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

<jats:p>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 (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M1"> <mi>E</mi> </math> </jats:inline-formula>), yield stress (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M2"> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>y</mi> </mrow> </msub> </math> </jats:inline-formula>), stress at break (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M3"> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>B</mi> </mrow> </msub> </math> </jats:inline-formula>), elongation at break (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M4"> <msub> <mrow> <mi>ε</mi> </mrow> <mrow> <mi>B</mi> </mrow> </msub> </math> </jats:inline-formula>), and toughness (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M5"> <mi>T</mi> </math> </jats:inline-formula>) were collected. The addition of the ZTC proved to show a reinforcing effect on the polymeric matrix, with an increase in both <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M6"> <mi>E</mi> </math> </jats:inline-formula> and <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M7"> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>y</mi> </mrow> </msub> </math> </jats:inline-formula>. Modelling of the mechanical properties was performed by applying Kerner’s and Pukánszky’s equations. Kerner’s model, applied on experimental <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M8"> <mi>E</mi> </math> </jats:inline-formula> values, returned a very good correspondence between collected and theoretical values. From the application of Pukánszky’s model to <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M9"> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>y</mi> </mrow> </msub> </math> </jats:inline-formula>, the obtained <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M10"> <mi>B</mi> </math> </jats:inline-formula> 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 (<jats:inline-formula> <math xmlns="http://www.w3.org/1998/Math/MathML" id="M11"> <msub> <mrow> <mi>σ</mi> </mrow> <mrow> <mi>T</mi> <mo>,</mo> <mi>B</mi> </mrow> </msub> </math> </jats:inline-formula>) was observed. The modified Pukánszky’s model gave a <jats:inline-formula> <math xmlns="http://www.w3. org/1998/Math/MathML" id="M12"> <mi>B</mi> </math> </jats:inline-formula> value lower than the one obtained for the yield, but still in the range of acceptable values for microcomposites. </jats:p>