Advanced Polyethylene Technologies—Controlled Material Properties

Knuuttila, Hilkka; Lehtinen, Ari; Nummila-Pakarinen, Auli

doi:10.1007/b13519

Cited by 80 publications

(81 citation statements)

References 10 publications

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“…In particular, the large difference in melt flow ratio between GMB4 and the three other GMBs suggests a difference in the catalyst used in the polymerisation of these resins. The inferred narrow molecular weight distribution of GMB4 suggests Metallocenes type catalysts whereas GMBs1, 2, and 3 with their inferred broader molecular weight distribution suggest a Ziegler-Natta or Phillips type catalyst (Löfgren et al 2004;Knuuttila et al 2004;Hsuan 2013). Thus, the Figure 11d indicate the time at which residual Std-OIT was reached at 115 and 105°C; at 95°C the residual values had not been reached at the time of writing.…”

Section: Surface Degradation and Scrmentioning

confidence: 99%

Effect of high temperatures on the physical and mechanical properties of HDPE geomembranes in air

Abdelaal

Rowe

Hsuan

et al. 2015

Geosynthetics International

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The effect of elevated temperatures, particularly between 95 and 115°C as encountered in some geoenvironmental applications, on the physical and mechanical properties of high-density polyethylene (HDPE) geomembranes (GMBs) is examined. Four commercially available HDPE GMBs were incubated in air at temperatures ≥ 85°C. Investigation of the thermograms by differential scanning calorimetry showed a significant change in the polymer morphology with an increase of the incubation temperature and duration, especially at 105 and 115°C. The morphological changes due to annealing involve thickening of the lamella crystals of the polymer and a change in the tie molecules joining the lamella crystals. The effect of annealing was most evident in the stress crack resistance of the GMB incubated at 105 and 115°C prior to polymer degradation. In particular, an increase in stress crack resistance due to annealing could mask the effects of polymer degradation at temperatures above 95°C. Changes in morphology did not affect melt index whose changes were largely attributed to polymer degradation.

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Section: Surface Degradation and Scrmentioning

confidence: 99%

Effect of high temperatures on the physical and mechanical properties of HDPE geomembranes in air

Abdelaal

Rowe

Hsuan

et al. 2015

Geosynthetics International

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“…Higher concentrations resulted in significant broadening of the molecular weight distribution which might come from the fact that different sites incorporated the comonomer with different efficiencies. One might suppose, moreover, that-as with Ziegler-Natta systems-the catalytic active sites which produced macromolecules with shorter chains had also the tendency to incorporate more comonomer and the longer chains were more linear [37]. The DSC thermograms of polyethylene and ethylene/1-octene copolymers obtained at different comonomer concentrations are presented in Fig.…”

Section: Resultsmentioning

confidence: 99%

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

2013

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Ethylene/1-olefin copolymerization using vanadium and titanium complexes bearing tetradentate [O,N,N,O]-type ligand and EtAlCl 2 or MAO as a cocatalyst is carried out. In the presence of the vanadium complex activated with EtAlCl 2 is observed (a) negative ''comonomer effect'', (b) high comonomer incorporation and narrow chemical composition distribution (CCD), (c) unexpected copolymer microstructure, and (d) increased molecular weight of copolymers when compared with the homopolymer. In contrast, titanium catalyst gives copolymers with lower 1-olefin content and broad CCD. Supported complexes show higher activity, lower 1-olefins incorporation and give copolymers with ultra high molecular weights.

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“…In these processes the catalyst preparation and pretreatment steps usually take place in a separate reactor unit, where the operating conditions (e.g., solvent, temperature, and pressure) can be different compared to the polymerization reactor conditions [9,28]. The purpose of this study is to carry out the smallscale polymerization experiments under conditions which would be as close as possible to the industrial process.…”

Section: Methodsmentioning

confidence: 99%

“…The prepolymerized polymer is commonly produced in a separate reactor before the main polymerization reactor (i.e., prepolymerizer). In industry this concept has already been widely adopted and implemented in different multistage processes (e.g., Unipol, Spherilene, and Borstar5) [9,10].…”

Section: Introductionmentioning

confidence: 99%

Optimal Catalyst and Cocatalyst Precontacting in Industrial Ethylene Copolymerization Processes

Aigner

Paulik

Krallis

et al. 2016

Journal of Polymers

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In industrial-scale catalytic olefin copolymerization processes, catalyst and cocatalyst precontacting before being introduced in the polymerization reactor is of profound significance in terms of catalyst kinetics and morphology control. The precontacting process takes place under either well-mixing (e.g., static mixers) or plug-flow (e.g., pipes) conditions. The scope of this work is to study the influence of mixing on catalyst/cocatalyst precontacting for a heterogeneous Ziegler-Natta catalyst system under different polymerization conditions. Slurry ethylene homopolymerization and ethylene copolymerization experiments with 1-butene are performed in a 0.5 L reactor. In addition, the effect of several key parameters (e.g., precontacting time, and ethylene/hydrogen concentration) on catalyst activity is analyzed. Moreover, a comprehensive mass transfer model is employed to provide insight on the mass transfer process and support the experimental findings. The model is capable of assessing the external and internal mass transfer limitations during catalyst/cocatalyst precontacting process. It is shown that catalyst/cocatalyst precontacting is very important for the catalyst activation as well as for the overall catalyst kinetic behavior. The study reveals that there is an optimum precontacting time before and after which the catalyst activity decreases, while this optimum time depends on the precontacting mixing conditions.

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Advanced Polyethylene Technologies—Controlled Material Properties

Cited by 80 publications

References 10 publications

Effect of high temperatures on the physical and mechanical properties of HDPE geomembranes in air

Effect of high temperatures on the physical and mechanical properties of HDPE geomembranes in air

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

Optimal Catalyst and Cocatalyst Precontacting in Industrial Ethylene Copolymerization Processes

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