Heitor Luiz Ornaghi

Native Cellulose: Structure, Characterization and Thermal Properties

In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations.

Influence of fiber hybridization on the dynamic mechanical properties of glass/ramie fiber-reinforced polyester composites

This study aims to evaluate the influence of fiber hybridization and frequency on the dynamic mechanical properties of ramie/glass hybrid fiber-reinforced polyester composites. The storage modulus (E′), loss modulus (E″) and damping behavior (tan δ) were evaluated as a function of different relative glass/ramie fiber volume ratios. For the storage modulus, the importance of the reinforcement effect above Tg was revealed. Also, the peak height, peak width at half-height and relaxation area were investigated for the loss modulus and tan δ curves, showing the influence of a shoulder below Tg for each case. Finally, the tan δ peak shifts to higher temperatures by increasing the frequency. Higher activation energy was observed for 75% glass fiber-containing composites.

Isolation and Characterisation of Cellulose Nanowhiskers from Microcrystalline Cellulose Using Mechanical Processing

In this study, the production of cellulose nanowhiskers (CNW) from microcrystalline cellulose (MCC) by a mechanical grinding process in a super mass colloider was evaluated. MCC and CNW samples were evaluated by thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The stress/strain characterisation of the films was performed by dynamic mechanical equipment. The morphological analysis showed the formation of a nanowhiskers/nanoscale structure in the CNW sample. The FTIR analysis of the CNW sample showed absorption band that is characteristic of cellulose. The XRD analysis indicated a small decrease in the crystallinity index and crystallite size, although the cellulose type-I structure was maintained. No changes were observed in the thermal stability of the CNW sample after the mechanical grinding process until 350 °C. A greater increase in the Young modulus was observed for the CNW sample.