Continuous Cooling Curves Diagrams of Propene/Ethylene Random Copolymers. The Role of Ethylene Counits in Mesophase Development

Cavallo, Dario; Azzurri, Fiorenza; Floris, Roberto; Alfonso, Giovanni Carlo; Balzano, Luigi; Peters, Gwm Gerrit

doi:10.1021/ma902865e

Cited by 75 publications

(82 citation statements)

References 53 publications

(145 reference statements)

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“…is defined as the difference between the equilibrium melting temperature, T m = 195°C for iPP [36], and the shear temperature, T γ̇. The dependence of the melting temperature from the pressure was taken in account according to the well known Clapeyron equation [37]:…”

Section: Extended Dilatometrymentioning

confidence: 99%

Application of a multi-phase multi-morphology crystallization model to isotactic polypropylenes with different molecular weight distributions

Troisi

Arntz

Roozemond

et al. 2017

European Polymer Journal

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A B S T R A C TFlow-induced crystallization at elevated pressure of a set of metallocene isotactic polypropylenes (iPP) possessing different molecular weight distributions is studied using extended dilatometry experiments in an apparatus able to apply elevated pressure (up to 1200 bar) and strong shear flow (shear rates up to 180 s −1 ). The effect of flow on the crystallization temperature was quantified and the samples were analyzed using X-ray diffraction to measure the relative amounts of different crystal phases.The experimental results were used to test a flow induced crystallization model framework recently developed in our group which can describe the complex crystallization behavior of iPP and includes formation of multiple morphologies (spherulites, shish-kebab structure with lamellar branching) and crystal phases (α β , and γ ). Almost all model parameters were left unchanged, except for the temperature description of the quiescent crystal growth rate and nucleation density (experimentally measured using optical microscopy) and an extra parameter which takes into account the fraction of high molecular weight for the creation of flow-induced nuclei.The model describes rather good the experimentally observed trends for what regards crystallization temperature and amount of α and γ -phase but substantial discrepancies were found in the amount of β-phase formed. This could be related to the presence of 2,1 insertion errors in metallocene samples which could inhibit the formation of this crystal phase.

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Section: Extended Dilatometrymentioning

confidence: 99%

Application of a multi-phase multi-morphology crystallization model to isotactic polypropylenes with different molecular weight distributions

Troisi

Arntz

Roozemond

et al. 2017

European Polymer Journal

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“…Isotactic polypropylene (iPP) also shows such a bimodal behavior on cooling from the melt [5,10,[12][13][14]. By the same token, the heterogeneous and homogeneous nucleation mechanisms are dominant in the higher and lower temperature regions, respectively.…”

Section: Introductionmentioning

confidence: 99%

Vitrification and crystallization of poly(butylene-2,6-naphthalate)

et al. 2015

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A B S T R A C TThe differential fast scanning calorimetry (DFSC) technique has been successfully applied to study the vitrification and crystallization of poly(butylene-2,6-naphthalate) (PBN). The cooling rate larger than 6000 K/s could make the PBN vitrify and the cooling rate larger than 30,000 K/s reduced effectively the development of the active nuclei. The critical cooling rate of 30,000 K/s is three times as large as that of the recently reported poly(e-caprolactone) (PCL)'s. Namely, it turned out that PBN is a hard-to-vitrify polymer. The heating rate faster than 7000 K/s could prevent the cold crystallization from the proper glassy state. In the less severe cooling and heating rates than 30,000 K/s and 7000 K/s, respectively, a variety of structure formations, such as the nucleation, the mesophase formation, the crystallization and their multiple melting behaviors, have been observed.

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“…An analogous behavior was found by us for propene/ethylene copolymers. 30 This effect can easily be justified by considering the influence of copolymer composition on the crystallization kinetics of the monoclinic form. Indeed, it is well accepted that any type of counit acts as a defect hindering crystallization.…”

mentioning

confidence: 99%

“…Polymer films around 250-300 μm thick, with a chromelalumel μ-thermocouple embedded in the midplane, were prepared according to the procedure earlier described. 30 The films were confined by 20 μm thick aluminum foil tightly wrapped around them; this enabled efficient thermal exchange and low X-ray absorbance. Fast cooling experiments were performed in a home-built quenching device.…”

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confidence: 99%

Real-Time WAXD Detection of Mesophase Development during Quenching of Propene/Ethylene Copolymers

et al. 2010

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Mesomorphic Phase in Isotactic Polypropylene. Synthetic semicrystalline polymers are generally characterized by a certain amount of disorder along the chains due to defects in the chemical constitution, in the configuration of neighboring repeating units, or in the conformation of a portion of molecule in the solid state. 1 When the polymer crystallizes under certain conditions, all these defects may hinder the packing of the chains, leading to a large amount of structural disorder. The definition of a crystalline unit cell becomes problematic when the degree of disorder is particularly high, and a structure with features intermediate between those of the crystalline and amorphous states is obtained. 2 This solid phase is usually referred to as "mesomorphic form" or "solid mesophase", and it is rather frequently encountered in semicrystalline polymers. 3,4 Because of its industrial relevance, the mesophase of isotactic polypropylene (i-PP), which is easily obtained by quenching the molten polymer, has been extensively investigated. 5-18 Its structure is consistent both with the presence of small bundles of parallel chains in 3/1 helical conformation, with short-range lateral order, 5 and with a conformationally disordered glass, characterized by defects in the handedness of the helices. 6 The typical features of i-PP mesomorphic structure are reflected by its macroscopic properties, e.g., density, 7 intrinsic birefringence, 8 and elastic modulus, 9 which lay between those of the amorphous state and of the monoclinic structure. Formation and thermal stability of the i-PP mesophase have been investigated in detail. [10][11][12][13][14][15][16][17][18] The mesomorphic structure is metastable, and on heating between 40 and 80°C, it undergoes a transformation into the thermodynamically stable crystalline R-form. [10][11][12][13][14] The formation of the mesophase has been extensively studied by Piccarolo et al. [15][16][17][18] For the i-PP homopolymers, they demonstrated that a competition between formation of crystalline and mesomorphic order sets in on increasing cooling rate, and eventually, the latter prevails above ca. 100°C/s. Associated with the development of the different structures, profound changes in the morphology have been reported. The typical cross-hatched lamellae of the R-form spherulites are replaced in the semimesomorphic samples by small nodular morphologies lacking of any superstructure. [15][16][17][18] Kinetic Aspects of Mesophase Crystallization. The kinetic aspects governing the development of the mesomorphic form are less understood, mainly because most of the information is obtained by ex-situ investigation of quenched samples. Formation of mesomorphic phases in semicrystalline polymers takes place only at very high undercooling, which are difficult to attain for a polymer exhibiting relatively high maximum crystallization rate as i-PP. One possibility to circumvent this problem is the cold crystallization of amorphous thin films ultraquenched below the glass transition. Isothermal crystal...

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Continuous Cooling Curves Diagrams of Propene/Ethylene Random Copolymers. The Role of Ethylene Counits in Mesophase Development

Cited by 75 publications

References 53 publications

Application of a multi-phase multi-morphology crystallization model to isotactic polypropylenes with different molecular weight distributions

Application of a multi-phase multi-morphology crystallization model to isotactic polypropylenes with different molecular weight distributions

Vitrification and crystallization of poly(butylene-2,6-naphthalate)

Real-Time WAXD Detection of Mesophase Development during Quenching of Propene/Ethylene Copolymers

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