Recycled newspaper cellulose fiber (RNCF) reinforced poly(lactic acid) (PLA) biocomposites were fabricated by a microcompounding and molding system. RNCF-reinforced polypropylene (PP) composites were also processed with a recycled newspaper fiber content of 30 wt % and were compared to PLA/RNCF composites. The mechanical and thermal-mechanical properties of these composites have been studied and compared to PLA/talc and PP/talc composites. These composites possess similar mechanical properties to talc-filled composites as a result of reinforcement by RNCF. The tensile and flexural modulus of the biocomposites was significantly higher when compared with the virgin resin. The tensile modulus (6.3 GPa) of the PLA/RNCF composite (30 wt % fiber content) was comparable to that of traditional (i.e. polypropylene/talc) composites. The DMA storage modulus and the loss modulus of the RNCF-PLA composites were found to increase, whereas the mechanical loss factor (tan δ) was found to decrease. Differential scanning calorimetry (DSC) thermograms of neat PLA and of the composites exhibit nearly the same glass transition temperatures and melting temperatures. The morphology evaluated by scanning electron microscopy (SEM) indicated good dispersion of RNCF in the PLA matrix. Thermogravimetric analysis (TGA) thermograms reveal the thermal stability of the biocomposites to nearly 350 °C. These findings illustrate that RNCF possesses good thermal properties, compares favorably with talc filler in mechanical properties, and could be a good alternative reinforcement fiber for biopolymer composites.
A mixture
design of experiment (DoE) was used to guide the fabrication
and analysis of sustainable poly(lactic acid) (PLA) and biobased poly(butylene
succinate) (BioPBS) 3D-printing filaments. The statistical DoE approach
was employed to investigate the correlation between the mechanical
properties of the PLA/BioPBS blends at different PLA and BioPBS wt
% and to obtain the linear regression models of the mechanical properties.
The statistical models help to design PLA/BioPBS blends with the desired
mechanical properties. The PLA/BioPBS filaments with different composition
ratios were 3D-printed via fused deposition modeling (FDM). The 3D-printability
of the polymer blends was determined by the flowability and dimensional
stability of the filaments, provided by fundamental rheological and
coefficient of linear thermal expansion (CLTE) studies. Preliminary
research found that the 3D-printability of PLA/BioPBS filaments with
BioPBS content higher than 50 wt % was unsuccessful due to high viscosity
and low thermal stability. These findings were verified with rheological
tests for a range of PLA/BioPBS blend ratios and thermomechanical
studies. Rheological results show a significant increase of the blend
viscosity when BioPBS content in the blend was >50%. Additionally,
the CLTE drastically increased with higher contents of BioPBS, making
the PLA/BioPBS filaments thermally unstable during FDM processing.
These results confirmed that the 3D-printability of PLA/BioPBS filaments
is greatly influenced by the blend viscosity and the printing temperature.
Rheological studies revealed that the viscosity range of a 3D-printable
PLA/BioPBS filament lies within 1000–100 Pa·s. Scanning
electron microscopy (SEM) and polarized optical microscopy (POM) images
confirmed that PLA and BioPBS are immiscible. However, the addition
of BioPBS improved the ductility and the crystallinity of PLA. The
3D printed PLA/BioPBS (90/10) blend showed an interesting result in
that it obtained higher tensile and impact strengths than the neat
PLA, which was attributed to crystallinity and morphological factors.
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