Mechanical properties of HDPE/textile fibers composites

AbstractThe use of natural fibers as reinforcement for thermoplastics has generated much interest due to the low cost, low density, high specific properties characteristics. In this work the mechanical properties of high density polyethylene/ textile fibers residues composites were studied. Effect of pretreatment with sulfuric acid on textile fibers to prepare composites was made to provide an improvement in mechanical properties of these materials. This treatment on fibers was evaluated by X-ray diffraction technique. Composites were produced in a thermokinetic mixer in the following composition: 5 and 10 wt% fibers. After mixing the samples were injection molding according to ASTM D-638 specification. Specimens were tested in tensile mode and composite fractures surface were analyzed in a scanning electron microscopy. Also was studied moisture absorption. Results showed that HDPE/ textile fibers residue presents good mechanical performance compared with high-density polyethylene

Decomposição Da Serapilheira Foliar De Floresta Nativa E Plantios De Pterogyne Nitens E Eucalyptus Urophylla No Sudoeste Da Bahia

The decomposition process regulates the accumulation of litter and nutrient cycling in forest ecosystems, being central to its maintenance. The objective of this study was to evaluate the dynamics of leaf litter decomposition in three forest ecosystems (semideciduous forest Montana and homogeneous stands of Pterogyne nitens Tul. and Eucalyptus urophylla ST Blake), located in Vitória da Conquista, Bahia, Brazil. To evaluate the decomposition, newly fallen leaves on the ground of trees and shrubs in each of the studied toppings were collected. The sheets were dried at 65 °C, and thereafter, 10 g portions were weighed and placed in litter bags, which were randomly distributed on the surface of the forest floor in each of the areas studied. Five litter bags at random were collected after 30, 60, 90, 120, 150 and 180 days of installation. After collection, the material contained in each litter bag was subjected to drying in an oven at 65 °C and weighed. Based on the obtained masses were estimated the percentage of the remaining mass, the rate of decomposition (k) and half-life time of the litter (t1/2). For chemical characterization three subsamples were separated from the dried leaf litter, which were ground and analyzed by determination of the total nitrogen, carbon, polyphenols, lignin and cellulose. The decomposition was related to environmental variables (precipitation, temperature and humidity) and the microenvironment (temperature and soil moisture).The total accumulated litter varied significantly between the settlements studied, the highest value was observed in the area of Eucalyptus urophylla (12,7 Mg ha-1), followed by native forest (6,9 Mg ha-1) and Pterogyne nitens (1,1 Mg ha-1). At the end of the six months of the experiment, Eucalyptus urophylla showed the greatest remaining mass (73,6%), followed by native forest (67,8%) and Pterogyne nitens (46,3%). The decomposition constant (k) was higher in litter of Pterogyne nitens (0,0054 g g-1 day), with lower values for native forest (0,0016 g g-1 day) and Eucalyptus urophylla (0,0015 g g-1day). The rate of decomposition of leaf litter of the peopling of Pterogyne nitens is in a superior position in relation to rates of native forest and stand of Eucalyptus urophylla, which provides the largest species ability to recycle organic matter and nutrients. The decomposition process in the studied ecosystems is influenced not only by the quality of the litter but also by the quality of their microenvironment. © 2016, Universidade Federal de Santa Maria. All rights reserved.2641141115