Raúl Rodríguez Anda

Características anatómicas, físico-mecánicas y de maquinado de la madera de mezquite (Prosopis velutina Wooton)

The anatomical, physical-mechanical and machining characteristics of the wood of velvet mezquite (Prosopis velutina) were determined. Five two-meter logs were collected from stumps in the state of Sonora. The anatomical study was carried out in compliance with IAWA. The physical-mechanical properties were evaluated according to the DIN standards. The machining was done manually, and the surface was evaluated according to the norm ASTM D 1666-87. The wood was found to have a diffuse to semi-annular porosity. Heartwood with abundant amber-colored deposits in the vessels and in the axial and radial parenchyma. Average length and thickness of the fibers of 863 µm and 4.3 µm, respectively. Paratracheal winged-aliform parenchyma. Homocellular core radii. Prismatic crystals abound in the chambered axial parenchyma. The basic density of the timber is very high (0.79 g cm -3 ) and its dimensional stability is good. Resistance to flexion was classified as medium (117 N mm -2 ), and the modulus of elasticity, as low (11 232 N mm -2 ). Resistance to longitudinal compression was classified as very high (87 N mm -2 ), and the modulus of elasticity, as low (11 915 N mm -2 ). Resistance to impact is rated fair (51 kJ m -2 ). In the presence of shearing, it is considered to be hard (19 N mm -2 ). Its Brinell hardness is rated very high (72 N mm -2 tangential; 73 N mm -2 radial and 96 N mm -2 longitudinal). Its response to gluing is considered to be good (Leve l 5; 7 N mm -2 ). Its machining is classified as good, and therefore cutting tools with tungsten carbide valve seats are required.

Properties of Thermoplastic Corn Starch Based Green Composites Reinforced with Barley (Hordeum vulgare L.) Straw Particles Obtained by Thermal Compression

Currently, greater environmental awareness promotes research and development advances in biodegradable materials; they represent an alternative that decreases the environmental impact caused by traditional synthetic plastics. This study consists of the development and characterization of thermoplastic corn starch-based composites, reinforced with barley straw particles made by thermal compression. The study materials were prepared by using three particle concentrations (5, 10, and 15 %), while the matrix (0 %) was used as a reference. A mechanical evaluation of all samples was carried out, as well as that of their water absorption properties. They were also characterized by scanning electron microscopy (SEM), infrared spectroscopy (FTIR), X-ray diffraction (XRD), and flammability tests. The inclusion of straw in the thermoplastic matrix increased water absorption and quickened carbon formation, although it also increased its tensile strength (7 MPa) and the Young’s modulus of activity (MOE) (420 MPa) with a 15 % reinforcement. The FTIR analysis highlights the presence of a carbonyl signal (1720 cm-1) caused by a thermal breakdown (caramelization) linked to barley particles. Moreover, X-ray diffraction demonstrated a VA-type crystallinity pattern (anhydrous) within the biocomposites and an increase of the crystallinity index, through incorporating barley particles in the thermoplastic corn starch-based matrix.