Kinetic of crystallization from the melt and chain folding in polyethylene fractions revisited: theory and experiment

Hoffman, John D.; Miller, Robert L.

doi:10.1016/s0032-3861(97)00071-2

Cited by 973 publications

(1,098 citation statements)

References 156 publications

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“…(valid for ToT g +100) 16 where U * is a 'universal' constant characteristic of the activation energy for transport of macromolecules through the melt onto the substrate, R is the gas constant, T N is the theoretical temperature at which all motion associated with viscous flow ceases, T m 0 is the equilibrium melting temperature and T is the crystallization temperature. Generally, the values assumed for U * and T N are 1500 cal mol À1 and T g À30, respectively, where T g is the glass transition temperature.…”

Section: Resultsmentioning

confidence: 99%

Estimation of polymer nucleation and growth rates by overall DSC crystallization rates

Raimo

2010

Polym J

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Isothermal crystallization of a polyoxymethylene copolymer in the temperature range of 423-429 K (150-156 1C) was performed using a differential scanning calorimeter (DSC) and data of crystalline development processed within the framework of a nucleation and growth model. Morphological investigations on DSC crystallized specimens were performed by scanning electron microscopy (SEM) and correlated to DSC data to obtain good estimations of spherulite growth rates in the explored temperature range. The accuracy of the growth rate has been enhanced by Hoffman regime analysis using reliable values of input parameters. Moreover, the function describing the number of growing spherulites as a function of time at constant temperature has been obtained.

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Section: Resultsmentioning

confidence: 99%

Estimation of polymer nucleation and growth rates by overall DSC crystallization rates

Raimo

2010

Polym J

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“…The surface free energy of the basal surface is 90 mJ/m 2 and the lateral surface is 11.8 mJ/m 2 for polyethylene lamellae. 12 Clearly, the higher energy basal surface prefers to remain in the bulk, while the much lower energy lateral surface is forced to lie in the melt surface plane. This is a useful condition, since the lamella thickness may be readily measured in the AFM images.…”

Section: Resultsmentioning

confidence: 99%

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Mirabella

2006

J Polym Sci B Polym Phys

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ABSTRACT:The HoffmanLauritzen theory of secondary, surface nucleation and growth was primarily relied upon for about 40 years after its introduction in about 1960 to rationalize the crystallization of flexible chain polymers into lamellar crystals. However, in about 1998, Strobl and coworkers introduced a different model for crystallization, based on the stagewise formation of lamellae. Two major components of this model were as follows: (1) the concept of the formation of a mesomorphic melt as a precursor to crystallization and (2) the control of the melting temperature range of lamellar crystals of homogeneous polyolefin copolymers by an inner degree of order or perfection rather than on the crystal thickness. The first concept is in disagreement with the HL theory and the second with the Gibbs-Thomson theory, which associates melting temperature with lamella thickness. In the present study, differential scanning calorimetry and atomic force microscopy were successfully employed to monitor the in situ quiescent crystallization of polyethylene homopolymer and copolymer. In the present study, evidence was not found to support the concept of lamellae with equal thickness melting over a broad temperature range. Some evidence was found that might be interpreted to support the concept of a mesomorphic melt as a precursor to crystallization. At present, the model promoted by Strobl and coworkers appears to be at an uncertain stage at which strong proof or disproof are not available. However, this alternative model has injected a new vitality into the study of crystallization of flexible chain polymers.

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“…The appearance of all of the three regimes was first observed in the studies of fractions of cis-polyisoprene by Phillips and Vatansever [13]. Recently, regime crystallization kinetics in polyethylene was discussed in a great deal of detail, both theoretically and experimentally by Hoffman and Miller [10]. In the case where the growth rate data is not available or is too time-consuming to obtain, the overall crystallization rate (denoted by t Ϫ1 u , the reciprocal value of the time taken from the onset of the crystallization process to reach a certain value of relative crystallinity u ), obtained directly from the bulk crystallization, can also be used to observe regime crystallization in polymers.…”

Section: Introductionmentioning

confidence: 92%

“…In the context of the LH secondary nucleation theory [1][2][3][4][5][6][7][8][9][10], the linear growth rate G of a crystalline aggregate (e.g. spherulite or axialite) for each regime is dependent on the degree of undercooling, DT, and is defined by the following equation:…”

Section: Theoretical Backgroundmentioning

confidence: 99%

“…the LH secondary nucleation theory) has been developed and revised repeatedly in subsequent publications essentially by Hoffman and his co-workers [4][5][6][7][8][9][10]. The theory suggests that polymers crystallize in three different regimes, as opposed to the classical theory of secondary nucleation in which the deposition of a single nucleus on a growth face is followed by a rapid lateral spreading process.…”

Section: Introductionmentioning

confidence: 99%

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Regime crystallization in syndiotactic polypropylenes: re-evaluation of the literature data

Supaphol

Spruiell

2000

Polymer

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The Lauritzen and Hoffman secondary nucleation theory was applied to linear growth rate data of syndiotactic polypropylene taken from the literature. Observation of the distinctive upward change of slope in plots of log G ϩ U ‫ء‬ /2.303R(T c Ϫ T ∞ ) versus 1/2.303T c (DT)f suggested the regime II 3 III transition at the crystallization temperature of 110ЊC. Based on the input parameters judged to be the most accurate, the ratios of K g,III /K g,II were found to range from 1.7 to 2.2. Regardless of the crystal structure, if the growth is assumed to occur on the bc plane, the lateral surface free energy, s 11.3 erg cm Ϫ2 and the fold surface free energy s e 63.7^7.1 erg cm Ϫ2 were found. The latter leads to the average work of chain folding of q 7:4^0:8 kcal mol Ϫ1 . If the growth is assumed to occur on the ac plane, the fold surface free energy is found to be s e 82.4^9.1 erg cm Ϫ2 , while the lateral surface free energy is the same as previously noted. In this case, the work of chain folding of q 9:6^1:1 kcal mol Ϫ1 is found. These values are applicable to both regimes II and III. A detailed evaluation of the effects of changes in input parameters was also carried out. ᭧

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Kinetic of crystallization from the melt and chain folding in polyethylene fractions revisited: theory and experiment

Cited by 973 publications

References 156 publications

Estimation of polymer nucleation and growth rates by overall DSC crystallization rates

Estimation of polymer nucleation and growth rates by overall DSC crystallization rates

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Regime crystallization in syndiotactic polypropylenes: re-evaluation of the literature data

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