02440nas a2200205 4500008004100000022001400041245009400055210006900149260009900218300001400317490000700331520167100338653001902009653001902028653001702047100001202064700002102076700002002097856011702117 2011 eng d a0032-386100aInfluence of carbon-based nanofillers on the melt flow singularity of linear polyethylene0 aInfluence of carbonbased nanofillers on the melt flow singularit aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcJUN a3163-31740 v523 a

A quantitative power law relationship between molecular weight and flow criticalities is uncovered that links stick-slip theory with the melt flow singularity observed during capillary flow. The singularity arises from decrease in pressure during melt flow of linear polyethylene through capillary die in a narrow temperature window. The molecular origin of the window effect is attributed to slip flow arising from disengagement of chains adsorbed to melt-wall interface from free chains in melt. Considering the similar molecular configuration of the linear polyethylene and carbon nanotubes (CNTs), the stretched chain conformation of the adsorbed chains in the presence of CNTs is influenced. The potential to broaden the window temperature interval in the presence of CNTs is explored. For the study, multi-walled carbon nanotubes (MWCNTs) are added in the linear polyethylene. The influence of the filler aspect ratio on the window effect is further investigated in the presence of carbon black (CBs). The presence of MWCNTs broadens the window temperature interval and increases the decrease in pressure. Contrary to MWCNTs in the presence of CBs the extrusion window narrows and reduction in the pressure-decrease occurs. It is also found that the two carbon nanofillers have a significant impact on flow-induced solidification. Both, the crystallisation rate and the onset temperature of crystallisation, increase with the loading of the two nanofillers. A closer comparison between the two carbon nanofillers at the same loading suggests that the crystallisation is more influenced in MWCNT-PE composites. (C) 2011 Elsevier Ltd. All rights reserved.

10aCapillary flow10aCarbon fillers10aPolyethylene1 aXu, Han1 aLele, Ashish, K.1 aRastogi, Sanjay uhttp://library.ncl.res.in/content/influence-carbon-based-nanofillers-melt-flow-singularity-linear-polyethylene-001696nas a2200205 4500008004100000022001400041245010300055210006900158260007100227300001600298490000800314520090100322100002901223700002401252700001501276700002401291700002101315700003201336856012201368 2015 eng d a1520-610600aInsights into the molecular dynamics in polysulfone polymers from C-13 solid-state NMR experiments0 aInsights into the molecular dynamics in polysulfone polymers fro a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG a11287-112940 v1193 a

The molecular and segmental motions in three different grades of ductile polysulfone polymers; poly(ether sulfone) (PESU), polysulfone (PSU), and poly(phenyl sulfone) (PPSU) are probed using C-13 solid-state NMR experiments. Polarization inversion spin exchange at magic angle (PISEMA) experiments indicates that the phenyl rings in the polymers are undergoing pi-flip motions on the order of 100 kHz. The temperature dependent PISEMA experiments show that the fraction of mobile regions that undergoes aromatic pi-flips is higher in PPSU than in the other two polymers. The center band only detection of exchange (CODEX) experiments was carried out and was unable to detect any slow segmental motions in the chains. A combination of C-13 spin-lattice relaxation time (T-1) and T-1-filtered PISEMA experiments show that the mobile regions in all the polymers are dynamically heterogeneous.

1 aEldho, Kavalakal, Mathai1 aRajamohanan, P., R.1 aAnto, Ralf1 aBulakh, Neelima, N.1 aLele, Ashish, K.1 aAjithkumar, Thalasseril, G. uhttp://library.ncl.res.in/content/insights-molecular-dynamics-polysulfone-polymers-c-13-solid-state-nmr-experiments-001979nas a2200241 4500008004100000022001400041245013400055210006900189260000900258300001100267490000800278520113700286653001201423653003001435653002901465653001301494653001801507100002101525700002301546700002701569700002101596856012001617 2022 eng d a0378-775300aInterdigitated flow field impact on mass transport and electrochemical reaction in high-temperature polymer electrolyte fuel cell0 aInterdigitated flow field impact on mass transport and electroch cJUN  a2313190 v5323 a

The enhanced performance of Polybenzimidazole (PBI) based high-temperature polymer electrolyte fuel cell (HT-PEFC) with interdigitated flow field over the other flow fields can be a consequence of higher average pressure developed on the flow field due to dead end in the channels or faster mass transport due to pressuredriven convection in the gas diffusion layer (GDL). In the present study, the effect of average pressure on the flow field and mass transport mechanism in the GDL on the HT-PEFC performance have been systematically decoupled. Three-dimensional simulation validated by experimental studies confirm that the enhanced performance in case of the interdigitated flow field is due to faster mass transport in the GDL and not due to higher average gas pressure. The simulation studies are performed on the interdigitated flow field and compared against the parallel flow field to have an insight into the effect of key operating and geometric parameters. There exists an optimum value for channel to rib ratio and current density saturates after an air stoichiometry of 4 which is validated by experiments.

10aHT-PEFC10aInterdigitated flow field10aMass transport mechanism10apressure10astoichiometry1 aAgarwal, Harshal1 aThosar, Aniket, U.1 aBhat, Santoshkumar, D.1 aLele, Ashish, K. uhttp://library.ncl.res.in/content/interdigitated-flow-field-impact-mass-transport-and-electrochemical-reaction-high