Compósitos particulados de polietileno de alta densidade e concha de molusco: efeito do teor e da granulometria

Abstract

In last years there has been a huge concern about environment. This present study aims to study the viability of using mollusk shell powder, as particulate reinforcement in polymer composites of High Density Polyethylene (HDPE), in order to this research contributes potentially to mitigate the environmental impact caused by increase of shell waste associated with mollusk commercial activities on the coast of Paraiba State. To this end, a study on influence of mollusk shell additions (for concentrations of 2, 5 and 8% in weight and for granulometries with both 200 and 325 meshes) in changing the mechanical, morphological, and thermal properties of pure HDPE is done. In addition, a titanate coupling agent was used to treat surfaces of mollusk shell powder of the composite having 5% in weight of shell. All composites were processed in a single-screw extruder with a mixing component (Madock) and specimens are molded by injection. It was performed a chemical characterization of the shell powder by X-ray fluorescence in order to identify its constituents and it was found 97.95% calcium oxide, which is the main constituent of calcium carbonate. In addition, it was performed a MFI analysis and thermal, morphological, and mechanical characterization for all composites as well as for pure HDPE. The MFI analysis of the composites showed only slight changed, therefore the mollusk shell did not influence definitely on rheological behavior of the pure HDPE.The cristalinity degree of the pure UHWPE increased when mollusk shell powder was increased. The composition of 5% in weight with granulometry of 325 mesh produced the highest increase of cristalinity degree of non-treated powders, almost 29%, whereas 38% cristalinity degree was obtained when a 200-mesh composition of 5% in weight was treated with the titanate coupling agent. This behavior suggest a probable effect of particles as nucleating agent. Fracture surfaces show there is both low bonding among the phases and particle agglomerates, mainly in 8% composite for both granulometries. The addition of shell powder changed tensile mechanical properties of pure HDPE, where in major cases its stiffness was increased excepted for 5% compositions. Both the impact strength and bending mechanical properties of the pure HDPE were increased when the thinner shell powders were additioned. Hence shell powder is a potential particle reinforcement for use in HDPE composites.