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Crystallization in Polymer Science

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

Deadline for manuscript submissions: closed (15 February 2023) | Viewed by 15720

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Dr. Ryan M. Van Horn

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Guest Editor

Department of Chemical and Biomolecular Engineering, Lafayette College, Easton, PA 18042, USA
Interests: polymer crystallization; block copolymers; biodegradable polymers

Special Issue Information

Dear Colleagues,

Crystallization of polymers continues to be a primary area of fundamental research. Many questions about the formation and growth of polymer crystals persist nearly 100 years after their discovery. While finding answers is technologically important for applications in commodity and advanced use plastics, knowledge and expertise in this area is waning. This Special Issue aims to publish works from early- and mid-career researchers interested in solving fundamental questions, developing structure–property relationships, and evaluating crystalline behavior in advanced materials for energy or bio-based polymer systems.

Dr. Ryan M. Van Horn
Guest Editor

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Keywords

crystallization
structure–property relationships
polymer crystallization
block copolymers

Published Papers (7 papers)

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Research

17 pages, 5376 KiB

Open AccessArticle

Influence of Fusion Temperature on Nonisothermal Crystallization Kinetics of Polyamide 6

by Ahmed Nasr and Petr Svoboda

Polymers 2023, 15(8), 1952; https://doi.org/10.3390/polym15081952 - 20 Apr 2023

Cited by 4 | Viewed by 2152

Abstract

The effect of fusion temperature and duration on the nonisothermal crystallization kinetics of polyamide 6 (PA6) was investigated using differential scanning calorimetry (DSC) and a polarized optical microscope (OM). The rapid cooling method involved heating the polymer above its melting point, holding it at this temperature to ensure complete melting, and then rapidly cooling it to the crystallization temperature. By monitoring the heat flow during cooling, the crystallization kinetics of PA6 were characterized, including the degree of crystallinity, crystallization temperature, and crystallization rate. The study found that changing the fusion temperature and duration significantly impacted the crystallization kinetics of PA6. Increasing the fusion temperature decreased the degree of crystallinity, with smaller nucleation centers requiring a higher degree of supercooling for crystallization. The crystallization temperature shifted towards lower temperatures, and the crystallization kinetics slowed down. The study also found that lengthening the fusion time raised the relative crystallinity, but any further increase did not result in a significant change. The study showed that an increase in fusion temperature led to a longer time needed to reach a given level of crystallinity, reducing the crystallization rate. This can be explained by the thermodynamics of the crystallization process, where higher temperatures promote molecular mobility and crystal growth. Moreover, the study revealed that decreasing a polymer’s fusion temperature can lead to a greater degree of nucleation and faster growth of the crystalline phase, which can significantly impact the values of the Avrami parameters used to characterize the crystallization kinetics. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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15 pages, 3249 KiB

Open AccessArticle

Two-Stage Evolution of Gamma-Phase Spherulites of Poly (Vinylidene Fluoride) Induced by Alkylammonium Salt

by Tatsuaki Miyashita and Hiromu Saito

Polymers 2022, 14(18), 3901; https://doi.org/10.3390/polym14183901 - 18 Sep 2022

Cited by 2 | Viewed by 1565

Abstract

We investigated the evolution of the γ-phase spherulites of poly(vinylidene fluoride) (PVDF) added to 1 wt% of tetrabutylammonium hydrogen sulfate during the isothermal crystallization at 165 °C through polarized optical microscopy and light scattering measurements. Optically isotropic domains grew, and then optical anisotropy started to increase in the domain to yield spherulite. Double peaks were seen in the time variation of the Vv light scattering intensity caused by the density fluctuation and optical anisotropy, and the Hv light scattering intensity caused by the optical anisotropy started to increase during the second increase in the Vv light scattering intensity. These results suggest the two-stage evolution of the γ-phase spherulites, i.e., the disordered domain grows in the first stage and ordering in the spherulite increases due to the increase in the fraction of the lamellar stacks in the spherulite without a change in the spherulite size in the second stage. Owing to the characteristic crystallization behavior, the birefringence in the γ-phase spherulites of the PVDF/TBAHS was much smaller than that in the α-phase spherulites of the neat PVDF. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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15 pages, 11704 KiB

Open AccessArticle

Unique Periodic Rings Composed of Fractal-Growth Dendritic Branching in Poly(p-dioxanone)

by Kuan-Ying Huang, Eamor M. Woo and Selvaraj Nagarajan

Polymers 2022, 14(4), 805; https://doi.org/10.3390/polym14040805 - 19 Feb 2022

Cited by 2 | Viewed by 1892

Abstract

Amorphous poly(p-vinyl phenol) (PVPh) was added into semicrystalline poly(p-dioxanone) (PPDO) to induce a uniquely novel dendritic/ringed morphology. Polarized-light optical, atomic-force and scanning electron microscopy (POM, AFM, and SEM) techniques were used to observe the crystal arrangement of a uniquely peculiar cactus-like dendritic PPDO spherulite, with periodic ring bands not continuingly circular such as those conventional types reported in the literature, but discrete and detached to self-assemble on each of the branches of the lobs. Correlations and responsible mechanisms for the formation of this peculiar banded-dendritic structure were analyzed. The periodic bands on the top surface and interior of each of the cactus-like lobs were discussed. The banded pattern was composed of feather-like lamellae in random fractals alternately varying their orientations from the radial direction to the tangential one. The tail ends of lamellae at the growth front spawned nucleation cites for new branches; in cycles, the feather-like lamellae self-divided into multiple branches following the Fibonacci sequence to fill the ever-expanding space with the increase of the radius. The branching fractals in the sequence and the periodic ring-banded assembly on each of the segregated lobs of cactus-like dendrites were the key characteristics leading to the formation of this unique dendritic/ringed PPDO spherulite. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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17 pages, 12257 KiB

Open AccessArticle

Estimating the Relative Crystallinity of Biodegradable Polylactic Acid and Polyglycolide Polymer Composites by Machine Learning Methodologies

by Jing Wang, Mohamed Arselene Ayari, Amith Khandakar, Muhammad E. H. Chowdhury, Sm Ashfaq Uz Zaman, Tawsifur Rahman and Behzad Vaferi

Polymers 2022, 14(3), 527; https://doi.org/10.3390/polym14030527 - 28 Jan 2022

Cited by 30 | Viewed by 3489

Abstract

Biodegradable polymers have recently found significant applications in pharmaceutics processing and drug release/delivery. Composites based on poly (L-lactic acid) (PLLA) have been suggested to enhance the crystallization rate and relative crystallinity of pure PLLA polymers. Despite the large amount of experimental research that has taken place to date, the theoretical aspects of relative crystallinity have not been comprehensively investigated. Therefore, this research uses machine learning methods to estimate the relative crystallinity of biodegradable PLLA/PGA (polyglycolide) composites. Six different artificial intelligent classes were employed to estimate the relative crystallinity of PLLA/PGA polymer composites as a function of crystallization time, temperature, and PGA content. Cumulatively, 1510 machine learning topologies, including 200 multilayer perceptron neural networks, 200 cascade feedforward neural networks (CFFNN), 160 recurrent neural networks, 800 adaptive neuro-fuzzy inference systems, and 150 least-squares support vector regressions, were developed, and their prediction accuracy compared. The modeling results show that a single hidden layer CFFNN with 9 neurons is the most accurate method for estimating 431 experimentally measured datasets. This model predicts an experimental database with an average absolute percentage difference of 8.84%, root mean squared errors of 4.67%, and correlation coefficient (R²) of 0.999008. The modeling results and relevancy studies show that relative crystallinity increases based on the PGA content and crystallization time. Furthermore, the effect of temperature on relative crystallinity is too complex to be easily explained. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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12 pages, 2075 KiB

Open AccessArticle

Significantly Enhanced Crystallization of Poly(ethylene succinate-co-1,2-propylene succinate) by Cellulose Nanocrystals as an Efficient Nucleating Agent

by Siyu Pan, Zhiguo Jiang and Zhaobin Qiu

Polymers 2022, 14(2), 224; https://doi.org/10.3390/polym14020224 - 6 Jan 2022

Cited by 4 | Viewed by 1518

Abstract

Poly(ethylene succinate-co-1,2-propylene succinate) (PEPS) is a novel aliphatic biodegradable polyester with good mechanical properties. Due to the presence of methyl as a side group, the crystallization rate of PEPS is remarkably slower than that of the poly(ethylene succinate) homopolymer. To promote the potential application of PEPS, the effect of cellulose nanocrystals (CNC) on the crystallization behavior, crystalline morphology, and crystal structure of PEPS was investigated in this research with the aim of increasing the crystallization rate. CNC enhanced both the melt crystallization behavior of PEPS during the cooling process and the overall crystallization rate during the isothermal crystallization process. The crystallization rate of PEPS became faster with an increase in CNC content. The crystalline morphology study directly confirmed the heterogeneous nucleating agent role of CNC. The crystal structure of PEPS remained unchanged in the composites. On the basis of the interfacial energy, the nucleation mechanism of PEPS in the composites was further discussed by taking into consideration the induction of CNC. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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21 pages, 4088 KiB

Open AccessArticle

Crystal Nucleation and Growth in Cross-Linked Poly(ε-caprolactone) (PCL)

by Timur Mukhametzyanov, Jürn W.P. Schmelzer, Egor Yarko, Albert Abdullin, Marat Ziganshin, Igor Sedov and Christoph Schick

Polymers 2021, 13(21), 3617; https://doi.org/10.3390/polym13213617 - 20 Oct 2021

Cited by 7 | Viewed by 1910

Abstract

The crystal nucleation and overall crystallization kinetics of cross-linked poly(ε-caprolactone) was studied experimentally by fast scanning calorimetry in a wide temperature range. With an increasing degree of cross-linking, both the nucleation and crystallization half-times increase. Concurrently, the glass transition range shifts to higher temperatures. In contrast, the temperatures of the maximum nucleation and the overall crystallization rates remain the same, independent of the degree of cross-linking. The cold crystallization peak temperature generally increases as a function of heating rate, reaching an asymptotic value near the temperature of the maximum growth rate. A theoretical interpretation of these results is given in terms of classical nucleation theory. In addition, it is shown that the average distance between the nearest cross-links is smaller than the estimated lamellae thickness, which indicates the inclusion of cross-links in the crystalline phase of the polymer. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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12 pages, 2333 KiB

Open AccessArticle

Crystallization of Random Metallocene-Catalyzed Propylene-Based Copolymers with Ethylene and 1-Hexene on Rapid Cooling

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

Polymers 2021, 13(13), 2091; https://doi.org/10.3390/polym13132091 - 25 Jun 2021

Cited by 3 | Viewed by 2157

Abstract

Propylene-based random copolymers with either ethylene or 1-hexene as comonomer, produced using a metallocene catalyst, were studied regarding their crystallization behaviors, with a focus on rapid cooling. To get an impression of processing effects, fast scanning chip calorimetry (FSC) was used in addition to the characterization of the mechanical performance. When comparing the comonomer type and the relation to commercial grades based on Ziegler–Natta-type catalysts, both an interaction with the catalyst-related regio-defects and a significant difference between ethylene and 1-hexene was observed. A soluble-type nucleating agent was found to modify the behavior, but to an increasingly lesser degree at high cooling rates. Full article

(This article belongs to the Special Issue Crystallization in Polymer Science)

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