small as hydrogen. Poly(e-caprolactone)–clay nanocomposites prepared by in situ polymerization of e-caprolactone in organoclay galleries show a substantial reduction in water adsorption. Polysiloxane nanocomposites produced from poly(dimethylsiloxane) and organoclay mixtures have improved in tensile properties, thermal stability and resistance to swelling solvents. Organoclay-poly(l-lactide) composite film was obtained by solvent casting technique. Clay nanolayers dispersed in liquid crystals act as structure directors and form hybrids composites that can be switched from being highly opaque to highly transparent by applying an electric field of short duration.

2,332 citations


Journal ArticleDOI
Abstract: The review briefly outlines the advantages of high voltage electron microscopy (HVEM) as an extension of conventional transmission electron microscopy (CTEM) and discusses the various areas of materials science where benefits should be gained. An assessment of the various applications carried out so far, covering the study of heavy metals, ceramics and minerals, large-scale structures, dynamic processes and radiation damage, is then made, from which it is concluded that the development of HVEM largely has been successful. Attention is drawn to recent scanning transmission electron microscope (STEM) results which indicate that HVEM is the only method at present available which will allow the examination of thick crystalline specimens. Nevertheless, the addition of a scanning facility to an HVEM would greatly increase the range of information obtained and points the way to a new generation of HVEM's.

1,699 citations


Journal ArticleDOI
01 Dec 2001-Polymer
Abstract: Polypropylene (PP)/clay nanocomposites (PPCN) were prepared via grafting-melt compounding by using a new kind of co-intercalation organophilic clay which had a larger interlayer spacing than the ordinarily organophilic clay only modified by alkyl ammonium. One of the co-intercalation monomers was unsaturated so it could tether on the PP backbone by virtue of a grafting reaction. The larger interlayer spacing and strong interaction caused by grafting can improve the dispersion effect of silicate layers in the PP matrix, which was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The mechanical properties of PPCN were improved with the addition of clay. The incorporation of silicate layers also gave rise to a considerable increase of the storage modulus (stiffness) and a decrease of the tan δ value, demonstrating the reinforcing effect of clay on the PP matrix. Besides, the glass transition temperature ( T g ) of PPCN decreased in the presence of the silicate layers. The addition of clay did not change the crystal structure of PP, however silicate layers acted as nucleating agents for the crystallization of PP.

554 citations


Journal ArticleDOI
Abstract: Layered silicate based polymer nanocomposites have gained significant technological interest because of the recent commercialization of nylon 6 and polypropylene based materials. Aside from the natural interests in understanding and improving the processing of these hybrids, viscoelastic measurements have also proven to be a sensitive tool to probe the mesoscale structure and the strength of polymer–nanoparticle interactions.

351 citations