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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 (E a ) 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 E a 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.

The effect of filler addition and coupling agent content on the mechanical properties and morphology of wood plastic composites was examined. Using wood flour as the reinforcement filler and recycled expanded polystyrene as the thermoplastic matrix polymer, a particle-reinforced composite was prepared using a co-rotating twin-screw extruder. In the sample preparation, four levels of filler loading (10, 20, 30, and 40 wt%) and three levels of coupling agent content (1, 2, and 4 wt%) were used. The influence of particle size and particle morphology was also evaluated. The results showed that short fibers provide a higher specific surface area, enlarging the contact surface area with the polymer matrix. A wood flour loading of more than 20 wt% caused a decrease in the mechanical properties studied. The addition of 2 wt% of coupling agent improved the interfacial adhesion between the polymer matrix and wood flour and increased the flexural and impact strengths of the lignocellulosic composites. Addition of a coupling agent content greater than 2 wt% caused a reduction in the mechanical properties evaluated. A morphological study revealed that the positive effect of coupling agent on the interfacial adhesion of wood flour reinforced the expanded polystyrene composites.

Polymers are vastly employed for numerous purposes in different industrial segments and generate soaring quantities of discarding in the environment. This research analyzed the degradability/biodegradability of polypropylene films (PP) and Bioriented polypropylene (BOPP) polymers after 11 months interred in the São Giácomo landfill in Caxias do Sul. Comparing the buried PP film to a sample of virgin PP, two peaks of degrading activity appeared at the TG curve as well as structure modification typified by occurrence of new absorption bands at FTIR, which can be credited to changes in crystallinity. Thermal analysis carried out on the buried PP and BOPP showed decreases in the percentage of crystallinity due to chain scission. The major reduction was observed in the PP, since its crystallinity is a consequence of polymerization instead of chain orientation processes, as in BOPP. Cracks and erosion of the polymer surface were detected in both PP and BOPP, indicating degrading processes by microorganisms.

The dynamic mechanical properties of wood flour (WF) reinforced recycled expanded polystyrene (r-EPS) composites were investigated as a function of the WF content and coupling agent used. With the incorporation of WF into the polystyrene the storage modulus (E 0 ) and loss modulus (E 00 ) were found to increase and the mechanical damping (tan d) decreased. The use of coupling agents improved the storage modulus and reduced the damping peak values of the composites because of the improved WF/matrix interfacial adhesion. The height of the damping peaks was found to be dependent on the content of maleic anhydride groups and the weight average molecular weight (M w ) of the coupling agent used. Finally, the experimental results were compared with the theoretical predictions for tan d and the storage modulus.

This study aims to evaluate the influence of pro-oxidant additive and accelerated aging on the degradation of polyethylene (PE) samples in simulated soil, in accordance with ASTM G160-03. Films of polyethylene with and without pro-oxidant additive were studied, before and after 72 hours of accelerated aging. The films were initially characterized by analyses of Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR) (to evaluate the Carbonyl Index (CI)). The films were exposed for 30, 60 and 90 days in simulated soil, with controlled moisture and soil pH. The results showed the degradation of polyethylene films through an increase of CI in samples with additive and accelerated aging after 30 days of exposure, and a decrease, after 60 and 90 days, indicating the uptake of material oxidation by-products by microorganisms. The polyethylene films without pro-oxidant additive after accelerated aging showed greater structural and surface modifications, as compared to films with the additive.

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