A Phenomenological Model for Flow-Induced Crystallization

Dairanieh, Issam S.; McHugh, A. J.; Doufas, Antonios K.

doi:10.1177/073168449901800506

Cited by 7 publications

(11 citation statements)

References 6 publications

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“…Dairanieh et al16 thought that the polymer crystallizing system was composed of two phases, the amorphous phase and the crystalline phase. Under isothermal condition, as the molecular chains crystallized, some of the polymer chains were transferred from the amorphous to the crystalline phase.…”

Section: Experiments and Theorymentioning

confidence: 99%

“…δ is the unite tensor, u is the velocity, λ a is the relaxation time of the amorphous phase, λ a ϕ is a characteristic time, superscript q represents a quiescent condition. f is considered to be16, 19: where k is crystallization kinetics constant, m is the Avrami index, ϕ ∞ is the maximum of crystallinity, and λ ϕ is a characteristic time for crystallization.…”

Section: Experiments and Theorymentioning

confidence: 99%

“…In recent years, a macroscopic, continuum approach was proposed by Dairanieh et al,16–19 in which the amorphous phase in the melt was described as an ensemble of dumbbells and the crystallites were treated as rigid rods. It has been shown that the model is capable of predicting the experimental results of flow birefringence data and the necking phenomenon of the polymer 16–19. Another advantage of the continuum model is that it is able to give the information of two phases, such as the extension of the molecular chain in amorphous and the orientation of crystallinity in crystalline.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, at first we investigated the FIC process of HDPE with rheometry, in which the steady shear flow and preshear flow were performed on the HDPE melts, respectively. Second, mainly according to the previously theoretic work by Doufas et al,19 some characteristic times and dimensionless structural variables involved in the model were supplemented into their continuum model 16. Based on the modifications, a complete dimensionless expression of the continuum model were deduced to predict the whole crystallization kinetics of HDPE in different shear flow fields.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Prediction of the flow‐induced crystallization in high‐density polyethylene by a continuum model

Yu¹,

Zhang²,

Wang³

et al. 2009

J Polym Sci B Polym Phys

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In this work, the isothermal flow-induced crystallization (FIC) of highdensity polyethylene (HDPE) under a simple shear flow was investigated. Two experimental modes, including steady shear and preshear treatment, were performed on the polymer melt. Based on the nonequilibrium thermodynamic theory, the FIC process of HDPE was predicted through the modification of a continuum FIC model. The theoretical predictions of the evolution of both the viscosity in steady shear flow and the complex modulus under preshear treatment were essentially related to the crystallinity of HDPE, in agreement with the experimental findings. Both experimental and predicted results showed that the applied flow field could accelerate the crystallization kinetics of HDPE significantly. However, the effect of the intensity of shear flow on the crystallization of HDPE was finite, showing a saturation phenomenon, namely, the accelerated degree of crystallization tending to level off when the shear rate was large enough. In additional, it was found that the predicted crystallinity of HDPE was very low in induction period either in steady shear flow or by preshear treatment.

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Section: Experiments and Theorymentioning

confidence: 99%

Section: Experiments and Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Prediction of the flow‐induced crystallization in high‐density polyethylene by a continuum model

Yu¹,

Zhang²,

Wang³

et al. 2009

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

show abstract

“…McHugh et al [7 to 9] simulated both low-and high-speed melt spinning in combination with the model based on the formalism of Dairanieh et al [6,34]. They included the combined effects of the flow-induced crystallization, viscoelasticity, filament cooling, air drag, inertia, surface tension and gravity.…”

Section: Introductionmentioning

confidence: 99%

Simulation and Experimental Verification of Crystallization and Birefringence in Melt Spinning of PET

Kim

Isayev

Kwon

2006

International Polymer Processing

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A novel approach for the numerical simulation of the development of crystallinity and birefringence on the spinline was proposed. The approach was based on the calculation of elastic recovery and crystalline and amorphous orientation functions without making any assumption about freezing. To model crystallization, the amorphous orientation function and the flow effect on the equilibrium melting temperature elevation due to the entropy reduction between the oriented and unoriented melts were incorporated. The crystalline orientation function was calculated from the frozen-in elastic recovery. The entropy change and frozen-in elastic recovery calculation were based on a nonlinear viscoelastic constitutive Eq. with the crystallinity and temperature dependent viscosity and relaxation time. The crystalline and amorphous contributions to the overall birefringence were obtained from the crystalline orientation function and the flow birefringence, respectively. The temperature, diameter, density, and birefringence profile in both lowand high-speed spun PET fibers were predicted and compared with the experimental data from literature. Theoretical predictions were found to be in agreement with the published experimental data.

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A comparison of induction time and crystallization rate for syndiotactic polystyrene

Sudduth

Kyarala

Sheng

2002

Polymer Engineering & Sci

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One objective of this study was to measure the crystalkation parameters for syndiotactic polystyrene (M, = 244,000) to support a computer simulation of this material in an injection molding application. A second objective was to introduce a new crystallization rate equation that adequately predicts crystallization rates over a broader temperature range than the Hofhnan-Lauritzen equation. A third objective was to establish a new clearly defined method for determining the true induction time of a semicrystalline polymer as a function of temperature. The new uystallization rate equation introduced in this study has been formulated to give appropriate crystallization rate constants for all the temperatures currently usable with the Hoffinan-Lauritzen equation. In addition, this new equation also predicts appropriate crystallization rate constants outside the range of the Hofhnan-Iauitzen equation from temperatures significantly below the glass transition temperature, Tg. to temperatures sigmficantly above the melting point, T , . Interestingly, the isolation of the true isothermal induction times from apparent induction times in this study nicely mirrored the isothermal crystallization rates at each specific temperature. Both the true induction time and the crystallization rate curves were found to be similarly unsymmetrical as a function of temperature. Also, the temperature at the minimum induction time and the temperature at the peak crystallization rate determined from nonisothermal crystallization rate measurements were found to be nearly identical. Consequently, the results from this study strongly suggest that there is a significant and potentially very useful relationship between induction time analysis and crystallization rate kinetics.

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A Phenomenological Model for Flow-Induced Crystallization

Cited by 7 publications

References 6 publications

Prediction of the flow‐induced crystallization in high‐density polyethylene by a continuum model

Prediction of the flow‐induced crystallization in high‐density polyethylene by a continuum model

Simulation and Experimental Verification of Crystallization and Birefringence in Melt Spinning of PET

A comparison of induction time and crystallization rate for syndiotactic polystyrene

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