Caracterização mecânica e térmica de compósitos de matriz polimérica à base de PHB reforçados com quasicristal

Abstract

Composites are materials designed to match the desirable characteristics of two or more materials of a different nature. These are constituted by a reinforcing phase consisting of fibers or particles dispersed in a matrix or continuous phase. Polyhydroxybutyrate (PHB) has a strong industrial potential, but its thermal instability and fragility restrict its applications. Therefore, to correct the impairment of these properties, a reinforcing phase such as the quasicrystalline alloy (Al62Cu25.5Fe12.5) can be added in the polymer matrix. This alloy exhibits properties of high hardness, low surface energy and low coefficient of friction, good resistance to oxidation and corrosion and high resistance to wear. Therefore, the aim of the present work was to characterize mechanically and thermally PHB composites reinforced with quasicrystalline alloy. The composites were prepared by varying the percentage of the quasicrystalline phase in 2%, 4% and 6% by volume in the PHB polymer matrix. The specimens were obtained by hot pressing and the mechanical tests of flexural strength, tensile strength and Shore D hardness were performed. Thermal analysis was also performed by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Further, the samples were analyzed by scanning electron microscopy (SEM). There was an increase in Shore D hardness as the concentration of the quasicrystalline phase in the composite was increased. However, there was no increase in the maximum stress and elongation of the specimens tested in traction and flexion. Only the flexural modulus of elasticity increased. In the thermal characterization by TG and DSC, addition of the quasicrystalline phase did not interfere in the thermal degradation of PHB. In differential scanning calorimetry (DSC) it was observed that, even at different heating rates, the samples had a similar behavior, having two endothermic melting peaks. Thus, it was possible to obtain PHB-based polymer matrix composites with better hardness and thermal stability properties.