Molar Mass and Molecular Weight Distribution Determination Of UHMWPE Synthesized Using a Living Homogeneous Catalyst

Talebi, Saeid; Duchateau, Robbert; Rastogi, Sanjay; Kaschta, Joachim; Peters, Gwm Gerrit; Lemstra, PJ Piet

doi:10.1021/ma902297b

Cited by 112 publications

(126 citation statements)

References 56 publications

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“…as described in the literature 22,23,24 and the results are shown in Figure 2. A two-step procedure was carried out to prepare the electrically conductive composites with the two types of UHMWPEs: first, the required amount of dried GON was weighed and redispersed in 40 ml of water by 15 min ultrasonication, in parallel the required amount of PE was dispersed in acetone and stirred for 10 min.…”

Section: Determination Of Molecular Weight and Molecular Weight Distrmentioning

confidence: 75%

Unique Rheological Response of Ultrahigh Molecular Weight Polyethylenes in the Presence of Reduced Graphene Oxide

et al. 2014

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The paper addresses the difference in electrical conductivities and rheological properties between two nanocomposites of reduced graphene oxide nanosheets (rGON) with commercial ultrahigh molecular weight polyethylene (C_PE) and a low-entanglement-density UHMWPE synthesized under controlled conditions (Dis_PE). It has been found that composites made with Dis_PE can reach conductivities at least 100 times higher than those made with C_PE on doing thermal treatment at lower temperatures. However, the difference in the electrical conductivity diminishes when both sets of samples are given a high temperature treatment. This phenomenon is attributed to the difference in morphology of the polymer matrices, for example, grain boundaries between the nascent particles. Furthermore, rheological analyses of the two sets of UHMWPE/rGON nanocomposites conclusively demonstrate differences in the interaction between polyethylene chain segments of the disentangled UHMWPE and rGON, compared to the entangled commercial UHMWPE. Both composites show minima in the storage modulus at a specific graphene composition. The strong interaction of polyethylene chains with the filler inhibits disentangled UHMWPE to achieve the thermodynamic equilibrium melt state, whereas in the commercial sample, having a broader molar mass distribution, the higher adhesion probability of the long chains to the graphene surface lowers the elastic modulus of the polymer melt. Correlation between the percolation threshold for electrical conductivity and rheological response of the composites has also been discussed.

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Section: Determination Of Molecular Weight and Molecular Weight Distrmentioning

confidence: 75%

Unique Rheological Response of Ultrahigh Molecular Weight Polyethylenes in the Presence of Reduced Graphene Oxide

et al. 2014

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“…Reaction time is varied to tailor differences in molar mass and entangled state of the crystals. A more detailed description of the polymer synthesis and molar mass determination by means of linear rheology can be found elsewhere [Romano et al (2013); Talebi et al (2010)]. …”

Section: A Materialsmentioning

confidence: 99%

Stress relaxation in the nonequilibrium state of a polymer melt

Andablo‐Reyes

Boer

Romano

et al. 2014

Journal of Rheology

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An experimental study on the criteria for failure of polymer melts in uniaxial extension: The test case of a polyisobutylene melt in different deformation regimes J. Rheol. 54, 605 (2010) SynopsisThe influence of entanglement density on the constraint renewal time is studied experimentally in transitory nonequilibrium polymer melts. The entanglement density, as quantified by the rubber elasticity, increases as the linear polymer melt transforms into the equilibrium state. The relaxation modulus obtained from linear step-strain deformations, performed at different points during the equilibration, shows an increase in constraint renewal time as the entanglement density increases. The normalized relaxation modulus curves collapse onto a single curve by rescaling the time axis with a factor G 0 ðtÞ 0:9 (where G 0 ðtÞ is the normalized instantaneous modulus). These findings suggest that, though the relaxation time increases with the increasing number of entanglements, the mechanism responsible for stress relaxation, after application of step-strain, is similar to that in a fully entangled melt. V C 2014 The Society of Rheology.

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“…The topology can be tailored by controlling the crystallization kinetics either by dissolution and crystallization or controlled polymerization [2,3,4,5]. The influence of molar mass on the topology of non-crystalline phase has been a subject of interest where the nature of the mobile phase is probed by solid state NMR [6,7].…”

Section: Introductionmentioning

confidence: 99%

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

et al. 2016

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Recently, the influence of reduced graphene oxide nanoplatelets (rGON) on the rheological response of polymers has been a subject of interest. In the case of disentangled UHMWPE, it has been shown that the chain-filler interaction in the UHMWPE/rGON composite results into an everlasting non-equilibrium melt state having heterogeneous distribution in entanglement density. In this study, a thermal analysis protocol is used to follow the influence of the non-equilibrium polymer melt on the crystallization kinetics of disentangled UHMWPE with, and without, rGON. The analysis is carried out by means of differential scanning calorimetry (DSC) and the results are supported by rheology. When the disentangled UHMWPE sample, without the filler rGON, is left to crystallize under isothermal condition after melting, two endothermic peaks are observed: the high temperature peak (close to the equilibrium melting point, 141.5 °C) is related to the melting of crystals obtained on crystallization from the disentangled domains of the heterogeneous (nonequilibrium) polymer melt, whereas the low melting temperature peak is related to the melting of crystals formed from entangled domains of the melt. On increasing the annealing time in melt (160 °C), the enthalpy of the lower melting temperature peak increases at the expense of the high melting temperature peak, confirming a transformation of the nonequilibrium polymer melt to a fully entangled equilibrium melt state. However, independent of the equilibrium or non-equilibrium melt state, the recurrence of the high melting temperature peak is observed when the samples synthesized using the single-site catalytic system are left to isothermal crystallization at a specific temperature. The recurrence of the high melting temperature, close to the equilibrium melting point of the polymer, questions the differences in entanglements formed before and after polymerization in these high molar masses. The differences in the topological constraints are likely to influence the difference in melting temperatures of the isothermally crystallized samples. In the presence of rGON, the melting response of disentangled UHMWPE crystallized from its heterogeneous melt state changes; at a specific filler concentration, it is observed that the high endothermic peak remains independent of the annealing time in melt. This observation strengthens the concept that in the presence of the filler, chain dynamics is arrested to an extent that the nonequilibrium melt state having lower entanglement density is retained, facilitating the formation of crystals having high melting temperature. IntroductionThe topology of methylene segments in the non-crystalline region of the semi-crystalline polymer Ultrahigh Molecular Weight Polyethylene (UHMWPE), has a profound influence on the mechanical deformation either uniaxially or biaxially [1]. The topology can be tailored by controlling the crystallization kinetics either by dissolution and crystallization or controlled polymerization [2,3,4,5]. The influence of mo...

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Molar Mass and Molecular Weight Distribution Determination Of UHMWPE Synthesized Using a Living Homogeneous Catalyst

Cited by 112 publications

References 56 publications

Unique Rheological Response of Ultrahigh Molecular Weight Polyethylenes in the Presence of Reduced Graphene Oxide

Unique Rheological Response of Ultrahigh Molecular Weight Polyethylenes in the Presence of Reduced Graphene Oxide

Stress relaxation in the nonequilibrium state of a polymer melt

Heterogeneous Distribution of Entanglements in a Nonequilibrium Polymer Melt of UHMWPE: Influence on Crystallization without and with Graphene Oxide

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