The production of a material with rigid, multifunctional three-dimensional porous structure at a low cost is still challenging to date. In this work, a light and rigid carbon foam was prepared using rice husk as the basic element through a simple fermentation process followed by carbonization. For the fermentation process, the amount of biological yeast (7.5 g for the carbon foam CA-1P and 5 g for the carbon foam CA-2P) was used to evaluate its influence on the morphology of the foams. In order to prove that the heat treatment made in the foam alters the hydrophilic character of the rice husk foam, a chemical treatment with steam deposition was carried out. The foams were characterized by the following analyzes: apparent density, micrograph, thermogravimetry, contact angle, water sorption capacity and thermal conductivity. Visually, the CA-1P foams presented a structure with larger pores due to the greater amount of yeast used in its formulation. The heat treatment of rice potato foams proved to be as efficient as the chemical treatment for water contact angle above 90º, proving the ability of the foams to repel water/moisture. The thermal conductivity of the foams (0.029 and 0.026 W m-1 K-1 for CA-1P and CA-2P, respectively) was close to the conductivity of polyurethane foams (0.032 W m-1 K-1). Thus, the method used in the production of the carbon foams produced from the rice husk proved to be effective. In addition, the foams produced have the potential to be used for thermal insulation.
ABSTRACT The growth of oil exploration and transport in marine environments brings concern over potential environmental disasters caused by oil spills. Thus, various materials are being developed and studied in order to minimize environmental impacts caused by these oil spills. Among these materials, the use of sorbents has appeared as a great potential technique for the treatment of effluents, by separating and collecting oil in the aqueous medium. This work describes the development of a sorbent system based on acetylated microfibrillated cellulose. Initially, cellulose fibers were modified by an acetylation reaction and thereafter, by a mechanical process using a wheel mill grinding. To produce the sorbent system, fibers were coated by three different types of envelopes to prevent leakage during the sorption experiment. Main results indicate a higher oil sorption by sorbents with higher oil viscosity and higher grammage of the envelope. Acetylated microfibrillated cellulose showed low water adsorption and high selectivity to oil and greater oil sorption values than commercially sorbent currently used, based on polypropylene fibers.
In this study, polymer composites using low-density polyethylene (LDPE) and layered hydroxide salts (LHS) were synthesized. The following compositions of LHS were obtained Zn5(OH)8(An-)2/n.yH2O, where A was varied in order to obtain hydrophilic (A = NO3-) or hydrophobic (A = DDS- - dodecyl sulfate or DBS- - dodecyl benzene sulfonate). Synthesis was carried out by co-precipitation in alkaline medium and drying, being followed by characterization via Fourier-transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and scanning electron microscopy. A variable amount of filler was then incorporated into the LDPE via extrusion, which was then injection molded to obtain specimens for evaluating tensile properties (Young's modulus, tensile strength, strain at break and toughness). For comparison, the sodium salts of the surfactants (NaDDS and NaDBS) were also used as fillers in LDPE. The X-ray diffraction results indicated that the hydrophobic LHS were exfoliated in the polymer matrix, whereas the hydrophilic LHS was only delaminated. In the LDPE composites, melting and crystallization temperatures were nearly constant, along with the crystallinity indexes. The mechanical properties were mainly varied when the organophilic LHS was used. Overall, fillers based on LHS, especially those containing hydrophobic anions, may be interesting alternatives in the production of reinforced thermoplastics.
The objective of this study is to develop expanded composites of poly(ethylene-co-vinyl acetate) (EVA) filled with two vegetable reinforcements (banana fiber or wood flour) as well as to evaluate the influence of the type, size and concentration of these reinforcements on the cell growth and their morphological, mechanical, thermal and physical properties. The results indicated that the natural fibers act as nucleating agents and affect the cells stability during the formation of the cellular structure in the expanded composites. The mechanical properties of the expanded composites are directly related to the composite expansion degree. Comparative results of the use of vegetable residues indicate that wood flour reinforcement provides more homogeneous cells, while banana fibers restrict the expandability of the composite and its density.
The present work describes the synthesis and characterization of Zn/Al layered double hydroxides (HDL) in the molar ratio 2:1, which were intercalated with hydrated chlorine ions and anions derived from the azo dyes methylorange (AM) and orange II (AII). After characterization, the materials were used as fillers into high density polyethylene (HDPE) and the nanocomposites were prepared by extrusion and injection, following the norm ASTM D638-10. The filler contents varied from 0.1 to 2% (including the sodium dye salts) and the homogeneous nanocomposites were evaluated in relation to their structural, thermal and mechanical properties. In general, after the fillers' addition there is only a small influence in the melting and crystallization temperature of HDPE. For HDLs intercalated with the anionic dye AM and both sodium dyes, the mechanical properties presented a small influence on Young's modulus and tensile strength and an increase in elongation compared to pure HDPE and an inverse behavior was observed for the anion AII, in addition to the HDL containing hydrated chlorine anions.
O presente trabalho descreve a síntese e caracterização de hidróxidos duplos lamelares (HDL) de Zn/Al na razão molar 2:1, os quais foram intercalados com íons cloreto hidratados e ânions derivados dos corantes azo alaranjado de metila (AM) e alaranjado II (AII). Após caracterização, os materiais foram utilizados como cargas em polietileno de alta densidade (PEAD) e nanocompósitos foram preparados por extrusão e injeção, seguindo a norma ASTM D638-10. Os teores de cargas variaram de 0,1 até 2% (incluindo-se os sais de sódio dos corantes) e os nanocompósitos homogêneos foram avaliados em relação as suas propriedades estruturais, térmicas e mecânicas. De modo geral, após a adição das cargas existe somente uma pequena influência na temperatura de fusão e cristalização do PEAD. Para os HDLs contendo o pigmento intercalado com o ânion do corante AM e sais de sódio de ambos os corantes, as propriedades mecânicas apresentaram leve aumento do módulo e tensão de ruptura e diminuição do alongamento em relação ao polímero puro e um comportamento inverso foi observado para o ânion AII, além do HDL contendo ânions cloreto hidratados.
In this work the influence of alkaline treatment on banana fiber (BF) and its use as reinforcement agent in expanded composites of poly(ethylene-co-vinyl acetate) - EVA were assessed. The mixing process for the composite was performed in an open roll mill, with composites being then shaped and expanded in a thermal press using variable volume molds. The composites were evaluated as for their mechanical, thermal and morphological properties. The results indicate that the alkali treatment promotes the extraction of less stable BF components such as lignin, hemicellulose, waxes and low molecular weight oils. The use of BF in the composites imparts reduction in mechanical properties of tensile and tear strength compared to neat EVA, owing to the moderate properties of the polymer-fiber interface. In expanded composites, the mechanical properties decreased with the reduction in density due to a higher amount of void spaces within the composites. However, the specific mechanical properties of tear strength showed improved results with 10 phr BF in all molds.
Neste trabalho foi avaliada a influência do tratamento alcalino na fibra de bananeira (FB) e seu uso como agente de reforço em compósitos expandidos de poli(etileno-co-acetato de vinila) - EVA. O processo de mistura dos compósitos ocorreu em um misturador de rolos aberto e após conformados e expandidos em uma prensa aquecida com moldes de volumes variáveis. Os compósitos foram avaliados por suas propriedades mecânicas, térmicas e morfológicas. Os resultados indicam que o tratamento alcalino promove a extração de componentes menos estáveis na FB, tais como a lignina, hemicelulose, ceras e óleos de baixo peso molecular. O uso da FB nos compósitos proporciona um decréscimo das propriedades mecânicas de resistência à tração e rasgo em relação ao EVA puro devido a moderadas propriedades de interface polímero-fibra. Nos compósitos expandidos, as propriedades mecânicas decrescem com a diminuição da densidade em função da maior presença de espaços vazios no interior dos compósitos, porém as propriedades mecânicas específicas de resistência ao rasgo apresentaram melhores resultados com 10 pcr de FB em todos os moldes utilizados.
This work examined the influence of different chemical blowing agents (CBA), one endothermic and one exothermic, at the same concentration (2% by mass), on poly(acid lactic), PLA foams. The CBA was incorporated into the PLA in a single-screw extruder, and the foams were expanded by heating in an electric oven under free pressure conditions. Foam degradation in a simulated soil was performed according to the ASTM G160-03 standard. Changes in the physical-chemical, morphological and mechanical properties were used to evaluate the degradation. The results indicated that the different chemical blowing agents led to different mechanical and morphological properties for the foams, which resulted from the nature and decomposition rate of the blowing agents. Cells in the foams accelerated the degradation since they facilitated the infiltration of water toward the interior of the polymer and triggered the degradation process by hydrolysis.
This study aimed at evaluating the consumption, removal and secondary dispersal of seeds of Mucuna urens (Fabaceae - Faboideae) in an Atlantic Forest fragment in the Municipal Park of Lagoa do Peri, Florianópolis, SC. The biometric pattern and consumption by invertebrates of 100 seeds were evaluated. The removal and secondary dispersion were evaluated at 120 and 25 seeds, respectively. The average length, width and mass of seeds was 2.87±0.19 cm, 2.83±0.23 cm and 5.04±1.60 g, respectively, and forty-one percent of seeds were consumed by beetles Curculionidae, Scolytinae. There was no relationship between the length and the width of the seeds consumed and not consumed, and the consumed mass was significantly less than those not consumed, due to the fact that the Scolytinae feed the cotyledons. The agoutis (Dasyprocta azarae) removed 74.16% (n = 89) of the seeds. This rodent scattered 48% and buried 36% of the seeds, at an average distance of 8.06 m (± 7.46 m) ranging from 1.00 to 35.90 m. The secondary dispersion and hoarding seeds of M. urens by agoutis decreases the probability of predation by other vertebrates and invertebrates and increases the chances to occur the germination in favorable sites, helping in the propagation of the species.
No presente estudo foram avaliados o consumo, a remoção e a dispersão secundária de sementes de Mucuna urens (Fabaceae - Faboideae) em um fragmento de Floresta Atlântica, no Parque Municipal da Lagoa do Peri, Florianópolis, SC. O padrão biométrico e o consumo por invertebrados foram avaliados em 100 sementes. A remoção e a dispersão secundária foram avaliadas em 120 e 25 sementes, respectivamente. A média do comprimento, largura e massa das sementes foi de 2,87±0,19 cm, 2,83±0,23 cm e 5,04±1,60 g, respectivamente, e 41% estavam consumidas por besouros Curculionidae, Scolytinae. Não houve relação do comprimento e da largura das sementes consumidas e não consumidas, sendo a massa das consumidas significativamente menor do que as não consumidas, devido aos escolitíneos se alimentarem do cotilédone. As cutias (Dasyprocta azarae) removeram 74,16% (n = 89) das sementes. Esse roedor dispersou 48% e enterrou 36% das sementes, a uma distância média de 8,06 m (± 7,46 m), variando de 1,00 a 35,90 m. A dispersão secundária e o estocamento das sementes de M. urens por cutias diminui a probabilidade de predação por outros vertebrados e invertebrados e aumenta as chances de ocorrer a germinação em sítios favoráveis, ajudando na propagação da espécie.