A disentangled state using TiCl4/MgCl2 catalyst: a case study of polyethylene

Heidari, Amin; Zarghami, Hamid Reza; Talebi, Saeid; Rezaei, Mehran

doi:10.1007/s13726-018-0648-z

Cited by 11 publications

(6 citation statements)

References 38 publications

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“…Controlling the polymer synthesis conditions in the reactor presents an advanced technique to obtain less entangled products. [ 62,63 ] The polymerization can be regulated by using a single site catalyst, evenly dispersing and separating catalysts to an extent, [ 64 ] or decreasing the number of catalytic sites. It can be seen from Figure that the heterogeneous synthesis polymer chains are highly folded around the catalyst interface.…”

Section: Control Of Polymer Chain Entanglementmentioning

confidence: 99%

Control of Polymer Properties by Entanglement: A Review

Kong

Yang

Zhang

et al. 2021

Macro Materials & Eng

103

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Chain entanglement, either cohesional or topological, distinguishes polymers from other engineering materials. It impedes the movement of molecular segments and influences the polymer rheology, morphology, and mechanical properties. Although a high level of entanglement can increase the polymer toughness, excessive entanglement should be avoided because it causes a high melt viscosity making the processing difficult. This review tended to elucidate the influence of entanglement on the polymer structure, determining the material properties and processability. A wide range of methods used to fine control the degrees of chain entanglement are summarized. The methods are applicable to polymers in solutions, melts, and condensed states with advantages and limitations discussed in detail. The authors also examined the effect of the entanglement on polymer crystallization—the mechanism remains a controversial issue. This review will provide general guidance to designing and processing polymer materials with desired properties via a rational route of controlling the chain entanglement.

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Section: Control Of Polymer Chain Entanglementmentioning

confidence: 99%

Control of Polymer Properties by Entanglement: A Review

Kong

Yang

Zhang

et al. 2021

Macro Materials & Eng

103

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“…It was 8500 s for the nascent polymer with M w = 9.2 × 10 6 g mol −1 . When this polymer was annealed 10 min at 200 °C this time was shortened to 5700 s. Recently Heidari et al produced disentangled UHMWPE using a heterogeneous Ziegler–Natta catalyst and observed re‐entangling after 500–2500 s, depending on the polymerization conditions. Unfortunately, the molecular masses of the studied materials were not presented, although they were probably above 10 6 g mol −1 .…”

Section: Process Of Re‐entanglingmentioning

confidence: 99%

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Pawlak

2019

Macro Chemistry & Physics

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Macromolecules form entanglements, the presence of which determines many of the polymer's properties; in solution, melt, and solid state. In this review, how the properties of polymers (rheological, thermal, and mechanical), depend on the concentration of the entanglements, is discussed. Although a typical polymer is characterized by the equilibrium density of entanglements, there are methods that can be applied for the reduction of this density. The methods used most often include dissolving a polymer and rapid freezing, crystallization during polymerization, and crystallization from a cooled dilute solution. The properties of disentangled polymers are significantly different from the properties of fully entangled polymers. These properties are discussed in relation to their dependence on the density of the entanglements. The disentangled material can be re‐entangled by the annealing of the polymer; however, reaching the equilibrium density of the entanglements is usually a slow process. It means that a polymer may be processed without losing its disentanglements. The properties of the re‐entangled polymer are usually close to the properties of the initial polymer.

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“…The morphology of polymer will be changed and its crystal structure will disappear gradually when heating above the melting temperature of polymer. With the increase of time and temperature, thermodynamically stable system will be achieved, and the polymer chains tend to be a completely entangled state in this time 34 . The important manifestation of entanglement in long chains is the presence of a rubber platform region, where the modulus is basically invariable, which is called the platform modulus.…”

Section: Resultsmentioning

confidence: 99%

“…With the increase of time and temperature, thermodynamically stable system will be achieved, and the polymer chains tend to be a completely entangled state in this time. 34 The important manifestation of entanglement in long chains is the presence of a rubber platform region, where the modulus is basically invariable, which is called the platform modulus. According to the elastic theory of rubber, the density of entanglement network can be characterized by the modulus of rubber platform when the system reaches thermodynamic equilibrium, and the influence of crystal structure has been eliminated in this time.…”

Section: Entanglement Dilutionmentioning

confidence: 99%

Regulating the dissolving system of ultra‐high molecular weight polyethylene to enhance the high‐strength and high‐modulus properties of resultant fibers

Wang

Song

et al. 2022

J of Applied Polymer Sci

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The molecular weight loss of ultra‐high molecular weight polyethylene (UHMWPE) fibers is extremely serious in comparison with raw materials due to the high temperature and strong shearing during dissolving process. In this study, decalin was introduced as preswelling solvent and the dissolving system was regulated to improve the solubility of UHMWPE in paraffin oil without severe degradation so as to prepare UHMWPE fibers with high molecular weight retention and low entanglement. UHMWPE was preswelling in decalin with different content, the mass ratio of decalin to UHMWPE were 1:1, 1.5:1, 2:1, 2.5:1, and 3:1. All UHMWPE fibers were prepared by gel‐spinning and hot‐drawing. UHMWPE fibers possess the highest molecular weight after preswelling of UHMWPE in decalin (with a mass ratio of 3:1 to UHMWPE, namely UPE/dec‐s‐3 sample). What's more, the entanglement of UHMWPE fibers gained from UPE/dec‐s‐3 sample has been observably diluted in comparation to that from UPE‐neat and other swollen samples. More importantly, the tensile strength and modulus of UHMWPE fibers obtained from UPE/dec‐s‐3 sample can reach 31.41 and 1446.26 cN/dtex, increased by 15.1% and 14.3% compared with UPE‐neat fibers, respectively. Besides, the thermal and crystallization behavior of UHMWPE fibers prepared from swollen UHMWPE have also been boosted.

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A disentangled state using TiCl4/MgCl2 catalyst: a case study of polyethylene

Cited by 11 publications

References 38 publications

Control of Polymer Properties by Entanglement: A Review

Control of Polymer Properties by Entanglement: A Review

The Entanglements of Macromolecules and Their Influence on the Properties of Polymers

Regulating the dissolving system of ultra‐high molecular weight polyethylene to enhance the high‐strength and high‐modulus properties of resultant fibers

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