Melting points of homogeneous random copolymers of ethylene and 1‐alkenes

Clas, S.‐D.; McFaddin, Douglas; Russell, K. E.; Scammell-Bullock, M. V.; Peat, I. R.

doi:10.1002/pola.1987.080251114

Cited by 48 publications

(30 citation statements)

References 10 publications

(2 reference statements)

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“…An EP eopolymer with a density of 896 kg m -3 (about 89 mol% ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [wC (7)] calculated from these reflections using the two-phase model was in good agreement with we(T) calculated from Cp measurements using DSC. The Cp measurements also enabled calculation of the baseline Cp and the excess Cp.…”

Section: Introductionmentioning

confidence: 84%

“…This means that in the case of ethylene-propylene copolymers the relationship between e.g. crystallization/ melting temperature and comonomer content will not be the same as in the case of ethylene-octene copolymers [5,7].…”

Section: Homogeneous Copolymersmentioning

confidence: 99%

“…In ethylene copolymers the microchain structure is also important [1,4,5]. First of all, the type of comonomer is an important variable [6][7][8][9][10]. Another important parameter when it comes to properties is the amount of comonomer incorporated into the chain.…”

Section: --4466/96/$ 5 O0 9 1996 Akaddmiai Kiadd Budapest John mentioning

confidence: 99%

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Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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Ethylene-propylene (EP) and ethylene-octene (EO) copolymers polymerized with the aid of homogeneous vanadium and metallocene catalysts were compared by DSC and time-resolved simultaneous SAXS-WAXS-DSC at scanning rates of 10 and 20~ rain -1 using synchrotron radiation. An EP eopolymer with a density of 896 kg m -3 (about 89 mol% ethylene) after compression moulding gave orthorhombic WAXS reflections. The crystallinity as a function of temperature [wC(7)] calculated from these reflections using the two-phase model was in good agreement with we(T) calculated from Cp measurements using DSC. The Cp measurements also enabled calculation of the baseline Cp and the excess Cp. The SAXS measurements revealed a strong change in the long period in cooling and in heating. The SAXS invariant as a function of temperature showed a maximum in both cooling and heating, which could be explained from the opposing influences of the crystallinity and the electron density difference between the two phases. Two EO eopolymers with densities of about 871 kg m -3 (about 87 mol% ethylene) no longer showed any clear WAXS reflections, although DSC and SAXS measurements showed that these eopolymers did crystallize. The similarity between the results led to the conclusion that the copolymers, though based on different catalyst systems -vanadium and metallocene -did not have strongly different sets of propagation probabilities of chain growth during polymerization. On the basis of a Monte Carlo simulation model of crystallization and morphology, based on detailed knowledge of the mierochain structure, the difference between WAXS on the one hand and DSC and SAXS on the other could be explained as being due to loosely packed cryz,tallized ethylene sequences in clusters. These do cause the density and the electron density of the cluster to increase (which is measurable by SAXS) and the enthalpy to decrease (which is measurable by DSC) but the clusters are too small and/or too imperfect to give constructive interference in the case of WAXS. Of an EP copolymer with an even lower ethylene content (about 69 mol%), the crystallization and melting processes could still be readily measured by DSC and SAXS, which proves that these techniques are eminently suitable for investigating the crystallization and melting behaviour of the copolymers studied.

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Section: Introductionmentioning

confidence: 84%

Section: Homogeneous Copolymersmentioning

confidence: 99%

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Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Mathot

Scherrenberg

Pijpers

et al. 1996

Journal of Thermal Analysis

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“…Copolymers of ethylene with an a-olefin obtained with single-site vanadium based [1][2][3][4] or metallocene catalysts [5] are characterized by a relatively narrow molar mass distribution and a homogeneous inter-and intramolecular distribution of comonomer units [6][7][8]. Copolymerization with fairly bulky a-olefin monomers like 1-octene results in hexyl branches that are excluded from the crystals, lowering the crystallinity and hence the physical density [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Characterization of the dual crystal population in an isothermally crystallized homogeneous ethylene-1-octene copolymer

Rabiej

Goderis

Janicki

et al. 2004

Polymer

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“…[27] The DSC-measurements show slightly lower melting and glass transition points for the copolymer as is described in the literature, this is probably due to the particular microstructure of the copolymer obtained. [60,61] A closer insight into the microstructure of the copolymer is possible by 13 C NMR. In the spectrum of the hydrated polybutadiene (see Fig.…”

Section: Microstructurementioning

confidence: 99%

Gas-phase polymerization of 1,3-butadiene with supported half-sandwich-titanium-complexes

Kaminsky¹,

Strübel

2000

Macromol. Chem. Phys.

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Using half‐sandwich‐titanium‐complexes polybutadiene (BR) can be produced with a particular microstructure of about 81% cis, 18% 1,2, and 1% trans units. A stirred bed reactor and a fluidized bed reactor were constructed for gas‐phase polymerization of 1,3‐butadiene by cyclopentadienyltrichlorotitanium (CpTiCl3) on MAO (methylaluminoxane) impregnated silica (MAO/SiO2). The major determinant of polymerization activity and molecular weight is the AlMAO/Ti‐ratio on the carrier. Polymerization activity increases to 14 500 kg BR/(mol Ti*h) with a molecular weight of 1.9×106 g/mol and the catalyst becomes noticeably more stable. Activity further increases when the CpTiCl3 catalyst is prealkylated with small quantities of TIBA (triisobutylaluminium). Systematic methodological experimentation of the heterogenization suggests that a Ti(III)‐species is responsible for polymerization. The gas‐phase polymerization of 1,3‐butadiene reveals a rate of polymerization which is considerably greater than the equivalent rate in the homogeneous system. The polymers all have similar characteristics, pointing to the same active species. The microstructure of the polybutadiene produced was investigated by spectroscopic measurements and by hydration; a preference to block structures of 1,2‐units could not be established.

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Melting points of homogeneous random copolymers of ethylene and 1‐alkenes

Cited by 48 publications

References 10 publications

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Dynamic DSC, SAXS and WAXS on homogeneous ethylene-propylene and ethylene-octene copolymers with high comonomer contents

Characterization of the dual crystal population in an isothermally crystallized homogeneous ethylene-1-octene copolymer

Gas-phase polymerization of 1,3-butadiene with supported half-sandwich-titanium-complexes

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