Vinicios Pistor

Materials produced from plant biomass: Part I: evaluation of thermal stability and pyrolysis of wood

This paper compares the thermal stability of the sawdust of different wood species, an important factor in producing reinforced polymers. The compositions of two wood species, Pinus taeda and Eucalyptus grandis, were determined to evaluate the influence of the main wood components on the thermal stability of this material. The two species were submitted to thermogravimetric analysis at different heating rates to calculate the activation energy (Ea) using the Flynn-Wall-Ozawa (FWO) and Kissinger methods. The results suggest that larger quantities of holocellulose and lignin associated with lower extractive contents give the wood greater thermal stability. The Ea values calculated for the two species were in the range of 146-165 kJ.mol-1. Evaluation of the activation energy values offers a simplified means to better understand the thermal decomposition of the sawdust of different wood species used in developing composites.

Structural Characteristics and Thermal Properties of Native Cellulose

In 1838 the French chemist Anselme Payen discovered and isolated cellulose from green plants [1-2]. After more than 170 years of the discovery of the “sugar of the plant cell wall”, consumers, industry and government are increasingly demanding products from renewable and sustainable resources that are biodegradable, non-petroleum based, carbon neutral and at the same time generating low environmental, animal/human health and safety risks [3]. Therefore, cellulose is one of the most abundant material on earth and the most common organic polymer, representing about 1.5 x 1012 tons of the annual biomass production [1,3]. Cellulose is considered an almost inexhaustible source of raw material for the increasing demand for environmentally friendly and biocompatible products. Therefore, wood remains one of the most important raw material source for obtaining cellulose, but other sources can be used as well. Natural cellulose-based materials (wood, hemp, cotton, sisal, ramie, etc.) have been used as engineering materials for thousands of years and their use currently continues as demonstrated by the huge number of forest products-based worldwide industries, such as paper, textiles, etc. Such cellulose derivatives produced on an industrial scale are used for coatings, laminates, optical films and sorption media, as well as for property-determining additives in building materials, composites and nanocomposites, pharmaceuticals, foodstuffs and cosmetics [2-3]. As a consequence, several reviews and scientific papers have been published on cellulose research in the last two decades [2-4].

Materials produced from plant biomass: part II: evaluation of crystallinity and degradation kinetics of cellulose

In this study Eucalyptus grandis (CEG) and Pinus taeda (CPT) cellulose fibers obtained from kraft and sulfite pulping process, respectively, were characterized using Fourier transform infrared (FTIR) spectroscopy and thermogravimetry (TGA). The degradation kinetic parameters were determined by TGA using Coats and Redfern method. FTIR results showed that CPT presented a more ordered structure with higher crystallinity than CEG. Thermogravimetric results showed that CPT had a higher thermal stability than CEG. The kinetic results revel that for CEG the degradation mechanism occurs mainly by random nucleation, although phase boundary controlled reactions also occurs while for CPT the degradation process is more related with phase boundary controlled reactions. Results demonstrated that differences between thermal stability and degradation mechanisms might be associated with differences in the cellulose crystalline structure probably caused by different pulping processes used for obtaining the cellulose fibers.