Kinetic prediction of molecular weight distribution in bimodal polyethylene from heterogeneous post-metallocene catalysis

Atashrouz, Saeid; Rahmani, Amir M.; Nasernejad, Bahram; Balzade, Zahra

doi:10.1016/j.matchemphys.2020.123466

Cited by 9 publications

(8 citation statements)

References 47 publications

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“…22,23 The effects of microstructural characteristics on the rheological properties of bimodal polyethylene are investigated too. [24][25][26][27][28][29][30][31][32] In most of these studies, a HMW polyethylene is blended with a LMW one. For example, Szanto et al investigated the effects of MWD on viscoelastic properties of linear multimodal properties.…”

Section: Introductionmentioning

confidence: 99%

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Jandaghian

Maddah

Sepahi³

et al. 2021

J of Applied Polymer Sci

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In this paper, using a comprehensive study, we have investigated the effect of various polymerization parameters during the synthesis of bimodal polyethylene resins on their rheological and mechanical properties. Bimodal polyethylene resins were synthesized in two subsequent stages in a lab-scale reactor by manipulating a set of parameters such as C 2 /H 2 ratios in the first and second stages, the split value, and the comonomer type. The results showed that the comonomer type and C 2 /H 2 ratio of the second stage of the polymerization are the most critical parameters that control the final resins' slow crack growth resistance properties. On the other hand, the shear-thinning behavior of the resins is mainly controlled by the first-stage polymers. Although the C 2 /H 2 ratio of the first stage results in a moderate effect on the rheological properties of the final resins, its split value governs the flow characteristics of the final molten polymers under high shear rates.

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Section: Introductionmentioning

confidence: 99%

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Jandaghian

Maddah

Sepahi³

et al. 2021

J of Applied Polymer Sci

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“…Generally, an empirical relation between the melting temperature and PE density is defined. , Therefore, it will be possible to estimate the melting temperature for different densities of PE (i.e., different slices of PE with different densities). In our previous study, the following relation was proposed between the melting point and density …”

Section: Resultsmentioning

confidence: 99%

Prediction of Temperature and Concentration Profiles in an Industrial Polymerization Fluidized Bed Reactor under Condensed-Mode Operation

Atashrouz

Rahmani

Nasernejad

et al. 2021

Ind. Eng. Chem. Res.

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Condensed mode operation of gas-phase ethylene polymerization adds more complexity to the hydrodynamics of fluidized bed reactors (FBRs). This study aims at the development of an industrial ethylene polymerization FBR model operating in condensed mode, and in this regard, the classical two-phase theory was modified. Two modeling strategies were investigated: a simple twophase model (model I) and a more complex one taking the presence of a wet zone (model II) into consideration. To access the predictive capabilities of the two models, model predictions were compared with plant data. The absolute relative deviation percentages for model I in prediction of the production rate and catalyst flow rate were 10.4 and 14.8, respectively. However, these errors for model II were 0.80 and 10.36, respectively. It was observed that the temperature profile predicted by model I was more consistent with that of plant data when the bubble diameter was considered to be small because of enhanced heat transfer rates between the bubble and emulsion phases. However, this assumption was not necessary for model II, and assuming a maximum stable bubble diameter for bubbles in the reactor, which is a more realistic assumption, the predicted temperature profile was reasonable. According to the results of model II, two zones, wet (including liquid droplets) and dry (including evaporated liquid), are formed in the condensed-mode operation of FBRs. It was found that for low-condensing agent flow rates (70 ton/h in this study), the difference between process conditions (concentration and temperature) of wet and dry zones increases (ΔC = 22.16 mol/m 3 and ΔT = 40.19 K), which can produce bimodal polyethylene (PE). Furthermore, a search strategy was developed based on the imperialist competitive algorithm and model II to find polymerization conditions needed to produce a PE grade with a specified microstructure. The results showed that the proposed algorithm is efficient for such a purpose. The sensitivity analysis of model I proved that in low gas velocities, the emulsion phase temperature is very sensitive to the catalyst flow rate. Moreover, the results of model I demonstrate that the dependency of temperature and monomer concentration of the emulsion phase on particle elutriation is negligible, especially under normal operating conditions.

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“…Pipe grade bHDPEs typically have very low average comonomer contents (up to 0.25 mol%) while film grades have higher comonomer contents (≈0.5 to 2.0 mol%). [ 2,6,11–13 ]…”

Section: Introductionmentioning

confidence: 99%

“…Pipe grade bHDPEs typically have very low average comonomer contents (up to 0.25 mol%) while film grades have higher comonomer contents (≈0.5 to 2.0 mol%). [2,6,[11][12][13] Very often, the differences in the microstructures of bHD-PEs are small such that at bulk sample level, materials with different properties may be indistinguishable. The processability and end-use of the products may be very different although the average composition is the same.…”

Section: Introductionmentioning

confidence: 99%

Reverse Engineering of Chemically Similar Bimodal High Density Polyethylenes: A Comprehensive Study Using Advanced Chromatographic Techniques

Ndiripo

Lamola

Ndlovu

et al. 2022

Macro Materials & Eng

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Bimodal high‐density polyethylene (bHDPE) is a complex, multicomponent polyethylene (PE) material whose synthesis in a multistage process can be challenging. Three bHDPEs with good and bad end‐use properties are reverse engineered using advanced analytical techniques. Average chemical composition is determined using 13C NMR and 1‐butene is identified as the comonomer for the good resin (bHDPE 1) while 1‐hexene is the comonomer in bHDPE 2 and 3. The presence of comonomer in the high molar mass fractions of the samples is shown using high‐temperature triple‐detection size exclusion chromatography (HT‐SEC‐d3). Chemical composition separation using high‐temperature interaction chromatography (HT‐IC) is achieved using porous graphitic carbon (PGC) and silica stationary phases. Some problems in temperature gradient interaction chromatography (TGIC) on PGC are overcome by using a non‐adsorptive stationary phase, enabling better separation and visualization of homopolymer and copolymer components. Coupling HT‐SEC in 2D liquid chromatography (2D‐LC) analyses at high temperatures reveals the presence of a larger copolymer component in bHDPE 1 at high elution volume. In contrast, bHDPE 2 and bHDPE 3 have copolymer components at low elution volumes, indicating poor comonomer distribution in the copolymer component which ultimately explains the poor mechanical properties at similar comonomer contents.

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Kinetic prediction of molecular weight distribution in bimodal polyethylene from heterogeneous post-metallocene catalysis

Cited by 9 publications

References 47 publications

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Effects of polymerization parameters on the slow crack growth resistance and rheological properties of bimodal polyethylene resins

Prediction of Temperature and Concentration Profiles in an Industrial Polymerization Fluidized Bed Reactor under Condensed-Mode Operation

Reverse Engineering of Chemically Similar Bimodal High Density Polyethylenes: A Comprehensive Study Using Advanced Chromatographic Techniques

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