Glass transition, crystallinity, resin stiffness, and branch distribution in metallocene and Ziegler-Natta ethylene 1-olefins

Keating, M. Y.; Lee, I-Hwa

doi:10.1080/00222349908212439

Cited by 29 publications

(5 citation statements)

References 22 publications

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“…The Zhang and Keating method was used to quantify comonomer distribution in subsets using SSA data. , The arithmetic mean ( L n ) and weighted mean ( L w ) of lamellae thickness as well as the broadness index values ( L w / L n ) of different particle subsets are listed in Table . Particles in subset C are characterized by a lower L w value and broadness index.…”

Section: Resultsmentioning

confidence: 99%

“…Arithmetic mean ( L n ) and weighted mean ( L w ) lamellae thickness of the subsets were calculated according to the following formulas: , where L n is the arithmetical mean lamellae thickness, L w is the weighted mean lamellae thickness, L i is the lamellae thickness corresponding to i th peak in the SSA curve, and x i is the segment of the i th peak in the SSA curve. Melting enthalpy of each peak in the SSA curve has been determined, and its contribution in total area was calculated to obtain each individual peak segment.…”

Section: Experimental Sectionmentioning

confidence: 99%

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Variation of Comonomer Content in LLDPE Particles with Different Sizes from an Industrial Fluidized Bed Reactor

Rashedi

Sharif

2015

Ind. Eng. Chem. Res.

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Properties of linear low-density polyethylene (LLDPE) are highly influenced by molecular weight distribution and comonomer content. Our study quantifies comonomer content variation for LLDPE particles with different sizes. Powder from the fluidized-bed reactor was sieved to subsets with different sizes. FTIR showed a meaningful difference in average comonomer content among subsets. To study comonomer content distribution in each subset, successive self-nucleation and annealing (SSA) thermal fractionation via differential scanning calorimetry (DSC) was performed. This study showed that each subset not only differs in the average comonomer content but also in comonomer content distribution. Particles with a median diameter of 1500 μm had the highest average comonomer content, which was different from that of the final product. Minimum average comonomer content and narrowest comonomer distribution was observed in the smallest particles with median diameter of 750 μm and high molecular weight.

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Section: Resultsmentioning

confidence: 99%

Section: Experimental Sectionmentioning

confidence: 99%

Variation of Comonomer Content in LLDPE Particles with Different Sizes from an Industrial Fluidized Bed Reactor

Rashedi

Sharif

2015

Ind. Eng. Chem. Res.

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“…10. Storage modulus for mPEs in the temperature range of −50 to 80°C has been attributed to rigidity and stiffness of these materials [10, 27]. That in turn can be related to crystalline and amorphous structure and their connectivity of the samples.…”

Section: Resultsmentioning

confidence: 99%

“…Four metallocene PEs (mPEs), one LDPE, one conventional LLDPE, and one ULDPE (ultra low density PE) were used in this work. They are listed in Table 1 along with corresponding co‐monomer content [10–14]. Attane 4201 is a very low density PE developed by Dow Chemical based on Ziegler–Natta catalyst.…”

Section: Methodsmentioning

confidence: 99%

Rheological, physical, and thermal characterization of single‐site catalyst based polyethylenes for seal layer applications

Sadeghi

Ajji

2011

Polymer Engineering & Sci

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Four single-site metallocene catalyst based polyethylenes (mPEs), one ultra low density polyethylene, one conventional linear low density polyethylene (LLDPE), and one low density polyethylene (LDPE) were selected to characterize the effect of side chain branches on physical and mechanical properties. Rheological experiments were carried out to extract complex viscosity and elasticity as a function of frequency. Elongational viscosity tests were also performed to assess long chain branching. For some mPEs, sparse long chain branching improved shear thinning and elasticity of the chains in melt state. During elongation, mPEs with a narrow linear chain distribution showed initially greater melt strength whereas for longer elongation, the mPEs with long chain branching lead over in strength. Cast films were produced from the mPEs and their physical (such as crystallinity, crystal size) and mechanical properties were tested. A double melting peak was observed in the differential scanning calorimetry thermograms of the mPE films. A relatively sharp strain hardening behavior in tensile tests was observed for the mPEs films when compared to LLDPE. Fourier transform infrared was used as an effective and fast method to investigate side chain length. It was found that the positioning of side chain, co-monomer length, and content influence the melting behavior of mPE films.

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“…A number of studies have been conducted investigating the advantages of metallocene catalyzed polyethylene in the rotational molding industry. Metallocene polyethylene materials have the ability to control molecular weight distribution more narrowly than the resins produced using conventional Ziegler-Natta catalysts [12]. Metallocene polyethylenes possess rheological and physical properties that are desirable in rotomolding [13] and offer some significant process advantages [14].…”

Section: Introductionmentioning

confidence: 99%

Rotational Foam Molding of Metallocene Catalyzed Polyethylene: CBA Screening and Process Characteristics

Emami

Takács

Vlachopoulos

2010

Journal of Cellular Plastics

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The objective of this work is to investigate the effects of different chemical blowing agents (CBAs) and processing conditions on the cellular structure of foamed metallocene polyethylene and characterize an appropriate blowing agent. An experimental study was conducted to produce metallocene polyethylene foams in dry-blending-based rotational foam molding. The critical processing parameters that optimize the foam structure have been identified through modifications of the molding conditions. The physical properties and cellular structure of the final foamed parts were also examined. The foaming performance of exothermic and endothermic CBAs was studied. It was revealed that selecting a suitable CBA is crucial as the foam structure depends significantly on the properties of the blowing agent. Exothermic blowing agents resulted in greater foam density reduction and exhibited a wider processing window compared to endothermic blowing agents. It was found that a balance between different properties of the blowing agent is required to achieve control over the foam structure.

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Glass transition, crystallinity, resin stiffness, and branch distribution in metallocene and Ziegler-Natta ethylene 1-olefins

Cited by 29 publications

References 22 publications

Variation of Comonomer Content in LLDPE Particles with Different Sizes from an Industrial Fluidized Bed Reactor

Variation of Comonomer Content in LLDPE Particles with Different Sizes from an Industrial Fluidized Bed Reactor

Rheological, physical, and thermal characterization of single‐site catalyst based polyethylenes for seal layer applications

Rotational Foam Molding of Metallocene Catalyzed Polyethylene: CBA Screening and Process Characteristics

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