Diego Giraldo

Horse chestnut (Aesculus hippocastanum L.) starch: Basic physico-chemical characteristics and use as thermoplastic material.

Starch isolated from non-edible Aesculus hippocastanum seeds was characterized and used for preparing starch-based materials. The apparent amylose content of the isolated starch was 33.1%. The size of starch granules ranged from 0.7 to 35 μm, and correlated with the shape of granules (spherical, oval and irregular). The chain length distribution profile of amylopectin showed two peaks, at polymerization degree (DP) of 12 and 41-43. Around 53% of branch unit chains had DP in the range of 11-20. A. hippocastanum starch displayed a typical C-type pattern and the maximum decomposition temperature was 317 °C. Thermoplastic starch (TPS) prepared from A. hippocastanum with glycerol and processed by melt blending exhibited adequate mechanical and thermal properties. In contrast, plasticized TPS with glycerol:malic acid (1:1) showed lower thermal stability and a pasty and sticky behavior, indicating that malic acid accelerates degradation of starch during processing.

Hyperbranched polyester polyol plasticized tapioca starch/low density polyethylene blends

In this work, low density polyethylene (LDPE)/plasticized starch (TPS) blends were prepared. The TPS employed in this study was obtained by plasticization of tapioca starch with a hyperbranched polyester polyol. Differential scanning calorimetry analysis showed that the melting temperature increased with the TPS content. The opposite effect was exhibited in the crystallization temperature and additional changes were not observed during the heating. X-ray diffraction analysis showed a reduction in intensity of the peak at Bragg’s angle 17.5°, proving a diminution on A type crystallinity with the increasing amount of LDPE. Micrographs obtained by scanning electron microscopy exhibited starch granules without destructure. TPS acted as a filler to LDPE, since the mechanical properties (Young’s modulus and tensile strength) improved ostensibly. The Young’ modulus and tensile strength decreased with the amount of LDPE, however, the elongation at break exhibited an opposite behavior.

Characterization of Leather Wastes from Chrome Tanning and its Effect as Filler on the Rheometric Properties of Natural Rubber Compounds

Chrome tanning generates large amounts of leather wastes (LW) which have become a considerable environmental issue. In this work, particulate LW with and without urea treatment were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) under inert and oxidative atmospheres, and elemental analysis. Then treated LW (TLW) were incorporated in natural rubber compounds, seeking to find another way of disposal for this type of residue. The effect of TLW on rheometric properties of rubber composites during vulcanization was evaluated, including parameters related to leather particles dispersion in the matrix. It was found that TLW contained chromium and sulfur remaining from tanning, which could affect the properties of rubber compounds. During TGA analysis, oxidation of chromium into LW was increased as an effect of urea treatment. It was observed that TLW improved rubber processability during open two-roll mill mixing process. Rheometric characteristics allowed to identify a decreased TLW particle dispersion into the compound with the increase of its content in the composites. Stiffness of vulcanized composites and the kinetic of the vulcanization varied with TLW content, as an effect of the interaction of TLW with the rubber compound. Particulate leather wastes morphology could facilitate its mechanical interlocking with the polymeric matrix. The development of these type of composites will enable another profitable use for this type of waste.

Characterization of fique fibers and evaluation of mechanical properties, abrasive wear resistance, and processability of NR/SBR/BR-fique fibers composites

In this work, fique fibers used in Colombia’s footwear industry were characterized, functionalized, and added to a natural rubber/butadiene styrene rubber/polybutadiene (NR/SBR/BR) matrix. The morphological analysis of the fibers revealed a preferential orientation with formation of thin layers. The mixing of the composites was carried out in an open roll mill. Curing properties of the compounds were measured by using a moving disk rheometer to establish the effect of the fibers addition in the vulcanization parameters. Abrasive wear resistance, mechanical, and aging properties were evaluated. Processing conditions feasible to obtain NR/SBR/BR-fique fibers composites for commercial applications with suitable mechanical properties were found.