Flow-induced crystallization of propylene/ethylene random copolymers

Housmans, JW Jan-Willem; Peters, Gwm Gerrit; Meijer, Heh Han

doi:10.1007/s10973-009-0532-3

Cited by 46 publications

(49 citation statements)

References 54 publications

(81 reference statements)

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“…Therefore, the innermost layer of random copolymers (named L3 + 4, see . 35 Accordingly, the lamellar linear growth rate under quiescent conditions decreases with the increase of ethylene content (see the Discussion section). Figure 6 shows a representative series of depth-sectioned WAXD patterns for RACO3.…”

Section: Resultsmentioning

confidence: 93%

“…All three materials have very similar weight-average molecular mass M w ≈ 310 kg/mol and a polydispersity of M w /M n ≈ 3.4, but vary in their ethylene content between 0-7.3 mol %. Their molecular and physical properties 35 are summarized in Table 1. In this study, the homopolymer is denoted as "iPP" while the copolymers are denoted as "RACO3" and "RACO7", according to their respective ethylene content in mol %.…”

Section: Methodsmentioning

confidence: 99%

“…Recent studies found that adding ethylene monomer to the propylene chain can improve transparency, relative softness and low-temperature impact strength. [32][33][34] Also, it has been found that the presence of ethylene monomer along the polypropylene chain disturbs the chain regularity and, consequently, decreases polymer crystallization ability; [34][35][36] e.g., its presence decreases crystallinity and linear growth rate and, moreover, induces the formation of the orthorhombic γ-phase. 36,37 However, the effects above have mostly been studied for quiescent crystallization, or under a rheometric flow 35 unable to impose high shear stresses similar to those typically encountered in industrial processing conditions.…”

Section: Introductionmentioning

confidence: 99%

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High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

Fernandez-Ballester

Cavallo

et al. 2013

Macromolecules

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IntroductionSemicrystalline polymers are usually processed from their molten state and subjected to intense shear and/or elongation flows. Such flow fields not only accelerate crystallization kinetics, which shortens the processing time, but can also change the morphology from isotropic spherulites to highly oriented shish-kebab structures 1-3 and, as a consequence, determine the ultimate product properties. Therefore, understanding the interplay between strong flow fields and the resulting structures is of importance for designing processing procedures to tailor these end product properties.Considerable work [4][5][6][7] has been devoted to this topic in the past half century. Many researchers have focused on the relation between shear flow and polymer crystallization, because shear fields are easily created with rotational 3 or sliding 8,9 plate-plate devices, on rotational rheometers, 10,11 and in pressure driven slit flows. 12,13 These test geometries are typically combined with time-resolved characterization techniques like mechanical spectrometry, 10, 11, 14 light scattering, 15,16 birefringence, 13, 17 X-ray scattering 7,18,19 and Fourier transform infrared (FTIR) spectroscopy, 9, 20, 21 etc. Significant progress has been made in understanding shear-induced crystallization, 4-7 while some of the fundamental issues remain unsolved. In particular, knowledge of basic mechanism of crystallization under high shear rates and stress-close to realistic processing conditions-is still limited. The need for such information is becoming urgent in order to improve the latest simulation models, since the results of numerical predictions of, for example, injection molding, 22 have to be validated and further refined from experimental evidence.Imposing a strong shear flow at chosen high shear rates or stresses under well-defined conditions requires a specially designed flow device. Both the pressure-driven slit flow apparatus constructed by Janeschitz-Kriegl et al. 12 and improved by Kornfield et al.,13 and the piston-driven slit rheometer developed by Mackley et al. 23 and modified by Peters and coworkers, 24,25 can operate in the high stress region (of the order of 0.1 MPa) and are easily combined with time-resolved birefringence 24,26 and/or X-ray scattering [27][28][29][30] AbstractCrystallization of an isotactic polypropylene (iPP) homopolymer and two propylene/ethylene random copolymers (RACO), induced by high-stress shear, was studied using in situ synchrotron wide-angle X-ray diffraction (WAXD) at 137 °C. The "depth sectioning" method (Fernandez-Ballester, Journal of Rheology 53:5 (2009), pp. 1229−1254) was applied in order to isolate the contributions of different layers in the stress gradient direction and to relate specific structural evolution to the corresponding local stress. This approach gives quantitative results in terms of the specific length of fibrillar nuclei as a function of the applied stress. As expected, crystallization becomes faster with increasing stress-from the inner to the outer layer-for...

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Section: Resultsmentioning

confidence: 93%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

Fernandez-Ballester

Cavallo

et al. 2013

Macromolecules

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“…A great effort1, 7, 21–29 has been made to study the role of higher molecular weight or longer molecular chains in the shear induced crystallization of polymers, and has suggested that the longer molecular chains can greatly accelerate the formation of shish‐kebab structures under shear. More recently, Kimata et al,30 Housmans et al31 and Zhao and coworkers32, 33 suggested that the shish structure consists of both long‐ and short molecular chains. According to our results, we suggest that the thread‐like crystal comes from the numerous stable nuclei that align tightly in the direction of shear.…”

Section: Resultsmentioning

confidence: 99%

Effect of molecular weight on crystallization of semirigid poly(phenylene sulfide) under shear flow

Zhang

2011

J of Applied Polymer Sci

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Isothermal crystallization of poly(phenylene sulfide) with three molecular weights (M w ¼ 22k, 48k, and 52k, respectively) under shear condition has been investigated. It appears that shear can induce all these three PPS samples to form a thread-like crystal structure which consists of the numerous stable nuclei that align tightly in the direction of shear. Crystallization kinetics of PPS has been greatly influenced by shear flow. Higher shear rate and long shear time can lead to decrease of spherulite growth rate of PPS. Also, the spherulite growth rate of PPS is affected by supercoolings and molecular weight. For the lower molecular weight (M w ¼ 22k), the spherulite growth rate is independent on the shear rate and shear time; while for the higher ones (M w ¼ 48k and 52k), with the increasing of shear rate, the spherulite growth rate of PPS increases to reach maximum at first, and then decreases. The lower the crystallization temperature is, the more the spherulite growth rate changes, showing that higher orientation of molecular chains can be obtained more easily with increased supercooling. A model has been proposed to explain the mechanism of thread-like crystal formation under shear flow.

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“…[134,135] More recently, Pantani et al studied the kinetics of crystallizing polymers under flow conditions using Rheo-Microscopy. [136][137][138] Further studies were carried out by Koscher and Fulchiron [139] and Housmans et al [140] who aimed for experimental evidence to validate theoretical models of flowinduced crystallization.…”

Section: Rheo-microscopymentioning

confidence: 99%

Polymer Crystallization Studied by Hyphenated Rheology Techniques: Rheo‐NMR, Rheo‐SAXS, and Rheo‐Microscopy

Räntzsch

Özen

Ratzsch

et al. 2018

Macro Materials & Eng

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Rheological set‐ups with in situ analytical sensors, combine information on the flow and deformation behavior of soft matter, with simultaneous insights into structural and dynamic features. Furthermore, they permit the study of soft matter under well‐defined flow conditions. Herein are presented hyphenations of rheology and nuclear magnetic resonance (NMR), small angle X‐ray scattering (SAXS), and optical microscopy. They are employed to unravel relationships between the molecular dynamics, morphology, and rheology of crystallizing polymers. The results confirm a physical gelation process during polymer crystallization, mediated by the interaction of growing superstructures at volume fractions of 10–15%. The buildup of row‐nucleated structures during flow‐induced crystallization is found to reduce the time of gelation as detected by the rheological response. These investigations help to clarify the crystallization mechanism, structure–property relationships, and the hardening behavior of crystallizing polymers.

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Flow-induced crystallization of propylene/ethylene random copolymers

Cited by 46 publications

References 54 publications

High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

High-Stress Shear-Induced Crystallization in Isotactic Polypropylene and Propylene/Ethylene Random Copolymers

Effect of molecular weight on crystallization of semirigid poly(phenylene sulfide) under shear flow

Polymer Crystallization Studied by Hyphenated Rheology Techniques: Rheo‐NMR, Rheo‐SAXS, and Rheo‐Microscopy

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