Crystal polymorphism of polylactide and its composites by X-ray diffraction study

Hsieh, Ya-Ting; Nozaki, Shuhei; Kido, Makoto; Kamitani, Kazutaka; Kojio, Ken; Takahara, Atsushi

doi:10.1038/s41428-020-0343-8

Cited by 47 publications

(28 citation statements)

References 46 publications

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confidence: 99%

“…In this regard, extensive efforts have been made in recent years focusing on regulating the crystallization behavior of PLA by adding a nucleating agent. The inorganic nucleating agents used for PLA include nanoparticles and nanolayered materials, such as talc, sepiolite, modified montmorillonite, carbon nanotubes, halloysite nanotube, hydroxyapatite, and carbon black. , These nucleating agents have shown a remarkable nucleation effect but hardly help with increasing the crystallinity. The reported organic nucleating agents for PLA mainly cover amides, − hydrazine/hydrazide, − phenylmalonate, aromatic sulfonate derivatives, phenyl phosphate, − biuret, phthalimide, zinc lactate, zinc citrate complex, PDLA, branched PLA, amino acids, and poly(amino acids) .…”

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Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

et al. 2021

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We report on enhancing crystallization and heat resistance of poly(l-lactic acid) (PLLA) by d-sorbitol as a small molecule nucleating agent via melt blending. During the reheating process, the cold crystallization disappeared and the crystallinity of nucleated PLLA exceeded 50%. The heat deflection temperature of PLLA was elevated from 56 to 132 °C by simply increasing the mold temperature (90 °C) without an additional annealing treatment. We also observed the polymorphic crystals of PLLA during melt crystallization, i.e., the coexistence of hexagonal and lenticular crystals, along with their various geometrical aggregates in addition to plenty of conventional spherulites. On the basis of the fact that the nonisothermal crystallization temperature of PLLA (110 °C at a cooling rate of 10 °C/min) was higher than the melting point of d-sorbitol (about 93 °C), we speculated that d-sorbitol promoted the crystallization of PLLA through a homogeneous nucleation mechanism.

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Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

et al. 2021

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“…PLA has a shape and exhibits a 10/3 helical conformation packed into an orthorhombic (or pseudo-orthorhombic) unit cell. To date, PLA is known to have four distinct crystalline forms: α, β, γ, and ε forms and two irregular modifications of the α forms, namely α′ and α″ forms [35]. The intensity relationship curve for 2θ obtained a broad diffraction peak and did not have a defined and sharp peak from the test results.…”

Section: X-ray Diffraction Analysismentioning

confidence: 97%

The Effect of Multi-Extrusion Process of Polylactic Acid on Tensile Strength and Fracture Morphology of Filament Product

Syaifuddin

Suryanto²,

Suprayitno³

2021

JMEST

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Polylactic acid (PLA) is one of the most used materials in FDM 3D Printing. Large-scale consumption of PLA on an industrial scale could cause environmental and efficiency problems. Thus, PLA waste and industry waste need to be recycled to limit excessive waste. This study aimed to investigate the change in mechanical property, morphology, and structure of mechanically recycled PLA. Recycling was performed 12 times using the extrusion process with an extrusion temperature nozzle of 170°C. The SEM, structural analysis, and amorphous-crystalline analysis used XRD. The results showed a gradual decrease of tensile strength from each recycle with a total of 20% (13.22 MPa). The decrease percentage equalled the number of recycling. After the 9 th recycle, PLA experienced a drastic tensile strength decrease, in which the 12 th recycle tensile strength had a 14% (8.17 MPa) reduction. The morphology analysis of the tensile test sample presented significant morphology change, in which morphology defects such as void, flakes, and cracks appeared after the 6 th recycle. Although, until 12 times extrusion, it did not significantly affect the PLA phase shape. Mechanical recycle using a multi-extrusion process is not recommended exceeding six times.

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“…Distinct peaks in the WAXD intensity profile acquired at 0 • and 90 • suggested the presence of an anisotropic crystalline structure in the raw fiber, and crystalline reflections in the 2D pattern implied the orientation of crystalline c-axis along the fiber axis. The crystalline peaks observed at 2θ = 15.0 • , 16.7 • , 19.1 • , and 22.4 • can be assigned to the (004), (110)/(200), (203), and (015) reflections of the α-form crystal of PLLA with the pseudo-orthorhombic unit cell of a = 1.07 nm, b = 0.595 nm, and c = 2.78 nm, which contains two 10 3 helices [38]. It should be noted that the crystalline peak of PCL was not observed because the composition of PCL in the PLCL copolymer was too low to form PCL crystals.…”

Section: Waxd Analysismentioning

confidence: 99%

Laser-Assisted Melt Electrospinning of Poly(L-lactide-co-ε-caprolactone): Analyses on Processing Behavior and Characteristics of Prepared Fibers

et al. 2022

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The laser-assisted melt electrospinning (LES) method was utilized for the preparation of poly(L-lactide-co-ε-caprolactone) (PLCL) fibers. During the process, a carbon dioxide laser was irradiated, and voltage was applied to the raw fiber of PLCL. In situ observation of fiber formation behavior revealed that only a single jet was formed from the swelling region under the conditions of low laser power and applied voltage and feeding rate, whereas multiple jets and shots were produced with increases in these parameters. The formation of multiple jets resulted in the preparation of thinner fibers, and under the optimum condition, an average fiber diameter of 0.77 μm and its coefficient of variation of 17% was achieved without the formation of shots. The estimation of tension and stress profiles in the spin-line was also carried out based on the result of in situ observation and the consideration that the forces originated from surface tension, electricity, air friction, and inertia. The higher peak values of tension and stress appearing near the apex of the swelling region corresponded to the formation of thinner fibers for the condition of single-jet ejection. Analyses of the molecular orientation and crystallization of as-spun fibers revealed the formation of a wide variation of higher order structure depending on the spinning conditions.

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Crystal polymorphism of polylactide and its composites by X-ray diffraction study

Cited by 47 publications

References 46 publications

Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

Enhanced Nonisothermal Crystallization and Heat Resistance of Poly(l-lactic acid) by d-Sorbitol as a Homogeneous Nucleating Agent

The Effect of Multi-Extrusion Process of Polylactic Acid on Tensile Strength and Fracture Morphology of Filament Product

Laser-Assisted Melt Electrospinning of Poly(L-lactide-co-ε-caprolactone): Analyses on Processing Behavior and Characteristics of Prepared Fibers

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