Characterization of commercial linear low-density polyethylene by TREF-DSC and TREF-SEC cross-fractionation

Zhang, Mingqian; Lynch, David T.; Wanke, Sieghard E.

doi:10.1002/(sici)1097-4628(20000214)75:7<960::aid-app13>3.3.co;2-i

Cited by 8 publications

(10 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, the emergence of multiple melting behaviors indicates that the chains with similar longest length of crystallizable sequences can also contain a broad intramolecular D ‐LA distribution. Similar results have been obtained for isotactic PP35 and commercial linear low‐density polyethylene (LLDPE) 51, 52. On the other hand, the intermolecular heterogeneity is evident on the different melting ranges of each fraction.…”

Section: Resultssupporting

confidence: 77%

See 1 more Smart Citation

Stereochemical heterogeneity of biodegradable poly(L‐lactide) homopolymer as revealed by temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

Luo

Huo

Lin

et al. 2012

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

Commercial poly(L‐lactide) is typically heterogeneous in chain structure due to the existence of a small amount of D‐lactyl units that are produced by the racemization reactions during the synthesis. In this article, the stereochemical heterogeneity of two commercial poly(L‐lactide) was investigated with temperature rising elution fractionation (TREF) and successive self‐nucleation/annealing (SSA) thermal fractionation. For both samples, three fractions were collected and characterized with rotatory power analysis and DSC. The fractions show distinct optical purity and DSC results, which reflect the structure differences among them directly. After SSA treatment, the observation of multiple endotherms for each physically separated fraction confirms the fractionated sample contains a heterogeneous intermolecular and intramolecular distribution of defects. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

show abstract

Section: Resultssupporting

confidence: 77%

“…Similar results have been obtained for isotactic PP 35 and commercial linear lowdensity polyethylene (LLDPE). 51,52 On the other hand, the intermolecular heterogeneity is evident on the different melting ranges of each fraction.…”

Section: Successive Self-nucleation/annealing Thermal Fractionationmentioning

confidence: 99%

Stereochemical heterogeneity of biodegradable poly(L‐lactide) homopolymer as revealed by temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

Luo

Huo

Lin

et al. 2012

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

show abstract

“…Rheological and physicomechanical properties of these polymers depend on their molecular‐weight characteristics, comonomer content, and short chain branching (SCB) distribution. Many publications1–12 were devoted to studying ethylene/α‐olefin copolymerization on supported Ziegler catalysts (titanium–magnesium catalysts [TMCs]) and molecular structure of the resulting copolymers. It was shown2, 6–8, 10–13 that the introduction of comonomer usually results in a decrease in molecular weight ( M w ) of the polymer.…”

Section: Introductionmentioning

confidence: 99%

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

Nikolaeva

Matsko

Mikenas

et al. 2012

J of Applied Polymer Sci

View full text Add to dashboard Cite

The data on the effect of comonomer (propylene and 1‐hexene) on molecular weight (Mw), molecular weight distribution (MWD), and content of terminal double bonds were obtained for ethylene/α‐olefin copolymers produced over a supported titanium–magnesium catalyst (TMC) upon polymerization in the absence of hydrogen. The experimental data on the effect of comonomer concentration on Mw of polymers were used to calculate the ratios between the effective rate constants of chain transfer with monomer and the propagation rate constant. It was shown that the effective rate constant of chain transfer with monomers increases in the row of monomers: ethylene < 1‐hexene < propylene. Meanwhile, the data on the effect of copolymers on content of terminal double bonds of various types demonstrate that different reactions of chain transfer with comonomer may simultaneously occur during copolymerization. It results in simultaneous formation of terminal vinylidene and trans‐vinylene bonds. Therefore, the calculated rate constants of chain transfer with comonomer are complex values, which include the rate constants of chain transfer with comonomer occurring via different mechanisms. The data on MWD, short chain branching (SCB) and terminal double bonds content of different types were obtained by molecular weight fractionation of copolymers followed by the analysis of narrow fractions. The analysis of the data on MWDs of SCB and terminal double bonds shows that active sites of the TMC are considerably heterogeneous with respect to the rates of different chain transfer reactions with monomers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

show abstract

“…The SNA [13] experiments were conducted with a Perkin-Elmer Pyris Diamond DSC instrument equipped with an Intracooler III. Nitrogen purge (20 mL/min) was used during the measurements for preventing oxidation of the samples.…”

Section: Successive Nucleation/annealing (Sna)mentioning

confidence: 99%

The effect of modality on linear low-density polyethylene crystallization behaviour at high and very high supercoolings

Märtson

Krumme²,

Gavrilkina³

et al. 2009

Proc. Estonian Acad. Sci.

View full text Add to dashboard Cite

Isothermal crystallization rates of uni-and bimodal linear low density polyethylenes having similar average molar mass and branching content were analysed at various temperatures in a very high supercooling range by means of a novel methodchip nanocalorimetry. At a particular crystallization temperature within the lower range of temperatures the bimodal material crystallized slower than the unimodal one, whereas at moderate supercooling temperatures bimodal polyethylene materials have earlier been reported to crystallize faster. Comparison to a high and moderate range of supercoolings was also made using an inhouse built hot stage polarized light microscopy system. The difference gives evidence of a different crystallization mechanism caused by modality, which can have a strong impact on the application properties of the material.

show abstract

Characterization of commercial linear low-density polyethylene by TREF-DSC and TREF-SEC cross-fractionation

Cited by 8 publications

References 12 publications

Stereochemical heterogeneity of biodegradable poly(L‐lactide) homopolymer as revealed by temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

Stereochemical heterogeneity of biodegradable poly(L‐lactide) homopolymer as revealed by temperature rising elution fractionation and successive self‐nucleation/annealing thermal fractionation

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

The effect of modality on linear low-density polyethylene crystallization behaviour at high and very high supercoolings

Contact Info

Product

Resources

About