Addition Of Wood Particles Research Articles

Crystallinity and impact strength improvement of wood-polylactic acid biocomposites produced by rotational and compression molding

Polylactic acid is one of the most used biopolymers due to its overall properties and biodegradability. Nevertheless, polylactic acid has important drawbacks such as brittleness, low thermal stability, and higher cost than most commodity polymers. In order to overcome those disadvantages without compromising biodegradability, the addition of wood particles and thermal annealing on the crystallinity and impact strength of wood-polylactic acid biocomposites were studied. The samples were prepared by compression and rotational molding using two different wood particles: white ash and tzalam. The results showed that thermal annealing at 100 °C, 40 minutes, increased the crystallinity up to 60 % and also improved the thermal stability of polylactic acid and its biocomposites as determined via dynamic mechanical analysis. The specimens not exposed to thermal annealing exhibited important storage modulus loss above 60 °C, which mostly disappeared with the thermal treatment. Furthermore, the impact strength was substantially increased by the thermal treatment. Additionally, accelerated weathering tests showed that the thermally annealed samples had better dimensional stability growing their potential applications over a wider range of conditions

Avaliação do desempenho de painéis cimento-madeira fabricados com duas espécies florestais em combinação com casca de arroz

O presente trabalho objetivou avaliar o desempenho de painéis compostos de cimento e diferentes proporções de duas espécies de madeira combinadas com casca de arroz. Foram produzidos painéis experimentais cujas proporções de partículas de madeira utilizadas foram de 0-25-50-75 e 100%, enquanto a proporção de cascas de arroz foi de 100-75-50-25 e 0%, respectivamente. As espécies de madeiras utilizadas no estudo foram Eucalyptus grandis W. Hill ex Maiden e Pinus elliottii Engelm. Para determinar a qualidade dos painéis foram avaliadas as propriedades físicas (massa específica; absorção de água e inchamento em espessura após 2 e 24 horas de imersão) e as propriedades mecânicas (MOE e MOR em flexão estática e ligação interna), de acordo com a ASTM D-1037 (1999). Os resultados obtidos foram discutidos a partir da literatura, incluindo as recomendações do processo Bison (1978) para painéis cimento-madeira comerciais. Os painéis produzidos com partículas de pinus apresentaram desempenho nos testes de absorção e inchamento em espessura para imersão de 24 horas, inferior se comparado aos painéis fabricados com partículas de eucalipto. A adição de cascas de arroz, contudo, melhorou as propriedades físicas dos painéis fabricados tanto com partículas de pinus, quanto com partículas de eucalipto. Quanto maior a quantidade de cascas de arroz adicionada à chapa, menores foram as taxas de absorção de água e inchamento em espessura. As propriedades mecânicas dos painéis foram afetadas positivamente com a proporção de partículas de madeira. Sendo que o pinus apresentou melhores resultados para o módulo de elasticidade e a ligação interna; o eucalipto apresentou melhor performance para o módulo de ruptura. A adição de cascas de arroz representou perda de resistência mecânica para todos os tratamentos em todas as propriedades avaliadas.

Effect of Wood Fibers on the Rheological and Mechanical Properties of Polystyrene/Wood Composites

The effects of wood fibers on the rheological and mechanical properties of polystyrene/wood (PS/wood) composites were investigated. The composites with different ratios of PS and wood were prepared by means of internal mixer and, additionally, two different sizes of the wood particles were used, such as ∼100 and ∼600 µm. The rheological properties were studied using capillary rheometer, apparent shear rate, apparent shear stress, apparent viscosity, power law index, and flow activation energy at a constant shear stress were determined. The rheological results showed that the shear stress–shear rate variations obeyed a power law equation, and the composites exhibited shear thinning. The flow activation energy of the composites increased with the addition of wood particles. Mechanical results showed that stress at break of the composites was higher than that of pure PS, whereas the strain at break and impact strength of the composites were lower than that of PS. In addition, the mechanical properties of the present composites were improved when the small size of wood particles were incorporated.

Enhanced enzyme production with the pelleted form of D. squalens in laboratory bioreactors using added natural lignin inducer

White-rot fungi are extensively used in various submerged biotechnology processes to produce ligninolytic enzymes. Transfer of the process from the laboratory to the industrial level requires optimization of the cultivation conditions on the laboratory scale. An interesting area of optimization is pellet growth since this morphological form solves problems such as the decreased oxygen concentration, limited heat, and nutrient transport, which usually occur in dispersed mycelium cultures. Many submerged fermentations with basidiomycetes in pellet form were done with Phanerochaete, Trametes, and Bjerkandera species, among others. In our study, another promising basidiomycete, D. squalens, was used for ligninolytic enzyme production. With the addition of wood particles (sawdust) as a natural inducer and optimization of mixing and aeration conditions in laboratory stirred tank (STR) and bubble column (BCR) reactors on pellet growth and morphology, the secretion of laccase and the manganese-dependent peroxidase into the medium was substantially enhanced. The maximum mean pellet radius was achieved after 10days in the BCR (5.1mm) where pellets were fluffy and 5days in the STR (3.5mm) where they were round and smooth. The maximum Lac activity (1,882Ul(-1)) was obtained after 12days in the STR, while maximum MnP activity (449.8Ul(-1)) occurred after 18days in the BCR. The pellet size and morphology depended on the agitation and aeration conditions and consequently influenced a particular enzyme synthesis. The enzyme activities were high and comparable with the activities found for other investigations in reactors with basidiomycetes in the form of pellets.

Moderation of Entrance Pressure Drop and Extrudate Swelling of Wood Fiber/Polypropylene Composites Melt in Rotating-Die Extrusion Process

A novel rotating-die system was proposed to moderate the elastic swelling for molten polypropylene (PP) and wood/polypropylene (WPP) composite. The results suggested that the neat PP and WPP melts followed the psuedoplastic non-Newtonian pattern. The rotation of the die could moderate the extrusion load and entrance pressure drop. The die rotation effect appeared to be very pronounced for the PP with high wood contents and high extrusion rates. The decreases in extrusion load and entrance pressure drop were related with reductions of melt viscosity due to shear heating effect. The results practically implied that use of the rotating die system could increase the productivity in the extrusion process. In terms of elastic swelling, in all cases, it was found that the swelling ratio of neat PP and WPP melt composite increased with increasing shear rate, but for any given shear rates, the addition of wood particles and the use of rotating die caused decreases in swell ratio of the melts, the wood content being more well-defined than the die rotating speed.

Improvement of Structural and Thermal Stabilities of PVC and Wood/PVC Composite by Zn and Pb Stearates, and Zeolite

Three different chemical stabilizers were introduced into neat PVC and a wood/PVC composite (containing 50 phr wood flour) to improve their thermal and structural stabilities. The changes in CIE yellowness index, polyene index, %wt loss, and decomposition temperature (Td) were monitored. The effects of type and content of thermal stabilizers, thermal ageing time, and the presence of wood flour were our main interests. The experimental results suggested that the additions of Zn and Pb stearates into PVC and wood/PVC composite could improve the thermal stability of the PVC. At the test temperature of 177°C, the additions of Zn and Pb stearates could improve the thermal stabilities of PVC by retarding the upzipped reaction and by reducing the conjugated double bonds in PVC, Pb stearate being the most suitable for thermally stabilizing the PVC. Around the Td range (∼264°C), the addition of Zn stearate reduced the Td value of PVC whereas that of Pb stearate had no effect on the change in Td value. Zeolite loading could shift the Td value of the PVC from 264 to 280°C. The addition of wood particles increased the polyene content and decreased the decomposition temperature of the PVC. The effect of wood flour on the thermal and structural changes of PVC overruled that of thermal stabilizer loading.