Transient and athermal effects in the crystallization of polymers. I. Isothermal crystallization

Sajkiewicz, Paweł

doi:10.1002/polb.10227

Cited by 18 publications

(19 citation statements)

References 51 publications

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“…According to the researchers of several articles (e.g., 7), the only case in which the proportionality between nucleation and growth rates is fulfilled is the predetermined nucleation. However, as it was shown for isothermal crystallization of various polymers,1, 8, 9 the whole nucleation process registered experimentally, including nucleation on heterogeneities and growth of athermal nuclei, occurs sporadically. In addition, the isokinetic models neglect the transient and athermal effects.…”

Section: Introductionmentioning

confidence: 86%

“…The determination of crystallinity P relies on exponent n . Considering that there is no reliable method for the determination of exponent n from nonisothermal crystallization, we decided to use n = 3 as determined previously by DSC from isothermal crystallization1 (the sporadic nucleation with m = 2).…”

Section: Methodsmentioning

confidence: 99%

“…The crystallization rate, K [ T ( t ), t ], at a particular cooling rate, , was determined with eq 9. The determination of K [ T ( t ), t ] through the temperature differentiation of the product ( P · ) was preceded, as in the case of isothermal measurements,1 by numerical extrapolation of the plot of P versus temperature into the region of very small crystallinity, below the sensitivity threshold of the instrument. Because of the limited instrumental sensitivity, the very low crystallinities are ascribed to 0.…”

Section: Methodsmentioning

confidence: 99%

“…The first part of this article1 was devoted to the kinetics of isothermal crystallization of polymers. The coexistence of various mechanisms of nucleation makes this process quite complex and difficult for quantitative interpretation.…”

Section: Introductionmentioning

confidence: 99%

“…This model considers two additional effects in the crystallization process—transient (relaxational) and athermal. They are described more fully in the first part of the article 1. The consequence of both effects is the direct dependence of the crystallization rate on time leading to the deviation of the actual crystallization rate from the steady‐state value defined by the external conditions (temperature, pressure, etc.).…”

Section: Introductionmentioning

confidence: 99%

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Transient and athermal effects in the crystallization of polymers. II. Nonisothermal crystallization

Sajkiewicz

2002

J Polym Sci B Polym Phys

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Nonisothermal crystallization of several polymers was investigated with differential scanning calorimetry and optical microscopy. The results indicated that as in the case of isothermal processes, crystallization starts with nucleation on noncompletely melted crystalline residues. It is assumed that if the crystalline residues are subcritical at melting temperatures, they can become stable by an athermal mechanism during cooling. There is also some contribution of nucleation on heterogeneities. The next mechanism of nucleation is a classical homogeneous process occurring by thermal fluctuations. The results showed the non-steady-state character of the nonisothermal crystallization of polymers. In the investigated range of cooling rates, the non-steadystate character of nonisothermal crystallization of polymers is dominated by the transient thermal effects. In the range of high temperatures, the transient homogeneous nucleation can be interpreted with the Ziabicki model, and the steady-state rate determined from nonisothermal experiments coincides with the rate determined in isothermal crystallization. The athermal nucleation occurring at the beginning of crystallization from noncompletely melted aggregates seems to be independent of the applied cooling rate.

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Section: Introductionmentioning

confidence: 86%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Transient and athermal effects in the crystallization of polymers. II. Nonisothermal crystallization

Sajkiewicz

2002

J Polym Sci B Polym Phys

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Benzene physical and chemical organogels: Effect of network scaffolding on the thermodynamic behavior of entrapped solvent molecules

Markovic¹,

Ginic‐Markovic²,

Dutta³

2004

J of Applied Polymer Sci

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This paper presents a thermodynamic investigation of the benzene physical and chemical organogels, using differential scanning calorimetry (DSC) and intends to draw an appropriate relationship between the gel network structure and the properties. Physical gels, formed by an aluminium soap of fatty acid, and chemical gels, created by in situ cross-linking of a siloxane copolymer are investigated. The effects of the type and quantity of the gelators and their corresponding network mesh size distribution in the gels on crystallization, melting, and their kinetics are examined. It appears that the kinetics of crystallization of the entrapped solvent is significantly affected by the quality of the gel network scaffolding and can be treated successfully by the Avrami equation of crystallization. From the melting behavior of the entrapped solvent crystallites, quantitative information about the number of solvent molecules bound per molecule of the gelator has been extracted. DSC proves to be a reliable technique to evaluate the population distribution of solvent molecules trapped in the physical and chemical organogel network scaffolding. The state of the solvent may be treated as a probe to understand the structure of the gels.

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Nucleation parameter and size distribution of critical nuclei for nonisothermal polymer crystallization: The influence of the cooling rate and filler

Kocic

Lederhofer

Kretschmer

et al. 2014

J of Applied Polymer Sci

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The nucleation parameter K g of filled PP, HDPE, and PA6 is determined through nonisothermal DSC measurements. A novel method is proposed for the determination of the size distribution of critical nuclei, where the most commonly found fraction l Ã peak was obtained as a peak value. The models are tested at different cooling rates and different filler loadings. K g varies up to a certain cooling rate and afterwards remains constant. The introduction of talc in PP and HDPE facilitates nucleation and thus reduces K g . An opposite trend occurs upon the addition of bentonite in PA6. The changes of K g and l Ã peak are reflected on sample morphology, as confirmed with SAXS. The ratio between the final crystal thickness and l Ã peak amounts to approx. 2 and thus agrees well with the one listed in literature. The simple linear correlations of the obtained K g are established with Young's modulus and yield stress.

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Transient and athermal effects in the crystallization of polymers. I. Isothermal crystallization

Cited by 18 publications

References 51 publications

Transient and athermal effects in the crystallization of polymers. II. Nonisothermal crystallization

Transient and athermal effects in the crystallization of polymers. II. Nonisothermal crystallization

Benzene physical and chemical organogels: Effect of network scaffolding on the thermodynamic behavior of entrapped solvent molecules

Nucleation parameter and size distribution of critical nuclei for nonisothermal polymer crystallization: The influence of the cooling rate and filler

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