Wood fluorescence of commercial timbers marketed in Mexico

A market survey conducted in Mexico yielded 579 wood specimens attributed to 92 genera belonging to 40 families. The fluorescence characteristics of these timbers and their extracts were determined. Additional tests were conducted for the presence of natural saponins and aluminium. The combustion behavior (burning splinter test) was also studied. The results obtained largely concur with information on wood fluorescence and other physical characteristics published earlier. The families Fabaceae, Anacardiaceae and Rubiaceae showed positive fluorescence for a large number of genera or species. Vochysia was the only genus with a positive reaction to the test for aluminium. The froth test for natural saponins can contribute to wood identification in specific cases. The results of the burning splinter test are unambiguous only as regards the difference between charcoal and ash; ash characteristics (consistency, color) are difficult to interpret and their successful application in wood identification considered doubtful. The use of fluorescence and other physical features can be a very useful adjunct to the classical methods of wood identification in specific cases arising from the market situation and may be applied as rapid and easy tests to verify certain identifications

Wood fluorescence of commercial timbers marketed in Mexico

A market survey conducted in Mexico yielded 579 wood specimens attributed to 92 genera belonging to 40 families. The fluorescence characteristics of these timbers and their extracts were determined. Additional tests were conducted for the presence of natural saponins and aluminium. The combustion behavior (burning splinter test) was also studied. The results obtained largely concur with information on wood fluorescence and other physical characteristics published earlier. The families Fabaceae, Anacardiaceae and Rubiaceae showed positive fluorescence for a large number of genera or species. Vochysia was the only genus with a positive reaction to the test for aluminium. The froth test for natural saponins can contribute to wood identification in specific cases. The results of the burning splinter test are unambiguous only as regards the difference between charcoal and ash; ash characteristics (consistency, color) are difficult to interpret and their successful application in wood identification considered doubtful. The use of fluorescence and other physical features can be a very useful adjunct to the classical methods of wood identification in specific cases arising from the market situation and may be applied as rapid and easy tests to verify certain identifications

Wood and Natural Fiber-Based Composites (NFCs)

The chapter on wood and natural fiber-based composites (NFCs) first briefly discusses the historical development of NFCs. Then, the chapter outlines the types of natural fibers as well as the factors that promote their increasing use in commercial products. The types of polymers and additives used are also described in this section. Next, the processes used to manufacture natural fiber composites are described. Molding and injection processes are the most common processes used and are emphasized in that section. The properties and durability of natural fiber composites are discussed afterwards. Further, the chapter discusses the factors that influence durability and performance of these materials along with the methods used for testing durability. Other topics discussed in this chapter are factors that affect decay of wood-plastic composites, and uses of wood-plastic composites. � 2013 John Wiley & Sons, Inc

Selectionism: Complex outcomes from simple processes

This work investigates the combination of different fiber sizes (self-hybridization) on the mechanical properties of composite materials. High density polyethylene composites based on agave and pine fibers were prepared using different ratios of long and short fibers. Furthermore, the effect of coupling agent (maleated polyethylene) versus self-hybridization was evaluated. Several studies in the past have shown that coupling agents can improve the mechanical properties of natural fiber composites. Nevertheless, this study shows that a combination of two particle sizes is also an interesting option to increase mechanical properties like impact strength, as well as tensile and flexural moduli. On the other hand, the presence of coupling agent enhanced the fiber-matrix interfacial adhesion and its effect was more evident on the tensile strength. " 2015, Springer Science+Business Media New York.",,,,,,"10.1007/s10924-014-0706-3",,,"http://hdl.handle.net/20.500.12104/44442","http://www.scopus.com/inward/record.url?eid=2-s2.0-84925486001&partnerID=40&md5=b64d33236cca4589f7a554381f2368b8",,,,,,"1",,"Journal of Polymers and the Environment",,"12

Self-hybridization and Coupling Agent Effect on the Properties of Natural Fiber/HDPE Composites

This work investigates the combination of different fiber sizes (self-hybridization) on the mechanical properties of composite materials. High density polyethylene composites based on agave and pine fibers were prepared using different ratios of long and short fibers. Furthermore, the effect of coupling agent (maleated polyethylene) versus self-hybridization was evaluated. Several studies in the past have shown that coupling agents can improve the mechanical properties of natural fiber composites. Nevertheless, this study shows that a combination of two particle sizes is also an interesting option to increase mechanical properties like impact strength, as well as tensile and flexural moduli. On the other hand, the presence of coupling agent enhanced the fiber-matrix interfacial adhesion and its effect was more evident on the tensile strength. © 2015, Springer Science+Business Media New York

Strength properties and natural durability of Avocado (Persea americana Mill.) branch wood [Propiedades de resistencia y durabilidad natural de la madera de ramas de aguacate (Persea americana Mill.)]

This paper reports on mechanical properties and natural durability of avocado branch wood (Persea americana Mill.) with the objectives of providing a reliable property profile and to promote the rational use of this abundant yet largely neglected natural resource. The mechanical properties (static bending, compression, shear, impact bending) and hardness were determined in accordance with European standards (CEN). Natural durability was assessed according to the European standard EN 350-1 (agar block test) using the white rot fungi Trametes versicolor and Phanerochaete chrysosporium, and the brown rot fungus Postia placenta. Avocado trees yield a low to medium density (0,44-0,54-0,64 g/cm3 at 12% mc) branch wood with below average strength under static bending, compression and tension parallel to the grain and average values for longitudinal shear, impact bending and hardness. The wood is rated non-resistant (class 5 according to EN 350-1) and thus is not suitable for exterior applications unless treated. Considering its property profile and the small dimensions available, avocado wood is recommended for general carpentry, furniture, interior paneling, glue-boards for closets and cabinets, and glue-lams for indoor framework

Propiedades de resistencia y durabilidad natural de la madera de ramas de aguacate (Persea americana Mill.)

This paper reports on mechanical properties and natural durability of avocado branch wood (Persea americana Mill.) with the objectives of providing a reliable property profile and to promote the rational use of this abundant yet largely neglected natural resource. The mechanical properties (static bending, compression, shear, impact bending) and hardness were determined in accordance with European standards (CEN). Natural durability was assessed according to the European standard EN 350-1 (agar block test) using the white rot fungi Trametes versicolor and Phanerochaete chrysosporium, and the brown rot fungus Postia placenta. Avocado trees yield a low to medium density (0,44-0,54-0,64 g/cm3 at 12% mc) branch wood with below average strength under static bending, compression and tension parallel to the grain and average values for longitudinal shear, impact bending and hardness. The wood is rated non-resistant (class 5 according to EN 350-1) and thus is not suitable for exterior applications unless treated. Considering its property profile and the small dimensions available, avocado wood is recommended for general carpentry, furniture, interior paneling, glue-boards for closets and cabinets, and glue-lams for indoor framework

Evaluation of accelerated decay of wood plastic composites by Xylophagus fungi

The resistance to fungal attack of wood plastic composites (WPCs) containing 40% polypropylene and 60% either pine, maple or oak, wt%/wt%, was examined. WPCs specimens were made using the hot press system. Resistance to decay was evaluated using soil block and agar tests. Test specimens were exposed to either white-rot fungi, Trametes versicolor or Phanerochaete chrysosporium, or the brown-rot fungi Gloeophyllum trabeum or Postia placenta for six or 12 weeks. Moisture content and weight loss were used to assess the extent of decay of WPCs. Rates of decay in WPCs exposed in soil-block tests were greater than those exposed in the agar. WPCs containing either maple or oak were more susceptible to fungal attack then those containing pine. © 2009

PMS and ZAMS stars associated with the dark cloud LDN 1655

This study examines the effect of particle size and wood flour content on the properties of polystyrene filled with white oak flour. Wood-plastic ratios 10:90, 30:70 and 50:50% (wt/wt) and particle size 40, 50, 65 and 100 mesh were used. Tensile, bending and impact bending strength as well as the melt flow index were evaluated. Additionally, composite density and water absorption capacity were also tested. Scanning electronic microscopy revealed good adhesion between wood particles and polystyrene. Results show that mechanical properties are strongly influenced by wood flour content and particle size. A reduction in tensile module, elongation and deflection were observed, however, the bending module was increased. Impact strength increased with particle size and content. Melt flow index values are reduced with the increasing amount of filler content while water absorption increases with the amount of wood particles. " The Author(s) 2012.",,,,,,"10.1177/0021998312470149",,,"http://hdl.handle.net/20.500.12104/43612","http://www.scopus.com/inward/record.url?eid=2-s2.0-84891135847&partnerID=40&md5=dacdc487e6a0a5233081c3758214e8cd",,,,,,"2",,"Journal of Composite Materials",,"20

Physical and mechanical properties of wood plastic composites polystyrene-white oak wood flour

This study examines the effect of particle size and wood flour content on the properties of polystyrene filled with white oak flour. Wood-plastic ratios 10:90, 30:70 and 50:50% (wt/wt) and particle size 40, 50, 65 and 100 mesh were used. Tensile, bending and impact bending strength as well as the melt flow index were evaluated. Additionally, composite density and water absorption capacity were also tested. Scanning electronic microscopy revealed good adhesion between wood particles and polystyrene. Results show that mechanical properties are strongly influenced by wood flour content and particle size. A reduction in tensile module, elongation and deflection were observed, however, the bending module was increased. Impact strength increased with particle size and content. Melt flow index values are reduced with the increasing amount of filler content while water absorption increases with the amount of wood particles. © The Author(s) 2012