Shear flow effects on polymer melts crystallization: kinetics features

Bove, L.; Nobile, Maria Rossella

doi:10.1002/1521-3900(200203)180:1<169::aid-masy169>3.0.co;2-a

Cited by 19 publications

(14 citation statements)

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“…However, as reported by Bonnet et al8 for a DGEBA/MCDEA system with a low PEI concentration showing a particulate structure, RIPS from an epoxy matrix was followed by a rapid decrease of η* instead of the increase that takes place for sPS–(DGEBA/MCDEA) mixtures. Additionally, it is well known that during the isothermal crystallization of semicrystalline thermoplastics, η* increases when crystallization starts,24–27 and this confirms CIPS in the sPS–(DGEBA/MCDEA) system.…”

Section: Resultssupporting

confidence: 56%

Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

Tercjak

Serrano

Remiro

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:The rheological behavior of thermosetting epoxy mixtures modified with thermoplastic syndiotactic polystyrene (sPS) was monitored during the curing of the epoxy resin. The selected thermosetting system was diglycidyl ether of bisphenol A cured with 4,4Ј-methylene bis(3-chloro-2,6-diethylaniline) in the presence of various compositions of sPS (from 2.5 to 12.5 wt %). The storage and loss shear moduli of the systems were monitored during network formation. The validity of the Winter-Chambon criterion for the accurate determination at the gelation point from rheological data was demonstrated. The influence of the sPS concentration on the dynamic rheological properties of the samples was investigated. The experimental data showed that at sPS concentrations lower than 7.5 wt %, phase separation induced a quick increase in the viscosity, which was related to a crystallization-induced phase separation of sPS. For sPS concentrations higher than 7.5 wt %, near the phase-inversion composition, the rheological behavior of the mixtures was characteristic of a cocontinuous structure. After the viscosity jumped at the onset of phase separation, a decrease in the viscosity was found, and later on, the viscosity increased again because of gelation. Additionally, the influence of the cure temperature on the rheological properties was studied.

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Section: Resultssupporting

confidence: 56%

Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

Tercjak

Serrano

Remiro

et al. 2006

J of Applied Polymer Sci

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“…The molecular weight distribution was determined by a size exclusion chromatography, with weight‐average molar mass

{\overset{true‾}{M}}_{normalw}

of 376 kg mol −1 , polydispersity index

{\overset{true‾}{M}}_{normalw} / {\overset{true‾}{M}}_{normaln}

of 6.7, and a meso pentads content 87.6%. The peculiar characteristic of the material is that the rheology and the crystallization kinetics of the same resin was the focus of several studies …”

Section: Methodsmentioning

confidence: 99%

“…The peculiar characteristic of the material is that the rheology and the crystallization kinetics of the same resin was the focus of several studies. [4,9,[11][12][13][14][15][16][17][18]…”

Section: Methodsmentioning

confidence: 99%

Evolution of iPP Relaxation Spectrum during Crystallization

Pantani

Speranza

Titomanlio

2014

Macro Theory & Simulations

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The linear viscoelastic response, usually described through the moduli G′(ω) and G″(ω), is widely employed to investigate the material properties because it is strictly related to the microstructure of thermoplastics. In a semi-crystalline polymeric material both the amount (degree of crystallinity) and the morphology of the crystalline phase strongly influence the polymer rheological behavior. In order to obtain information about the effect of crystallinity on the linear viscoelastic functions, the parameters of the linear multi-mode Maxwell equation have been determined by fitting literature data of G′(ω) and G″(ω) collected at different crystallinity degrees. The analysis of the resulting spectra, at least in the considered frequency and crystallinity range, clearly shows that the relaxation times of all modes increase with crystallinity in the same way. On the other hand, the parameters Gi of faster modes do not depend upon the crystallinity, whereas the parameters Gi increase with crystallinity only for the slowest modes. These results are very relevant to the rheology evolution during solidification: it is not sufficient to analyze only one viscoelastic function during crystallization, the relaxation time for instance; also the moduli change, and their increase seems concentrated to the modes having the largest relaxation times

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“…Crystallization of polymers has been a subject of continuous study since researchers realized its importance to industrial processing several decades ago 1. In the past ten years, most studies have focused on flow‐induced crystallization (FIC)2–5 of polymers. The main reason is that FIC is an important experimental phenomenon and is usually observed during polymer processing.…”

Section: Introductionmentioning

confidence: 99%

Modeling of flow‐induced crystallization in blends of isotactic polypropylene and poly(ethylene‐co‐octene)

Zhang

et al. 2012

Polymer International

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Poly(ethylene-co-octene) (PEOc) has been shown to provide a high toughening contribution to isotactic polypropylene (iPP). The theoretical modeling of flow-induced crystallization (FIC) of blends of iPP and PEOc is not much reported in the literature. The aim of the present work is to clarify the FIC of iPP upon addition of PEOc in terms of theoretical modeling. The crystallization of iPP and PEOc blends in flow is simulated by a modified FIC model based on the conformation tensor theory. Two kinds of flow fields, shear flow and elongational flow, are considered in the prediction to analyze the influence of flow field on the crystallization kinetics of the polymer. The simulation results show that the elongation flow is much more effective than shear flow in reducing the dimensionless induction time of polymer crystallization. In addition, the induction time of crystallization in the blends is sensitive to the change of shear rate. In comparison with experimental data, the modified model shows its validity for the prediction of the induction time of crystallization of iPP in the blends. Moreover, the simulated relaxation time for the blends becomes longer with increasing percentage of PEOc in the blends.

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Shear flow effects on polymer melts crystallization: kinetics features

Cited by 19 publications

References 0 publications

Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

Evolution of iPP Relaxation Spectrum during Crystallization

Modeling of flow‐induced crystallization in blends of isotactic polypropylene and poly(ethylene‐co‐octene)

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