Elen B. A. V. Pacheco

Revisão dos tratamentos químicos da fibra natural para mistura com poliolefinas

The use of natural fibers as reinforcement in polymer composites has been a focus of interest. However, these composites exhibit lower mechanical properties than those of pure polymers because of the low interfacial interactions between the hydrophobic polymer matrix and the hydrophilic fiber. To overcome this problem, different chemical treatments applied to the fibers have been reported. One of the most used treatments is mercerization, which can improve adhesion between the fiber and polymeric matrix. Another chemical treatment involves the use of acids (stearic and oleic acids). The chemically treated fibers used in composite materials showed improved mechanical properties.

Mechanical and Morphological Properties of Polypropylene and Regenerated Tire-Rubber Blends

Mechanical properties and morphology of blends prepared from polypropylene (PP) and 5–20 wt% of regenerated tire-rubber (RgR) were studied. The samples were prepared in a twin-screw extruder. The addition of maleic anhydride-functionalized polypropylene (PP-g-MAH) was also investigated. Tensile and flexural moduli, tensile strength at break, elongation at break and Izod impact resistance at 23°C were increased by the addition of 15 wt% of regenerated rubber and 5 wt% of PP-g-MAH. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) analyses showed some interaction between PP and RgR and considerable modification of the compatibilized mixture morphology. The fracture surface of the blend with PP-g-MAH showed a better interaction between the PP matrix and the regenerated rubber domains, for all blends. Well-dispersed particles of the rubber in the polypropylene matrix were observed. DSC showed that PP crystallizes on cooling at lower temperatures as the RgR content increases. The decrease in crystallization temperature is more evident for blends with 5 wt% PP-g-MAH.

Management of plastic wastes at Brazilian ports and diagnosis of their generation

This study evaluated the management of plastic wastes at 20 Brazilian maritime ports, from three sources: vessels, leased and non-leased areas. The data were obtained from documents on port wastes organized in a relational database with defined protocols (closed form). Analysis of the spreadsheets prepared and field visits revealed that the main bottleneck in managing plastic wastes at ports is their segregation. In general, more material is segregated and sent for recycling from leased areas than non-leased ones (administered by the government). This relatively better performance in managing the wastes generated in leased areas is probably due to the need for private operators to comply with the international standards such as the Code of Environmental Practice to satisfy the international market.

Propriedades térmicas de compósitos de polipropileno e bentonita organofílica

A Brazilian polycationic bentonite clay was used for producing an organophilic clay with the quaternary ammonium salt, cetyltrimethylammonium chloride. The salt treated clay (BENT-org) and untreated clay (BENT) were characterized by infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Then, each clay was mixed with polypropylene (PP) by melt intercalation in a counter-rotating twin-screw extruder. The composites were characterized by XRD, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results from FTIR and XRD showed the presence of specific groups of the ammonium salt and their intercalation in between the clay layers. XRD analyses of the composites with 3 and 5 wt. (%) of BENT-org revealed peaks displaced towards smaller angles, suggesting the intercalation of the chain polymer into the clay layers. DSC results indicated that the clay may have acted as a nucleating agent as seen from the increase in the Tcc (crystallization temperature in the cooling) of the composites. Consistent with the TG results, the incorporation of clay into PP improved the thermal stability of the polymer in the composites with 5 wt. (%) of BENT and 3 and 5 wt. (%) of BENT-org.

Processo de organofilização de vermiculia brasileira com cloreto de cetiltrimetilamônio

The vermiculite (VMT), 2:1 aluminosilicate family clay from the state of Goias, Brazil, was used for the production of an organophilic clay. First, the VMT was treated with sodium chloride to obtain the homo-ionic sodium clay. The organophilic clay was, then, obtained from the reaction with the quaternary ammonium salt, cetyltrimethyl ammonium chloride. The clay treated with organic salt and the untreated one were characterized by X-ray fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results of XRF evidenced the change in the chemical composition of the VMT after the exchange reactions with NaCl and the organic salt. The FTIR results showed the presence of the characteristic groups of the salt in the clay and the XRD confirmed the intercalation among the layers of the clay. The TGA results demonstrated that the organophlic clay presented other bands of decomposition, besides those presented by natural VMT, corresponding to the decomposition of the quaternary ammonium salt.

Morphological, Thermal and Mechanical Properties of Polypropylene and Vermiculite Blends

Morphological, thermal and mechanical properties of blends prepared from polypropylene (PP) and 1, 3 and 5 wt% of vermiculite (VMT) were studied. The samples were prepared in a twin-screw extruder. The addition of maleic anhydride-functionalized polypropylene (PP-g-MAH) was also investigated. The blend morphologies were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal properties of the composites were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The DSC results showed that PP crystallizes on cooling at higher temperatures as VMT content increases. The increase in crystallization temperature was most evident for blends with 5 wt% VMT. The TGA results showed that the use of VMT particles to fill polypropylene increased the thermal stability of the composite. The mechanical properties, tensile modulus and tensile strength at yield point of the PP improved by the presence of VMT.

Regeneration of Vulcanized Compounds Based on Butadiene-Styrene Copolymer

A chemomechanical regeneration system was used for the recycling of SBR-based (butadiene-styrene copolymer) elastomer waste. The effect of the addition of mixtures of TBBS (N-tert-butyl-2-benzothiazole sulphenamide), stearic acid, zinc oxide, and sulfur on the rheometric, mechanical, and swelling properties of SBR-based elastomers was evaluated. These mixtures were utilized as a regeneration agent for vulcanizated rubber, at room temperature. The incorporation of the regeneration agent into elastomers waste was performed in a open mill. This agent regeneration also acts as a vulcanization agent at high temperatures. The results showed that after regeneration, the waste was still capable of being revulcanized without the necessity of incorporating any other additive or another virgin elastomeric matrix. The mechanical properties showed satisfactory values for the revulcanized regenerated waste, despite the low plasticity of these materials before recuring.

Mercado para produtos reciclados à base de PET/HDPE/Ionômero

The expansion of the market for polyethylene terephthalate (pet), considered a world phenomenon, is happening in brazil. The main market for pet is the soft drink bottles. The use of pet instead of glass brings several advantages, including lighter weight, better impact resistance, and lower transportation costs. Possible markets were studied for pet/hdpe blends in proportion 75/25 with small amounts of a compatibilizer. The results of the study indicate that possible markets would be containers for special uses and car parts.

Rheological Behavior of Renewable Polyethylene (HDPE) Composites and Sponge Gourd (Luffa cylindrica) Residue

The present study reports the results of rheological behavior of renewable composites, based on a matrix of high density polyethylene (HDPE), made from ethanol distilled from sugarcane, and lignocellulose filler from waste generated in the processing of sponge gourds for bathing use. The composites were prepared with 10, 20, 30, and 40%wt of filler in a twin-screw extruder. The materials were analyzed in a parallel plate rheometer and a melt-flow indexer. The composite morphology was determined by scanning electron microscopy. The composite viscosity increased with filler content, suggesting possible formation of filler agglomerates. This result was confirmed by Cole-Cole diagrams.

Substituição da fibra de vidro por fibra de bananeira em compósitos de polietileno de alta densidade: parte 1. Avaliação mecânica e térmica

A utilizacao de residuo de fibra natural em substituicao a fibra de vidro foi avaliada. Foram estudados compositos de polietileno de alta densidade, HDPE, e fibra de bananeira com 10, 20, 30 e 40% (m/m) de fibra. Compositos com fibra de vidro, mesma matriz polimerica e nas mesmas proporcoes, foram preparados para comparacao. Os compositos foram obtidos em extrusora dupla-rosca co-rotacional interpenetrante e os corpos de prova foram preparados por injecao. As propriedades mecânicas sob tracao, flexao e impacto foram avaliadas. As propriedades termicas foram analisadas por calorimetria diferencial de varredura (DSC) e analise termogravimetrica (TG). A incorporacao de fibra de bananeira no HDPE resultou no aumento de cristalinidade do polimero. Houve, tambem, consideravel aumento no grau de reforco mecânico nos compositos pela incorporacao da fibra natural. Foi possivel comprovar a substituicao da fibra de vidro pela fibra de bananeira em determinados percentuais, quando misturados ao HDPE, sem prejuizo as propriedades. A analise termogravimetrica dos compositos mostrou que o inicio de degradacao se deu numa faixa de temperatura intermediaria entre a da fibra e a da matriz polimerica.