Molecular dynamic in binary mixtures and polymer blends with large difference in glass transition temperatures of the two components: A critical review

Ngai, K. L.; Valenti, Sofia; Capaccioli, S.

doi:10.1016/j.jnoncrysol.2019.119573

Cited by 21 publications

(20 citation statements)

References 116 publications

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“…PLLA/PDLA blends were one T g peak approximately 58 ℃ for all the samples. The glass transition temperature of the two components is the major factor determining the dynamics and thermodynamic properties [ 35 ]. One of the Tg peaks of the blend samples indicates that samples are mixed homogeneously with both polymer matrixes, Figure 2 [ 36 ].…”

Section: Resultsmentioning

confidence: 99%

“…Neat PLLA and PDLA polymers had only one T m peak at approximately 175 °C, corresponding to the HC, while there were two T m peaks at 175 °C and 225 °C for the blends with mass ratios of 9/1, 8/2, 7/3, 6/4, and 5/5. A higher T m at approximately 225 °C corresponded to the stereocomplex crystallization (SC) fusion in PLLA/PDLA blends [ 35 , 36 ] due to the simultaneous HC and SC. Moreover, the fact that the T m positions did not shift with different sample compositions indicates that the PLLA/PDLA undergoes stereocomplex and the PLLA undergoes HC almost independently [ 3 ].…”

Section: Resultsmentioning

confidence: 99%

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Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Park

Hong

2021

Polymers

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Poly (l-lactic acid) (PLLA) is a promising biomedical polymer material with a wide range of applications. The diverse enantiomeric forms of PLLA provide great opportunities for thermal and mechanical enhancement through stereocomplex formation. The addition of poly (d-lactic acid) (PDLA) as a nucleation agent and the formation of stereocomplex crystallization (SC) have been proven to be an effective method to improve the crystallization and mechanical properties of the PLLA. In this study, PLLA was blended with different amounts of PDLA through a melt blending process and their properties were calculated. The effect of the PDLA on the crystallization behavior, thermal, and mechanical properties of PLLA were investigated systematically by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized optical microscopy (POM), dynamic mechanical analysis (DMA), and tensile test. Based on our findings, SC formed easily when PDLA content was increased, and acts as nucleation sites. Both SC and homo crystals (HC) were observed in the PLLA/PDLA blends. As the content of PDLA increased, the degree of crystallization increased, and the mechanical strength also increased.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Park

Hong

2021

Polymers

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“…The ubiquitous presence of the JG -relaxation and the inseparable relations of its relaxation times to that of the -relaxation (Eq.3) supported by many corroborative evidences such as given in Refs. [ 33,78,79,80,81,82,83 ] are critical in restoring the verity of the dynamics obtained by using dielectric permittivity spectroscopy of polar glass-formers. On the other hand, the presence of the JG -relaxation and its relations to the -relaxation were not recognized in the papers of Körber et al [ 19,84 ], Gabriel et al [ 43 ], and Pabst et al [ 46 ], and the consequence is that they were not able to reach the same conclusion.…”

Section: Discussionmentioning

confidence: 99%

Is there Universality in the Dielectric Response of Polar Glass Formers?

Ngai

Wojnarowska

Paluch

2021

Preprint

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The frequency dispersion of structural α-relaxation obtained from broadband dielectric spectroscopy measurements is relatively narrow in many polar glass-formers. On the other hand, it becomes much broader when probed by other techniques, including photon correlation spectroscopy (PCS), nuclear magnetic resonance (NMR), and mechanical shear modulus. Therefore, the dynamics of glass-formers observed by dielectric permittivity spectroscopy (DS) is called into question. Herein we propose a way to resolve this problem. First, we point out an unresolved Johari-Goldstein (JG) β-relaxation is present nearby the α-relaxation in these polar glass-formers. The dielectric relaxation strength of the JG β-relaxation is sufficiently weak compared to the α-relaxation so that the narrow dielectric frequency dispersion faithfully represents the dynamic heterogeneity and cooperativity of the α-relaxation. However, when the other techniques are used to probe the same glass-former, there is a reduction of relaxation strength of α-relaxation relative to that of the JG β-relaxation. Additionally, the separation between the α and the JG β relaxations in dielectric permittivity) decreases when probed by mechanical shear modulus. These changes in relation of α- to JG β-relaxation, when examined by the other techniques, engender the non-negligible contribution of the latter to the former. Hence the apparent α-relaxation is broader than observed by the dielectric permittivity. The broadening is artificial because it is due to a confluence of the α and JG β relaxations with a disparity in their relaxation strengths much less when the other techniques than by dielectric permittivity are used. This explanation is supported by showing the α-relaxation of polar glass-formers becomes broader when the dielectric data are represented in terms of the electric modulus instead of permittivity. The broadening, in this case, is again due to a reduction of the relaxation strength of the α-relaxation relative to that of the JG β-relaxation in the electric modulus representation. A corollary of the explanation applicable to weakly polar glass-formers having JG β-relaxation widely separated from the α-relaxation is the prediction that the frequency dispersion of dielectric α-relaxation is nearly the same as that of the electric modulus, and there is no significant additional broadening when probed by the other techniques. A host of experimental data from the literature and our new measurements are given to support the explanation for polar glass-formers and the ancillary prediction for weakly polar glass-formers. Thus the narrow frequency dispersion of the intense relaxation in polar glass-formers observed by dielectric permittivity is real and genuinely represents the dynamically heterogeneous and cooperative dynamics of α-relaxation. By contrast, the broad dispersion found by the other techniques is artificial and misleading.

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“…The ratio of the components is selected in such a way that a standard processing would be possible. The physical mixing of polymers is done which results in obtaining a material in which one of the polymers is a matrix and the other is a filler [3].…”

Section: Introductionmentioning

confidence: 99%

“…Further physical modification leads to the change of the mixture's structure, molecular interaction and dispersion degree [3,4]. The properties of such composition would depend on the content of the components, the way of its preparation and mutual interaction of the components [5,6].…”

Section: Introductionmentioning

confidence: 99%

Properties of Mixed Polypropylene / Polylactide after Multiple Processing

Fabijański¹,

Garbarski²

2020

Preprint

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Polypropylene (PP) is commonly used in the polymer processing industry. Its feature is a good chemical resistance, it is non-toxic and not harmful to people. Polypropylene is widely used in the manufacturing of food packages, laboratory and medical equipment, electric cables insulators, automotive parts, toys and furniture. The application of this material enables us to obtain complicated shapes of big surfaces. It is also highly recyclable. Polylactide (PLA) is a product of the so called “green chemistry” because it is obtained from the renewable raw materials (biomass). As its price is higher compared to the traditional polymers, its repeated use (recycling) is of high interest. Due to the same reason (cost) the mixtures of PLA with other polymers are applied. In this paper the results of testing the PP/PLA mixtures of various mass ratio of the components are presented. Technical terms of preparing and processing such mixtures have been practically tested. Also the mechanical strength was determined based on the static tensile tests. The results showed that those mixtures can be repeatedly processed. Even five-times reprocessing does not cause essential drop of mechanical properties

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Molecular dynamic in binary mixtures and polymer blends with large difference in glass transition temperatures of the two components: A critical review

Cited by 21 publications

References 116 publications

Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Is there Universality in the Dielectric Response of Polar Glass Formers?

Properties of Mixed Polypropylene / Polylactide after Multiple Processing

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