Determination of Nucleus Density in Semicrystalline Polymers from Nonisothermal Crystallization Curves

Menyhárd, Alfréd; Bredács, Márton; Simon, Gergely; Horváth, Z.

doi:10.1021/acs.macromol.5b00275

Cited by 22 publications

(28 citation statements)

References 41 publications

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“…The results are shown in Figure 7, being in agreement with earlier publications. [ 3,50,51,52 ] This indicates clearly that our approach harmonizes with the trends observed earlier on other real samples and further supports our new model for the description of the light scattering in semicrystalline polymers.…”

Section: Resultssupporting

confidence: 87%

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Modeling of light scattering and haze in semicrystalline polymers

Molnár

Sepsi

Erdei

et al. 2020

Journal of Polymer Science

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This article reports a new model approach for the description of light scattering in semicrystalline polymers, to describe more precisely the influence of supermolecular structure on the optical properties. This is the first study in which light scattering of polymer films has been modeled using exact Mie scattering theory of radially anisotropic spheres. As a model material a well‐known polymer, isotactic polypropylene (iPP) was used. Samples were prepared with different sample thicknesses and crystalline structures in order to identify the key parameters of light scattering in polycrystalline polymeric systems. Validation haze measurements were carried out with a spectrophotometer equipped with a 150 mm snap‐in integrating sphere. It was found that the optical properties of the polycrystalline sample can be described using multiple light scattering on these scattering centers. Good agreement was found between the simulated and experimentally measured haze values which proves the reliability and applicability of our new approach.

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Section: Resultssupporting

confidence: 87%

“…According to earlier studies and our earlier experiences, nucleus density is a very important factor, which influences predominantly the optical properties. [ 4,50 ] It can be seen from the experimental results, that the higher is the crystallization temperature the smaller is the nucleus density.…”

Section: Methodsmentioning

confidence: 99%

Modeling of light scattering and haze in semicrystalline polymers

Molnár

Sepsi

Erdei

et al. 2020

Journal of Polymer Science

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“…[18,19] Nowadays these NAs are used as clarifiers because the nucleus density is very large in their presence. [15,[20][21][22] iPP is a polymorphic polymer, which has four crystalline modifications, namely α-, β-, γ, and the recently discovered ε-forms. [23][24][25][26] Most of the NAs induce the formation of the thermodynamically stable modification of the polymers, thus the majority of NA applied in iPP promote the formation of α-modification.…”

Section: Introductionmentioning

confidence: 99%

“…[ 18,19 ] Nowadays these NAs are used as clarifiers because the nucleus density is very large in their presence. [ 15,20–22 ]…”

Section: Introductionmentioning

confidence: 99%

Self‐organization of micro reinforcements and the rules of crystal formation in polypropylene nucleated by non‐selective nucleating agents with dual nucleating ability

Menyhárd

Molnár

Horváth

et al. 2020

Polymer Crystallization

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This work demonstrates and models the self-organization of mixed polymorps in polymers containing simultaneously growing phases with different growth rates. The model was verified and demonstrated in isotactic polypropylene nucleated by a nonselective nucleating agent. The crystallization and melting processes were studied by calorimetry (DSC) and polarized light microscopy (PLM). The morphology of the samples was investigated using PLM and scanning electron microscopy (SEM). The fundamental rules of the formation of two polymorphic modifications developing simultaneously on the same nucleating particle are introduced. A simple equation is suggested to predict the morphological geometry on the lateral surface of the nucleating agent. The results indicated good agreement between the predicted and observed geometry. The proposed model explains the self-organization of micro-sized reinforcements of α-modification in the matrix of β-iPP. Although the proposed equation was tested for this particular case it is a general equation for all structures in which different polymorphs are growing simultaneously with different growth rates.

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“…Most recent publications deal with crystallization of isotactic polypropylene at high cooling rate and with applied pressure for a wide range of new processing conditions [17,18] that would have not been allowed a few decades ago. Under these novel conditions, it has been also possible to determine the nucleation density from DSC curves [17,19] and the linear growth rates of spherulites at different temperatures [19]. However, as said before, this paper does not directly focuses on the widely explored temperature dependence of the crystallization rate, but rather on the time dependence of the crystallization rate, especially during impingement.…”

Section: Introductionmentioning

confidence: 99%

Growth of spherulites: foundation of the DSC analysis of solidification

Raimo

2015

ChemTexts

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Solidification is a practically and theoretically important issue, since it allows to design experimental conditions for desired material properties and also to discuss basic relationships between thermodynamics, kinetics and morphology. In this article, an overview on the crystallization theory and on the main traditional techniques to determine the crystallization rates, under constant and variable external temperature, is provided. The differences and similarities of isothermal and non-isothermal crystallization mechanisms are highlighted in the framework of the nucleation and growth theory, also by comparisons of the differential scanning calorimetry (DSC) peaks. The origin, broadness and symmetry of DSC peaks are explained in detail by considering the need for heat removal from the solid front and the coalescence of grains that originated in several points of the liquid phase. Although impingement is responsible for the general slowdown of crystallization, it is shown that the growth rate of a spherulite in the initial stage of coalescence continues to increase up to a maximum even if with a rate of change (i.e., a growth ''acceleration'') lower than that before impingement.

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Determination of Nucleus Density in Semicrystalline Polymers from Nonisothermal Crystallization Curves

Cited by 22 publications

References 41 publications

Modeling of light scattering and haze in semicrystalline polymers

Modeling of light scattering and haze in semicrystalline polymers

Self‐organization of micro reinforcements and the rules of crystal formation in polypropylene nucleated by non‐selective nucleating agents with dual nucleating ability

Growth of spherulites: foundation of the DSC analysis of solidification

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