Effect of Level of Crystallinity on Melt Memory Above the Equilibrium Melting Temperature in a Random Ethylene 1-Butene Copolymer

Chen, Xuejian; Mamun, Al; Alamo, Rufina G.

doi:10.1002/macp.201500068

Cited by 41 publications

(49 citation statements)

References 22 publications

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“…The experimental evidence is consistent with a kinetic nature of melt memory . Even when cooling from the same melting temperature, the increase of crystallization temperature depends on molecular weight, the initial level of crystallinity or on how the standard crystalline state is prepared.…”

Section: Introductionsupporting

confidence: 73%

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Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Chen

Alamo

2018

Polymer International

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The effects of annealing time and molecular weight on the strong melt memory effect observed in random ethylene 1‐alkene copolymers are analyzed in a series of model ethylene 1‐butene copolymers with 2.2 mol% branches. Melt memory is associated with molten clusters of ethylene sequences from the initial crystals that remain in close proximity and are unable to diffuse quickly to the randomized melt state, thus increasing the recrystallization rate. Melt memory persists even for greater than 1000 min annealing indicating a long‐lived nature of the clusters that only fully dissolve at melt temperatures above a critical value (>160 °C). Below the critical melt temperature, molecular weight and annealing temperature have a strong influence on the slow kinetics of melt memory. For the copolymers analyzed, slow dissolution of clusters is experimentally observed only for Mw < 50 000 g mol−1. More stable clusters that survive higher annealing temperatures display slower dissolution rates than clusters remaining at lower temperatures. The threshold crystallinity level to enable melt memory (Xc,threshold) decreases with increasing molecular weight and decreasing annealing temperature similarly to the variation of the chain diffusivity in the melt. The process leading to melt memory is thermally activated as the variation of Xc,threshold with temperature follows Arrhenius behavior with high activation energy (ca 108 kJ mol−1) that is independent of molecular weight. © 2018 Society of Chemical Industry

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Section: Introductionsupporting

confidence: 73%

“…The thermal protocol was repeated with lowering T 1 in successive cycles to achieve higher crystallinity levels prior to approaching heterogeneous T melt . Various T 1 were chosen within the span of the crystallization exotherm from the homogeneous melt as detailed in a prior work …”

Section: Methodsmentioning

confidence: 99%

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Chen

Alamo

2018

Polymer International

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“…[6][7][8][9][10][11]15,16 However, there have been several investigations where any possible memory from such remnant crystalline domains is deliberately wiped out, but still observing melt-memory effects during second crystallization. 5,[12][13][14][17][18][19][20][21] As a classic example, Schultz observed that the maximum crystallization rate of linear polyethylene can be significantly lower if the sample was prepared at higher melt temperatures. 5 The same feature has been observed in other polymers as well.…”

Section: Introductionmentioning

confidence: 99%

“…13,17,19 Sometimes a distinction is made between two kinds of memory effects. 21 If the melt temperature is lower than the equilibrium melting temperature, some remnant crystalline domains could linger around and become responsible for melt-memory. In the other case, the melt temperature is above the equilibrium melting temperature as in the case of Schultz's experiment, and still the memory effect is manifest upon recrystallization.…”

Section: Introductionmentioning

confidence: 99%

Communication: Theory of melt-memory in polymer crystallization

Muthukumar

2016

The Journal of Chemical Physics

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Details of crystallization processes of a polymer at the crystallization temperature T c from its melt kept initially at the melt temperature T m depend profoundly on the nature of the initial melt state and often are accompanied by memory effects. This phenomenon is in contrast to small molecular systems where the supercooling (T 0 m − T c ), with T 0 m being the equilibrium melting temperature, and not (T m − T c ), determines the nature of crystallization. In addressing this five-decade old puzzle of melt-memory in polymer crystallization, we present a theory to describe melt-memory effects, by invoking an intermediate inhomogeneous melt state in the pathway between the melt and crystalline states. Using newly introduced dissolution temperature T

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“…Semicrystalline polymers, such as polypropylene (PP) and polyethylene (PE), are naturally translucent or opaque, because crystals aggregate into large complexes known as spherulites . The size of these spherulites is generally larger than the wavelength of visible light resulting in light scattering and high haze of the material.…”

Section: Introductionmentioning

confidence: 99%

Clarification of linear low‐density polyethylene using Bis‐oxalamide compounds

Wang

Santos

Banks

et al. 2017

Polymer Engineering & Sci

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The clarifying effect of using bis‐oxalamide compounds on linear low density polyethylene (LLDPE) has been investigated for the first time. It was demonstrated that the haze of a commercial LLDPE resin, DOWLEX™ 2045G, can be reduced up to 50% by adding 0.2 wt % of a bis‐oxalamide clarifying agent. The investigations on the crystalline morphology revealed that the density of spherulite cores increased with increasing concentration of bis‐oxalamide N5. Through an investigation of structure‐property relationships based on the tunable bis‐oxalamide structure, it was demonstrated that the combination of linear alkyl core and cyclohexyl pendant groups showed the best clarification. The interactions of clarifying molecules were simulated using dynamic molecular simulation. The simulation suggested that the rigidity of the core functionality played a role on the hydrogen bonding in the intermolecular network, which may contribute to the macroscopic clarification performance. POLYM. ENG. SCI., 58:142–149, 2018. © 2017 Society of Plastics Engineers

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Effect of Level of Crystallinity on Melt Memory Above the Equilibrium Melting Temperature in a Random Ethylene 1-Butene Copolymer

Cited by 41 publications

References 22 publications

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

Communication: Theory of melt-memory in polymer crystallization

Clarification of linear low‐density polyethylene using Bis‐oxalamide compounds

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