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A simple approach towards the compatibilization of polylactide (PLA) and hydroxyapatite (HAp) nanoparticles nanocomposites is here presented. An amphiphilic diblock copolymer, consisting of poly(ethylene glycol) (PEG) and PLA block was prepared and used to form an interphase between PLA matrix and HAp nanofiller. This copolymer was next mixed with HAp to intimly deposit PEG block on the HAp surface. Effective hydrophobization via PLA chains presence on the surface of the modified nanoparticles was attested via dispersion test in chloroform. Finally, the as modified HAp nanoparticles were blended in PLA. Thermal analyses showed a Tg superior to human body temperature. Dynamic mechanical and morphological analysis attested for improved dispersion and deagglomeration state of the nanoparticles in PLA. Interfacial mechanical properties studies recorded an increase of 150% in compressive modulus compared with neat PLA. In vitro bioactivity assay showed beneficial effect on the mineralization process in simulated body fluid when the interphase is created. This improvement of mechanical properties and bioactivity combined with a simple production process as extrusion make these materials suitable choice for potential load bearing applications. [ABSTRACT FROM AUTHOR]

In this work, a systematic study on the humidity-activated shape memory properties of dual-responsive shape memory bionanocomposites with both humidity- and thermally-activated shape memory effects is reported. The study is performed through humidity-mechanical cycles in an Instron machine with a temperature chamber equipped with an ultrasonic humidity generator. In particular, the bionanocomposites studied are based on blends of ethylene-vinyl acetate (EVA) and thermoplastic starch reinforced with natural bentonite. In our previous work, thermomechanical cycles are performed by using EVA-induced crystallization and a preliminary humidity-activated shape memory test is designed. Herein, the shape memory results of both blends and their nanocomposites reflect the very good ability to humidity-activated recover of the initial shape with values higher than 80%. Moreover, the ability to fix the temporary shape of this systems is very good, especially when nanofillers are added. The compatibilizer effect of natural bentonite is demonstrated by means of different techniques such as scanning emission microscopy and mapping by confocal Raman spectroscopy. [ABSTRACT FROM AUTHOR]

ABSTRACT Poly(lactic acid) (PLA) nanocomposites characterized by multifunctional end-use properties are of high interest as new biosourced materials for the production of smart films, fibers, and injection-molded components. In this work, PLA-ZnO nanocomposites designed for the extrusion of films were obtained by melt-compounding PLA with up to 5 wt % ZnO rod-like nanoparticles, nanofiller previously surface-treated with a specific silane (triethoxycaprylylsilane). To improve the processing and performances of nanocomposites such as their stability at high temperature, the addition of a selected chain-extender (CE) was considered. It was revealed that the co-addition of nanofiller (ZnO) and epoxy functional styrene-acrylate oligomeric CE (Joncryl® ADR 4300F) leads to a very significant enhancement of the properties (molecular, rheological, thermal, etc.) of PLA-ZnO nanocomposites. After addition of 1% CE into nanocomposites, the PLA molecular weights were found to be nearly twofold higher, while the isothermal tests (at 220 and 240°C) confirmed a significant increase in thermal stability. Because the CE plays a key role in limiting the degrading effects of ZnO, due to a gain in melt viscosity and increased molecular mass, a better ability to process nanocomposites by extrusion was found. The good nanofiller dispersion and specific end-use characteristics owing to the presence of ZnO nanoparticles (such as UV shielding) were again confirmed on extruded films. These developments are being viewed as a promising approach that can open new perspectives in the application of PLA-ZnO nanocomposites with specific end-use properties (UV protection, antibacterial, gas-barrier, and self-cleaning) at larger scale. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42480. [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]

ABSTRACT Nanocomposites of equimolar enantiomeric polylactide blends with multiwall carbon nanotubes (MWCNTs) were prepared by a solvent casting/sonication procedure. The first objective of the study was to investigate the effect of MWCNTs as nucleating agents for the selective crystallization of the polylactide (PLA) stereocomplex to obtain PLA-based nanocomposites. Transmission Electron Microscopy (TEM) studies revealed large agglomerates and poor distribution of the non-functionalized MWCNTs within the matrix. To enhance the compatibility between PLA and MWCNTs, pyrene-end-functionalized PLLA (py-end-PLLA) nanocomposites were prepared because of the ability of the pyrene moieties to interact with the MWCNTs via π−π stacking, and were subsequently blended with poly( d-lactide) (PDLA) to investigate the possibility of achieving nanocomposites in which the enantiomeric blend crystallizes as stereocomplex. The resulting nanocomposites were characterized by Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), TEM, and Nuclear Magnetic Resonance Spectroscopy (NMR), revealing that MWCNTs were efficient nucleating agents for the overall crystallization of the blends. Interestingly, full stereocomplexation could be achieved with the aid of soft specific thermal treatments. According to these results, the addition of small amounts of MWCNTs combined with a mild thermal treatment might extend the processing window for the preparation of polylactides exclusively crystallized in the stereocomplex form. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 4327-4337, 2013 [ABSTRACT FROM AUTHOR]

Cellulose nanocrystals (CNC), extracted from cellulose fibers by the mean of acid hydrolysis, were subjected to ring opening polymerization of d-Lactide initiated from the hydroxyl groups available at their surface. The resulting CNC-g-PDLA nanohybrids were incorporated in poly( l-lactide) (PLLA) matrix through melt-blending and the obtained nanocomposites were characterized in terms of their thermo-mechanical properties. Surface-induced polylactide (PLA) stereocomplexation resulting from the co-crystallization of grafted PDLA chains and unbounded PLLA ones from the matrix was evidenced. Acquired results and a thorough comparison with their counterparts grafted with PLLA chains reveal the effects of the stereocomplexed PLA structure surrounding CNC. Important alterations of both crystalline structure and its behavior of the final materials were observed originated from an efficient nucleation effect induced by the addition of these nanohybrids. Significant enhancement of the mechanical performances was also obtained most probably brought by the stereocomplexation that stiffens and stabilize further the percolation network. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Biodegradable nanoscale-reinforced starch-based products were prepared from an in situ chemically modified thermoplastic starch and poly(butylene adipate -co-terephthalate) (PBAT) through reactive processing. Natural montmorillonite (hydrophilic Cloisite Na) and organophilic Cloisite 30B were studied. In situ chemically modified thermoplastic starch (MTPS) was first prepared starting from (nano)clay (previously swollen in glycerol as plasticizer), and maleic anhydride (MA) as an esterification agent. Then, these nanoscale-reinforced MTPS was reactively melt-blended with PBAT through transesterification reactions promoted by MA-derived acidic moieties grafted onto the starch backbone. The tensile and barrier properties of resulting (nano)composites were studied. High-performance formulations with superior tensile strength (>35 MPa as compared with 16 MPa for the PBAT- g-MTPS copolymer) and break elongation (>800%) were obtained, particularly with Cloisite30B. Better water vapor and oxygen barrier properties of nanoscale-reinforced MTPS- g-PBAT were achieved rather than the PRECURSORS. Wide angle X-ray diffraction and transmission electronic microscopy analyses show that partial exfoliation of the clay platelets was observed within the PBAT- g-MTPS graft copolymer-Cloisite 30B nanocomposite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 [ABSTRACT FROM AUTHOR]

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]

Abstract In this work, the thermal degradation and the disintegrability under composting conditions of melt-processed blends based on ethylene-vinyl acetate and thermoplastic starch, EVA/TPS, as well as their nanocomposites, reinforced with natural bentonite, were studied. A special emphasis was first put on the influence of starch on the morphology, thermomechanical properties and hydrophilicity of these blends before composting analysis. In fact, the materials were characterized in terms of morphological, mechanical, thermal and structural properties as well as wettability performance, obtaining information about the immiscibility of the blends and their compatibilization when natural bentonite is used. The thermal stability of starch was increased according with the EVA content in the blend, while the compatibility between both polymeric phases was increased by adding the nanoclays. Consequently, the disintegration under composting condition at laboratory scale level of the obtained materials was conducted and the thermal and chemical-structural properties as well as the surface microstructural changes of recovered samples at different stages of disintegration were studied. Disintegration tests showed that EVA/TPS blends and their nanocomposites presented positive interactions, which delay the disintegration of TPS matrix in compost, thus improving TPS stability. Moreover, blending biodegradable polymers such as TPS with non-biodegradable polymers like EVA leads to the increase of compostable polymer percentage in partially-degradable materials giving a possible solution for the end-life of these materials after their use. Highlights • The thermal, chemical-structural as well as surface microstructural changes of disintegrated sample were studied. • Natural bentonite increase the EVA/TPS compatibility delaying the disintegration of TPS matrix in compost. • Melt-blending TPS with EVA increase the stability of starch-based materials. [ABSTRACT FROM AUTHOR]

The addition of two-dimensional nanomaterials to a polymer matrix is a widely known manner to mechanically reinforce the material. The stress-transfer in the polymeric matrices, however, depends on an array of filler and matrix properties as well as on their interface. In this work, we discuss the effects of the distinct levels of interaction of graphene oxide, reduced graphene oxide and molybdenum disulfide with poly(vinyl butyral) in the reinforcement of the polymer. For that, we employed the micromechanical analysis model originally developed by Young et al., which describes the reinforcement behavior of graphene nanoplatelets in a wide range of polymer matrices. Then, using an innovative approach derived from such analysis, we propose novel methods to mathematically evaluate the effects of the filler content upon the polymer/filler interface, and for the determination of the mechanical percolation threshold. [Display omitted] • The reinforcement of poly(vinyl butyral) by GO and MoS 2 is analyzed using a micromechanical analysis. • The influence of the polymer/filler interactions on the reinforcement is discussed. • An innovative approach to assess the mechanical percolation threshold is presented. [ABSTRACT FROM AUTHOR]

Shape-memory polymers (SMPs) as stimuli-responsive shape-changing polymers are of great interest for fundamental research and technological innovation. In this contribution, a brief review of the recent trends in the field of SMPs is presented with particular focus on their structure, shape-memory effects and working mechanism. A special attention is paid to smart multi-responsive and multi-functional SMP materials as emerging technological class. They are mainly described as shape-memory nanocomposites (SMCs) where the incorporation of functional (in)organic nanofillers in the SMP matrices is purposely carried out. Potential applications of the SMCs-based materials as medical and biomimetic devices, self-healing systems, self-deployable structures, actuators, sensors, etc. or their direct implementation in the industry are finally outlined. [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]