Dispersão da lignina Kraft em PBSA e suas interações: efeito da concentração e condições de processamento

Abstract

Serious environmental issues have been caused by the massive consumption of plastic products. One of many strategies to reduce the environmental impacts is the development of bio-based and biodegradable polymeric materials. In general, biodegradable polymers have limited production capacity and, consequently, higher costs. Lignin, on the other hand, is abundant in vegetable tissues and is obtained majorly as by-product of the paper industry. Consequently, it exhibits renewability, high availability and low cost. The incorporation of lignin in the biodegradable polymer poly(butylene succinate-co-adipate) (PBSA) can provide more competitive costs and functional properties to it, like UV radiation protection. In this work, PBSA-based films were extruded with lignin nominal concentrations from 0 to 15 wt.%, with different processing parameters. The influence of composition and extrusion conditions (temperature and screw rotation) were assessed by structural, thermal, rheological, morphological and mechanical analysis. The results showed that lignin dispersion is strongly influenced by the processing conditions. Phase compatibility was observed and, also, evidences of possible partial miscibility between lignin and PBSA were found. However, the presence of lignin catalyzed the hydrolytic degradation of PBSA during the extrusion processes due to lignin’s acid character. Additionally, experimental results clarified, to a certain extent, the dualistic particle-macromolecular behavior of lignin, which seem to vary with the conditions of extrusion and analysis. Lignin restricted the molecular mobility of PBSA when the samples were in the solid state and during their crystallization, but caused a lubricating effect when the system was submitted to shear strain in the melt state. The extent of these effects was shown to depend on lignin dispersion levels and, consequently, on the processing parameters.