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The present work deals with the building of novel, fully bio-based polyamide 11 (PA11)/polylactide (PLA) diblock copolymers (PA11 x PLA y ). The adopted two-step synthetic strategy involves first the preparation of an amino-terminated PA11 prepolymer ( i.e. , having the amino end-group available and the carboxylic one protected), to be employed subsequently as a macro-initiator in the ring-opening polymerization of d -lactide (or l -lactide). Upon tuning the lactide conversion, diblock copolymers with different PA11/PLA ratios are targeted and achieved, as demonstrated by 1 H NMR and TGA analysis. The thermal properties of these double-crystalline polymers are characterized by means of DSC. Finally, fast stereocomplexation is demonstrated upon mixing the enantiomeric PA11 x PLA y diblock pairs. Indeed, the idea behind these systems is to conjugate the properties of PLA with those of the high-performance PA11, in a cumulative rather than intermediate fashion, as for widely reported random poly(ester amide)s, but without phase separation occurring, which is the case for PLA/PA11 immiscible blends. In addition, the presence of the stereocomplex, well-known for its improved chemical/thermal resistance over PLA homopolymer, could impart even further quality to the final materials. [ABSTRACT FROM AUTHOR]

A multiscale characterization approach is developed to resolve the structure of inclusions in polylactide (PLA) plasticized with acrylated poly(ethylene glycol) (acrylPEG) by reactive extrusion. Scanning transmission X-ray microscopy (STXM) coupled with near-edge X-ray absorption fine structure (NEXAFS) nanospectroscopy demonstrates that these inclusions have a core-shell morphology. This technique also proves that the inclusions consist of polymerized acrylPEG (poly(acrylPEG)), which is also confirmed by elastic modulus measurement using an atomic force microscope. The shell consists of poly(acrylPEG)-rich domains, while the core is less rich in the polymerized plasticizer. Upon drawing, the density of the inclusion's core and shell markedly decreases as shown by microcomputed X-ray tomography measurements, and no inclusion-matrix debonding is observed. At the same time, sub-micrometer cracks are noted between inclusions by STXM/NEXAFS imaging, which may result from the presence of crosslinking points restricting the local chain mobility. Novel knowledge about the reactive extrusion-induced PLA structure is released. [ABSTRACT FROM AUTHOR]

Poly(lactide)/halloysite nanotubes (PLA/HNT) nanocomposites with crystalline matrix were obtained by cold crystallization and examined. Neat HNT and HNT treated with N,N′- ethylenebis(stearamide) (EBS) were used as nanofillers. Reference materials, PLA and PLA/EBS blend, prepared in the same way, were also considered. The influence of HNT and/or EBS content on the crystallinity and morphology of PLA matrix, as well as on the dynamic mechanical and optical properties of the materials, was determined. The nanocomposites contained well-distributed HNT, with only occasional agglomerates. HNT, EBS-treated HNT and EBS influenced the morphology of the crystalline PLA matrix and the amounts of the disorder α’ (termed also δ) and order α crystallographic forms of PLA. Crystallinity increased stiffness of the materials compared to their counterparts with the amorphous matrix. Owing to the crystallinity and the presence of the nanofillers, the storage modulus at 20 °C and 60 °C increased by up to 30 and 60%, respectively, compared to neat amorphous PLA. Interestingly, at lower nanofiller content the crystalline nanocomposites with EBS were more transparent than neat crystalline PLA. [ABSTRACT FROM AUTHOR]

Amorphous polylactide/halloysite nanotube (PLA/HNT) nanocomposites were prepared and examined. Neat HNT and HNT treated with N,N' - ethylenebis(stearamide) (EBS) were used as nanofillers. The role of HNT and/or EBS content on the cold crystallization of amorphous PLA matrix, HNT dispersion, as well as on the dynamic mechanical and optical properties of the materials was determined. The PLA/HNT-based nanocomposites contained well-distributed nanotubes and occasionally micron-sized aggregates, especially at high loading. HNT, EBS treated HNT and EBS influenced the cold crystallization of PLA, therefore the formation of the disorder α′ and the order α crystallographic forms of PLA. The nanocomposites exhibited increased stiffness and decreased transparency compared to the neat PLA. Due to the reinforcing effect and additional specific features of HNT, the addition of the nanofiller allows tuning of the properties of the nanocomposites with amorphous PLA matrix. [ABSTRACT FROM AUTHOR]

In the present work, sustainable flame retardant polylactide (PLA) compositions, containing cellulose–phosphorus combinations, have been studied. The effect of combining MicroCrystalline Cellulose (MCC) or NanoCrystalline Cellulose (NCC) with phosphorus, on thermal stability and flame retardant properties of PLA was investigated by thermogravimetric analysis (TGA), cone calorimeter and UL-94 tests. Phosphorus was introduced either by chemical grafting on cellulose or by coadditive melt blending by using a bio-based phosphorous agent, i.e., aluminum phytate. In both cases, the charring effect of cellulose was enhanced. The phosphorylation process used allowed grafting 16.5 wt% of P as determined by Inductively Coupled Plasma analysis (ICP). However, this process led to the generation of water soluble cellulose and to the loss of the nanometric particle shape. For this reason, the phosphorylation of cellulose has been performed only on the microcrystalline particles. Using 20 wt% of phosphorylated MCC (MCC-P) allowed reaching V0 at UL-94 test but did not result in significant reduction of pHRR. Significant pHRR reduction was obtained only when aluminum phytate was combined with phosphorylated MCC (P-MCC). As far as NCC was concerned, the use of a phosphorylated-NCC was not required since the simple combination of aluminum phytate and NCC allowed reaching significant decrease of the pHRR actually at the level of the value found when MCC-P was used in combination with aluminum phytate. The high specific surface area of NCC proved very useful to promote the formation of a better insulating charred layer. [ABSTRACT FROM AUTHOR]

Among currently available bio-based polymers, polylactide (PLA) and its (nano)composites have interesting physical and mechanical properties (high tensile strength and stiffness, good processability, biodegradability...). However, they have relatively low thermal stability at high temperature, low toughness and are extremely brittle, all of these drawbacks being obstacles to their utilization in many engineering applications. In this study, PLA-halloysite nanotubes (HNT) nanocomposites are modified by co-addition of a plasticizer (tributyl citrate (TBC)), aiming at reaching mechanical properties suitable for automotive applications. Properties of nanocomposites at different plasticizer contents are characterized with the aim to reach the best compromise between high tensile and flexural strengths and rigidities (ascribed to the matrix and HNT) and impact resistance, ductility, crystallization rat,e and degree of crystallinity, in particular. Results show that plasticized PLA-HNT nanocomposites are very interesting bio-based alternatives for automotive applications, when the plasticizer content is carefully chosen. [ABSTRACT FROM AUTHOR]