Characterization of PLA–hemp biocomposites produced by hot-pressing

This study investigates the thermal, chemical, physical, morphological, and mechanical properties of hot-pressed PLA-hemp biocomposites produced without compatibilizers. Hemp particles below 75 µm were composed of PLA at 3%, 6%, and 9 wt%, and neat PLA was evaluated in both granular and extruded forms. The composition was compounded using a twin-screw extruder and converted into plates by hot pressing. TGA showed that extrusion slightly improved the thermal stability of neat PLA, whereas hemp addition reduced degradation temperatures. DSC results demonstrated that hemp fibers increased earlier crystallization and the crystallinity of the PLA matrix. FTIR spectra showed that the interaction between PLA and hemp was mainly physical but there is no evidence of new chemical bond formation. Water absorption and thickness swelling increased with hemp content, reaching the highest values in PLA-H9. Surface roughness was significantly affected by sample type, while tensile and flexural strengths decreased after hemp incorporation. SEM images depicted fiber pull-out, interfacial debonding, and micro voids, confirming limited matrix–fiber adhesion. Overall, hemp addition improved bio-based content but reduced strength without compatibilization.