Search

Poly(lactic acid) or polylactide (PLA), a biodegradable polyester produced from renewable resources, is used for various applications (biomedical, packaging, textile fibers and technical items). Due to its inherent properties, PLA has a key-position in the market of biopolymers, being one of the most promising candidates for further developments. Unfortunately, PLA suffers from some shortcomings, whereas for the different applications specific end-use properties are required. Therefore, the addition of reinforcing fibers, micro- and/or nanofillers, and selected additives within PLA matrix is considered as a powerful method for obtaining specific end-use characteristics and major improvements of properties. This review highlights recent developments, current results and trends in the field of composites based on PLA. It presents the main advances in PLA properties and reports selected results in relation to the preparation and characterization of the most representative PLA composites. To illustrate the possibility to design the properties of composites, a section is devoted to the production and characterization of innovative PLA-based products filled with thermally-treated calcium sulfate, a by-product from the lactic acid production process. Moreover, are emphasized the last tendencies strongly evidenced in the case of PLA, i.e., the high interest to diversify its uses by moving from biomedical and packaging (biodegradation properties, “ disposables ”) to technical applications (“ durables ”). [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNT) and polylactide (PLA) were dry-mixed and melt-compounded to produce PLA nanocomposites with up to 12 wt-% nanofiller. The key characteristics of PLA-HNT nanocomposites were evidenced as follows: good nanofiller distribution and dispersion assessed by transmission electron microscopy (TEM), high tensile strength (values above 60 MPa) and mechanical rigidity, with Young's modulus increasing with HNT loading. The impact resistance of PLA is not decreased, whereas as it was revealed under dynamic solicitation (DMA), addition of HNT led to the notable enhancement of storage modulus. The degradation by photooxidation of PLA-HNT nanocomposites was compared to pristine PLA. The chemical modifications were evidenced by infrared (IR) and UV–visible spectroscopy, whereas from IR absorbance at 1845 cm -1 was determined the rate of degradation. Like in the case of other natural clays, HNT had a dramatic pro-degradant effect on the photooxidation of PLA, ascribed to the presence of chromophoric groups and/or iron impurities. Indeed, by comparing nanofillers of different purity, the photooxidation of PLA was found significantly reduced using HNT having about four times lower traces of iron. The choice of HNT of adequate purity or/and its purification is looked as powerful method to reduce the photooxidative degradation of PLA nanocomposites. [ABSTRACT FROM AUTHOR]

Concerning new polylactide (PLA) applications, the study investigates the toughening of PLA–CaSO4 β-anhydrite II (AII) composites with bio-sourced tributyl citrate (TBC). The effects of 5–20 wt.% TBC were evaluated in terms of morphology, mechanical and thermal properties, focusing on the enhancement of PLA crystallization and modification of glass transition temperature (Tg). Due to the strong plasticizing effects of TBC (even at 10%), the plasticized composites are characterized by significant decrease of Tg and rigidity, increase of ductility and impact resistance. Correlated with the amounts of plasticizer, a dramatic drop in melt viscosity is also revealed. Therefore, for applications requiring increased viscosity and enhanced melt strength (extrusion, thermoforming), the reactive modification, with up to 1% epoxy functional styrene–acrylic oligomers, was explored to enhance their rheology. Moreover, larger quantities of products were obtained by reactive extrusion (REX) and characterized to evidence their lower stiffness, enhanced ductility, and toughness. In current prospects, selected samples were tested for the extrusion of tubes (straws) and films. The migration of plasticizer was not noted (at 10% TBC), whereas the mechanical and thermal characterizations of films after two years of aging evidenced a surprising preservation of properties. [ABSTRACT FROM AUTHOR]

The melt–mixing of polylactide (PLA) with micro- and/or nanofillers is a key method used to obtain specific end-use characteristics and improvements of properties. So-called "insoluble" CaSO4 (CS) β-anhydrite II (AII) is a mineral filler recently considered for the industry of polymer composites. First, the study proves that AII made from natural gypsum by a specifically thermal treatment is highly stable compared to other CS forms. Then, PLAs of different isomer purity and molecular weights (for injection molding (IM) and extrusion), have been used to produce "green" composites filled with 20–40 wt.% AII. The composites show good thermal and mechanical properties, accounting for the excellent filler dispersion and stability. The stiffness of composites increases with the amount of filler, whereas their tensile strength is found to be dependent on PLA molecular weights. Interestingly, the impact resistance is improved by adding 20% AII into all investigated PLAs. Due to advanced kinetics of crystallization ascribed to the effects of AII and use of a PLA grade of high L-lactic acid isomer purity, the composites show after IM an impressive degree of crystallinity (DC), i.e., as high as 50%, while their Vicat softening temperature is remarkably increased to 160 °C, which are thermal properties of great interest for applications requiring elevated rigidity and heat resistance. [ABSTRACT FROM AUTHOR]

Various zeolites (4A, Y, 13X) and related fillers (molecular sieves and coal fly ash) were used to prepare PLA composites and to assess their degrading effect on the polyester matrix under different processing conditions, at various zeolite/filler loadings. In this objective, untreated fillers, as well as washed and thermally activated zeolites, were used. PLA–zeolite composites were produced by melt-blending step followed by the evaluation of rheological information and molecular and thermal characteristics. The degradation of PLA during the preparation and processing of PLA–zeolite composites, or due to the presence of fillers, was evidenced by specific analyses (SEC, DSC, TGA, TG-FTIR). PLA degradation was mainly dependent on the nature of zeolite, filler loading, and thermal and processing history. The results of the study suggest that a stronger degradation effect is obtained by the addition of zeolite 4A into PLA (at loading of 5–10%) with respect to other zeolites (e.g., 13X and Y). It was also revealed the key roles of the temperature and residence time (as parameters in melt-mixing process), free alkalinity level, and water uptake in determining the ultimate characteristics of composites. The washing and thermal activation pretreatments of fillers have diminished in some cases the degradation of PLA matrix. Finally, the study also highlights the zeolite grades capable of being used to produce new PLA composites with competitive properties and those that could be of interest to improve PLA recycling by pyrolysis. [ABSTRACT FROM AUTHOR]

In this work the thermally-activated shape memory response of biodegradable nanocomposites based on PLA/PCL blend reinforced with different type of cellulose nanocrystals has been reported, and compared with those of the neat matrix, at the same transition temperature of 55 °C and at the same different deformations, 50%, 100% and 150%. In particular, cellulose nanocrystals have been synthesized and then functionalized by “grafting from” reaction by ring opening polymerization of both PLLA and PCL using the OH groups onto the cellulose nanocrystals surface as initiators for the reaction. The morphology, thermal and mechanical analysis have been performed in order to obtain the parameters for the thermo-mechanical shape memory cycles. Moreover, the addition of the CNC-based nanofillers on the compatibility of PLA-PCL blends in 70:30 proportion has been evaluated. All the biodegradable nanocomposite formulations showed excellent shape memory response, similar to those of the neat matrix, with strain recovery ratio and strain fixity ratio higher than 80% and 90%, respectively. This fact indicates that in this case, the shape memory response of the nanocomposites is mainly controlled by the response of the neat blend and they are slightly influenced by the increase of compatibility between the components of the blend. In addition, all nanocomposite films were fully disintegrated under composting conditions confirming their biodegradable nature, obtaining that the presence of CNC-based nanofillers speeds up the disintegration rate of the nanocomposites in comparison with the pure matrix. [ABSTRACT FROM AUTHOR]

The effect of UV light on polylactide/poly(methyl methacrylate) (PLA/PMMA) blends produced by melt-extrusion with a special emphasis on the peculiar influence of PLA stereocomplexes on the photochemical behavior of the blends is the focus of this paper. Stereocomplexable PLA have been prepared by melt-blending of high-molecular-weight poly( l -lactide) (PLLA), poly( d -lactide) (PDLA) and PMMA. The photochemical behavior of resulting PLA/PMMA blends was studied by irradiation under photooxidative conditions (λ > 300 nm, temperature of 70 °C and in the presence of oxygen). The chemical modifications induced by UV light irradiation were analyzed using infrared spectroscopy (IR) and size exclusion chromatography (SEC). Morphological changes were studied by differential scanning calorimetry (DSC) and atomic force microscopy (AFM). It was shown that PDLA and PMMA don't affect the rate of photooxidation of PLLA. However, PLA stereocomplexes have a strong impact on the morphology of the blends during photochemical ageing. [ABSTRACT FROM AUTHOR]

As a result of increasingly stringent environmental regulations being imposed on the automotive sector, ecofriendly alternative solutions are being sought through the use of next-generation bioplastics and biocomposites as novel vehicle components. Thanks to its renewability, low cost, high strength, and rigidity, poly(lactic acid), PLLA, is considered a key material for such applications. Nevertheless, to compete with traditional petroleum-sourced plastics some of the properties of PLLA must be improved to fulfill the requirements of the automotive industry, such as heat resistance, mechanical performance (especially in terms of ductility and impact toughness), and durability. This review focuses on the properties required for plastics used in the automotive industry and discusses recent breakthroughs regarding PLLA and PLLA-based materials in this field. [ABSTRACT FROM AUTHOR]

This work focused on the determination of crystallization kinetics of neat polylactide (PLA) and a plasticized grade of PLA obtained by reactive extrusion (pPLA), as a function of thermomechanical recycling. In particular, the materials were submitted to repeated extrusion and injection procedures to simulate recycling. Prior reprocessing, spherulitic growth rate determined by polarized light optical microscopy indicated that pPLA crystallized into much smaller spherulites as compared to PLA. This finding was explained by a lower nucleation energy barrier promoted by the plasticization of pPLA. Isothermal overall crystallization kinetics were determined by differential scanning calorimetry measurements. It was found that pPLA crystallized much faster than neat PLA due to the plasticization effect. With increasing the number of processing cycles up to 5, PLA crystallization rate gradually increased, while at the same time that of pPLA remained constant. This result was explained by more important degradation mechanisms in PLA as compared to pPLA that enhanced chain mobility, as shown by molecular weight measurements. Moreover, pPLA had a very high initial chain mobility that is maintained regardless of the number of processing cycles. However, the final crystallinity degree was lower in reprocessed pPLAs, as grafting and cross-linking reactions produced during reactive extrusion interrupt crystallizable linear crystallizable sequences and reduced the amount of crystals formed. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

Employing the hydroxyl groups on the surface of Cloisite® 30B montmorillonite (Cl30B), the ring-opening polymerization of l-lactide was performed with a metal-free catalyst to yield a PLLA-g-Cl30B nanohybrid with low Mn grafted PLLA chains (i.e., 9 kg mol−1). This nanohybrid was then melt mixed with PLA 4032D from NatureWorks, which is a slow-crystallizing PLA as it contains 2% d-isomers and has a high Mn value (i.e., 123 kg mol−1). The samples were characterized by TEM, WAXS, SAXS, DSC and Polarized Light Optical Microscopy (PLOM) in order to study their crystallization kinetics in depth. The dispersion of the nanoclay was excellent and much better in the PLA/PLLA-g-Cl30B nanocomposites in comparison to PLA/Cl30B blends prepared as reference. In order to ascertain the role of the nanoclay, analogue PLA/PLLA blends without Cl30B were also prepared. The spherulitic crystallization kinetics from the melt was determined for all samples. The growth rate of neat PLA was accelerated approximately 3 times by incorporating the PLLA-g-Cl30B nanohybrid with an inorganic content of 5%. The overall crystallization kinetics from the glassy state of PLA was also accelerated in a similar way by the nanohybrid addition. Nevertheless, the PLA/PLLA blends crystallized even faster indicating that the dominant effect that causes the acceleration of the crystallization of PLA is the plasticization of PLA by the low Mn PLLA molecules. The changes in Tg of PLA also support this explanation. In the case of the PLA/PLLA-g-Cl30B nanocomposites, even though the plasticizing effect of the PLLA chains still dominates, their action is counterbalanced by their tethering on one end, as they are grafted to the surface of the exfoliated clay nanoplatelets. [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]

A novel biobased plasticizer made of cardanol is designed for poly(lactide) (PLA). This cardanol-derived plasticizer, i.e., methoxylated hydroxyethyl cardanol (MeCard), is synthesized through methoxylation of the double bonds on the side chain of cardanol, and characterized by 1H NMR and mass spectrometry. The plasticization effect of MeCard on the molecular structure, morphology, thermal and mechanical properties of PLA is evaluated and compared to that of a commercial cardanol, i.e., hydroxyethyl cardanol (pCard). The plasticization efficiency of MeCard is demonstrated by a substantial decrease of the glass transition temperature and storage modulus together with a significant increase of the elongation at break as compared to neat PLA. Moreover, MeCard exhibits higher plasticization performance than pCard toward PLA. Such behavior is related to a higher miscibility and compatibility between PLA and MeCard thanks to the methoxylation of the double bonds on the side chain of cardanol as shown by SEM micrographs. [ABSTRACT FROM AUTHOR]

This article reports on the successful preparation and characterization of cellulose nanocrystals (CNCs) surface-modified with polylactide (PLA) and poly(butylene succinate) (PBS) binary mixed homopolymer brushes. Their synthesis was designed as a three-step procedure combining polyester synthesis and surface-modification of CNCs with simultaneous polyester grafting via a heterogeneous copper(I)-catalyzed azide-alkyne cycloaddition reaction. For comparison, single homopolymer brushes tethered to CNCs (PLLA-g-CNC and PBSBDEMPAM-g-CNC) were obtained applying the same procedure. The hairy nanoparticles were characterized in terms of chemical composition and thermal properties. Spectroscopic analyses suggested "rippled" microphase separation of both immiscible homopolyesters in the mixed brushes, while others showed impeded homopolyester crystallization after surface-grafting. A synergistic relationship between the polyesters and CNCs was also suggested, i.e., the polyester grafting increases the CNC thermal resistance, while CNC presence imparts char formation. The as-obtained binary homopolymer brushes tethered to nanoparticles makes these surface-modified cellulosic nanomaterials attractive as compatibilization/reinforcement agents for PLA/PBS blends. [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]

To improve the Heat Deflection Temperature of polylactide (PLA), nanocomposites were prepared with modified cellulose nanocrystals (CNCs) by melt blending. The preparation of acetate and lactate modified CNCs (AA- and LA-CNCs) was performed by a green one-pot dual acid (organic acid and HCl) method such that acid hydrolysis and Fischer Esterification occur in tandem. The degree of substitution for AA-CNCs and LA-CNCs, determined by FTIR, are 0.12 and 0.13, respectively. Relative to unmodified CNCs, esterification of CNC surfaces with lactate and acetate moieties resulted in a 40 °C increase in thermal stability. At 5 wt% loading of CNCs, LA-CNCs gave superior reinforcement below and above the glass temperature of PLA, corresponding to a 31% and 450% increase in PLA's storage modulus compared to neat PLA. An increase in PLA's heat deflection temperature by 10 °C and 20 °C was achieved by melt-blending PLA with 5 and 20% LA-CNCs, respectively. The above studies provide indirect evidence that LA-CNCs were best dispersed (lowest tendency to aggregate) in the PLA matrix. This hypothesis was confirmed through direct visualization using AFM. Thus, a simple modification strategy for CNCs was devised that enables the formation of PLA nanocomposites with high extents of nanofiber dispersion within the matrix. Furthermore, the dispersion of CNCs in PLA matrices is profoundly influenced by relatively small changes in the modification chemistry, in this case, appending lactate vs. acetate groups. [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]

Abstract: For the first time the preparation of defect-free fibers from immiscible blends of high molar mass poly(lactic acid) (PLA) and poly(butylene succinate) (PBS) in the whole range of the polyester weight ratios is shown. Electrospinning using the solvent–nonsolvent approach proved most appropriate. Moreover, electrospinning revealed crucial for the obtaining of PLA/PBS materials maintaining integrity. DSC and XRD analyses attested for a plasticizing effect and for increased PLA crystallinity at PBS addition to PLA. The mechanical properties of the PLA/PBS mats were controlled by the alignment of the fibers and changed from plastic to brittle materials upon increasing the PBS content. Drug loading and tests against pathogenic microorganisms suggested that the obtained mats can find application as antibacterial fibrous materials. [Copyright &y& Elsevier]

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]

Abstract: The synthesis of novel poly(ester-urethane)s (PEUs) based on polylactide was carried out. It was performed by a catalysed two-step reaction process, i.e., ring-opening polymerization (ROP) and chain extension reaction in bulk. For this purpose, α,ω-dihydroxyl PLA macrodiols were synthesized by catalysed ROP and employed as precursors that reacted in the melt with 4,4′-diisophenylmethane diisocyanate (MDI) and 4,4′-diaminodiphenylmethane (MDA) as coupling agent and chain extender, respectively. The PEUs were characterized by DSC, Polarized Light Optical Microscopy and X-ray techniques. The PEUs were generally characterized by higher cold crystallization temperature, lower melting temperature and slower cold crystallization kinetics as compared to the PLA precursors. The Avrami equation modelled the entire isothermal cold crystallization process. The synthesis variables that had the largest impact on the crystallization and thermal properties of the PEUs were the molecular weight of the PLA precursors and the [NCO]/[OHPLA + NH2] ratio, which could be readily tailored by the investigated reactive melt-processing. [Copyright &y& Elsevier]

Abstract: PLA/CaSO4 composites were prepared from uncoated and stearic acid coated filler particles in a wide composition range. The strength of interfacial adhesion was estimated quantitatively with three independent methods. Structure was characterized by DSC, XRD and SEM measurements, while mechanical properties by tensile and instrumented impact tests. The results proved that adhesion is twice as strong in composites prepared with the uncoated particles than in those containing the coated filler. Coating changes also local deformation processes around the particles. Although debonding is the dominating micromechanical deformation process in all composites, local plastic deformation is larger around coated particles. The extent of this deformation depends very much also on the local distribution of particles. The final properties and performance of the composites depend unambiguously on the micromechanical deformation processes occurring during loading, on debonding and the subsequent plastic deformation. Stearic acid used for the coating of the filler seems to dissolve in the polymer and locally change its properties. [Copyright &y& Elsevier]

In the category of biopolymers, polylactide or polylactic acid (PLA) is one of the most promising candidates considered for future developments, as it is not only biodegradable under industrial composting conditions, but it is produced from renewable natural resources. The modification of PLA through the addition of nanofillers is considered as a modern approach to improve its main characteristic features (mechanical, thermal, barrier, etc.) and to obtain specific end-use properties. Iron oxide nanoparticles (NPs) of low dimension (10–20 nm) such as magnetite (Fe3O4), exhibit strong magnetization in magnetic field, are biocompatible and show low toxicity, and can be considered in the production of polymer nanocomposites requiring superparamagnetic properties. Accordingly, PLA was mixed by melt-compounding with 4–16 wt.% magnetite NPs. Surface treatment of NPs with a reactive polymethylhydrogensiloxane (MHX) was investigated to render the nanofiller water repellent, less sensitive to moisture and to reduce the catalytic effects at high temperature of iron (from magnetite) on PLA macromolecular chains. The characterization of nanocomposites was focused on the differences of the rheology and morphology, modification, and improvements in the thermal properties using surface treated NPs, while the superparamagnetic behavior was confirmed by VSM (vibrating sample magnetometer) measurements. The PLA−magnetite nanocomposites had strong magnetization properties at low magnetic field (values close to 70% of Mmax at H = 0.2 T), while the maximum magnetic signal (Mmax) was mainly determined by the loading of the nanofiller, without any significant differences linked to the surface treatment of MNPs. These bionanocomposites showing superparamagnetic properties, close to zero magnetic remanence, and coercivity, can be further produced at a larger scale by melt-compounding and can be designed for special end-use applications, going from biomedical to technical areas. [ABSTRACT FROM AUTHOR]

Due to the added value conferred by zinc oxide (ZnO) nanofiller, e.g., UV protection, antibacterial action, gas-barrier properties, poly(lactic acid) (PLA)–ZnO nanocomposites show increased interest for utilization as films, textile fibers, and injection molding items. The study highlights the beneficial effects of premixing ZnO in PLA under given conditions and its use as masterbatch (MB), a very promising alternative manufacturing technique. This approach allows reducing the residence time at high processing temperature of the thermo-sensitive PLA matrix in contact of ZnO nanoparticles known for their aptitude to promote degradation effects onto the polyester chains. Various PLA–ZnO MBs containing high contents of silane-treated ZnO nanoparticles (up to 40 wt.% nanofiller specifically treated with triethoxycaprylylsilane) were produced by melt-compounding using twin-screw extruders. Subsequently, the selected MBs were melt blended with pristine PLA to produce nanocomposite films containing 1–3 wt.% ZnO. By comparison to the more traditional multi-step process, the MB approach allowed the production of nanocomposites (films) having improved processing and enhanced properties: PLA chains displaying higher molecular weights, improved thermal stability, fine nanofiller distribution, and thermo-mechanical characteristic features, while the UV protection was confirmed by UV-vis spectroscopy measurements. The MB alternative is viewed as a promising flexible technique able to open new perspectives to produce more competitive multifunctional PLA–ZnO nanocomposites. [ABSTRACT FROM AUTHOR]

• A sustainable aqueous cellulose nanofiber surface PEGylation. • Effective filler dispersion within PLA through melt-processing. • Rheological percolating CNF network in the composites holding 20 wt.% of PEG. • Load bearing capacity of well entangled cellulose nanofibers. Considering the appealing need for an industrially viable approach, this works aims at demonstrating the rapid and easy melt processing of Polylactide (PLA) bio-composites reinforced with cellulose nanofibrils (CNF). For this purpose and against to their high propensity to self-aggregate on processing, an aqueous CNF-based suspension in the presence of polyethylene glycol (PEG) followed by a gentle drying way were performed to provide melt-processable CNF-based masterbatches. Morphological observations coupled with rheological analyses confirmed how the strategy of the PEG-based masterbatch approach facilitated the formation of a well-dispersed and strongly interacting CNF network within the polymeric matrix. At temperatures above T g , thermo-mechanical characterization showed that the load-bearing capacity of the web-like CNF network was even more apparent and counteracted the PEG plasticizing effect. Thermogravimetric analysis evidenced that in the case of selective positioning at the PLA-PEG interface, CNF mitigated the negative impact of PEG addition on the PLA thermal stability. These results revealed the successfulness of our sustainable organic solvent-free approach to prepare melt-processable CNF masterbatches, which can be readily converted into conventional industrially scalable melt-processing techniques. [ABSTRACT FROM AUTHOR]

The purpose of this work was to investigate the feasibility to manufacture enteric capsules, which could be used in compounding pharmacies, by fused-deposition modeling. It is well-known that conventional enteric dip coating of capsules in community pharmacies or hospitals is a time-consuming process which is characterized by an erratic efficacy. Fused-deposition modeling was selected as a potential 3D printing method due its ease and low-cost implementation. Before starting to print the capsules, an effective sealing system was designed via a computer-aided design program. Hot melt extrusion was used to make printable enteric filaments. They were made of the enteric polymer, a plasticizer and a thermoplastic polymer, namely Eudragit® L100-55, polyethylene glycol 400 and polylactic acid, respectively. Riboflavine-5′-phosphate was selected as a coloured drug model to compare the efficacy of the 3D printed capsules to that of enteric dip coated capsules as they are currently produced in community pharmacies and hospitals. Different parameters of fabrication which could influence the dissolution profile of the model drug, such as the layer thickness or post-processing step, were studied. It was demonstrated that our 3D printed enteric capsules did not release the drug for 2 h in acid medium (pH 1.2). However, they completely dissolved within 45 min at pH 6.8 which allowed the release of a minimal amount of 85% w/w of drug as it was recommended by the European Pharmacopoeia 9th Edition for enteric products. [ABSTRACT FROM AUTHOR]

A correction to the article "Design of New Cardanol Derivative: Synthesis and Application as Potential Biobased Plasticizer for Poly (lactide)" that was published in the 2016 issue is presented.

The influence of the molecular weight on the formation and crystallization of PLA stereocomplexes was studied. Equimolar mixtures were prepared from poly (l-lactic acid) (PLLA) and poly (d-lactic acid) (PDLA) in solution. The thermal properties were studied by differential scanning calorimetry (DSC) and compared with the corresponding PLA homopolymers. The melting temperatures of the samples of PLLA / PDLA were higher compared to the homopolymers, indicating the formation of a more stable crystalline structure characteristic of stereocomplexes. It was also found that the stereocomplexes crystallize faster than homopolymers. Moreover it was found that upon increasing the molecular weight of the homopolymers, glass transition temperatures and melting were increased and the crystallization kinetics exhibited a complex trend. [ABSTRACT FROM AUTHOR]