Grafting of poly(stearyl acrylate) on cellulose fiber as 3D-printable HDPE composites

This paper aimed to produce a bio-based filament, suitable for 3d printing (Fused Deposition Modeling), made of surface modified cellulose fiber and high density polyethylene. The cellulose fiber (CF) were first surface modified and transformed into a CF-based macroinitiator through an esterification reaction with the 2-Bromoisobutyric acid. We finally study the ability of this CF-based macroinitiator to initiate a Single Electron Transfer-Living Radical Polymerization (SET-LRP) with an hydrophobic monomer: the stearyl acrylate. The grafting of poly(stearly acrylate) onto the cellulose fiber is strongly increasing the adhesion, compatibility of the modified fiber with the hydrophobic host matrix (HDPE). Finally, the resulting hydrophobic fibers were extruded with the high density polyethylene (HDPE) through a counter-rotating twin-screw extruder, yielding a bio-based filament suitable for FDM 3d printing. The successful surface modifications, such as the correct incorporation of the modified fiber into the thermoplastic matrix, were characterized through ATR-FTIR, 13C CP-MAS NMR, FE-SEM, and mechanical testing. Throughout those characterization techniques, it could be concluded that this surface modification significantly improves the compatibility of the fibers with HDPE. Finally, the 3D printing properties of the composite were tested and compared to those of pure HDPE through the 3d printing of simples objects. It was concluded that the printability of the composite made with poly(stearyl acrylate)-grafted cellulose overcome the problem (shrinkage, warpage, print fidelity) meet with the printing of pure HDPE.