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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]

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]

Lignin and phytic acid combinations were used as a simple route for developing bio-based flame retardant systems in PLA. The composites were prepared by melt blending and their mechanical, thermal and fire properties have been explored. Combining these two additives has been shown to present an interesting way of limiting the negative effect of each of them and for improving the properties of the resulting materials. On the first hand, the presence of phytic acid enables better dispersion of lignin particles into the matrix, limiting PLA thermal degradation induced by lignin. On the second hand, lignin enables important reduction of the composite hygroscopy induced by the presence of phytic acid. Moreover, combining lignin and phytic acid leads to significant reduction up to 44% of peak of heat release rate (pHRR) during cone calorimeter test as well as obtaining V-2 classification in UL-94 test. Some positive effects of the binary combinations on the composites mechanical properties have also been evidenced (increase of the elongation at break from 3.1% to 12.6% for one formulation). [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 this work, a sustainable approach was developed to melt-blend and enhance the compatibility of the immiscible blend of polylactide (PLA) and poly(acrylonitrile–butadiene–styrene) (ABS). Cardanol, a bio-based phenolic compound, was used as an interfacial (reactive) compatibilizer. The blending was conducted by a solvent-free reactive extrusion. The incorporation of cardanol resulted in an enhancement of the compatibility evidenced by the decrease of ABS nodules size within PLA from few micrometres to several tens of nanometres and the convergence of both polymers Tα around 68.5 °C. In-depth investigation evidenced that cardanol grafted onto ABS during the reactive extrusion via its phenolic ring, leading to a substantial plasticizing effect and a significant decrease of the surface energy of ABS, similar to those of PLA. This work paves the way to a multitude of new compatibilization strategies based on the reaction of phenolic compounds during the extrusion of PLA and ABS. [ABSTRACT FROM AUTHOR]

The present study focuses on the use of lignin, which is the second most abundant constituent of the biomass, as sustainable flame retardant additive for polylactide (PLA). Indeed, thanks to its aromatic structure, lignin could be advantageously used, in polymeric matrices, as a char promotor agent that can allow some reduction of the combustion rate. An original and simple approach, based on a two-step phosphorus/nitrogen chemical modification, is proposed to enhance the flame retardant effect of lignin in PLA. This approach has been applied on two different lignins, i.e. kraft and organosolv lignins. The effect of the plant origin, extraction mode of lignin as well as it chemical modification on both its structure and properties was investigated by using several characterization techniques. Fire properties and thermal behavior of PLA composites containing 20 wt% of both untreated and treated lignins were characterized by using cone calorimeter, UL-94 and thermogravimetric analysis (TGA). Results showed that the incorporation of untreated lignins led to a flame retardant action in PLA thanks to the formation of char but also to a significant loss of the thermal stability of PLA and to an important decrease of its time to ignition. In contrast, both phosphorus/nitrogen chemically treated lignins were found to limit PLA thermal degradation during melt processing as well as during TG experiments and also to significantly improve fire retardant properties allowing to reach V0 classification at UL-94. In this paper we also deeply investigated the nature of the gases evolved during thermal decomposition of treated and untreated lignins by using TGA-Mass spectrometer and cone calorimeter – FTIR couplings. [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]

Cellulose acetate (CA) with a degree of substitution (DS) of 2.5 and polylactic acid (PLLA) were plasticized by melt extrusion using triacetin. Blends of resulting thermoplastic materials were then prepared and characterized by their tensile strength and differential scanning calorimetry (DSC). Thermal analysis revealed the invariability of the PLLA glass transition temperature in all blends, indicating that the compounds were immiscible. Grafted d/l lactide to CA copolymers were prepared by reactive melt processing using CA with different degree of substitution i.e. 2.1 and 2.5 and evaluated as CA/PLLA blend compatibilizer. The compatibility of the blends was investigated by scanning electron microscopy (SEM). Results showed that blend compatibility was improved evidencing the best performance of grafted copolymers with long grafted chains as blend compatibilizer of CA/PLLA blends. Finally, compatibilized blends compositions with enhanced ultimate elongation were achieved by using plasticized PLLA instead of neat PLLA. [ABSTRACT FROM AUTHOR]

Highlights: [•] Stereoisomers of PLLA and PDLA grafted directly at clay surface via metal-free ROP. [•] These nanohybrids were melt-processed with commercial PLA to obtain nanocomposite. [•] Grafting from approach enables to design full stereocomplex by solvent-free melting. [•] Grafting from and stereocomplexation improve rigidity and thermal properties of PLA. [•] Nanocomposites obtained show a significant improvement in oxygen-barrier properties. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanocomposites of PLA and surface-treated ZnO rod-like nanoparticles. [•] Changes in PLA inherent permeation properties dependent on temperature and loading. [•] Good antibacterial activity against Gram-positive and Gram-negative bacteria. [•] The antibacterial performance was found to be time-dependent. [Copyright &y& Elsevier]

Abstract: By applying electrospinning new fibrous materials from a stereocomplex formed between a high molar mass poly(l-lactide) (HPLLA) and a copoly(ester urethane) (CPEU) based on poly(d-lactide) (PDLA) and poly(butylene succinate) (PBS) blocks (PDLA-b-PBS) were prepared. The stereocomplex formation was evaluated by means of differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. In contrast to electrospun mats of HPLLA and HPLLA/PDLA-OH in which the polymers were in the amorphous state, it was found that the presence of PBS allowed the formation of a crystalline phase in the fibrous materials from HPLLA/PDLA-b-PBS. Annealing at 100°C for 8h enabled reorganization of the polymer segments within the fibers and the appearance for all of the samples of crystalline diffractions in the XRD patterns. A melting temperature of about 200°C was registered in the DSC thermograms of pristine and annealed mats from HPLLA/PDLA-OH and HPLLA/PDLA-b-PBS; evidence for stereocomplex formation. It was shown that besides stereocomplex crystallites PBS and PLA crystallites existed as well when using CPEUs with a higher PBS content. The obtained data from the thermogravimetric analysis (TGA) showed that the thermal stability of the stereocomplex-based fibrous materials depended on the PBS content. [Copyright &y& Elsevier]