<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gote, Ravindra P.</style></author><author><style face="normal" font="default" size="100%">Mandal, Dipa</style></author><author><style face="normal" font="default" size="100%">Patel, Ketan</style></author><author><style face="normal" font="default" size="100%">Chaudhuri, Krishnaroop</style></author><author><style face="normal" font="default" size="100%">Vinod, C. P.</style></author><author><style face="normal" font="default" size="100%">Lele, Ashish K.</style></author><author><style face="normal" font="default" size="100%">Chikkali, Samir H.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Judicious reduction of supported Ti catalyst enables access to disentangled ultrahigh molecular weight polyethylene</style></title><secondary-title><style face="normal" font="default" size="100%">Macromolecules</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2018</style></year><pub-dates><date><style  face="normal" font="default" size="100%">JUN </style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">51</style></volume><pages><style face="normal" font="default" size="100%">4541-4552</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;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 MgCl2 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 [A1]/[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 degrees C, which is a characteristic melting transition for a dis-UHMVVPE. The disentangled state of the nascent PE and its M-w and MVVD 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.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">12</style></issue><custom3><style face="normal" font="default" size="100%">Foreign</style></custom3><custom4><style face="normal" font="default" size="100%">5.835</style></custom4></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Chaudhuri, Krishnaroop</style></author><author><style face="normal" font="default" size="100%">Lele, Ashish K.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Rheological quantification of the extent of dissolution of ultrahigh molecular weight polyethylene in melt-compounded blends with high density polyethylene</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Rheology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">blends</style></keyword><keyword><style  face="normal" font="default" size="100%">Disentangled UHMWPE</style></keyword><keyword><style  face="normal" font="default" size="100%">double reptation</style></keyword><keyword><style  face="normal" font="default" size="100%">HDPE</style></keyword><keyword><style  face="normal" font="default" size="100%">Mathematical modeling</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2020</style></year><pub-dates><date><style  face="normal" font="default" size="100%">JAN</style></date></pub-dates></dates><volume><style face="normal" font="default" size="100%">64</style></volume><pages><style face="normal" font="default" size="100%">1-12</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Melt compounding of ultrahigh molecular weight polyethylene (UHMWPE) with high density polyethylene (HDPE) promises to be an alternative route to prepare bimodal polyethylene grades. However, complete dissolution of UHMWPE in HDPE cannot be guaranteed during melt compounding. Indeed, in an earlier work [K. Chaudhuri et al., Polym. Eng. Sci. 59, 821-829 (2019)], it was shown that a fully entangled UHMWPE did not mix well with commercial HDPE. However, a disentangled UHMWPE (dPE) could be melt-mixed in the same HDPE as evidenced qualitatively by rheological measurements. The present work is focused on quantifying the extent of dissolution of dPE in HDPE. The proposed method involves fitting rheological models for linear viscoelasticity of entangled bimodal blends of polydisperse polymers to dynamic oscillatory shear data and extracting information on the extent of dissolved species. The time-dependent diffusion model of des Cloizeaux is used along with the theory of double reptation (DR) to describe the dynamics of polydisperse homopolymers and also to extract the molecular weight distribution of the UHMWPE sample. A quadratic mixing rule, consistent with the DR model, is used to describe the dynamics of bimodal blends. Melt-mixed dPE/HDPE blends were prepared and characterized for their linear viscoelastic response by frequency sweep tests. The blends showed complex behavior with multiple crossover points, especially for the higher content of dPE. The bimodal model was then fit to the experimental frequency sweep data to determine the only unknown parameter, namely, the extent of dissolved dPE. It was found that a considerable fraction of dPE is dissolved in HDPE during melt compounding.&lt;/p&gt;
</style></abstract><issue><style face="normal" font="default" size="100%">1</style></issue><work-type><style face="normal" font="default" size="100%">Article</style></work-type><custom3><style face="normal" font="default" size="100%">&lt;p&gt;Foreign&lt;/p&gt;
</style></custom3><custom4><style face="normal" font="default" size="100%">&lt;p&gt;3.711&lt;/p&gt;
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