Desenvolvimento de compósitos híbridos de polipropileno carregados com alumina e reforçados com fibra de vidro

Abstract

In this work, composite materials made from polypropylene (PP) and alumina (Al2O3), as well as from polypropylene and glass fiber (GF) were developed, aiming to improve the polymer thermal and mechanical properties. The effect of each reinforcement element, as well as of the hybrid reinforcement, on the polymer properties was evaluated. The influence of some process variables such as: the surface treatment of alumina with vinyltrietoxisilane, the addition of a coupling agent, polypropylene grafted with maleic anhydride (PP-g-MA), the surface treatment of glass fiber with γ-aminopropyltriethoxy- silane and with an alkaline NaOH solution, on the properties of the composites, PP/Al2O3 and PP/Fiber Glass, respectively, were also investigated. The tensile, flexural and impact properties of the obtained materials were determined. The thermal properties were evaluated through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and thermal conductivity measurements. The morphology of the samples was examined by using scanning electron microscopy (SEM). The results obtained showed that the alumina and glass fibers surface treatments exerted no effect on the interfacial adhesion between the matrix and the reinforcements. The composite prepared with 5 wt.% Al2O3 , 20 wt.% of glass fiber in nature and 2 wt.% of PP-g-MA was the material that presented the better combination of mechanical. Due to the poor adhesion properties, the composites processed with the reinforcement elements without any superficial treatment even presented superior mechanical properties. The addition of PP-g-MA to the composites, however, promoted better adhesion between the polypropylene and the reinforcements leading to obtaining better mechanical properties, showing the higher values of impact resistance, Young Modulus, tensile resistance, flexural modulus and resistance. This material presented impact resistance higher than the impact resistance of polypropylene. The thermal conductivity of polypropylene was not improved with the development of the composites. However, the thermal stability was higher than that of polypropylene. The results obtained shows that this material may be used in engineering applications where strong and hard PP based materials with good impact properties and satisfactory thermal stability are necessary.