02034nas a2200229 4500008004100000022001400041245016400055210006900219260011000288300001400398490000600412520112200418100001201540700002201552700001701574700001401591700001901605700002101624700001401645700001801659856012701677 2012 eng d a1744-683X00aNanocomposite silica surfactant microcapsules by evaporation induced self assembly: tuning the morphological buckling by modifying viscosity and surface charge0 aNanocomposite silica surfactant microcapsules by evaporation ind aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcDEC a1955-19630 v83 a

Nanocomposite microcapsules of silica and surfactants have been synthesized using evaporation induced self-assembly through spray drying. It was established using electron microscopy and small-angle neutron/X-ray scattering experiments that the viscosity of the virgin dispersion and surface charge of colloidal components play a significant role in the buckling of spray droplets during drying. Hollow spherical grains are realized at relatively low viscosity and higher surface charge while mushroom like grains manifest at higher viscosity and lower surface charge. In the intermediate conditions, deformed doughnut shaped microcapsules are obtained. Scattering experiments establish the presence of the organization of micelle like aggregates of surfactants in the dried grains and also corroborate with the observations from electron microscopy. A plausible mechanism regarding the chronological pathways of morphological transformation is illustrated. Computer simulation, based on buckling of an elastic shell using a surface evolver, has been attempted in order to corroborate the experimental results.

1 aSen, D.1 aBahadur, Jitendra1 aMazumder, S.1 aVerma, G.1 aHassan, P., A.1 aBhattacharya, S.1 aVijai, K.1 aDoshi, Pankaj uhttp://library.ncl.res.in/content/nanocomposite-silica-surfactant-microcapsules-evaporation-induced-self-assembly-tuning-002033nas a2200181 4500008004100000022001400041245007900055210006900134260011000203300001200313490000700325520132300332100002701655700002601682700001801708700002101726856010401747 2013 eng d a0148-605500aNecking in extrusion film casting: the role of macromolecular architecture0 aNecking in extrusion film casting the role of macromolecular arc aSTE 1 NO 1, 2 HUNTINGTON QUADRANGLE, MELVILLE, NY 11747-4502 USAbJOURNAL RHEOLOGY AMER INST PHYSICScMAR a559-5830 v573 a

Extrusion film casting (EFC) is used on an industrial scale to produce several thousand tons of polymer films and coatings. While significant research has been carried out on necking of films of viscoelastic melts in EFC, the influence of macromolecular chain architecture on the necking behavior is not yet fully understood. In the present research, we have explored experimentally and theoretically the effects of long chain branching and molecular weight distribution on the extent of necking during EFC. Polyethylenes of essentially linear architecture but having narrow and broad molecular weight distributions, and polyethylenes having long chain branching were used for experimental studies. The EFC process was analyzed using the one-dimensional flow model of Silagy et al. [Polym. Eng. Sci. 36(21), 2614-2625 (1996)] in which multimode molecular constitutive equations namely the ``extended pom-pom'' equation (for long chain branched polymer melts) and the ``Rolie-Poly (Rouse linear entangled polymers)'' equation (for linear polymer melts) were incorporated. We show that the model qualitatively captures the salient features of the experimental data thereby elucidating the role of chain architecture on the extent of necking. (C) 2013 The Society of Rheology. [http://dx.doi.org/10.1122/1.4788911]

1 aPol, Harshawardhan, V.1 aThete, Sumeet, Suresh1 aDoshi, Pankaj1 aLele, Ashish, K. uhttp://library.ncl.res.in/content/necking-extrusion-film-casting-role-macromolecular-architecture-002229nas a2200289 4500008004100000022001400041245010000055210006900155260005700224300001100281490000700292520129500299653001301594653001401607653000901621653001101630653001201641653001801653653001701671100002301688700001801711700002201729700002601751700001801777700002101795856012301816 2014 eng d a0035-451100aNonisothermal analysis of extrusion film casting process using molecular constitutive equations0 aNonisothermal analysis of extrusion film casting process using m a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGERcJAN a85-1010 v533 a

Extrusion film casting (EFC) is a commercially important process that is used to produce several thousand tons of polymer films and coatings. In a recent work, we demonstrated the influence of polymer chain architecture on the extent of necking in an isothermal film casting operation (Pol et al., J Rheol 57:559-583, 2013). In the present research, we have explored experimentally and theoretically the effects of long-chain branching on the extent of necking during nonisothermal film casting conditions. Polyethylenes of linear and long-chain branched architectures were used for experimental studies. The EFC process was analyzed using the 1-D flow model of Silagy et al. (Polym Eng Sci 36:2614-2625, 1996) in which the energy equation was introduced to model nonisothermal effects, and two multimode constitutive equations, namely the ``extended pom-pom'' (XPP, for long-chain branched polymer melts) equation and the ``Rolie-Poly stretch version'' (RP-S, for linear polymer melts) equation, were incorporated to account for the effects of polymer chain architecture. We show that the model does a better job of capturing the qualitative features of the experimental data, thereby elucidating the role of chain architecture and nonisothermal conditions on the extent of necking.

10aBranched10aExtrusion10aFilm10aLinear10aNecking10aNonisothermal10aPolyethylene1 aPol, Harshawardhan1 aBanik, Sourya1 aAzad, Lal, Busher1 aThete, Sumeet, Suresh1 aDoshi, Pankaj1 aLele, Ashish, K. uhttp://library.ncl.res.in/content/nonisothermal-analysis-extrusion-film-casting-process-using-molecular-constitutive-002314nas a2200157 4500008004100000245012400041210006900165260000800234300001000242490000700252520170300259100002201962700001801984700002702002856012702029 2017 eng d00aNew insights into the use of multi-mode phenomenological constitutive equations to model extrusion film casting process0 aNew insights into the use of multimode phenomenological constitu cJAN a35-710 v333 aThis article is concerned with the effect of the individual viscoelastic relaxation modes of a polymer melt on its behavior in polymer melt extrusion film casting process. We compare the predicted versus experimentally obtained film necking or neck-in profile as a function of draw ratio. The predicted necking profile was obtained using well-established one-dimensional isothermal flow kinematics and consisted of using two different phenomenological constitutive equations, upper convected Maxwell and Phan-Thien-Tanner, with a discrete spectrum of relaxation times. The numerical simulations, containing the two different phenomenological constitutive equations, provided an insight into the effect of the slow and the fast relaxing modes on the stresses, strains, and strain/extensional rates that develop in the molten polymer film as it is stretched from the die exit to the chill-roll. The slow relaxing modes follow trends that are directly proportional to strain (similar to Hookean solids), whereas the fast relaxing modes follow trends that are directly proportional to the stretch rate (in accordance with Newton's law of viscosity). Comparing the numerical predictions with the experiments showed that predictions using the upper convected Maxwell constitutive equation best described the long-chain branched polymers (like low-density polyethylene, which shows extensional strain hardening) in the extrusion film casting process. On the other hand, predictions using the Phan-Thien-Tanner constitutive equation best described the linear polymers (like linear low-density polyethylene, which does not show noticeable extensional strain hardening) in the extrusion film casting process.1 aThete, Sumeet, S.1 aDoshi, Pankaj1 aPol, Harshawardhan, V. uhttp://library.ncl.res.in/content/new-insights-use-multi-mode-phenomenological-constitutive-equations-model-extrusion-film