Since epoxy resins are used as composite matrix with excellent results, and silica is one of the fillers most often employed, this study compared the performance of rice husk ash (RHA) as filler in epoxy composites, in replacement for high-purity silica. Composites were molded containing 20%, 40%, and 60% (wt) silica or RHA. Viscosity analysis, infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) as well as mechanical and water absorption tests were carried out to evaluate composites. Glass transition temperature after curing and thermal degradation temperature of all samples analyzed were approximately 140 ºC and 370 ºC, respectively. RHA and silica exhibited similar mechanical and water absorption characteristics, indicating that rice husk ash may be a suitable replacement for silica. SEM imaging showed good filler dispersion and distribution in the polymer matrix, highlighting the more effective adhesion interface between RHA particles and the matrix.

Filmes base PELBD + PEBD contendo 5% de sorbato de potássio (SK) foram preparados por extrusão plana. Os filmes com e sem SK foram caracterizados por calorimetria exploratória diferencial (DSC) e fluorescência de Raios X por dispersão de comprimento de onda (WDXRF). O perfil de migração do SK foi acompanhado por FTIR/ATR e UV-Vis e sua influência na curva de selagem (hot tack) dos filmes foi determinada. A adição de SK não causou alteração nas propriedades térmicas do polietileno na concentração estudada, porém a migração do SK para a superfície do filme interferiu na curva de selabilidade, atuando como uma impureza, causando diminuição da força de selagem em faixa de temperaturas mais baixas.

Films produced with blends of linear low density polyethylene and low density polyethylene (LLDPE + LDPE) containing 5 wt % of potassium sorbate (KS) were prepared by flat film extrusion. These films were characterized by differential scanning calorimetry and wavelength dispersive X-ray fluorescence. The migration profile of KS was followed by Attenuated Total Reflection-Fourier Transform Infrared and Ultraviolet spectroscopies and its effect on the sealing curve was determined. The addition of 5% of KS showed no effect in the thermal properties of polyethylene. However, the sealing properties were slightly affected by KS migration, acting as an impurity in the sealed area, which needed a higher sealing force at lower temperatures.