Study Using a Mixed Full Factorial Design of The Effects of Matrix–Reinforcement Interactions on the Mechanical and Optical Properties of Starch-Based Bioplastics

Bioplastics offer an alternative to conventional petrochemical-based plastics. This type of plastic has many advantages. However, when synthesized from bioresources without the addition of reinforcing agents, they exhibit poor mechanical and optical performance; it is therefore necessary to incorporate reinforcing agents to improve their properties. In this study, a mixed full factorial design (2³) was applied by combining three continuous factors (CNF-Raw, CNF-Alkaline, CNC) and a four-level categorical factor corresponding to the oxidized starch matrices (Oxpot, Oxyam, Oxcas, Oxcor). The results showed that the Oxyam matrix (D₂) potentiates the effect of the fibers, simultaneously improving the breaking strength (R₁), elongation at break (R₂), and opacity (R₃) of the films. The D₂X₁ interaction revealed a notable synergy between the matrix and the reinforcements, regardless of the response obtained. The results also showed that Test 26 offers a satisfactory balance between the mechanical and optical properties of the ATP film. The values obtained for R₁, R₂, and R₃ were 95.3 MPa, 17.06%, and 17.56%, respectively. SEM analysis revealed the presence of microcracks and scattered, unconnected discontinuities in the film’s internal structure