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This study investigated mechanical properties of biocomposites developed from recycled polylactic acid (PLA) from packaging industry and treated cellulosic fibers from pulp and paper solid waste. Microwave and enzymatic treatments were used for extraction and surface modification of hydrophilic cellulosic fibers. Enzymatic treatment was specifically performed for activation of hydroxyl groups and improvement of adhesion between matrix and fibers including controlling the length of cellulosic fibers with size reduction of around 50% (142 and 127 μm for primary and mixed biosolids, respectively) as compared to microwave treatment. Microwave treatment produced cellulosic fibers of 293 and 341 μm, for primary and mixed biosolids, respectively. Mechanical properties of biocomposites with 2% (w/w) of treated cellulosic fibers (Young's Modulus 887.83 MPa with tensile strain at breakpoint of 7.22%, tensile stress at yield 41.35 MPa) was enhanced in comparison to the recycled PLA (Young's Modulus 644.47 ± 30.086 MPa with tensile strain at breakpoint of 6.01 ± 0.83%, tensile stress at yield of 29.49 ± 3.64 MPa). Scanning electron microscopy revealed size reduction of cellulosic fibers. X-ray diffraction and Fourier transform infrared spectroscopy confirmed strong mechanical properties of novel biocomposites. [ABSTRACT FROM AUTHOR]

Biodegradable fiber-reinforced biocomposites from steam-exploded coconut fibers and polylactic acid (PLA) and polybutylene succinate (PBS) plastic were developed in this study. Biocomposite filaments and samples were produced using a commercial-scale screw extruder and a 3D printer, respectively. In-depth mechanical and thermal analyses were also performed. The results showed that the tensile strengths of PLA mixed with 3% coconut fiber (PLA97/F3) and 6% coconut fiber (PLA94/F6) decreased by approximately 22% and 23%, respectively, compared to the 64% reduction of that of the original PLA after four-week storage. The bending modulus of the PLA/fiber composite was better than that of the original PLA (21–29% higher), whereas a 5–8% improvement was observed for the PLA/PBS/fiber composites. The impact strengths of PLA97/F3 and PLA77/PBS20/F3 were approximately 8.5% and 7.4% higher than those of the original PLA and PLA/PBS, respectively. During the degradation test, both PLA97/F3 and PLA77/PBS20/F3 exhibited higher tensile strengths than the original materials. Finally, this research presents encouraging results for the production of biodegradable fiber-reinforced biocomposites that are applicable to 3D printing platforms. The final products can be used as replacement or aftermarket components of automobiles. • PLA, PBS, and steam-exploded coconut fiber were used for filament production. • The 3D-printed biocomposites were subjected to mechanical and thermal tests. • Coconut fiber is effective as a natural fiber reinforcement material. • The products have higher tensile strengths than original materials during degradation test. [ABSTRACT FROM AUTHOR]