Toughened Renewable Bio-polyester Blends Achieved through Crystallization Retardation by Acetylated Cellulose Fibers

Acetylation was explored as a technique to make cellulose fibers more compatible within a poly(lactic acid)/poly(3-hydroxybutyrate) polymer matrix. Acetylation was performed to degrees of substitutions 1.74, 2.52, and 2.8, and fibers were used in loadings from 0–20% by weight. Results showed no tensile strength improvements due to poor dispersion and fiber size reduction with fiber addition, but there were increases in modulus in the non-acetylated fiber sample and fully acetylated [degree of substitution (DS) 2.8] fiber samples. Composites containing modified fibers showed an increase in strain at break by as much as 200% at low loading levels. Acetylated cellulose acted as a nucleation retardant, while unmodified cellulose fibers acted as a nucleating agent. Results indicated the importance of fiber size, fiber, dispersion, and fiber–polymer interactions for final properties. Acetylated fiber reinforcement showed some promise for increasing maximum strain and compatibility of composites, which could allow for future investigations into filler chemistry–final property relationships, especially in applications like 3D printing where increased toughness is desired for some polymers.