Computer simulation of the melting kinetics of polymer crystals under condition of modulated temperature

Toda, Akihiko; Arita, Takeshi; Tomita, Chiyoko; Hikosaka, Masamichi

doi:10.1016/s0040-6031(99)00021-0

Cited by 22 publications

(8 citation statements)

References 20 publications

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“…The existence of a melting kinetics of crystals superheated above their melting points was first suggested for extended-chain crystals of polyethylene (PE) by Wunderlich et al , , using isothermal and nonisothermal conventional differential scanning calorimetry (DSC) measurements. In subsequent conventional DSC examinations of the heating-rate dependence of the melting peak of chain-folded polymer crystals, − the dependence was examined using a model supposing a superheating-dependent melting rate, which was originally developed for the analysis of the melting kinetics examined by temperature-modulated DSC. ,− It has been concluded that the melting rate is dependent on the superheating Δ T expressed by a power y that is stronger than unity, as Δ T y . The melting process was also examined by Kovacs et al − for once-folded- and extended-chain crystals of low-molar-mass poly(ethylene-oxide) (PEO) fractions, using microscopy and DSC.…”

Section: Introductionmentioning

confidence: 99%

Melting Kinetics of Superheated Polymer Crystals Examined by Isothermal and Nonisothermal Fast Scanning Calorimetry

2021

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Quantitative analyses of the melting kinetics of superheated polymer crystals, including the isothermal analysis of the time dependence of melting and nonisothermal analysis of the heating-rate dependence of melting, were carried out by fast scanning calorimetry on linear polyethylene that has a narrow melting temperature region. The time evolution of the decrease in the total crystallinity during melting was modeled using a first-order kinetic equation with a rate coefficient, which defines a characteristic melting time under isothermal conditions. A superheating-dependent rate coefficient characterizes the heating-rate dependence of the nonisothermal melting. The obtained results of both analyses consistently suggest the presence of a superheating-dependent melting kinetics unique to initially metastable long-chain polymer crystals with the melting rate nonlinearly dependent on superheating. The dependence is exponential at least in a certain range of superheating. Examinations of the dependence on crystallization temperature, which controls the thickness of lamellar crystals, suggest an activated process of detaching a whole crystalline stem. A possible mechanism of the activation barrier is discussed in connection with distinct types of chain folding.

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Section: Introductionmentioning

confidence: 99%

Melting Kinetics of Superheated Polymer Crystals Examined by Isothermal and Nonisothermal Fast Scanning Calorimetry

2021

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“…[13,14] "Melting kinetics" means that a kind of nucleation or diffusion-controlled kinetics plays an important role in melting. Therefore, the sample should be crystallized at high T c .…”

Section: Gibbs-thomson Plotmentioning

confidence: 99%

“…Based on the theoretical equation of "melting kinetics," [13,14] the T m was plotted against b 0.47 in Fig. 11.…”

Section: Wide-angle X-ray Scattering (Waxs) Patterns Of Melt-crystallmentioning

confidence: 99%

Conditions for Melt Crystallization Without Thermal Degradation and Equilibrium Melting Temperature of Atactic Poly(Vinyl Alcohol)

Endo

Amiya

Hikosaka

2003

Journal of Macromolecular Science, Part B

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Optimum conditions for melt crystallization without thermal degradation for atactic poly(vinyl alcohol) (PVA) were found for the first time. Thermal degradation of PVA in the melt has been too serious to permit crystallization from the melt. However, it was found that thermal degradation can be suppressed by selecting an appropriate solvent for film preparation, such as water without dimethyl sulfoxide (DMSO), by careful degassing before melting and by melting under high vacuum. As a result, the sample could be held in the melt at 2508C for 30 min and in the supercooled melt at 2208C for 480 min without thermal degradation. Therefore we could carry out the melt crystallization at a high crystallization temperature (T c ) in the range of 208 to 2218C and study the structures and morphologies of meltcrystallized PVA samples for the first time. The irregularly stacked lamellae were observed irrespective of T c . The thick lamellae with high T m , 24 nm and 236.18C, respectively, were obtained from the melt crystallization at T c ¼ 2208C; which indicates that the chain sliding diffusion is accelerated a little with increase of T c . However, the distribution of lamellar thickness was sharp, even for the sample crystallized at high T c , which indicated that the chain sliding diffusion is relatively 793 suppressed by the intermolecular hydrogen bonds. Hence, the lamellar thickening was suppressed during the crystallization, as compared with polyethylene (PE) and isotactic polypropylene (iPP). The equilibrium melting temperature ðT o m Þ of PVA was determined to be 2498C, applying an improved Gibbs -Thomson plot that was recently proposed by Yamada et al. The Hoffman-Weeks plot accidentally gave a similar T o m ¼ 2488C: It was confirmed that the lamellar thickness is inversely proportional to the degree of supercooling in the case of PVA crystals, which is the reason why both plots gave similar T o m :

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“…32 After transformation to the orthorhombic phase, ECC is close to perfect and has coherently scattering grain sizes of more than 200 nm normal to the direction of the molecular chain, as revealed by X-ray analysis. 33,34 Reversing and reversible melting of crystals with repeating units of CH 2 have been investigated for paraffins, 6 fractions of PE, 7 high-density PE, 7,[35][36][37][38][39][40][41][42] homogeneous linear low-density PE [poly(ethylene-co-octene-1)], 35,37,[43][44][45][46][47][48][49] and ultrahigh molar mass PE (UHMMPE). 50 -54 In this article, information gained from these research reports is combined to gain a clearer understanding of the melting of PE.…”

Section: Introductionmentioning

confidence: 99%

Reversible melting of polyethylene extended‐chain crystals detected by temperature‐modulated calorimetry

Pak¹,

Wunderlich²

2002

J Polym Sci B Polym Phys

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ABSTRACT:The melting and crystallization of extended-chain crystals of polyethylene are analyzed with standard differential scanning calorimetry and temperature-modulated differential scanning calorimetry. For short-chain, flexible paraffins and polyethylene fractions up to 10 nm length, fully reversible melting was possible for extendedchain crystals, as is expected for small molecules in the presence of crystal nuclei. Up to 100 nm length, full eutectic separation occurs with decreasingly reversible melting. The higher-molar-mass polymers form solid solution crystals and retain a rapidly decreasing reversible component during their melting that decreases to zero about 1.5 K before the end of melting. An attempt is made to link this reversible melting to the known, detailed morphology and phase diagram of the analyzed sample that was pressure-crystallized to reach chain extension and practically complete crystallization.

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Computer simulation of the melting kinetics of polymer crystals under condition of modulated temperature

Cited by 22 publications

References 20 publications

Melting Kinetics of Superheated Polymer Crystals Examined by Isothermal and Nonisothermal Fast Scanning Calorimetry

Melting Kinetics of Superheated Polymer Crystals Examined by Isothermal and Nonisothermal Fast Scanning Calorimetry

Conditions for Melt Crystallization Without Thermal Degradation and Equilibrium Melting Temperature of Atactic Poly(Vinyl Alcohol)

Reversible melting of polyethylene extended‐chain crystals detected by temperature‐modulated calorimetry

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