Thermal reversibility in crystalline morphology of LLDPE crystallites

Nam, Joo Young; Kadomatsu, Shigenobu; Saito, Hiromu; Inoue, Takashi

doi:10.1016/s0032-3861(01)00709-1

Cited by 23 publications

(14 citation statements)

References 35 publications

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“…It is also interesting to note that the enthalpy of the C p ′ endotherm of FC50‐HDPE was considerably larger than that of the C p NR endotherm. It is known that poorly crystallized polymers have a larger reversing melting contribution, whereas perfect crystals show little or none 4, 35. Therefore, the larger reversing contribution of FC50‐HDPE verifies the formation of thermally unstable crystals.…”

Section: Resultsmentioning

confidence: 98%

“…Nam et al35 studied the structural changes of LLDPE by small angle X‐ray scattering (SAXS) and TMDSC during the heating process. They also observed a broad, large reversing peak and a small, sharp nonreversing peak, suggesting continuous melting of a large fraction of thermally unstable thin lamellae that formed over a wide temperature range during cooling.…”

Section: Resultsmentioning

confidence: 99%

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Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry

Amarasinghe

Chen

Genovese

et al. 2003

J of Applied Polymer Sci

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Temperature modulated differential scanning calorimetry (TMDSC) was employed to study the melting and crystallization behavior of various polyethylenes (PEs). Samples of high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and very low density PE (VLDPE) with different crystal structures and morphologies were prepared by various thermal treatments (isothermal crystallization and slow, fast, and dynamic cooling). The reversing and nonreversing contributions, measured on the experimental time scale, were varied, depending on the crystal stability. A relatively large reversing melt contribution occurs for unstable crystals formed by fast cooling compared to those from slow cooling treatments. All samples of highly branched LDPE, LLDPE, and VLDPE showed a broad exotherm before the main melting peak in the nonreversing curve, suggesting crystallization and annealing of crystals to more stable forms. Other samples of HDPE, except when cooled quickly, did not show any significant crystallization and annealing before melting. The crystallinity indicated that dynamically cooled polymers were much more crystalline, which can be attributed to crystal perfection at the lamellar surface. A reversible melting component was also detected during the quasiisothermal TMDSC measurements. Melting is often accompanied by large irreversible effects, such as crystallization and annealing, where the crystals are not at equilibrium. Such phenomena during a TMDSC scan provide information on the polymer thermal history.

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Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry

Amarasinghe

Chen

Genovese

et al. 2003

J of Applied Polymer Sci

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“…To understand the crystallization kinetics of neat PLA before and after nanocomposite preparation at low T c (6 120°C), Nam et al [220] used time-resolved LS photometry, because this is a powerful tool for estimating the overall crystallization rate and its kinetics in super cooled crystalline polymer liquid [226]. For the kinetics of crystallization, they employed the integrated scattering intensity, i.e., the invariant Q is define as…”

Section: Crystallization Behavior and Morphology Of Biodegradable Polmentioning

confidence: 99%

Biodegradable polymers and their layered silicate nanocomposites: In greening the 21st century materials world

Ray¹,

Bousmina²

2005

Progress in Materials Science

1,411

185

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“…Higher birefringence of the blends suggests higher ordering of fibrils in spherulites because of the higher arrangement of the lamellae in the fibrils 46–48 . Spherical and distorted black PVP domains of several micrometers in size were observed in the spherulites of blends due to the phase‐separated structure, as shown in Figures 1 and 2.…”

Section: Resultsmentioning

confidence: 91%

Control of crystallization in two‐phase blends of poly(phenylene sulfide) and poly(vinylpyrrolidone)

Nara

Watanabe

Oyama

et al. 2020

Polymer Crystallization

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This paper reports for the first time the use of poly(N‐vinylpyrrolidone) (PVP) as an effective additive for controlling the melt crystallization behavior of poly(p‐phenylene sulfide) (PPS). The PPS/PVP blends form two‐phases, whose melt crystallization temperature decreases drastically upon the addition of PVP accompanied by a delayed onset of crystallization and a decreased crystallization rate. Monitoring spherulite growth during isothermal annealing revealed that in blends with less than 5 wt% of PVP the diminution of the crystallization rate of PPS is due to a decrease in both the nucleation rate and the spherulite growth rate, whereas in blends with higher PVP content the falloff in rate is mainly caused by slow nucleation. A change was observed in the glass transition temperature and melting temperature of PPS upon blending, suggesting that the blends are partially miscible. The delay in crystallization is likely due to the partial miscibility disturbing exclusion of PVP from the crystalline growth front.

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Thermal reversibility in crystalline morphology of LLDPE crystallites

Cited by 23 publications

References 35 publications

Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry

Thermal memory of polyethylenes analyzed by temperature modulated differential scanning calorimetry

Biodegradable polymers and their layered silicate nanocomposites: In greening the 21st century materials world

Control of crystallization in two‐phase blends of poly(phenylene sulfide) and poly(vinylpyrrolidone)

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