Water-induced structural changes in poly(lactic acid) and PLLA-clay nanocomposites

Beltrán, Freddys R.; Orden, M.U. de la; Lorenzo, Vicente; Pérez, Ernesto; Cerrada, María L.; Urreaga, Joaquín Martínez

doi:10.1016/j.polymer.2016.11.031

Cited by 47 publications

(50 citation statements)

References 49 publications

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“…Moreover, the FTIR-ATR spectra of the bionanocomposites show very slight changes in the intensity of the bands at 920 and 956 cm −1 ( Figure 4 b). These absorptions have been assigned to skeletal C–C stretching mode coupled with CH 3 rocking one [ 48 , 49 , 50 ]; while the band centered at 920 cm −1 corresponds to the 10 3 helix chain conformation, characteristic of the crystalline forms, the band at 956 cm −1 is assigned to the amorphous phase. In this work, the crystallinity degrees in the surface of the nanocomposites were calculated from the absorbances of the band at 955 cm −1 in the different materials, using Equation (1).…”

Section: Resultsmentioning

confidence: 99%

Effect of Iignocellulosic Nanoparticles Extracted from Yerba Mate (Ilex paraguariensis) on the Structural, Thermal, Optical and Barrier Properties of Mechanically Recycled Poly(lactic acid)

et al. 2020

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In this work, yerba mate nanoparticles (YMNs) were extracted from Ilex paraguairiencis yerba mate wastes and further used to improve the overall performance of mechanically recycled PLA (PLAR). Recycled PLA was obtained by melt reprocessing PLA subjected to an accelerated ageing process, which involved photochemical, thermal and hydrothermal ageing steps, as well as a final demanding washing step. YMNs (1 and 3 wt. %) were added to the PLAR during the melt reprocessing step and further processed into films. The main goal of the development of PLAR-YMNs bionanocomposites was to increase the barrier properties of recycled PLA, while showing good overall performance for food packaging applications. Thus, optical, structural, thermal, mechanical and barrier properties were evaluated. The incorporation of YMNs led to transparent greenish PLAR-based films with an effective blockage of harmful UV radiation. From the backbone FTIR stretching region (bands at 955 and 920 cm−1), it seems that YMNs favor the formation of crystalline domains acting as nucleating agents for PLAR. The morphological investigations revealed the good dispersion of YMNs in PLAR when they are used in the lowest amount of 1 wt. %, leading to bionanocomposites with improved mechanical performance. Although the addition of high hydrophilic YMNs increased the water vapor transmission, the addition of 1 wt. % of YMNs enhanced the oxygen barrier performance of the produced bionanocomposite films. These results show that the synergistic revalorization of post-consumer PLA and nanoparticles obtained from agri-food waste is a potential way for the production of promising packaging materials that meet with the principles of the circular economy.

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Section: Resultsmentioning

confidence: 99%

Effect of Iignocellulosic Nanoparticles Extracted from Yerba Mate (Ilex paraguariensis) on the Structural, Thermal, Optical and Barrier Properties of Mechanically Recycled Poly(lactic acid)

et al. 2020

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“…The sample weights were around 3 mg. A temperature interval from −30 to 180 °C was studied at a heating rate of 10 °C/min. For the determination of the crystallinity, a value of 93.1 J/g was used as the enthalpy of fusion of a perfectly crystalline material [ 16 , 33 ].…”

Section: Methodsmentioning

confidence: 99%

“…In spite of the aforementioned similitude, the crystalline differences between the α’ and the α lattices are related to the fact that the former is consistent with a hexagonal packing by X-ray diffraction (i.e., the ratio of a -axis to b -axis is

[ 11 ]), while the α crystal displays an orthorhombic unit cell. Moreover, vibrational spectroscopy has shown changes in the conformation and packing of PLA chains for the two crystalline phases [ 10 , 11 , 12 , 13 , 14 , 15 , 16 ]. The α phase consists of a 10 3 helix conformation, while the α’ chains exhibits a distorted helix one [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

“…Accordingly, numerous investigations have been focused on the enhancement of PLA crystallization kinetics [ 19 ] by adding nucleants to increase nucleation density or by incorporating plasticizers to boost chain mobility. Common nucleating agents used up to now include [ 16 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]: CaCO 3 , TiO 2 , talc, calcium lactate, carbon nanotubes, graphene oxide, nanoclay, and hydrazides.…”

Section: Introductionmentioning

confidence: 99%

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Composites Based on Poly(Lactic Acid) (PLA) and SBA-15: Effect of Mesoporous Silica on Thermal Stability and on Isothermal Crystallization from Either Glass or Molten State

et al. 2020

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Several composites based on an L-rich poly(lactic acid) (PLA) with different contents of mesoporous Santa Barbara Amorphous (SBA-15) silica were prepared in order to evaluate the effect of the mesoporous silica on the resultant PLA materials by examining morphological aspects, changes in PLA phases and their transitions, and, primarily, the influence on some final properties. Melt extrusion was chosen for the obtainment of the composites, followed by quenching from the melt to prepare films. Completely amorphous samples were then attained, as deduced from X-ray diffraction and differential scanning calorimetry (DSC) analyses. Thermogravimetric analysis (TGA) results demonstrated that the presence of SBA-15 particles in the PLA matrix did not exert any significant influence on the thermal decomposition of these composites. An important nucleation effect of the silica was found in PLA, especially under isothermal crystallization either from the melt or from its glassy state. As expected, isothermal crystallization from the glass was considerably faster than from the molten state, and these high differences were also responsible for a more considerable nucleating role of SBA-15 when crystallizing from the melt. It is remarkable that the PLA under analysis showed very close temperatures for cold crystallization and its subsequent melting. Moreover, the type of developed polymorphs did not accomplish the common rules previously described in the literature. Thus, all the isothermal experiments led to exclusive formation of the α modification, and the observation of the α’ crystals required the annealing for long times at temperatures below 80 °C, as ascertained by both DSC and X-ray diffraction experiments. Finally, microhardness (MH) measurements indicated a competition between the PLA physical aging and the silica reinforcement effect in the as-processed amorphous films. Physical aging in the neat PLA was much more important than in the PLA matrix that constituted the composites. Accordingly, the MH trend with SBA-15 content was strongly dependent on aging times.

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“…Prior to processing, milled PLA powder was crystallized, for 20 min at 100 °C [26], and dried for 2 h at 85 °C in a vacuum oven. Moreover, milled PCL powder and SFNP nanoparticle were dried in a vacuum oven at 40 °C and 85 °C for 2 h, respectively.…”

Section: Preparation Of the Polymer Blendsmentioning

confidence: 99%

Biodegradable Nanocomposites Developed from PLA/PCL Blends and Silk Fibroin Nanoparticles: Study on the Microstructure, Thermal Behavior, Crystallinity and Performance

et al. 2020

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Recently, the use of natural materials has grown in the plastics industry. In this study, silk fibroin nanoparticle (SFNP) was successfully synthesized from silk fibroin (SF) and analyzed by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The obtained results revealed that the well-ordered domains in SF were changed to an amorphous structure in SFNP and it was attributed to the cleavage of SF polypeptide chains upon acid hydrolysis. Then several blends of poly(lactic acid)/poly(Ԑ-caprolactone) (PLA/PCL) containing different amounts of PCL were prepared and characterized. Based on the test results the best properties were achieved in the blend with 30% of PCL. The addition of 1% of SFNP into this blend enhanced the compatibility between PLA and PCL and reduced the PCL droplet size from 1.170±92 μm to 794±46 nm, this was observed by scanning electron microscopy (SEM). Thermal analysis indicated that the presence of SFNP caused an improvement of thermal degradation stability of the PLA/PCL blend in the end set temperature range. The crystallization process also slowed and the crystal growth rate decreased from 0.34 to 0.31 min-1. Additionally, the use of SFNP increased (9.7%) the hardness value and reduced (15.7%) the water vapor permeability value of the PLA/PCL blend. The results of these experiments demonstrated that the prepared PLA/PCL/SFNP green nanocomposites have good potential for the food packaging applications.

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Water-induced structural changes in poly(lactic acid) and PLLA-clay nanocomposites

Cited by 47 publications

References 49 publications

Effect of Iignocellulosic Nanoparticles Extracted from Yerba Mate (Ilex paraguariensis) on the Structural, Thermal, Optical and Barrier Properties of Mechanically Recycled Poly(lactic acid)

Effect of Iignocellulosic Nanoparticles Extracted from Yerba Mate (Ilex paraguariensis) on the Structural, Thermal, Optical and Barrier Properties of Mechanically Recycled Poly(lactic acid)

Composites Based on Poly(Lactic Acid) (PLA) and SBA-15: Effect of Mesoporous Silica on Thermal Stability and on Isothermal Crystallization from Either Glass or Molten State

Biodegradable Nanocomposites Developed from PLA/PCL Blends and Silk Fibroin Nanoparticles: Study on the Microstructure, Thermal Behavior, Crystallinity and Performance

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