Synthesis of ultra high molecular weight polyethylene: A differentiate material for specialty applications

Padmanabhan, S.; Sarma, Krishna; Rupak, Kishor; Sharma, Sandeep

doi:10.1016/j.mseb.2009.10.026

Cited by 12 publications

(4 citation statements)

References 17 publications

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“…In this context, a paradigm shift could be achieved if a heterogeneous single-site catalyst yielding dis -UHMWPE can be accessed. Although highly desirable, access to single-site heterogeneous catalytic system is almost unexplored and rarely reported. − …”

Section: Introductionmentioning

confidence: 99%

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Gote¹,

Mandal²,

Patel³

et al. 2018

Macromolecules

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Heterogeneous Ziegler−Natta and homogeneous metallocene catalysts are known to produce ultrahigh molecular weight polyethylene (UHMWPE) in the entangled state. On the other hand, only (two) homogeneous single-site catalysts are reported to yield disentangled UHMWPE (dis-UHMWPE). This disparity between the two types of catalysts and the two states of polyethylene can be bridged if a heterogeneous single-site catalyst that can yield dis-UHMWPE is made accessible. Here, one-pot two-step synthesis of a MgCl 2 supported [Ti(OEt) 4 ] derived catalyst 1 with a two-stage activation strategy is reported to produce dis-UHMWPE. Second activation of catalyst 1 was performed by adding excess modified methylaluminoxane (MMAO12), and XPS analysis indicated that the catalyst existed in only Ti(III) state at [Al]/[Ti] ratio of 600. Catalyst 1 after second activation with MMAO12 was found to be highly active in ethylene polymerization and produced dis-UHMWPE. Polymerization conditions were tailored to obtain molecular weight (M w ) as high as 13 million g/mol PE. To the best of our knowledge, this is the first time a heterogeneous catalyst (catalyst 1) that displays pseudosingle site nature is able to produce dis-UHMWPE. The thus-prepared nascent polyethylene revealed a melting temperature of 141−144 °C, which is a characteristic melting transition for a dis-UHMWPE. The disentangled state of the nascent PE and its M w and MWD were further authenticated by rheological investigations. Isothermal time sweep oscillatory experiments in linear viscoelastic limit revealed a rapid rise in elastic modulus followed by equilibration to plateau modulus, which are characteristic features of the disentangled state. Thus, a pseudo-singlesite heterogeneous catalyst has been accessed, which upon second activation with excess MMAO12 led to the production of dis-UHMWPE.

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Section: Introductionmentioning

confidence: 99%

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Gote¹,

Mandal²,

Patel³

et al. 2018

Macromolecules

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show abstract

“…In the first DSC heating, the oriented crystals melt and when the polymer recrystallizes the more usual folded‐chain crystals are formed, which depends mainly on the polymer molecular weight rather than the size of crystalline regions . The observed change in melting temperature is reported for the nascent high molecular weight polyethylene, which has a higher melting point than the crystallized samples …”

Section: Discussionmentioning

confidence: 95%

“…The oriented crystalline fraction participates in the formation of an organized structure such as fibres . During polymerization, the polyethylene is formed well below its melting temperature and hence its nascent morphology is considerably influenced by the reaction conditions . In the first DSC heating, the oriented crystals melt and when the polymer recrystallizes the more usual folded‐chain crystals are formed, which depends mainly on the polymer molecular weight rather than the size of crystalline regions .…”

Section: Discussionmentioning

confidence: 99%

Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO₂ionic liquid system

Ochędzan‐Siodłak

Bihun

2015

Polym. Int.

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“…UHMWPE is generally produced in slurry reactors, and the choice of solvent is an important factor affecting the rate of polymerization reactions. − Kishor et al investigated the polymerization kinetics of UHMWPE synthesized by highly active Ziegler–Natta catalysts in different polymerization mediums in a slurry reactor and found that the solubility of ethylene depends on the number of carbon atoms of the solvent medium, and the higher the number of carbon atoms of the solvent, the lower the solubility of ethylene in the solvent. Besides, the higher the number of carbon atoms of straight chain alkanes, the higher the viscosity of the solvent, which in turn reduces the liquid-phase mass transfer coefficient of different reactants and the polymerization reaction rates such as the chain transfer reaction and chain propagation reaction.…”

Section: Introductionmentioning

confidence: 99%

Effects of Polymerization Medium on Nascent UHMWPE Properties and Sintered Material Performance

Fan

Chen

Zhou

et al. 2023

Ind. Eng. Chem. Res.

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High-performance and easy-processing UHMWPE products with less entanglement and small particle size are difficult to synthesize efficiently in the polymerization process. In this study, a mixture of heptane and light paraffin is proposed as the polymerization medium to control the concentration of ethylene in the slurry during polymerization. Influences of the mixture composition on the polymerization behavior of ethylene, the particle size and its distribution of nascent UHMWPE, and the initial entangled state of UHMWPE were explored. Experimental results showed that as the volume fraction of heptane decreased, the viscosity of the solvent mixture increased exponentially, and ethylene solubility as well as mass transfer coefficient of ethylene in solvent decreased, which greatly affected the ethylene polymerization rate. By adjusting the volume fraction of heptane in the polymerization medium, the particle size, initial entanglement state density, and molecular weight of nascent UHMWPE will be coordinately controlled. UHMWPE with smaller particle size, lower entanglement density, and higher molecular weight can be prepared using the conventional Ziegler–Natta catalyst and polymerization medium with a lower heptane content, and its sintered UHMWPE material shows good mechanical properties.

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Synthesis of ultra high molecular weight polyethylene: A differentiate material for specialty applications

Cited by 12 publications

References 17 publications

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO₂ionic liquid system

Effects of Polymerization Medium on Nascent UHMWPE Properties and Sintered Material Performance

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Synthesis of ultra high molecular weight polyethylene: A differentiate material for specialty applications

Cited by 12 publications

References 17 publications

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Judicious Reduction of Supported Ti Catalyst Enables Access to Disentangled Ultrahigh Molecular Weight Polyethylene

Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO2ionic liquid system

Effects of Polymerization Medium on Nascent UHMWPE Properties and Sintered Material Performance

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Direct synthesis of fibrous high molecular weight polyethylene using vanadium catalysts supported on an SiO₂ionic liquid system