High-density polyethylene fractionation with supercritical propane

Britto, L. J. D.; Soares, João B. P.; Penlidis, Alexander; Krukonis, Val J.

doi:10.1002/(sici)1099-0488(19990315)37:6<553::aid-polb7>3.0.co;2-l

Cited by 17 publications

(16 citation statements)

References 11 publications

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“…33,34 With increasing pressure in the fractionation, a systematic increase of the molar mass of the fractions was also observed indicating that the fractionation took place preferentially by molar mass. 33,34 The parent metallocene iPP comprises chains of weight-average molar mass of 204 000 g/mol with the most probable molar mass distribution. From this polymer, seven fractions were isolated with a range in molar mass from 86 000 to 383 000 g/mol and with similar narrow molar mass distributions of 1.3 ( 0.1 in all these fractions.…”

Section: Molecular Fractions From Metallocene Ipp and Z-n Ipp: Fractimentioning

confidence: 99%

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

et al. 2003

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The microstructures of two poly(propylene)s with matched molar masses and overall defect concentrations are inferred from the crystallization behavior of their narrow molar mass fractions. One poly(propylene) was produced with a MgCl2-supported Ziegler-Natta catalyst and the other with a metallocene catalyst. The fractions obtained from the metallocene isotactic poly(propylene) display a range in molar masses but each has the same defect concentration indicating a uniform intermolecular concentration of defects in the parent metallocene isotactic poly(propylene). These fractions provide direct evidence of the "single site" character of the metallocene catalyst. The variations of crystallization rates with molar mass reflect different chain diffusion/transport phenomena that are governed by the remnant entanglement state of the melt during crystallization. The molar mass fractions obtained from the ZN-iPP confirm that the interchain distribution of the nonisotactic content is broad in this polymer. The stereodefects are more concentrated in the low molar mass fractions. Furthermore, the invariance of the linear growth rates among the ZN fractions and the lack of formation of any significant content of the γ polymorph, even in the most defected fraction, is consistent with a nonrandom, blocky intramolecular distribution of defects in the ZN-iPP molecules. In contrast to the growth rates, the overall crystallization rates are a direct function of the primary nucleation density, which varies among the fractions and the unfractionated iPPs. Hence, the measured overall crystallization rates would be correlated with nucleation density and not necessarily with the microstructure of the iPP molecules. The crystallization data are also interpreted in light of results from pentad/heptad distributions predicted by two-state and threestate statistical models. Parameters from the models allow the prediction of sequence distribution curves that could be used to evaluate each of the models as to their consistency with the crystallization rate data.

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Section: Molecular Fractions From Metallocene Ipp and Z-n Ipp: Fractimentioning

confidence: 99%

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

et al. 2003

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“…In a very brief study by Britto et al,3 a comparison was made between the A‐TREF elution temperature profile and diluent DSC melting with trichlorobenzene (TCB) as a diluent for a high‐density polyethylene. Crystallization analysis fractionation (CRYSTAF), which yielded fractionation according to crystallinity similar to A‐TREF, was also compared.…”

Section: Introductionmentioning

confidence: 99%

Correlation of the elution behavior in temperature rising elution fractionation and melting in the solid‐state and in the presence of a diluent of polyethylene copolymers

Mirabella¹

2001

J Polym Sci B Polym Phys

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Compositionally homogeneous poly(ethylene-␣-olefin) random copolymers with 1-butene and 1-hexene comonomers have been studied. The melting of solutioncrystallized specimens of these copolymers in the presence of trichlorobenzene as a diluent with differential scanning calorimetry (DSC) is well correlated with analytical temperature rising elution fractionation (A-TREF) elution temperature profiles. This indicates that the A-TREF experiment is essentially a diluent melting experiment. Furthermore, the correction of the corresponding solid-state melting endotherms of these copolymers with Flory's diluent melting equation yields curves that also correlate very well with the DSC diluent melting curves and the A-TREF elution temperature profiles. Values of , the Flory-Huggins interaction parameter, are determined for these copolymers in trichlorobenzene. decreases as short-chain branching increases. The A-TREF elution temperature profiles of one of these copolymers are the same, within experimental error, for dilute-solution crystallizations of the copolymer performed over an extremely broad time schedule (10 s to 3 days). This indicates the profound effect of the branches, as limiting points of the ethylene sequences, in controlling the crystal thickness distribution, which in turn controls the melting point in the presence of the diluent, or the elution temperature from the A-TREF.

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“…An important advantage of this technique is that large polymer fractions can be obtained without generating hazardous liquid organic solvent waste (Britto et al, 1999b;Folie et al, 1997). Several versions of differential scanning calorimetry (DSC) proposed recently for analyzing polyolefins appear to be complementary to TREF and CRYST AF (Parikh et al, 1993;Starck, 1996).…”

Section: Britto Soares and Penlidismentioning

confidence: 99%

Observations on HDPE Characterization with a Microcalorimeter as a Complementary Tool to TREF and CRYSTAF

Britto

Soares

Penlidis

2000

Polymer Reaction Engineering

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Calorimetric measurements of high-density polyethylene (HDPE) crystallization and dissolution in dilute solution were performed in a microcalorimeter. The results were similar to those obtained from fractionation techniques such as TREF, CITREF and CRYSTAF. This suggests that a microcalorimeter can be used to investigate optimal experimental conditions for those techniques and as an alternative analysis technique for determining polyolefin microstructure.

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High-density polyethylene fractionation with supercritical propane

Cited by 17 publications

References 11 publications

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Correlation of the elution behavior in temperature rising elution fractionation and melting in the solid‐state and in the presence of a diluent of polyethylene copolymers

Observations on HDPE Characterization with a Microcalorimeter as a Complementary Tool to TREF and CRYSTAF

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High-density polyethylene fractionation with supercritical propane

Cited by 17 publications

References 11 publications

Crystallization Rates of Matched Fractions of MgCl2-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Crystallization Rates of Matched Fractions of MgCl2-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Correlation of the elution behavior in temperature rising elution fractionation and melting in the solid‐state and in the presence of a diluent of polyethylene copolymers

Observations on HDPE Characterization with a Microcalorimeter as a Complementary Tool to TREF and CRYSTAF

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Product

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Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure

Crystallization Rates of Matched Fractions of MgCl₂-Supported Ziegler Natta and Metallocene Isotactic Poly(Propylene)s. 1. The Role of Chain Microstructure