Unprecedented High-Modulus High-Strength Tapes and Films of Ultrahigh Molecular Weight Polyethylene via Solvent-Free Route

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Macromolocules, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: http://dx.doi.org/10.1021/ma200667

Heterogeneity in polymer melts from melting of polymer crystals

Semi-crystalline polymers containing amorphous and crystalline regions usually have intimately mixed chains. The resulting topological constraints (entanglements) in the amorphous regions limit the drawability in the solid state. By controlled synthesis the number of entanglements can be reduced. Ultimately, crystals composed of single chains are feasible, where the chains are fully separated from each other. If such separation can be maintained in the melt a new melt state can be formed. Here we show that through slow and carefully controlled melting such polymer crystals form a heterogeneous melt with more entangled regions, where the chains are mixed, and less entangled ones, composed of individually separated chains. Chain reptation, required for the homogenization of the entanglement distribution, is found to be considerably hindered. The long-lived heterogeneous melt shows decreased melt viscosity and provides enhanced drawability on crystallization. This novel route to create heterogeneous melt should be applicable to polymers in general

CO Oxidation Activity of Ag/TiO2 Catalysts Prepared via Oxalate Co-precipitation

Ag/TiO2 catalysts with different Ag loadings (2, 4, 7 and 10% (w/w)) have been prepared by means of co-precipitation of Ag- and TiO-oxalates followed by temperature programmed oxidation (TPO). The catalysts were subjected to CO oxidation in a flow reactor at atmospheric pressure and temperatures up to 573 K. Best conversion performance was obtained in a CO/O2 = 1:1 mixture over 10% Ag/TiO2 for which the temperature of 50% CO conversion was T50 = 333 K. The initial reaction rates were determined in a circulation reactor at low conversions and apparent activation energies between 13 and 25 kJ/mol were found for all catalysts. Transmission electron microscopy shows a broad range of nano-sized Ag particles on TiO2 (nearly pure anatase).info:eu-repo/semantics/publishe