Crystallization and melting behavior of polyethylene fractions obtained by various fractionation methods

Mathot, Vincent; Pijpers, M. F. J.

doi:10.1007/bf00255356

Cited by 46 publications

(10 citation statements)

References 8 publications

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“…It is worthy to noticing that when the branches content is higher than 12%, L and Lc remains essentially unchanged. For copolymers with low comonomer contents, the backbone chain length between branches is an important parameter which has a great influence on crystallization [34][35][36]. In the case of the copolymers with large amount of octene branches, the influence of chain length on crystallization is likely to be weak because the increased friction which reduced mobility and the flexibility of sequences for crystallization has reached a maximum to a certain degree.…”

Section: Resultsmentioning

confidence: 98%

Shear effects on crystallization behavior of poly(ethylene-co-octene) copolymers

Wen

et al. 2011

J Polym Res

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Crystallization behavior of sheared polymer melts of a series of poly(ethylene-co-octene)s with different octene content was investigated by different scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and synchrotron small-angle X-ray scattering (SR-SAXS) techniques. The DSC results indicated that the hexyl branches content had dramatic effects on the thermal properties and crystallinity of polyethylene. It was also found that shear had no obvious effects on the size of either crystallite or lamellae. However, both crystallite and lamellae were oriented by shearing, especially for the lamellae. All obtained results indicate that the initial states of the polymer melt play an important role in affecting the crystallization behaviors. The difference of the shear-induced crystalline structure evolution and the orientation between crystallite and lamellae support the preordered mesomorphic phase of flexible polymer crystallization process proposed by Strobl.

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Section: Resultsmentioning

confidence: 98%

Shear effects on crystallization behavior of poly(ethylene-co-octene) copolymers

Wen

et al. 2011

J Polym Res

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“…Such MW-dependency is well-known in crystallization of synthetic 556 polymers (Mathot & Pijpers, 1984) and is explained by the increased occurrence of 557 entanglements for polymers of higher MW. In addition, these entanglements are part of the 558 amorphous regions, which explains why starches with a higher AM DP have lower V H -type 559 crystallinity.…”

Section: Melting Of Residual Native Crystals 390mentioning

confidence: 98%

V-type crystal formation in starch by aqueous ethanol treatment: The effect of amylose degree of polymerization

et al. 2016

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“…Figure 1 shows that the information about the molecular structure provided by DSC is unambiguous particularly when the DSC curve is multi-peaked, as in the case of linear low density polyethylene, LLDPE, and very low density polyethylene, VLDPE. It will be clear that it takes more than DSC alone to enable a distinction to be made between homogeneous ethylene copolymers on the one hand and heterogeneous polyethylenes such as HDPE and LDPE on the other if they have the same single-peaked DSC curve [33]. In particular a determination of the comonomer content and DSC measurements on fractions obtained via a separation according to molar mass are necessary in such cases I341.…”

Section: Homogeneity and Heterogeneitymentioning

confidence: 99%

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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Crystallization and melting behavior of polyethylene fractions obtained by various fractionation methods

Cited by 46 publications

References 8 publications

Shear effects on crystallization behavior of poly(ethylene-co-octene) copolymers

Shear effects on crystallization behavior of poly(ethylene-co-octene) copolymers

V-type crystal formation in starch by aqueous ethanol treatment: The effect of amylose degree of polymerization

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

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