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

Rashedi, Reza; Sharif, Farhad

doi:10.1021/acs.iecr.5b02186

Cited by 9 publications

(7 citation statements)

References 28 publications

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“…Furthermore, in both grades a maximum value in MFI was detected in polymer particle size of 125–200 μm diameter. Occurrence of this maximum has already been reported by Rashedi and his coworker, 14 however, it seems that the value of polymer particle size where the maximum observed is depended on the catalyst nature. Here, since both studied grades were produced with a similar catalyst, the maximum in MFI was observed at the same particle diameter.…”

Section: Resultssupporting

confidence: 62%

“…All heating/cooling rates were 10°C/min. The Lamellar thickness was obtained from SSA curves employing Thomson–Gibbs equation 14 :

{normalT}_{normalm} = {normalT}_{normalm}^{0} (\frac{1 - 2 normalσ}{∆ normalH \times l_{c}})

Where l c is the lamellae thickness, T m is the middle temperature of each melt peak at SSA curves, T° m is the melting point of an infinite PE crystal (418 K), ΔH is the heat of fusion of the crystal with infinite lamellar thickness (288 × 10 6 J/m 3 ), and σ is the free energy of the lamellae surface (70 × 10 −3 J/m 2 ).…”

Section: Methodsmentioning

confidence: 99%

“…10 The same group also studied the relationship between comonomer content/ distribution and particle size of LLDPE powder obtained from an industrial gas phase plant. 14 HDPE is among the most demanded thermoplastic polymers with variable micro structures and vast ranges of applications. [15][16][17] There are four grades of HDPE (film, injection, pipe, and blow molding) depending on its processing techniques, and each one is best suited for different applications.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Mansouri

Emami

Yousefi

et al. 2022

J of Applied Polymer Sci

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In this study, the microstructural, flow, and mechanical properties of two commercially available high‐density polyethylene (HDPE) samples with different particle sizes were quantified. Specifically, two different blow molding and film grade HDPEs produced by the same catalyst under different conditions were acquired in powder form after dryer section of an industrial plant. They were fractioned according to their particle sizes into six samples: ≤125, 125–200, 200–315, 315–400, 400–500, and ≥ 500 μm. According to sieve analysis, the film grade (D50 = 304 μm) had larger particle sizes related to the counterpart injection sample (D50 = 289 μm). A peak value in density, bulk density, viscosity molecular weight (Mv), melt flow index (MFI), and comonomer content characteristics was found in the particles with the diameter of 125–200 μm in both samples, indicating extremely non‐homogeneity of these HDPE samples. Chemical composition distribution (CCD) of the as received polymers as well as sieved fractions was surveyed via SSA or TREF analyses. The film sample represented lower MFI and density and higher Mv and comonomer content in all fractions, originated from different reactor conditions during the samples synthesis, which translate into improved mechanical properties comparing with the blow molding sample.

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Section: Resultssupporting

confidence: 62%

“…All heating/cooling rates were 10°C/min. The Lamellar thickness was obtained from SSA curves employing Thomson–Gibbs equation 14 :

{normalT}_{normalm} = {normalT}_{normalm}^{0} (\frac{1 - 2 normalσ}{∆ normalH \times l_{c}})

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Mansouri

Emami

Yousefi

et al. 2022

J of Applied Polymer Sci

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“…Enhancement of ethylene polymerization activity by prepolymerization with propylene can be explained by enhanced particle fragmentation in the prepolymerization stage. The comonomer activation effect in ethylene/α-olefin copolymerization [ 31 ] can also be explained by enhancement of particle fragmentation, because lamellar thickness of copolymer is evidently smaller than that of ethylene homopolymer [ 53 , 54 ]. On the other side, MgCl 2 -supported Z–N catalysts with average pore size far larger than 20 nm are found to have a rather high [C*]/[Ti] ratio in ethylene polymerization [ 23 ], or show ethylene polymerization activity much higher than the level reported in this work [ 55 ].…”

Section: Resultsmentioning

confidence: 99%

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

Zhang

Jiang

et al. 2019

Polymers

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The kinetic behaviors of ethylene and propylene polymerizations with the same MgCl2-supported Ziegler–Natta (Z–N) catalyst containing an internal electron donor were compared. Changes of polymerization activity and active center concentration ([C*]) with time in the first 10 min were determined. Activity of ethylene polymerization was only 25% of that of propylene, and the polymerization rate (Rp) quickly decayed with time (tp) in the former system, in contrast to stable Rp in the latter. The ethylene system showed a very low [C*]/[Ti] ratio (<0.6%), in contrast to a much higher [C*]/[Ti] ratio (1.5%–4.9%) in propylene polymerization. The two systems showed noticeably different morphologies of the nascent polymer/catalyst particles, with the PP/catalyst particles being more compact and homogeneous than the PE/catalyst particles. The different kinetic behaviors of the two systems were explained by faster and more sufficient catalyst fragmentation in propylene polymerization than the ethylene system. The smaller lamellar thickness (<20 nm) in nascent polypropylene compared with the size of nanopores (15–25 nm) in the catalyst was considered the key factor for efficient catalyst fragmentation in propylene polymerization, as the PP lamellae may grow inside the nanopores and break up the catalyst particles.

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“…[46] Some centers can quickly copolymerize monomers and comonomers, but the resulting chains are short in length. [28,29,47] On the other hand, other centers do not tend to comonomers but produce chains with higher molecular weight. That is why we witness both molecular weight distribution (MWD) and chemical composition distribution (CCD) in copolymers made by ZNCs.…”

Section: Introductionmentioning

confidence: 99%

Clarifying the effects of comonomer distribution between short and long chains on physical and mechanical properties of ethylenic copolymers

Jandaghian

Sepahi²,

Hosseini³

et al. 2022

Polymer Engineering & Sci

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In this paper, two Zigler‐Natta catalysts (ZNCs) were used to synthesize a commercially available linear low‐density polyethylene (LLDPE), widely used in the packaging industry, on an industrial scale. The catalysts differ only in their ability to distribute comonomers between short and long chains. Both catalysts were fully characterized in the first section, and two similar ethylene/1‐butene copolymers were made using them. Afterward, the produced copolymers were fully characterized using different techniques; namely, differential scanning calorimetry (DSC), successive self‐nucleation and annealing (SSA), oxygen induction time (OIT), melt flow index (MFI), rheometric mechanical spectroscopy (RMS), and a wide range of mechanical experiments. It was revealed that while the presence of comonomers in short chains can reduce their resistance against oxidation (by more than 30%) and can cause a dramatic change in friction coefficients (by more than 20%), some of the other main mechanical properties of the made copolymers were independent of comonomer distribution between long and short chains. In addition, it was shown that ethylenic copolymers' strain hardening modulus (SHM) takes advantage of the homogenous distribution.

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

Cited by 9 publications

References 28 publications

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Structure–property relationship in film and blow molding type high‐density polyethylene polymers from a slurry‐process industrial plant

Comparative Study on Kinetics of Ethylene and Propylene Polymerizations with Supported Ziegler–Natta Catalyst: Catalyst Fragmentation Promoted by Polymer Crystalline Lamellae

Clarifying the effects of comonomer distribution between short and long chains on physical and mechanical properties of ethylenic copolymers

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