Molecular distribution analysis of melt‐crystallized ethylene copolymers

Chen, Fei; Shanks, Robert A.; Amarasinghe, Gandara

doi:10.1002/pi.1583

Cited by 35 publications

(26 citation statements)

References 51 publications

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“…According to ref. [19], at a very slow cooling rate (0.08℃/min), the crystals approach the equilibrium state and form highly ordered crystal. We extrapolate the onset crystallization temperatures obtained at 0.08℃/min rate.…”

Section: Thermal Fractionation With Dscmentioning

confidence: 99%

Investigation on chain structure of LLDPE obtained by ethylene in-situ copolymerization with DSC and XRD

Wang

Yan

2007

CHINESE SCI BULL

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Thermal segregations of LLDPE were treated with successive self-nucleation/annealing (SSA) on differential scanning calorimetry (DSC). Information on molecular heterogeneity of LLDPE was obtained. After SSA was treated, the multiple endothermic peaks were observed in the DSC thermograms during heating experiment. It is obtained that the thickness of different lamellas formed by segments of various lengths was 4-10 nm. X-ray diffraction (XRD) results showed that the crystallites dimensions of various reflections were about several dozens of nanometers. The ethylene/α-olefin copolymers and the copolymer via in-situ copolymerization were similar to each other for molecular heterogeneity and XRD characteristics, which revealed that it was possible to use the ethylene/α-olefin copolymers to simulate the copolymer via in-situ copolymerization of ethylene to simplify the complexity of the structure of the ethylene in-situ copolymer.LLDPE via in-situ copolymerization, ethylene and α-olefin copolymers, thermal segregation, XRD, DSC Linear low density polyethylenes (LLDPE) are commercially important polymers and are produced via copolymerization of ethylene and α-olefins such as 1-butene, 1-hexene, and 1-octene. Their properties are greatly influenced by various factors. The molecular structure of LLDPE has been investigated from different angles, such as the average content of comonomer, the intramolecular comonomer sequence distribution, and the distribution of comonomer among polymer chains, in addition to average molecular weights and molecular weight distribution. Halasz et al. [1] studied a series of ethylene/1-pentene, ethylene/1-hexene, and ethylene/1-octene copolymers and concluded that the melting temperatures and the crystallinity decrease with increasing chain length of the comonomer and the comonomer content. Moreover, they have investigated the crystallization kinetics of these copolymers. By investigating LLDPE resins based on 1-butene, 1-hexene and 1-octene, Gupta et al. [2] studied the effect of short chain length on the mechanical properties, and found that at higher deformation rates (ca. 1 m/s), the breaking strength of these films increased with increasing short chain branch length. Pan et al. [3] investigated the effect of branched structures on the performances of the copolymers synthesized from ethylene and 1-hexene, 1-decene and 1-tetradecene and 1-octadecene, respectively and found that 16-carbon side branch could co-crystallize effectively with backbone chain at low α-olefin incorporation, which is different from Yoon's result [4] .Recently, much attention has been paid to tandem catalysis of LLDPE production, involving the use of a single feed of ethylene and two catalysts. In this process, one catalyst oligomerizes the ethylene to an α-olefin, and the other is responsible for polymerizing the ethylene and incorporating the α-olefin into the growing polymer chain. Many contributions [5][6][7][8][9][10][11][12][13][14] such as the bi-

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Section: Thermal Fractionation With Dscmentioning

confidence: 99%

Investigation on chain structure of LLDPE obtained by ethylene in-situ copolymerization with DSC and XRD

Wang

Yan

2007

CHINESE SCI BULL

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“…Note that in Eqn (25),

T_{normalm}^{0}

is the equilibrium melting temperature of a crystalline homopolymer. For a random copolymer, this should be substituted for the corresponding equilibrium melting temperature

T_{m, copolym}^{0}

, which can be calculated using the Flory model:

\frac{1}{T_{normalm, copolym}^{0}} = \frac{1}{T_{m}^{0}} - \frac{R}{Δ H_{normalu}} \ln X_{normalA}

…”

Section: Mathematical Treatmentmentioning

confidence: 99%

“…The weight‐average lamellar thickness is given by

L_{wav} = \frac{true \sum_{i = 1}^{n} L_{lamella, i} χ_{i} ((), L_{lamella, i + 1} - L_{lamella, i})}{true \sum_{i = 1}^{n} χ_{i} ((), L_{lamella, i + 1} - L_{lamella, i})}

…”

Section: Mathematical Treatmentmentioning

confidence: 99%

Thermal behaviour of polyethylene‐block‐poly(methyl methacrylate) block copolymer: effect of multiple heating and cooling ratesversusmathematical artefact

Atiqullah

Hossain

Adamu

et al. 2014

Polymer International

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“…From the ethylene molar fraction, the MSL and degree of branching can be easily calculated with eqs 6 and 7, 43 or with the data from NMR measurements, it can be used vice versa:…”

Section: Dsc Analysismentioning

confidence: 99%

Thermal and mechanical analysis of metallocene‐catalyzed ethene–α‐olefin copolymers: The influence of the length and number of the crystallizing side chains

Piel

Starck

Seppälä

et al. 2006

J. Polym. Sci. A Polym. Chem.

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Copolymers of ethene and 1-octene, 1-dodecene, 1-octadecene, and 1-hexacosene were carried out with [Ph 2 C(2,7-ditert BuFlu)(Cp)]ZrCl 2 /methylalumoxane as a catalyst to obtain short-chain branched polyethylenes with branch lengths of 6-26 carbon atoms. This catalyst provided high activity and a very good comonomer and hydrogen response. In this study, the influence of the length and number of the side chains on the mechanical properties of the materials was investigated. The crystalline methylene sequence lengths of the copolymers and lamellar thicknesses were calculated after the application of a differential scanning calorimetry/successive self-annealing separation technique. By dynamic mechanical analysis, the storage modulus as an indicator of the stiffness and the loss modulus as a measure of the effect of branching on the a and b relaxations were studied. The results were related to the measurements of the polymer density and tensile strength to determine the effect of longer side chains on the material properties. The hexacosene copolymers had side chains of 24 carbons and remarkable material properties very different from those of conventional linear low-density polyethylenes. The side chains of these copolymers crystallized with one another and not only parallel to the backbone lamellar layer, depending on the hexacosene concentration in the copolymer. The side chains crystallized even at low hexacosene concentrations in the copolymer. A transfer of these results to 16 carbons

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Molecular distribution analysis of melt‐crystallized ethylene copolymers

Cited by 35 publications

References 51 publications

Investigation on chain structure of LLDPE obtained by ethylene in-situ copolymerization with DSC and XRD

Investigation on chain structure of LLDPE obtained by ethylene in-situ copolymerization with DSC and XRD

Thermal behaviour of polyethylene‐block‐poly(methyl methacrylate) block copolymer: effect of multiple heating and cooling ratesversusmathematical artefact

Thermal and mechanical analysis of metallocene‐catalyzed ethene–α‐olefin copolymers: The influence of the length and number of the crystallizing side chains

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