PLA/MFC

Crystallinity of PLA has a strong impact on its mechanical properties. Suryanegara et al. have prepared PLA/MFC nanocomposites in both fully amorphous and crystallized states. The tensile modulus and strength of pristine PLA were improved with an increase of MFC content in both amorphous and crystallized states. Dynamic mechanical analysis (DMA) has been used to study the effect of MFC reinforcement on the thermomechanical properties of PLA in both states and the results are shown in Figure 9.5. In the amorphous state, the storage modulus of pristine PLA below Tg is almost constant at around 3 GPa. Above Tg, the modulus drops to 4 MPa at 80 °C, and then increases to 200 MPa at 100 °C owing to the cold... 

PLA isotropic A PLA oriented O PLA-raixtuie° isotropic PLA-inixtuie oriented PLA-mixture reformed OPGA/PLA-mixture° 30 70 isotropic PGA/PLA-MFC 30 70 APGA oriented... 

Critical energy release rate under Mode I loading was also evaluated for the PLA/MFC and PLA/BF/MFC composites. Figure 9.7 shows the dimensions of the specimens for the fracture toughness tests. The critical energy release rate was calculated by Eq. (9.2) ... 

Figure 9.10 shows typical stress-strain curves of neat PLA resin, PLA/BF, and PLA/MFC composites. The bending strength and elastic modulus of the PLA/BF... 

ADS, Archer Daniels Midland CPC, CPC International MFCS, high fructose com syrup and/or glucose/fructose syrup sweetner Isomalt, hydrogenated isomaltulose sweetner and PLA,... 

Fig. 23.12 Typical stress-strain curves of MFC/PLA composites at different MFC fibre contents. Percentages indicate MFC fibre contents [69]...

Nakagaito AN, Fujimura A, Sakai T et al (2009) Production of microfibrillated cellulose (MFC)-reiirforced polylactic acid (PLA) nanocmnposites from sheets obtained by a paper-making-Uke process. Compos Sci Technol 69 1293—1297... 

Figure 18.15. (a) Overview of the MFC fracture surface, showing a hairy structure (arrow), and (b) larger magnification of PGA fibrils (arrow) in an isotropic PLA matrix... 

Figure 18.16. Comparison between conventional biodegradable materials and the MFC-PGA/PLA 30 70...

MFC-bone nail PGA/PLA 20 80 Z = tension side D = pressure side... 

Figure 18.17. SEM pictures of the fracture surfaces of injection molded bone nails (a) PLA bone nail with an isotropic structure (b) MFC-bone naU, PGA/PLA 30 70 (c) microfibrils on the tension side, magnification from (b)...

Figure 18.18. SEM pictures of the MFC fracture surfaces with different PGA content PGA/PLA 10 90 (left), and PGA/PLA 30 70 (right)...

Figure 18.19. Comparison of flexural stress deflection curves of a classical, injection molded PLA bone nail (dashed hne) with that of an isotropic, injection molded PGA/PLA-mixture (dotted line), and with the same mixture after MFC-treatment (fully drawn hne). All three curves are much lower than the one obtained with a confidential PLA mixture after processing by solid state extrusion (top, fully drawn line)...

Table 18.2. Relative improvements in modulus, strength and strain to failure conventional bone nail, vs. injection molded MFC-PGA/PLA 30 70, vs. PLA-mixture° after solid state extrusion...

Oksman et al. (2006) studied a new processing technique for manufacturing CNC/PLA nanocomposites. MFC was treated with iV,V-dimethylacetamide (DMAc) containing lithium chloride (LiCl) in order to swell the CNC and partly separate the cellulose whiskers. It was found that the extrusion process using liquid... 

Iwatake et al. developed a sustainable green composite by reinforcing PLA with micro fibrillated cellulose (MFC) and needle-leaf bleached kraft pnlp (NBKP), which improved the nano fiber network to large extent (2008). At 10 wt % nano fiber dispersion of MFCs in PLA, Young modulus and tensile strength improved by 40% and 25% without any reduction in yield strain, whereas NBKP reported rednction in yield strain and strength by 30% and 50% respectively. 

Fabrication Procedure of Developed Composite Using PLA, BF, and MFC (PLA/BF/MFC Composite)... 

The PLA, BF, and liquid-based MFC were put together into water and they were mixed for 15 min. Then, the immersion was filtered under vacuum pressure (0.06 MPa). The sheets obtained on the filter were dried at 105 °C in an electric oven to remove moisture. The obtained sheets were laminated and pressed at 190°C under 120 MPa pressure for 3 min. Figure 9.5 shows the PLA/BF/MFC composite fabricated through the process. 

Five kinds of samples having different MFC contents in weight were prepared to evaluate the effect of weight content of the MFC on the mechanical properties of the composite, as shown in Table 9.2. The content of the PLA was set to 50% in weight. 

Crack propagation behavior was observed for a special specimen of the PLA/BF and PLA/BF/MFC composite in which a single long fiber was longitudinally embedded in the matrix as shown in Figure 9.8. In this test, constraint strain was applied to the specimen, having initiated transverse crack in the matrix. 

Figure 9.9 shows the internal state and the magnified pictures of some PLA/BF/MFC specimens. It was observed that the BFs were well dispersed in the matrix and the resin-rich regions remarkably decreased for the specimen having an elevated content of the MFC. 

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