Design of Mechanical Properties of Poly(butylene-adipate-terephthalate) Reinforced with Zein-TiO2 Complex

Mechanical properties of polymer biocomposites are influenced by the interaction between the matrix and the filler surface. In this work, composites based on poly(butylene-adipate-terephthalate) (PBAT) filled with micrometric particles of zein-TiO2 complex (ZTC) were realized via solvent casting technique at different concentrations, equal to 0, 5, 10, and 20 wt%. After pelletization, the resulting materials were injection molded into standard specimens, employed for the uniaxial tensile test (UTT) characterization. From the stress-strain curves, Young’s modulus ( $E$ ), yield stress ( ${\sigma }_y$ ), stress at break ( ${\sigma }_B$ ), elongation at break ( ${\epsilon }_B$ ), and toughness ( $T$ ) were collected. The addition of the ZTC proved to show a reinforcing effect on the polymeric matrix, with an increase in both $E$ and ${\sigma }_y$ . Modelling of the mechanical properties was performed by applying Kerner’s and Pukánszky’s equations. Kerner’s model, applied on experimental $E$ values, returned a very good correspondence between collected and theoretical values. From the application of Pukánszky’s model to ${\sigma }_y$ , the obtained $B$ value showed a good interfacial interaction between the matrix and the filler. Due to the enhanced stiffness of the composites, a reduction in the true stress at break ( ${\sigma }_{T,B}$ ) was observed. The modified Pukánszky’s model gave a $B$ value lower than the one obtained for the yield, but still in the range of acceptable values for microcomposites.