Origin of the melt memory effect in polymer crystallization

Martins, José A.; Zhang, Weidong; Brito, A. M.

doi:10.1016/j.polymer.2010.07.010

Cited by 60 publications

(49 citation statements)

References 33 publications

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“…The memory effect could originate from some embryos (molecular clusters) that survive the thermal treatment and then Reprinted with permission from Arandia et al [8]. Copyright (2015) American Chemical Society become active nuclei once the temperature is lowered [26,44]. However, it is not clear why some embryos could survive the high temperatures applied.…”

Section: Crystalline Memorymentioning

confidence: 99%

“…The origin of precursors differs for any given polymer. According to some authors, some precursors are formed by shear flow in the melt [44,[78][79][80][81][82][83][84][85][86]. Shear flow is the origin of polymer chain orientation and their partial alignment.…”

Section: Crystalline Memorymentioning

confidence: 99%

“…In other words, L-PCL samples have a much higher crystalline memory than CPCLs of similar molecular lengths. Crystalline memory effects are a function of entanglement density [26,40,44,63,[122][123][124][125][126], and the entanglement density in LPCLs is significantly higher than in C-PCL as a result of its free chain ends. Therefore, partially disentangled PCL cyclic chains can reach a random coil conformation, or a uniform melt, faster than more entangled linear chains.…”

Section: Influence Of Confinement On Self-nucleation Behaviormentioning

confidence: 99%

See 2 more Smart Citations

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Michell

Múgica

Zubitur

et al. 2015

Advances in Polymer Science

126

303

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Self-nucleation (SN) is a special nucleation process triggered by selfseeds or self-nuclei that are generated in a given polymeric material by specific thermal protocols or by inducing chain orientation in the molten or partially molten state. SN increases the nucleation density of polymers by several orders of magnitude, producing significant modifications to their morphology and overall crystallization kinetics. In fact, SN can be used as a tool for investigating the overall isothermal crystallization kinetics of slow-crystallizing materials by accelerating the primary nucleation stage in a previous SN step. Additionally, SN can facilitate the formation of one particular crystalline phase in polymorphic materials. The SN behavior of a given polymer is influenced by its molecular weight, molecular topology, and chemical structure, among other intrinsic and extrinsic characteristics. This review paper focuses on the applications of DSC-based SN techniques to study the nucleation, crystallization, and morphology of different types of polymers, blends, copolymers, and nanocomposites.

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Section: Crystalline Memorymentioning

confidence: 99%

Section: Crystalline Memorymentioning

confidence: 99%

Section: Influence Of Confinement On Self-nucleation Behaviormentioning

confidence: 99%

See 1 more Smart Citation

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Michell

Múgica

Zubitur

et al. 2015

Advances in Polymer Science

126

303

View full text Add to dashboard Cite

show abstract

“…The special aspect of polymer crystallization is flow‐induced crystallization in the sheared melt, when the macromolecules are oriented and stretched with the local decrease of entanglements density by a process referred to as the convective constraint release . An acceleration of the crystallization kinetics is observed in a less viscous sheared melt, but without significant changes in the nucleation density, because the presence of nuclei having the critical size depends mainly on the surface energies and supercooling . The experimental data of Martins et al demonstrate that iPP melt sheared up to the steady state has 1/3 the number of initial entanglements and in isothermal conditions it crystallizes twice as fast ( Figure ).…”

Section: Characterization Of Entanglementsmentioning

confidence: 99%

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Pawlak

2019

Macro Chemistry & Physics

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Macromolecules form entanglements, the presence of which determines many of the polymer's properties; in solution, melt, and solid state. In this review, how the properties of polymers (rheological, thermal, and mechanical), depend on the concentration of the entanglements, is discussed. Although a typical polymer is characterized by the equilibrium density of entanglements, there are methods that can be applied for the reduction of this density. The methods used most often include dissolving a polymer and rapid freezing, crystallization during polymerization, and crystallization from a cooled dilute solution. The properties of disentangled polymers are significantly different from the properties of fully entangled polymers. These properties are discussed in relation to their dependence on the density of the entanglements. The disentangled material can be re‐entangled by the annealing of the polymer; however, reaching the equilibrium density of the entanglements is usually a slow process. It means that a polymer may be processed without losing its disentanglements. The properties of the re‐entangled polymer are usually close to the properties of the initial polymer.

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“…Melt memory effects have often been observed in the crystallization of polymer materials and have become one of the major research subjects in polymer science. [1][2][3][4][5][6][7][8][9][10][11] However, little detailed research has been performed regarding the memory of the positions of spherulites. Although there are several discussions of melt memory on the number of spherulite nuclei, [12][13][14] there is little discussion of the melt memory of spherulite positions.…”

Section: Introductionmentioning

confidence: 99%

Melt memory of a spherulite nucleus formed through a seeding process in the crystal growth of isotactic polystyrene

Hashimoto

O'ishi

Moriya

et al. 2015

Polym J

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The melt memory effect on the crystal growth of isotactic polystyrene is investigated using optical microscopy. After a spherulite is melted at a slightly higher temperature than the melting point and completely disappears, a polymer crystal nucleates and grows at the same position as the original spherulite when the temperature is decreased below the melting point. After the melting-recrystallization processes are repeated by raising and lowering the temperature, the melt memory effect becomes weak. This effect completely disappears at~40°C above the equilibrium melting point when the melt temperature is gradually increased during the melting-recrystallization processes. The formation of spherulite nuclei is promoted by the seeding process, which consists of the following consecutive procedures: quenching a sample to a temperature below the glass transition temperature and annealing the sample slightly above the glass transition temperature. At the initial stage, the number density of spherulites rapidly decreases with the cumulative melting time. After the initial stage, the number density of spherulites exponentially decays with the cumulative melting time and approaches a finite value. This asymptotic value decreases with the melt temperature.

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Origin of the melt memory effect in polymer crystallization

Cited by 60 publications

References 33 publications

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Melt memory of a spherulite nucleus formed through a seeding process in the crystal growth of isotactic polystyrene

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