Ricardo Manríquez-González

Bio-composites of cassava starch-green coconut fiber: Part II—Structure and properties

Development of any new material requires its complete characterization to find potential applications. In that direction, preparation of bio-composites of cassava starch containing up to 30 wt.% green coconut fibers from Brazil by thermal molding process was reported earlier. Their characterization regarding physical and tensile properties of both untreated and treated matrices and their composites were also reported. Structural studies through FTIR and XRD and thermal stability of the above mentioned composites are presented in this paper. FT-IR studies revealed decomposition of components in the matrix; the starch was neither chemically affected nor modified by either glycerol or the amount of fiber. XRD studies indicated increasing crystallinity of the composites with increasing amount of fiber content. Thermal studies through TGA/DTA showed improvement of thermal stability with increasing amount of fiber incorporation, while DMTA showed increasing storage modulus, higher glass transition temperature and lower damping with increasing fiber content. Improved interfacial bonding between the matrix and fibers could be the cause for the above results.

XRD and solid state 13C-NMR evaluation of the crystallinity enhancement of 13C-labeled bacterial cellulose biosynthesized by Komagataeibacter xylinus under different stimuli: A comparative strategy of analyses

The production and crystallinity of 13C bacterial cellulose (BC) was examined in static culture of Komagataeibacter xylinus with different chemical and physical stimuli: the addition of NaCl or cloramphenicol as well as exposure to a magnetic field or to UV light. Crystalline BC biosynthesized under each stimulus was studied by XRD and solid state 13C NMR analyses. All treatments produced BC with enhanced crystallinity over 90% (XRD) and 80% (NMR) compared to the control (83 and 76%, respectively) or to Avicel (77 and 62%, respectively). The XRD data indicated that the crystallite size was 80-85 Å. Furthermore, changes on the allomorphs (Iα and Iβ) ratio tendency of BC samples addressed to the stimuli were estimated using the C4 signal from 13C NMR data. These results showed a decrease of the allomorph Iα (3%) when BC was biosynthesized with UV light and chloramphenicol compared to control (58.79%). In contrast, the BC obtained with NaCl increased up to 60.31% of the Iα allomorph ratio.

Compósitos biodegradables elaborados a partir de almidón termoplástico y partículas de madera de fresno

The number of studies to develop biodegradable products from natural polymers has increased, among which starch is outstanding because it is a promising material for this purpose. The present work describes the production and characterization of biocomposites of corn starch reinforced with wood particles of ash-tree, for the method of thermo-compression. The biocomposites was prepared with particle sizes, 425 μm, 600 μm and 1.4 mm, as well as, in different ratios (5, 10 and 20 %) and a thermoplastic matrix (0 % particles) was used as reference. The obtained results demonstrated that it is possible to elaborate thermoplastic starch by the thermo-compression method. The ash wood particles incorporated into the thermoplastic matrix contributed to improve the tensile strength and elongation modulus, showing a good interface (matrix-particle) observed in the SEM images. The thermal treatment (annealing) applied to the specimens had a great effect in the results of tensile strength. The composites with 10 and 20 % wood particles and of 600 μm particle size presented the major values of mechanical resistance. The biocomposites are flammable but tend to auto-extinguish. During the process of plastification occurs a slight thermal degradation which causes the formation of carbonyl groups. Incorporating wood particles to the thermoplastic matrix decreased moisture absorption.

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.

Nutritional evaluation of mature seeds of Enterolobium cyclocarpum (parota) from diverse ecological zones in western Mexico

There is little information on the agroecological characteristics and chemical composition of some wild forage species in Mexico, which can be proposed as al...