02940nas a2200313 4500008004100000022001400041245010600055210006900161260007300230300001000303490000800313520191500321653001202236653002002248653002302268653002402291653000802315653000802323653000802331100001802339700002702357700002302384700001702407700001702424700002102441700002102462700002102483856012202504 2011 eng d a0377-025700aExtrudate swell of linear and branched polyethylenes: ALE simulations and comparison with experiments0 aExtrudate swell of linear and branched polyethylenes ALE simulat aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN a12-240 v1663 a

Extrudate swell is a common phenomenon observed in the polymer extrusion industry. Accurate prediction of the dimensions of an extrudate is important for appropriate design of dies for profile extrusion applications. Prediction of extrudate swell has been challenging due to (i) difficulties associated with accurate representation of the constitutive behavior of polymer melts, and (ii) difficulties associated with the simulation of free surfaces, which requires special techniques in the traditionally used Eulerian framework. In a previous work we had argued that an Arbitrary Lagrangian Eulerian (ALE) based finite element formulation may have advantages in simulating free surface deformations such as in extrudate swell. In the present work we reinforce this argument by comparing our ALE simulations with experimental data on the extrudate swell of commercial grades of linear polyethylene (LLDPE) and branched polyethylene (LOPE). Rheological behavior of the polymers was characterized in shear and uniaxial extensional deformations, and the data was modeled using either the Phan-Thien Tanner (PTT) model or the eXtended Pom-Pom (XPP) model. Additionally, flow birefringence and pressure drop measurements were done using a 10:1 contraction-expansion (CE) slit geometry in a MultiPass Rheometer. Simulated pressure drop and contours of the principal stress difference were compared with experimental data and were found to match well. This provided an independent test for the accuracy of the ALE code and the constitutive equations for simulating a processing-like flow. The polymers were extruded from long (L/D=30) and short (L/D=10) capillaries dies at 190 degrees C. ALE simulations were performed for the same extrusion conditions and the simulated extrudate swell showed good agreement with the experimental data. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

10aALE-FEM10aextrudate swell10aFlow birefringence10aMultiPass Rheometer10aPSD10aPTT10aXPP1 aGanvir, Vivek1 aGautham, Basavarsu, P.1 aPol, Harshawardhan1 aBhamla, Saad1 aSclesi, Lino1 aThaokar, Rochish1 aLele, Ashish, K.1 aMackley, Malcolm uhttps://library.ncl.res.in/content/extrudate-swell-linear-and-branched-polyethylenes-ale-simulations-and-comparison-002207nas a2200265 4500008004100000022001400041245006400055210006400119260006700183300001400250490000700264520134600271100002501617700001801642700002201660700001901682700001901701700001801720700002301738700002001761700001801781700002301799700002101822856009801843 2015 eng d a0032-388800aExtrusion film casting of long chain branched polypropylene0 aExtrusion film casting of long chain branched polypropylene a111 RIVER ST, HOBOKEN 07030-5774, NJ USAbWILEY-BLACKWELLcSEP a1977-19870 v553 a

Extrusion film casting (EFC) is an important melt processing operation which is extensively used to make polypropylene (PP) films. Linear PP shows significant amount of necking and draw resonance during EFC. One of the ways to reduce necking is to introduce long chain branches (LCB) on the polymer backbone. The long branches impart extensional strain hardening behavior thereby stabilizing the melt flow. In this work, we investigate the influence of long chain branching in polypropylene on the extent of necking in the EFC process. Laboratory scale EFC experiments were performed on homopolymer PP of linear and long chain branched architectures. Simulations of the EFC process were carried out using the one-dimensional flow model of Silagy et al., Polym. Eng. Sci.,36, 2614 (1996) into which we incorporate two different multi-mode molecular constitutive equations namely, the eXtended Pom-Pom' equation (XPP, for long chain branched PP) and the Rolie-Poly' equation (RP-S, for linear PP). Our experimental data confirm that presence of long chain branching in PP reduces the extent of necking and our numerical predictions show qualitative agreement with experimental data, thereby elucidating the role of chain architecture on the extent of necking. POLYM. ENG. SCI., 55:1977-1987, 2015. (c) 2014 Society of Plastics Engineers

1 aChikhalikar, Kalyani1 aBanik, Sourya1 aAzad, Lal, Busher1 aJadhav, Kishor1 aMahajan, Sunil1 aAhmad, Zubair1 aKulkarni, Surendra1 aGupta, Surendra1 aDoshi, Pankaj1 aPol, Harshawardhan1 aLele, Ashish, K. uhttps://library.ncl.res.in/content/extrusion-film-casting-long-chain-branched-polypropylene-002370nas a2200169 4500008004100000245015600041210006900197260000800266300001200274490000700286520169900293100001801992700001802010700001802028700002302046856013102069 2017 eng d00aEffect of viscoelastic relaxation modes on stability of extrusion film casting process modeled using multi-mode Phan-Thien-Tanner constitutive equation0 aEffect of viscoelastic relaxation modes on stability of extrusio cJUL a487-5000 v473 aExtrusion film casting (EFC) is a commercially important process that is used to produce a significant quantity of polymer films, sheets and coatings for both industrial and household applications. Recently, we have demonstrated the influence of polymer chain architecture on the extent of necking under isothermal as well as non-isothermal film casting operation for commercially relevant polyolefin based materials [1-4]. In the present research, we focus on another instability that frequently occurs in high-speed EFC process called as draw resonance. Draw resonance manifests itself as an instability that causes periodic fluctuations in both the width as well as thickness of the extruded molten film above a critical draw ratio (DR). In this work, we have carried out a linear stability analysis of the isothermal EFC process using a multi-mode Phan-Thien-Tanner (PTT) constitutive equation to determine the onset of draw resonance. We show that as the number of relaxation modes is increased there is a dramatic change in the stability regions. In particular, there is a marked variation in the stability regions obtained by Simulating the multi-mode model and those obtained by taking averaged relaxation time of the modes. Additionally, as the number of faster-relaxing modes in a multi-mode spectrum is progressively increased, the process becomes increasingly stable as the level of elasticity in the melt decreases. Finally, the addition of a long relaxation mode in a multi-mode spectrum is akin to adding a long chain branch to a linear polymer that leads to a reduction in film necking and in many cases to enhanced process stability. (C) 2017 Elsevier Inc. All rights reserved.1 aDhadwal, Renu1 aBanik, Sourya1 aDoshi, Pankaj1 aPol, Harshawardhan uhttps://library.ncl.res.in/content/effect-viscoelastic-relaxation-modes-stability-extrusion-film-casting-process-modeled-using02487nas a2200277 4500008004100000022001400041245012500055210006900180260000900249300001400258490000600272520153800278653002001816653002001836653003501856653002101891653001401912100002501926700002001951700001901971700002301990700001902013700002002032700003102052856012602083 2024 eng d a2637-610500aEnhancing the crystallization kinetics and mechanical properties of poly(lactic acid) blends for 3D printing application0 aEnhancing the crystallization kinetics and mechanical properties cMAY  a5754-57620 v63 a

3D printing of poly(lactic acid) (PLA) blends has been attempted to resolve issues such as inherent brittleness and slow crystallization rate of PLA. However, a persistent challenge remains in the form of phase separation or gradual migration of the blended soft polymer or plasticizers. To simultaneously enhance the miscibility of the blends and toughness of 3D-printed parts, a triblock copolymer PLA-PEG-PLA was synthesized and blended with PLA in varying proportions (5, 10, 15, and 20 wt %). Blending only 10-20 wt % low molecular weight PLA-PEG-PLA into PLA yielded a miscible blend that showed a 45-fold increase in elongation at break and a 23-fold enhancement in toughness over neat PLA. Scanning electron microscopy (SEM) images of fractured cross sections revealed a brittle to ductile transition in 3D-printed PLA/PLA-PEG-PLA samples. Isothermal crystallization studies and data analysis using the Avrami equation showed an enhancement in the crystal growth rate and overall rate of crystallization. The blends achieved half of their crystallinity in approximately 3 min, a significant improvement over the 9 min required by PLA alone. This underscores the efficiency of our approach. This was also evident in the spherulite growth of 3D-printed PLA and mPLA blends when examined using polarized optical microscopy (POM). To the best of our knowledge, this is the first report exploring the use of blends that include PLA and low molecular weight PLA-PEG-PLA triblock copolymers for 3D printing applications.

10aCrystallization10aFFF 3D printing10aPLA-PEG-PLA triblock copolymer10apoly(lacticacid)10atoughness1 aKothavade, Premkumar1 aYadav, Prashant1 aGopal, Animesh1 aPol, Harshawardhan1 aKafi, Abdullah1 aBateman, Stuart1 aShanmuganathan, Kadhiravan uhttps://library.ncl.res.in/content/enhancing-crystallization-kinetics-and-mechanical-properties-polylactic-acid-blends-3d02608nas a2200265 4500008004100000022001400041245009400055210006900149260000800218300000800226490000700234520172000241653002601961653002501987653002302012653002602035653002402061653002202085100001902107700002202126700002002148700002802168700002302196856012302219 2025 eng d a0250-470700aEnhancement of mechanical and rheological properties of PA-12 through silane modification0 aEnhancement of mechanical and rheological properties of PA12 thr cDEC a1460 v483 a

This research examines the effects of silane modifications on polyamide 12 (PA-12) to improve its mechanical and thermal properties. The study employs a reactive extrusion technique to integrate various silanes-Dynasylan (R) AMEO, Dynasylan (R) 1189, Dynasylan (R) DAMO and Dynasylan (R) VPS 4721-at different concentrations (0.25, 0.5 and 0.75%). Key findings reveal that silane modifications significantly enhance the tensile strength, impact resistance and viscoelastic behaviour of PA-12, with the Dynasylan (R) DAMO formulation achieving the highest tensile strength of 38.25 MPa vis-& agrave;-vis 8.02 MPa for PA-12. The modifications also resulted in a reduction of crystallinity by over 35%, contributing to improved toughness and impact strength. Rheological assessments indicate that the flow properties of PA-12 are positively altered, enhancing its complex viscosity and storage modulus, which are crucial for applications in automotive and aerospace industries. Thermal analysis through differential scanning calorimetry and thermogravimetric analysis confirms improved thermal stability, particularly in the 0.5% Dynasylan (R) AMEO-modified sample, exhibiting an onset temperature of 421.87 degrees C. The study emphasizes the importance of the silane type and dosage in tailoring PA-12's performance for advanced applications, suggesting future research directions to further refine silane-modification techniques for enhanced polymer performance. This research provides valuable insights into polymer-modification strategies, highlighting the potential for silane treatments to optimize the mechanical, thermal and rheological properties of PA-12 for diverse industrial applications.

10amechanical properties10aPolyamide 12 (PA-12)10areactive extrusion10arheological behaviour10asilane modification10athermal stability1 aJadhav, Pravin1 aMahajan, Digvijay1 aPatil, Prashant1 aUmbarkar, Shubhangi, B.1 aPol, Harshawardhan uhttps://library.ncl.res.in/content/enhancement-mechanical-and-rheological-properties-pa-12-through-silane-modification