Morphological and Rheological Properties of PLA, PBAT, and PLA/PBAT Blend Nanocomposites Containing CNCs

Abstract

Morphological and rheological properties of poly(lactic acid), PLA (semicrystalline and amorphous), and poly(butylene adipate-co-terephthalate), PBAT, and their blends (75 wt%/25 wt%; PLA/PBAT) were investigated in the presence of cellulose nanocrystals (CNCs) prepared from solution casting followed by melt mixing. For the solution casting step, the CNCs were either incorporated into the matrix, the dispersed phase, or both. The dispersion and distribution of the CNCs in the neat polymers and localization in their blends were analyzed via scanning electron microscopy (SEM) and atomic force microscopy (AFM). The highly dispersed CNCs in the solution cast nanocomposites were agglomerated after melt mixing. In the blends with 1 wt% CNCs, the nanoparticles were mostly localized on the surface of the PBAT droplets irrespective of their initial localization. The rheological behavior of the single polymer matrix nanocomposites and their blends was determined in dynamic and transient shear flow in the molten state. Upon melt mixing the complex viscosity and storage modulus of the solution cast nanocomposites decreased markedly due to re-agglomeration of the CNCs. Under shearing at 0.1 s−1, a significant droplet coalescence was observed in the neat blends, but was prevented by the presence of the CNCs at the interface in the blend nanocomposites.

Effect of Mixing Strategy on the Structure-Properties of the PLA/PBAT Blends Incorporated with CNC

“…2 compares the rheological properties of PLA/PBAT blends and PLA/PBAT blend nanocomposites containing 3 wt% of CNC prepared through three mixing strategies and two melt mixing method (mTSE and mIM). It has been confirmed that the solution casting method preserved the good dispersion of CNC in the PLA and PBAT [33][34][35][36][37] and hence, blend nanocomposites containing 3 wt% of CNC were prepared through melt mixing of solution-casted PLA/PBAT/CNC (m1 strategy), PLA/CNC (m2 strategy) and PBAT/CNC (m3 strategy) masterbatches.…”

“…3. The viscosity reduction with time could be an indication of the droplet coalescence or thermal degradation of PLA [37]. It can be seen that η + enhanced with 3 wt% addition of CNC, irrespective of the processing method and mixing strategy.…”

“…Therefore, the solvent dissolution is shown to be one of the most efficient methods to disperse CNC in polymers such as PLA and PBAT [32][33][34][35][36]. It has been reported that a combination of solution casting and melt mixing methods may result in a good level of CNC dispersion in PLA and PBAT [32,35,37]. Mohammadi et al [37] explored the localization of CNCs in PLA (amorphous and semicrystalline)/PBAT blend nanocomposites.…”

“…It has been reported that a combination of solution casting and melt mixing methods may result in a good level of CNC dispersion in PLA and PBAT [32,35,37]. Mohammadi et al [37] explored the localization of CNCs in PLA (amorphous and semicrystalline)/PBAT blend nanocomposites. Corresponding nanocomposites were prepared through firstly solution casting with different mixing strategies, and then melt mixing using an internal mixer.…”

Preparation and properties of PBAT/PLA composites modified by PVA and cellulose nanocrystals

“…However, PLA has high strength but poor toughness and impact and tear resistance 9 . Advances in functional modification technology of biodegradable materials are increasing owing to high‐mechanical strength, large specific surface area, high‐Young's modulus, and strong hydrophilicity of cellulose nanomaterials integrated with PBAT and PLA to yield high strength and toughness 10–11 …”