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The formation of polylactide stereocomplex (sc-PLA), involving the blending of poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA), enhances PLA materials by making them stronger and more heat-resistant. This study investigated the competitive crystallization behavior of homocrystals (HCs) and stereocomplex crystals (SCs) in a 50/50 PLLA/PDLA blend with added polyethylene glycol (PEG). PEG, with molecular weights of 400 g/mol and 35,000 g/mol, was incorporated at concentrations ranging from 5% to 20% by weight. Differential scanning calorimetry (DSC) analysis revealed that PEG increased the crystallization temperature, promoted SC formation, and inhibited HC formation. PEG also acted as a plasticizer, lowering both melting and crystallization temperatures. The second heating DSC curve showed that the pure PLLA/PDLA blend had a 57.1% fraction of SC while adding 5% PEG with a molecular weight of 400 g/mol resulted in complete SC formation. In contrast, PEG with a molecular weight of 35,000 g/mol was less effective, allowing some HC formation. Additionally, PEG consistently promoted SC formation across various cooling rates (2, 5, 10, or 20 °C/min), demonstrating a robust influence under different conditions. [ABSTRACT FROM AUTHOR]

While the brittle polylactide (PLA) has a high durability among bioplastics, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) with certain ductility exhibits facile compostability. The addition of polybutylene adipate terephthalate (PBAT) may also be used to improve the ductility and toughness of brittle bioplastics. Binary and ternary blends of PLA/PBAT/PHBH based on either PLA or PHBH as the matrix have been manufactured using a twin-screw extruder. The melt rheological, mechanical, and morphological properties of the processed samples were examined. Binary blends of PLA/PHBH show superior strength, with the PLA75/PHBH25 blend exhibiting a tensile strength of 35.2 ± 3.0 MPa, which may be attributed to miscible-like morphology. In contrast, blends of PLA with PBAT demonstrate low strength, with the PLA50/PBAT50 blend exhibits a tensile strength of 9.5 ± 2.0 MPa due to the presence of large droplets in the matrix. PBAT-containing blends exhibit lower impact strengths compared to PHBH-containing blends. For instance, a PLA75/PBAT25 blend displays an impact strength of 1.76 ± 0.1 kJ/m2, whereas the PHBH75/PBAT25 blend displays an impact strength of 2.61 ± 0.3 kJ/m2, which may be attributed to uniformly dispersed PBAT droplets. [ABSTRACT FROM AUTHOR]

This article reports the effects of the characteristics and selective localization of nanofillers on the morphology development and rheological properties of melt-processed polylactide/poly(butylene adipate-co-terephthalate) (PLA/ PBAT) blend composites. Four types of nanofillers (1 wt%) are used: nanoclay (Cloisite30B [C30B]), carbon nanotubes (CNTs), nanosilica, and graphene oxide (GO). Transmission electron microscopy studies reveal that C30B is localized mainly at the PLA/PBAT interface, whereas silica, GO, and CNT are localized in PBAT droplets, although some CNTs also appear toward the interface inside the PBAT. Despite their selective localization inside the PBAT, CNTs are found to be the most effective particles for droplet size reduction, whereas silica nanoparticles are ineffective. The CNT bundles recoil during melt blending, and eventually, their breakage facilitates droplet breakup. The effects of nanofiller localization and annealing under dynamic shear on the blend morphologies are also explored through rheological analysis. The results show an anomalous relationship with the morphologies of the composites. It is also found that both coalescence and thermal degradation are involved in the annealing process of the blends. Interestingly, the CNT-filled composites may have been transformed into co-continuous-like structures during annealing, unlike the other blends studied here. KEYWORDS blend, composites, nanofillers, PBAT, PLA, rheology, 1 | INTRODUCTION The use of biosourced polymers as an alternative to fossil-fuel-based polymers to mitigate carbon dioxide emissions has attracted attention from scientists, manufacturers, and governments. [1,2] These biobased [...]

Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co‐rotating twin‐screw extruder (TSE) in high (h)‐ and low (l)‐molecular‐weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D‐lactic acid equivalents content (D‐content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small‐amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low‐molecular‐weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA‐based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10−5 S/m) at a low loading of 0.5 wt.% MWCNTs. [ABSTRACT FROM AUTHOR]