Avaliação das propriedades de polietileno de baixa densidade (PEBD), poli(3-hidroxibutirato) (PHB) e de suas misturas com torta de mamona

Abstract

The search for new materials that can replace partially or totally polymers from petroleum has been a challenge for researchers in the field of materials science. Recently, a series of research has been undertaken for the development of biodegradable materials.The introduction of biopolymers or natural additives in the formulation of polyolefins used in the packaging industry, to accelerate the degradation of these materials and to obtain favorable cost / benefit ratio.. Castor cake is a lignocellulosic by-product of biodiesel production. Finding more applications for this material is mandatory in order to make the production chain of biodiesel viable. The aim of this study is to evaluate the effect of the addition of castor cake in the properties of mixtures of low density polyethylene (LDPE) and poly (3 hydroxybutyrate) PHB. The evaluation of biodegradation of the products obtained is one of the specific objectives of this work. To achieve the proposed objectives, mixtures of LDPE, PHB, and castor cake in different concentrations were processed in a co-rotating twin-screw extruder. The processability and the mechanical properties of the materials were evaluated by using standard tests. A statistical modeling of mixtures was used in order to evaluate the effect of the proportion of the blends components on the mechanical properties. An experimental design was performed in order to obtain the best processing conditions. Both methodologies were implemented by using Minitab software. The morphology of the blends was evaluated by scanning electron microscopy. Biodegradation was evaluated in simulated soil for different periods of time through determination of mass loss of samples. The results showed that the addition of PHB and castor oil cake to LDPE promotes the increasing of flexural strength and Young's modulus. The tensile and impact properties became poor with the addition of PHB and castor cake as well. The ternary mixtures with higher content of PHB degradation showed more pronounced biodegradation. Under the experimental conditions studied, there was no degradation of polyethylene and castor oil cake blends. The LDPE/PHB/castor oil cake (70/ 20 / 10 wt %) suffered more intense degradation than the binary blends. This fact suggests that the castor oil cake acts as a catalyzer for the blends degradation.