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Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Physics and Theory".

Deadline for manuscript submissions: closed (31 March 2021) | Viewed by 43905

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Special Issue Editors

Prof. Dr. Stefano Vecchio Ciprioti

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Guest Editor

Department of Basic and Applied Science for Engineering, Sapienza University of Rome, 00185 Roma, RM, Italy
Interests: thermodynamics of vaporization; thermodynamics of phase transitions; thermal stability; decomposition kinetics; ionic liquids
Special Issues, Collections and Topics in MDPI journals

Dr. Daniele Cangialosi

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Guest Editor

Centro de Fisica de Materiales (CFM), CSIC, Spain
Interests: glass transition; physical aging; differential scanning calorimetry (DSC); fast scanning calorimetry (FSC)

Special Issue Information

Dear Colleagues,

This Special Issue focuses on recent developments in research on the use of thermal analysis and calorimetry techniques to characterize polymeric and composite materials for many kinds of possible applications and model systems to provide insights into fundamental science. In the last decades, a huge number of studies on thermal behavior of different classes of organic, inorganic, and hybrid materials have been conducted with a view to assessing their thermal stability and phase transformation behavior, or to determine the best temperature(s) of their thermal treatment to induce in them specific properties.

In particular, we encourage the submission of papers that discuss the latest research in the area of fundamental aspects as well as topics of technological interest where thermal analysis can deliver information of utmost importance. The scope of this Special Issue encompasses the synthesis and structural, morphological, and thermal characterization of polymers, nanocomposites, and hybrid- and polymer-based materials used for different promising applications.

Of particular interest are studies where crystallization/melting, vitrification/non-equilibrium glassy dynamics, and formation of bound (adsorbed) layers at interfaces in nanocomposites are tackled, or contributions that investigate thermogravimetry (TG) and differential scanning calorimetry (DSC) to determine the shelf-life of polymers and nanocomposites.

Prof. Stefano Vecchio Ciprioti
Dr. Daniele Cangialosi
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

glass transition
physical aging
crystallization
interfacial phenomena
thermal stability
shelf-life

Published Papers (12 papers)

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Research

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29 pages, 8563 KiB

Open AccessArticle

Calorimetric and Dielectric Investigations of Epoxy-Based Nanocomposites with Halloysite Nanotubes as Nanofillers

by Hassan Omar, Glen J. Smales, Sven Henning, Zhi Li, De-Yi Wang, Andreas Schönhals and Paulina Szymoniak

Polymers 2021, 13(10), 1634; https://doi.org/10.3390/polym13101634 - 18 May 2021

Cited by 12 | Viewed by 2660

Abstract

Epoxy nanocomposites are promising materials for industrial applications (i.e., aerospace, marine and automotive industry) due to their extraordinary mechanical and thermal properties. Here, the effect of hollow halloysite nanotubes (HNT) on an epoxy matrix (Ep) was the focus of the study. The structure and molecular mobility of the nanocomposites were investigated using a combination of X-ray scattering, calorimetry (differential (DSC) and fast scanning calorimetry (FSC)) and dielectric spectroscopy. Additionally, the effect of surface modification of HNT (polydopamine (PDA) and Fe(OH)₃ nanodots) was considered. For Ep/HNT, the glass transition temperature (T_g) was decreased due to a nanoparticle-related decrease of the crosslinking density. For the modified system, Ep/m-HNT, the surface modification resulted in enhanced filler–matrix interactions leading to higher T_g values than the pure epoxy in some cases. For Ep/m-HNT, the amount of interface formed between the nanoparticles and the matrix ranged from 5% to 15%. Through BDS measurements, localized fluctuations were detected as a β- and γ-relaxation, related to rotational fluctuations of phenyl rings and local reorientations of unreacted components. A combination of calorimetry and dielectric spectroscopy revealed a dynamic and structural heterogeneity of the matrix, as confirmed by two glassy dynamics in both systems, related to regions with different crosslinking densities. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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13 pages, 2496 KiB

Open AccessArticle

Synthesis, Structural, Morphological and Thermal Characterization of Five Different Silica-Polyethylene Glycol-Chlorogenic Acid Hybrid Materials

by Michelina Catauro, Pavel Šiler, Jiří Másilko, Roberta Risoluti and Stefano Vecchio Ciprioti

Polymers 2021, 13(10), 1586; https://doi.org/10.3390/polym13101586 - 14 May 2021

Cited by 5 | Viewed by 1811

Abstract

The present study investigated the structure, morphology, thermal behavior, and bacterial growth analysis of novel three-component hybrid materials synthesized by the sol-gel method. The inorganic silica matrix was weakly bonded to the network of two organic components: a well-known polymer such as polyethylene glycol (PEG, average molar mass of about 4000 g/mol), and an antioxidant constituted by chlorogenic acid (CGA). In particular, a first series was made by a 50 wt% PEG-based (CGA-free) silica hybrid along with two 50 wt% PEG-based hybrids containing 10 and 20 wt% of CGA (denoted as SP50, SP50C10 and SP50C20, respectively). A second series contained a fixed amount of CGA (20 wt%) in silica-based hybrids: one was the PEG-free material (SC20) and the other two contained 12 and 50 wt% of PEG, respectively (SP12C20 and SP50C20, respectively), being the latter already included in the first series. The X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images of freshly prepared materials confirmed that all the materials were amorphous and homogeneous regardless of the content of PEG or CGA. The thermogravimetric (TG) analysis revealed a higher water content was adsorbed into the two component hybrids (SP50 and SC20) because of the availability of a larger number of H-bonds to be formed with water with respect to those of silica/PEG/CGA (SPC), where silica matrix was involved in these bonds with both organic components. Conversely, the PEG-rich materials (SP50C10 and SP50C20, both with 50 wt% of the polymer) retained a lower content of water. Decomposition of PEG and CGA occurred in almost the same temperature interval regardless of the content of each organic component. The antibacterial properties of the SiO₂/PEG/CGA hybrid materials were studied in pellets using either Escherichia coli and Enterococcus faecalis, respectively. Excellent antibacterial activity was found against both bacteria regardless of the amount of polymer in the hybrids. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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12 pages, 1131 KiB

Open AccessArticle

Physical Aging Behavior of a Glassy Polyether

by Xavier Monnier, Sara Marina, Xabier Lopez de Pariza, Haritz Sardón, Jaime Martin and Daniele Cangialosi

Polymers 2021, 13(6), 954; https://doi.org/10.3390/polym13060954 - 20 Mar 2021

Cited by 25 | Viewed by 3208

Abstract

The present work aims to provide insights on recent findings indicating the presence of multiple equilibration mechanisms in physical aging of glasses. To this aim, we have investigated a glass forming polyether, poly(1-4 cyclohexane di-methanol) (PCDM), by following the evolution of the enthalpic state during physical aging by fast scanning calorimetry (FSC). The main results of our study indicate that physical aging persists at temperatures way below the glass transition temperature and, in a narrow temperature range, is characterized by a two steps evolution of the enthalpic state. Altogether, our results indicate that the simple old-standing view of physical aging as triggered by the

α

relaxation does not hold true when aging is carried out deep in the glassy state. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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13 pages, 2371 KiB

Open AccessArticle

Promoting Interfacial Interactions with the Addition of Lignin in Poly(Lactic Acid) Hybrid Nanocomposites

by Bindu Patanair, Allisson Saiter-Fourcin, Sabu Thomas, Martin George Thomas, Poornima Parathukkamparambil Pundarikashan, Kalaprasad Gopalan Nair, Varsha Krishna Kumar, Hanna J. Maria and Nicolas Delpouve

Polymers 2021, 13(2), 272; https://doi.org/10.3390/polym13020272 - 15 Jan 2021

Cited by 18 | Viewed by 2369

Abstract

In this paper, the calorimetric response of the amorphous phase was examined in hybrid nanocomposites which were prepared thanks to a facile synthetic route, by adding reduced graphene oxide (rGO), Cloisite 30B (C30B), or multiwalled carbon nanotubes (MWCNT) to lignin-filled poly(lactic acid) (PLA). The dispersion of both lignin and nanofillers was successful, according to a field-emission scanning-electron microscopy (FESEM) analysis. Lignin alone essentially acted as a crystallization retardant for PLA, and the nanocomposites shared this feature, except when MWCNT was used as nanofiller. All systems exhibiting a curtailed crystallization also showed better thermal stability than neat PLA, as assessed from thermogravimetric measurements. As a consequence of favorable interactions between the PLA matrix, lignin, and the nanofillers, homogeneous dispersion or exfoliation was assumed in amorphous samples from the increase of the cooperative rearranging region (CRR) size, being even more remarkable when increasing the lignin content. The amorphous nanocomposites showed a signature of successful filler inclusion, since no rigid amorphous fraction (RAF) was reported at the filler/matrix interface. Finally, the nanocomposites were crystallized up to their maximum extent from the glassy state in nonisothermal conditions. Despite similar degrees of crystallinity and RAF, significant variations in the CRR size were observed among samples, revealing different levels of mobility constraining in the amorphous phase, probably linked to a filler-dimension dependence of space filling. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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18 pages, 3543 KiB

Open AccessArticle

Melt Memory Effects in Poly(butylene succinate) Studied by Differential Fast Scanning Calorimetry

by Leire Sangroniz, Connie Ocando, Dario Cavallo and Alejandro J. Müller

Polymers 2020, 12(12), 2796; https://doi.org/10.3390/polym12122796 - 26 Nov 2020

Cited by 14 | Viewed by 2456

Abstract

It is widely accepted that melt memory effect on polymer crystallization depends on thermal history of the material, however a systematic study of the different parameters involved in the process has been neglected, so far. In this work, poly(butylene succinate) has been selected to analyze the effect of short times and high cooling/heating rates that are relevant from an industrial point of view by taking advantage of fast scanning calorimetry (FSC). The FSC experiments reveal that the width of melt memory temperature range is reduced with the time spent at the self-nucleation temperature (T_s), since annealing of crystals occurs at higher temperatures. The effectiveness of self-nuclei to crystallize the sample is addressed by increasing the cooling rate from T_s temperature. The effect of previous standard state on melt memory is analyzed by (a) changing the cooling/heating rate and (b) applying successive self-nucleation and annealing (SSA) technique, observing a strong correlation between melting enthalpy or crystallinity degree and the extent of melt memory. The acquired knowledge can be extended to other semicrystalline polymers to control accurately the melt memory effect and therefore, the time needed to process the material and its final performance. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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13 pages, 1793 KiB

Open AccessEditor’s ChoiceArticle

Kinetic Study of the Thermal and Thermo-Oxidative Degradations of Polystyrene Reinforced with Multiple-Cages POSS

by Ignazio Blanco, Gianluca Cicala, Claudio Tosto and Francesco Agatino Bottino

Polymers 2020, 12(11), 2742; https://doi.org/10.3390/polym12112742 - 19 Nov 2020

Cited by 6 | Viewed by 1975

Abstract

A comprehensive kinetics degradation study is carried out on novel multiple cages polyhedral oligomeric silsesquioxane (POSS)/polystyrene (PS) composites at 5% (w/w) of POSS to assess their thermal behavior with respect to the control PS and other similar POSS/PS systems studied in the past. The composites are synthesized by in situ polymerization of styrene in the presence of POSSs and characterized by ¹H-NMR. The characteristics of thermal parameters are determined using kinetics literature methods, such as those developed by Kissinger and Flynn, Wall, and Ozawa (FWO), and discussed and compared with each other and with those obtained in the past for similar POSS/PS composites. A good improvement in the thermal stability with respect to neat polymer is found, but not with respect to those obtained in the past for polystyrene reinforced with single- or double-POSS cages. This behavior is attributed to the greater steric hindrance of the three-cages POSS compared with those of single- or double-cage POSS molecules. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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17 pages, 5575 KiB

Open AccessArticle

Characteristics of the Non-Isothermal and Isothermal Crystallization for the β Polymorph in PVDF by Fast Scanning Calorimetry

by Ernesto Pérez, Irene Angulo, Enrique Blázquez-Blázquez and María L. Cerrada

Polymers 2020, 12(11), 2708; https://doi.org/10.3390/polym12112708 - 16 Nov 2020

Cited by 8 | Viewed by 2447

Abstract

Structuring at very high rates has become one of the current and important topics of interest in polymer science, because this is a common protocol in the processing of films or fibers with industrial applicability. This work presents the study by fast scanning calorimetry, FSC, of poly(vinylidene fluoride), paying special attention to the conditions for obtaining the β phase of this polymer, because it is the one technologically more interesting. The results indicate that this β phase of poly(vinylidene fluoride) is obtained when the sample is isothermally crystallized at temperatures below 60 °C. Under non-isothermal conditions, the β polymorph begins to be observed at rates above 400 °C/s, although a coexistence with the α modification is observed, so that exclusively the β phase is obtained only at rates higher than 3000 °C/s. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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20 pages, 3181 KiB

Open AccessArticle

Competition between Structural Relaxation and Crystallization in the Glass Transition Range of Random Copolymers

by Jürgen E. K. Schawe and Claus Wrana

Polymers 2020, 12(8), 1778; https://doi.org/10.3390/polym12081778 - 8 Aug 2020

Cited by 21 | Viewed by 7697

Abstract

Structural relaxation in polymers occurs at temperatures in the glass transition range and below. At these temperatures, crystallization is controlled by diffusion and nucleation. A sequential occurrence of structural relaxation, nucleation, and crystallization was observed for several homopolymers during annealing in the range of the glass transition. It is known from the literature that all of these processes are strongly influenced by geometrical confinements. The focus of our work is copolymers, in which the confinements are caused by the random sequence of monomer units in the polymer chain. We characterize the influence of these confinements on structure formation and relaxation in the vicinity of the glass transition. The measurements were performed with a hydrogenated nitrile-butadiene copolymer (HNBR). The kinetics of the structural relaxation and the crystallization was measured using fast differential scanning calorimetry (FDSC). This technique was selected because of the high sensitivity, the fast cooling rates, and the high time resolution. Crystallization in HNBR causes a segregation of non-crystallizable segments in the macromolecule. This yields a reduction in mobility in the vicinity of the formed crystals and as a consequence an increased amount of so-called “rigid amorphous fraction” (RAF). The RAF can be interpreted as self-assembled confinements, which limit and control the crystallization. An analysis of the crystallization and the relaxation shows that the kinetic of both is identical. This means that the Kohlrausch exponent of relaxation and the Avrami exponent of crystallization are identical. Therefore, the crystallization is not controlled by nucleation but by diffusion and is terminated by the formation of RAF. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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15 pages, 2044 KiB

Open AccessEditor’s ChoiceArticle

Halloysite Nanotubes Coated by Chitosan for the Controlled Release of Khellin

by Lorenzo Lisuzzo, Giuseppe Cavallaro, Stefana Milioto and Giuseppe Lazzara

Polymers 2020, 12(8), 1766; https://doi.org/10.3390/polym12081766 - 7 Aug 2020

Cited by 61 | Viewed by 3949

Abstract

In this work, we have developed a novel strategy to prepare hybrid nanostructures with controlled release properties towards khellin by exploiting the electrostatic interactions between chitosan and halloysite nanotubes (HNT). Firstly, khellin was loaded into the HNT lumen by the vacuum-assisted procedure. The drug confinement within the halloysite cavity has been proved by water contact angle experiments on the HNT/khellin tablets. Therefore, the loaded nanotubes were coated with chitosan as a consequence of the attractions between the cationic biopolymer and the halloysite outer surface, which is negatively charged in a wide pH range. The effect of the ionic strength of the aqueous medium on the coating efficiency of the clay nanotubes was investigated. The surface charge properties of HNT/khellin and chitosan/HNT/khellin nanomaterials were determined by ζ potential experiments, while their morphology was explored through Scanning Electron Microscopy (SEM). Water contact angle experiments were conducted to explore the influence of the chitosan coating on the hydrophilic/hydrophobic character of halloysite external surface. Thermogravimetry (TG) experiments were conducted to study the thermal behavior of the composite nanomaterials. The amounts of loaded khellin and coated chitosan in the hybrid nanostructures were estimated by a quantitative analysis of the TG curves. The release kinetics of khellin were studied in aqueous solvents at different pH conditions (acidic, neutral and basic) and the obtained data were analyzed by the Korsmeyer–Peppas model. The release properties were interpreted on the basis of the TG and ζ potential results. In conclusion, this study demonstrates that halloysite nanotubes wrapped by chitosan layers can be effective as drug delivery systems. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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15 pages, 4262 KiB

Open AccessEditor’s ChoiceArticle

New Insights into Crystallization of Heterophasic Isotactic Polypropylene by Fast Scanning Chip Calorimetry

by Daniela Mileva, Jingbo Wang, Markus Gahleitner, Katalee Jariyavidyanont and René Androsch

Polymers 2020, 12(8), 1683; https://doi.org/10.3390/polym12081683 - 28 Jul 2020

Cited by 11 | Viewed by 3102

Abstract

The crystallization kinetics of metallocene-catalyzed heterophasic isotactic polypropylene composed of a matrix of isotactic polypropylene (iPP) and rubbery particles made of random ethylene–propylene copolymers (EPC), often denoted as heterophasic iPP copolymers, was analyzed as a function of the cooling rate and supercooling in nonisothermal and isothermal crystallization experiments, respectively. Fast scanning chip calorimetry (FSC) allowed assessing crystallization at processing-relevant conditions, and variation of the content (0–39 wt %) and composition (0–35 wt % propylene counits) of the EPC particles revealed qualitatively new insight about mechanisms of heterogeneous crystal nucleation. For neat iPP homopolymer, the characteristic bimodal temperature dependence of the crystallization rate due to predominance of heterogeneous and homogeneous crystal nucleation at high and low temperatures, respectively, is reconfirmed. At high temperatures, in heterophasic iPP, the here studied ethylene-(C2)-rich EPC particles accelerate crystallization of the iPP-matrix, with the acceleration or nucleation efficacy correlating with the EPC-particle content. The crystallization time reduces by more than half in presence of 39 wt % EPC particles. An additional nucleating effect of the EPC particles on iPP-matrix crystallization is detected after their crystallization, suggesting that liquid/rubbery particles are less effective than solid/semicrystalline particles in affecting crystallization of the surrounding iPP-matrix. At low temperature, homogeneous crystal nucleation in the iPP-matrix outpaces all heterogeneous nucleation effects, and the matrix-crystallization rate is independent of the sample composition. The obtained results lead to the conclusion that the crystallization kinetics of iPP can be affected significantly by the content and composition of EPC particles, even towards superfast crystallizing iPP grades. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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19 pages, 6844 KiB

Open AccessEditor’s ChoiceArticle

Calorimetric and Dielectric Study of Renewable Poly(hexylene 2,5-furan-dicarboxylate)-Based Nanocomposites In Situ Filled with Small Amounts of Graphene Platelets and Silica Nanoparticles

by Olawale Monsur Sanusi, Lazaros Papadopoulos, Panagiotis A. Klonos, Zoi Terzopoulou, Nourredine Aït Hocine, Abdelkibir Benelfellah, George Z. Papageorgiou, Apostolos Kyritsis and Dimitrios N. Bikiaris

Polymers 2020, 12(6), 1239; https://doi.org/10.3390/polym12061239 - 29 May 2020

Cited by 24 | Viewed by 3490

Abstract

Poly(hexylene 2,5 furan-dicarboxylate) (PHF) is a relatively new biobased polyester prepared from renewable resources, which is targeted for use in food packaging applications, owing to its great mechanical and gas barrier performance. Since both properties are strongly connected to crystallinity, the latter is enhanced here by the in situ introduction in PHF of graphene nanoplatelets and fumed silica nanoparticles, as well as mixtures of both, at low amounts. For this investigation, we employed Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dielectric spectroscopy (BDS). The fillers were found to improve crystallization in both the rate (increasing T_c) and fraction (CF), which was rationalized via the concept of fillers acting as crystallization agents. This action was found stronger in the case of graphene as compared to silica. BDS allowed the detection of local and segmental dynamics, in particular in PHF for the first time. The glass transition dynamics in both BDS (α relaxation) and DSC (T_g) are mainly dominated by the relatively high CF, whereas in the PHF filled uniquely with silica strong spatial confinement effects due to crystals were revealed. Finally, all samples demonstrated the segmental-like dynamics above T_g, which screens the global chain dynamics (normal mode). Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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Review

Jump to: Research

23 pages, 2446 KiB

Open AccessEditor’s ChoiceReview

Activation Energies and Temperature Dependencies of the Rates of Crystallization and Melting of Polymers

by Sergey Vyazovkin

Polymers 2020, 12(5), 1070; https://doi.org/10.3390/polym12051070 - 7 May 2020

Cited by 55 | Viewed by 7578

Abstract

The objective of this review paper is to survey the phase transition kinetics with a focus on the temperature dependence of the rates of crystallization and melting, as well as on the activation energies of these processes obtained via the Arrhenius kinetic treatment, including the treatment by isoconversional methods. The literature is analyzed to track the development of the basic models and their underlying concepts. The review presents both theoretical and practical considerations regarding the kinetic analysis of crystallization and melting. Both processes are demonstrated to be kinetically complex, and this is revealed in the form of nonlinear Arrhenius plots and/or the variation of the activation energy with temperature. Principles which aid one to understand and interpret such results are discussed. An emphasis is also put on identifying proper computational methods and experimental data that can lead to meaningful kinetic interpretation. Full article

(This article belongs to the Special Issue Recent Developments on Calorimetry and Thermal Analysis of Polymers and Nanocomposites)

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