Non-isothermal Crystallization of Semi-Crystalline Polymers: The Influence of Cooling Rate and Pressure

Drongelen, van M Martin; Roozemond, PC Peter; Peters, Gwm Gerrit

doi:10.1007/12_2015_344

Cited by 4 publications

(12 citation statements)

References 102 publications

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“…This demonstrates an advantage of our fluorescence technique over conventional DSC, that is, this fluorescence technique is capable of monitoring nonisothermal crystallization at faster cooling rates that are more relevant to the industrial polymer processing (e.g., injection molding, film blowing, and fiber spinning) conditions. [ 4 ]…”

Section: Resultsmentioning

confidence: 99%

“…It has been well established in the literature that the crystallinity attainable during nonisothermal crystallization typically decreases with increasing cooling rate. [ 4 ] As the crystallinity increases in the CN‐PLLA matrix, the rigidity or density of the local environment that surrounds the CN4OH dye labels is enhanced; and thus, the intramolecular motions (e.g., rotation) of these AIE luminogens are restricted by the neighboring crystals formed, which in turn promotes the radiative fluorescence emission. [ 42 ] A more detailed discussion on the correlation between the degree of crystallinity and fluorescence behavior will be provided in Section 3.1.3 below.…”

Section: Resultsmentioning

confidence: 99%

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Crystallization Behavior of Semicrystalline Polymers Characterized by an In Situ Fluorescence Technique and its Sensing Mechanism

Nile,

Feng,

Cabello

et al. 2023

Macro Chemistry & Physics

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In this study, fluorescence spectroscopy is used to study the bulk nonisothermal and isothermal crystallization of poly(L‐lactic acid) (PLLA) by monitoring in situ the temperature (T)‐ and time (t)‐dependent fluorescence intensity of the fluorophores incorporated into the PLLA matrix, respectively. The crystallization behavior characterized by fluorescence resemble those measured by conventional differential scanning calorimetry, confirming the validity of this fluorescence technique for sensing crystallization. Combined in‐situ fluorescence results and ex‐situ X‐ray diffraction characterizations demonstrate that this fluorescence technique shows great sensitivity not only to the degree of crystallinity but also to the crystalline microstructures formed during crystallization (e.g., α versus α' form PLLA crystals). Moreover, complementary fluorescence microscopy to this technique help reveal the intrinsic crystallization sensing mechanism: As crystals form during crystallization, the bulky fluorescent probes excluded from the crystalline regions reside in the rigid/mobile amorphous (i.e., non‐crystalline) regions of the resulting semicrystalline matrix, and their intramolecular motions are restricted by the neighboring crystalline domains and thus their fluorescence intensity is greatly enhanced upon crystallization. Because of its high sensitivity, fluorescence is powerful for studying the crystallization behavior of ultrathin polymer films (e.g., 75 nm) and elucidating confinement and interfacial effects through future studies.This article is protected by copyright. All rights reserved

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Crystallization Behavior of Semicrystalline Polymers Characterized by an In Situ Fluorescence Technique and its Sensing Mechanism

Nile,

Feng,

Cabello

et al. 2023

Macro Chemistry & Physics

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“…Investigations by Assmussen [33,34] showed that the compressibility decreases with the degree of branching of the polymers due to the hindered crystallization. Investigations by Drongelen et al [29] on iPP homopolymers at pressures of 5 and 25 MPa and cooling rates of 0.1 to 2.0 K/s showed that the formation of αand γ-phases always occurs combined with the γ-phase being formed preferentially at high pressures and decreasing cooling rates, as also described elsewhere [31,35,36]. In summary, for the formation of the crystalline phase in iPP, this means that the mesophase is preferentially formed at high cooling rates and low pressures, the α-phase at low cooling rates and low pressure, and the γ-phase at low cooling rates and high pressure.…”

Section: Introductionmentioning

confidence: 96%

“…Further studies focused on the effect of pressure on the crystallization [28][29][30][31][32]. Investigations by Assmussen [33,34] showed that the compressibility decreases with the degree of branching of the polymers due to the hindered crystallization.…”

Section: Introductionmentioning

confidence: 99%

Pressure- and Temperature-Dependent Crystallization Kinetics of Isotactic Polypropylene under Process Relevant Conditions

et al. 2021

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In this study, a non-nucleated homopolymer (HP) and random copolymer (RACO), as well as a nucleated HP and heterophasic copolymer (HECO) were investigated regarding their crystallization kinetics. Using pvT-measurements and fast scanning chip calorimetry (FSC), the crystallization behavior was analyzed as a function of pressure, cooling rate and temperature. It is shown that pressure and cooling rate have an opposite influence on the crystallization temperature of the materials. Furthermore, the addition of nucleating agents to the material has a significant effect on the maximum cooling rate at which the formation of α-crystals is still possible. The non-nucleated HP and RACO materials show significant differences that can be related to the sterically hindering effect of the comonomer units of RACO on crystallization, while the nucleated materials HP and HECO show similar crystallization kinetics despite their different structures. The pressure-dependent shift factor of the crystallization temperature is independent of the material. The results contribute to the description of the relationship between the crystallization kinetics of the material and the process parameters influencing the injection-molding induced morphology. This is required to realize process control in injection molding in order to produce pre-defined morphologies and to design material properties.

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“…There are numerous papers devoted to the modeling and the analysis of the crystallization kinetics [24][25][26][27][28][29][30][31][32][33][34][35], most of which are based on the Avrami-type models [36][37][38][39] under isothermal condition, or on Nakamura and Ozawa's equation for nonisothermal crystallization [40][41][42]. Specifically, the modified factors related to mechanical properties [24][25][26][27] have also included the effect of flow on the crystallization. The influence of the temperature gradient [29] and the confined volume [31][32][33][43][44][45][46] on the crystallization have also been further discussed.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of the relationship between the spherulitic microstructure and isothermal crystallization kinetics. Part I. 2-D analyses

Detrez

Roland

2019

Polymer

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In this paper, we proposed a numerical model to study the kinetic properties and the spherulite microstructure of a semi-crystalline polymer under isothermal crystallization, which further exhibits the potential in generating the 2D spherulitic structure according to the observations obtained by experimental techniques. Two characteristic parameters are introduced, namely, characteristic length L c and characteristic time t c , which are dependent on the growth rate, G and the nucleation rate, I. In addition, two non-dimensional parameters are introduced to model the nucleation saturation: L L / d c and t t / c , which is related to the thickness of nucleation exclusion zone L d , and the effective nucleation time t , respectively. In 2D modeling, the kinetics are confirmed by Avrami fitting, and the effects of the four characteristic parameters on the Avrami parameter n and the crystallization half-time t 0.5 are presented. The regularity of how the spherulite density or the mean radius of spherulites R change along with these parameters are also given, respectively. It shows that L c is the prominent parameter for the size of the spherulite, and t c controls t 0.5 as long as there is no nucleation saturation (= L 0 d and t). Besides, the existence of the nucleation saturation increases the mean radius of spherulites, but decreases n from 3 to 2 in 2-D modeling. Finally, a relationship between crystallization kinetics and microstructures is provided, giving a new perspective to estimate the nucleation rate.

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Non-isothermal Crystallization of Semi-Crystalline Polymers: The Influence of Cooling Rate and Pressure

Cited by 4 publications

References 102 publications

Crystallization Behavior of Semicrystalline Polymers Characterized by an In Situ Fluorescence Technique and its Sensing Mechanism

Crystallization Behavior of Semicrystalline Polymers Characterized by an In Situ Fluorescence Technique and its Sensing Mechanism

Pressure- and Temperature-Dependent Crystallization Kinetics of Isotactic Polypropylene under Process Relevant Conditions

Numerical study of the relationship between the spherulitic microstructure and isothermal crystallization kinetics. Part I. 2-D analyses

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