Rheological properties of PLA

Fig. 7.42 (a) Rheological properties of PLA/PBSA blends without chain extender (b) with chain extender (Eslami and Kamal 2013a, b)... 

This chapter is organized to provide a short yet detailed understanding of the fundamental rheological properties of PLAs extensive use of references is employed where appropriate. However, the chapter is meant to be self-contained, and so appropriate introductory material is also provided. Properties of the single chain are discussed and related to measurable quantities available from dilute solution viscometry. This is followed by a discussion of the single chain properties of PLA. Next, a brief discussion of the rheology of polymeric materials is provided. In this context, mathematical models are briefly discussed, including the... 

Epoxidized oils were also used to modify PLA Ali et ah (2009) reported that its use as a plasticizer to improve flexibility. Thermal and scanning electron microscope analysis revealed that epoxidized soybean oil is partially miscible with PLA. Rheological and mechanical properties of PLA/epoxidized soybean oil blends were studied by Xu and Qu (2009) Epoxidized soybean oil exhibited a positive effect on both the elongation at break and melt rheology. Al-Mulla et al. (2010b) also reported that plasticization of PLA (epoxidized palm oil) was carried out via solution casting process using chloroform as a solvent. The results indicated that improved flexibility could be achieved by incorporation of epoxidized palm oil. 

The rheological properties of the plastic phase (PLA/PHA) and the elastomer phase (NR) are vastly different, and so the blend is immiscible, leading to... 

Tensile and thermal properties of the Unear-branched blends were also measured and found to be equal within the statistical error of the experiments. The results suggest that excellent control over rheological behavior of PLA is possible through blending chain arehitectures without compromising mechanical properties. 

The above studies do not, however, capture a systematic description of PLA rheology across a broad range of stereo-optical compositions, as the materials studied possessed high (>90%) L-stereochemical center content. However, one study [3] does provide a comprehensive evaluation of the linear viscoelastic properties of PLA across a wide range of molecular weights and stereochemical compositions. The major points of this study are summarized here. This study also serves as the basis for the software included with this text for predicting viscoelastic properties of PLAs. 

The torque variation of blends during compounding can also indicate effect of MDI distribution. As expected, the addition of MDI increased the torque of pure PLA, due to molecular weight increase [45]. Similar results for other polyesters such as polycaprolactone (PCL) and poly(butyl-ene succinate adipate) (PBSB) have also been observed [44]. The highest torque values were recorded for the blends where MDI was distributed in the PLA phase, which further confirms the benefits of PLA phase distribution of MDI. The results of a detailed study of the rheological properties of the various blends will be reported in a separate paper. 

Figure 5,30 Rheological properties of a PLA-PBAT-ML2 b PLA-PBAT c PLA-PBAT-M d pure PLA...

Blends of PLA and AAC were studied to answer the question whether proeessabihty of PLA can be improved by mixing with AAC. First, the effect of mixing conditions on rheological properties of both... 

Xu, C., Yuan, D., Fu, L., and Chen, Y. (2014) Physical blend of PLA/NR with co-continuous phase structure preparation, rheology property, mechanical properties and morphology. Polym. 

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