Melt Memory Effect beyond the Equilibrium Melting Point in Commercial Isotactic Polybutene-1

Liu, Peiru; Xue, Yanhu; Men, Yongfeng

doi:10.1021/acs.iecr.8b06444

Cited by 25 publications

(20 citation statements)

References 53 publications

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“…It has been recently reported that the presence of impurities can affect melt memory. Men et al have shown that in commercial isotactic poly(butene-1) a melt memory effect could be detected at temperatures higher than the equilibrium melting point. However, when the sample was purified, this peculiar melt memory effect at temperatures higher than the equilibrium melting point disappeared.…”

Section: Discussionmentioning

confidence: 99%

Self-Nucleation Effects on Polymer Crystallization

2020

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The existence of a "memory" of the previous crystalline state, which survives melting and enhances re-crystallization kinetics by a self-nucleation process, is wellknown in polymer crystallization studies. Despite being extensively investigated, since the early days of polymer crystallization studies, a complete understanding of melt memory effects is still lacking. In particular, the exact constitution of self-nuclei is still under debate. In this perspective, we provide a comprehensive and critical overview of melt memory effects in polymer crystallization. After the phenomenology of the process and some key concepts are introduced, the main experimental results of the last decades are summarized. Analogies and discrepancies of the melt memory characteristics of different polymeric systems are highlighted. Based on this background, the most significant interpretations and theories of melt memory effects are described; underlining that different interpretations may apply to various specific cases. Recent insights on self-nucleation, gained thanks to a multi-technique approach (combining calorimetry, rheology, infrared and dielectric spectroscopy), are presented. The role of intra/inter-chain segmental contacts in the strength of melt memory effects, and the differences between homopolymers and copolymers behavior, are discussed. Finally, we identify areas where further research in the field is needed to shed light on the longstanding questions regarding the origin of melt memory effects in semi-crystalline polymers.

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Section: Discussionmentioning

confidence: 99%

Self-Nucleation Effects on Polymer Crystallization

2020

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“…Temperature and heat flow scales were performed using high pure indium and zinc as the standard. A nominal 5 mg of sample was scanned from 25 to 180 °C under a nitrogen atmosphere with a heating/cooling rate of 10 °C/min . Moreover, the crystallinity ( X DSC ) of PE is defined as follows where Δ H m is the melting enthalpy for tested samples, and Δ H m 0 = 287.3 J/g is the melting enthalpy of 100% crystallinity for PE .…”

Section: Methodsmentioning

confidence: 99%

Structure Evolution of Polyethylene in Sequential Biaxial Stretching along the First Tensile Direction

Chen

Kang

et al. 2019

Ind. Eng. Chem. Res.

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Two linear low-density polyethylene samples (PE-A and PE-B), with similar melt index and molecular weight but different molecular structures, were used to explore the structural evolution during sequential biaxial stretching. Only PE-A could be successfully stretched into a film with the biaxial draw ratio of 6 × 6. The interlamellae crossing adjacent lamellar stacks were observed in PE-A but not in PE-B, which could increase the lateral tie connection. Moreover, the amount of fibril was less in PE-A than that in PE-B and the fibrillar structure lacked tie chains between each other. In addition, the newly formed lamellae in PE-A (derived from fine lamellae) could lock the molecular chains of different crystals, which increased the lateral connection via anchoring the tie chains from adjacent lamellae. Therefore, the above specific structures increased the lateral connection and were beneficial for biaxial stretching. Furthermore, the relationship between molecular structure and condensed structure was also established.

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“…Here, it should be cautioned that in commercial polymers, memory effects above the equilibrium melting temperature may be caused by additives that can absorb polymer chains and act as potential nuclei. 67 In this work, all of the NBE copolymers were carefully synthesized without adding any processing additives, and they were precipitated several times to remove potential impurities to the greatest extent possible. Thus, the influence of additives could be ruled out in this work.…”

Section: Memory Effect Withmentioning

confidence: 99%

Influence of Steric Norbornene Co-units on the Crystallization and Memory Effect of Polybutene-1 Copolymers

Liao

Liu

et al. 2020

Macromolecules

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The incorporation of the secondary co-units may not only change the kinetics and polymorphism of crystallization but also affect the melting behavior of polymers, leading to the memory effect even above the equilibrium melting temperature. In this work, a series of butene-1/norbornene random copolymers with 0−4.57 mol % steric norbornene (NBE) co-units was synthesized using rac-ethyl(1-indenyl) 2 zirconium dichloride as the catalyst. The melt crystallization, solid-phase transition, and memory effect associated with incomplete melting were studied with differential scanning calorimetry and in situ wide-angle Xray diffraction. The results show that unlike the polybutene-1 homopolymer, which always generates tetragonal crystals, the presence of steric NBE co-units can cause the copolymers to crystallize into trigonal form I′. The correlations of crystallization polymorphism with the NBE concentration and temperature were quantitatively established. For copolymer NBE2.36, the threshold temperature for generating pure form I′ crystals is 70 °C, and this decreases to 55 °C when the NBE concentration is increased to 4.57%. Moreover, for crystallized tetragonal form II, its spontaneous phase transition into thermodynamically more stable form I was significantly accelerated. On the other hand, the melting behaviors of the copolymers were influenced by the incorporation of NBE co-units, leading to the appearance of a memory effect. Interestingly, the memory effect not only accelerates the crystallization kinetics but also alters the crystallization polymorphism; the formation of form I′ was enhanced relative to form II. At a melt temperature of 120 °C, the initial form II crystallites dominate the memory effects because of their large lamellar thickness, while at a higher melt temperature (140 °C), form I′ is dominant due to its high thermal stability.

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Melt Memory Effect beyond the Equilibrium Melting Point in Commercial Isotactic Polybutene-1

Cited by 25 publications

References 53 publications

Self-Nucleation Effects on Polymer Crystallization

Self-Nucleation Effects on Polymer Crystallization

Structure Evolution of Polyethylene in Sequential Biaxial Stretching along the First Tensile Direction

Influence of Steric Norbornene Co-units on the Crystallization and Memory Effect of Polybutene-1 Copolymers

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