Property form
Table 1. The gengral properties of PLA+ [34]
Table 2. The thermal properties of PLA+ [34]
Dynamic shear response
Figure 1. Function of the complex viscosities (η*) of the pure PLA and PLA/TiO2 nanocomposites [34]
The dynamic oscillatory shear measurements were performed on pure PLA and its nanocomposites to investigate the response of nanoparticles to the dynamic shearing. As shown in figure1, the complex viscosities (η*) of the pure PLA and PLA/TiO2 nanocomposites are plotted as a function of frequency (ω) in rad s−1. The η* of the PLA and its nanocomposites melt show only a small frequency dependence, revealing a Newtonian plateau at low frequency. Figure1 also indicates the dependence of complex viscosities of nanocomposites on the TiO2 content. Obviously, with low loading content of TiO2 (0.5 wt% and 1 wt%), the nanocomposites melt has a higher complex viscosity and theirs values are twice higher than that of the pure PLA. However, the complex viscosity values are close to the neat matrix when the TiO2 content is greater than 2 wt%.
Crystallinity
Figure 2. The DSC thermograms of PLA/PEG blend and its nanocomposites [35]
Therefore, to confirm the influence of incorporating xGnP into PLA on the mechanical enhancement of the composites, DSC is employed to measure the crystallinity difference between PLA/PEG blend and PLA/PEG/xGnP nanocomposites. For PLA/PEG blend and its nanocomposites, the DSC thermograms are shown in figure2. The melting curves have similar peaks, and the melting points of the PLA/PEG blend and the nanocomposites are almost the same. The crystallinity (Xc) in all samples is calculated as follows. The crystallinity of PLA/PEG nanocomposites is increased after adding the xGnP, which corresponds well with the XRD results. However, the change of PLA crystallinity is so slight that it cannot induce a significant impact on the mechanical properties of the composites. Therefore, the significant reinforcement of the strength and modulus for PLA/PEG nanocomposites can be mostly attributed to the homogeneous dispersion of xGnP in the polymer matrix and strong interactions between both components.
Life cycle of PLA+
Figure 3. The life cycle of PLA+ [35]
The life cycle of PLA+ including heating, stretching, shaping, cooling and some other steps which adapt to the mechanical properties and chemical properties of PLA+. And polylactic acid's biocompatibility is clearly displayed.
Temperature slope sweep
Figure 3. The temperature ramp sweep of different rigidity aromatic lignin and PLA biocomposites [36]
In view of the temperature ramp sweep results of different rigidity aromatic lignin and PLA biocomposites shown in figure3, the formation of the interfacial interaction is depicted. As indicated in figure3, the values of G′, G″, and η* of all samples decreased dramatically with increasing the temperature from 160 °C to 180 °C. Then a comparatively slower decline from 180 °C to 220 °C was seen, due to the complete melting of PLA. The decrease shows that the biocomposites turned to a viscous state gradually. In this range of temperature, the value of G″ was still higher than that of G′, values at the same temperature, which means that the viscous flow of PLA predominated rather than elastic deformation.
Obviously, it was exhibited that PLA/At-lignin biocomposites took possession of higher G′, G″, and η* values than pure PLA, PLA/Ac-lignin, and PLA/By-lignin biocomposites across the whole temperature range. This was also due to the formation of hydrogen bonding between PLA and At-lignin, as same as the results in frequency sweep.
Refenerce
[34] Zhang, H., Huang, J., Yang, L., Chen, R., Zou, W., Lin, X. and Qu, J., 2021. Preparation, characterization and properties of PLA/TiO2 nanocomposites based on a novel vane extruder.
[35] Chieng, B., Ibrahim, N., Yunus, W. and Hussein, M., 2021. Poly(lactic acid)/Poly(ethylene glycol) Polymer Nanocomposites: Effects of Graphene Nanoplatelets.
[36] Guo, J., Chen, X., Wang, J., He, Y., Xie, H. and Zheng, Q., 2021. The Influence of Compatibility on the Structure and Properties of PLA/Lignin Biocomposites by Chemical Modification.