Recycling leather waste: preparing and studying on the microstructure, mechanical, and rheological properties of leather waste/rubber composite

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Tribocorrosion behaviour of hot pressed CoCrMo−Al2O3 composites for biomedical applications

Alumina/alumina wear couple can lower the wear rates and thus metallic ion releasing on load bearing metallic implant materials. However, the low fracture toughness of ceramics is still a major concern. Therefore, the present study aims to process and to triboelectrochemically characterise the 5 and 10 vol.-%Al2O3 reinforced CoCrMo matrix composites. Corrosion and tribocorrosion behaviour of the composites were investigated in 8 g L−1 NaCl solution at body temperature. Corroded and worn surfaces were investigated by a field emission gun scanning electron microscope equipped with energy dispersive X-ray spectroscopy. After tribocorrosion experiments, wear rates were calculated using a profilometer. Results suggest that Al2O3 particle addition decreased the tendency of CoCrMo alloy to corrosion under both static and tribocorrosion conditions. However, no significant influence on the corrosion and wear rates was observed in composites mainly due to increased porosity and insufficient matrix/reinforcement bonding.

Influence of time evolution in the modulus of elasticity of concrete reinforced by carbon fibers

The modulus of elasticity is an important property for the behavior analysis of concrete structures. This research evaluated the strain difference between concrete specimens with and without the application of laminate carbon fiber composites as well as the variation time, in months, of the axial strength compression and modulus of elasticity. Through the experimental results, it is concluded that increases in compressive strength and modulus of elasticity are more significant in the specimens without reinforcement.

Natural fibers based composites - Technical and social issues

Brazil is the only country in South America to have an automotive supplier sector based on natural fibers. New opportunities are arising due to an increase demand by the car makers in applying natural fibers in their parts. Several crop fibers have been developed in Brazil. Among them can be listed caroa, piacava, pupunha, mutum and others of regional application. For the automotive industry, which requires large quantities with uniform quality, the alternatives are sisal (170,000 ton/yr), curaua (150 ton/yr in 2003), malva, 200 ton/yr; Brazil is the single largest producer country of sisal, and commercially, the only one in curaua. For South America, the alternatives are fique in Colombia, abaca in equator, flax in Argentina and curaua in Venezuela. It must be understood by the target countries of drugs, is that crop fiber can be an economic alternative to coca in the Andes region, therefore an instrument of land reform and drug reduction plantations. Several companies have a strong program of apply natural fibers based components in their products: Volkswagen do Brazil, DaimlerChrysler, General Motors do Brazil. Among their suppliers can be listed companies such Pematec (curaua), Toro (sisal, coir and jute), Incomer (sisal and jute), Ober (jute, curaua), Indaru (jute and sisal), Antolin (imported kenaf,) Tapetes Sao Carlos (sisal), Poematec (coir) and Art-Gore, with Woodstock'' wood and natural fibers). Figures about production and demand are discussed in the paper.

Leaf anatomy of rubber-tree clones

A seringueira é uma planta de fácil reconhecimento por ser lenhosa, de porte mediano a grande, que apresenta um padrão característico de desfolha e reenfolhamento e, sobretudo, pela produção de látex. O objetivo do trabalho foi efetuar um estudo anatômico e morfológico foliar, comparando os clones RRIM 600 e GT 1 de seringueira &91;Hevea brasiliensis (Wild. ex Adr. de Juss.) Muell.- Arg&93;, desenvolvidos sob as mesmas condições edáficas e climáticas, para obtenção de informações que possam fornecer subsídios para correlações com dados fisiológicos e também diferenciar os clones em relação ao conteúdo de fibras, espessamento de tecidos do parênquima paliçádico e do parênquima lacunoso, caracterização anatômica do pecíolo, número e tamanho de estômatos e fornecer dados referentes a morfologia foliolar. Foram realizadas secções transversais na região do mesófilo, nervura central e pecíolo, seguindo-se os métodos usuais de preparação de lâminas permanentes. Foram realizadas análises biométricas de extensões de tecidos dos parênquimas paliçádico e lacunoso e contagem do número de células do parênquima lacunoso. Paralelamente foram realizadas análises biométricas para aferições de estômatos. Não houve diferenças para a altura das células epidérmicas, altura e número de camadas do parênquima lacunoso e para o comprimento e para a maior largura do limbo foliolar. Porém houve variação para a espessura das células do parênquima paliçádico, sendo que GT 1 apresentou maior espessura em relação a RRIM 600. GT1 apresentou maior número de estômatos em relação a RRIM 600, porém com menor tamanho. GT1 apresentou maior diâmetro da nervura central da folha e do pecíolo e maior quantidade de fibras de esclerênquima que RRIM 600.

LDPE/EVA Composites for Antimicrobial Properties

Composites with antimicrobial activity are of great interest nowadays and the development of titanium dioxide with these functional properties presents interest in academic and industrial sectors.An approach to develop PE composite containing silver microparticles to have an antimicrobial effect is presented. To obtain such antimicrobial composites, LDPE/EVA were processed with Ag particles on TiO2 particles as inorganic carrier substance. Titanium dioxide nanoparticles (P-25) were covered with silver particles using Turkevich Method or citrate reduction method. The Ag/TiO2 particles were dispersed at concentration of 0,8 wt% and 1% wt% in LDPE/ethylene vinyl acetate copolymer (EVA)-(50% w/w) at the melt state in a Haake torque Rheometer. Silver microparticles were characterized with UV-Vis Spectroscopy. The composites thus prepared were characterized through XRD, Ares Rheometer, Scanning Electronic Microscopy (SEM) and JIS Z 2801 antimicrobial tests to study the effects of the addition of particles on rheological properties, morphological behavior and antimicrobial properties. The results showed that incorporation of silver/titanium dioxide particles on composites obtained systems with differents dispersions. The Ag/TiO2 particles showed uniform distribution of Ag on TiO2 particles as observed by SEM-EDX and antimicrobial tests according to JIS Z 2801 shows excellent antimicrobial properties.

Ionized-air-treated curaua fibers as reinforcement for phenolic matrices

Curaua fibers were treated with ionized air to improve the fiber/phenolic matrix adhesion.The treatment with ionized air did not change the thermal stability of the fibers. The impact strength increased with increase in the fiber treatment time. SEM micrographs of the fibers showed that the ionized air treatment led to separation of the fiber bundles. Treatment for 12 h also caused a partial degradation of the fibers, which prompted the matrix to transfer the load to a poorer reinforcing agent during impact, thereby decreasing the impact strength of the related composite. The composites reinforced with fibers treated with ionized air absorbed less water than those reinforced with untreated fibers.

Cellulose nanocomposites with nanofibres isolated from pineapple leaf fibers for medical applications

Nanocellulose is the crystalline domains obtained from renewable cellulosic sources, used to increase mechanical properties and biodegrability in polymer composites. This work has been to study how high pressure defibrillation and chemical purification affect the PALF fibre morphology from micro to nanoscale. Microscopy techniques and X-ray diffraction were used to study the structure and properties of the prepared nanofibers and composites. Microscopy studies showed that the used individualization processes lead to a unique morphology of interconnected web-like structure of PALF fibers. The produced nanofibers were bundles of cellulose fibers of widths ranging between 5 and 15 nm and estimated lengths of several micrometers. Percentage yield and aspect ratio of the nanofiber obtained by this technique is found to be very high in comparison with other conventional methods. The nanocomposites were prepared by means of compression moulding, by stacking the nanocellulose fibre mats between polyurethane films. The results showed that the nanofibrils reinforced the polyurethane efficiently. The addition of 5 wt% of cellulose nanofibrils to PU increased the strength nearly 300% and the stiffness by 2600%. The developed composites were utilized to fabricate various versatile medical implants. (C) 2011 Elsevier Ltd. All rights reserved.