@article {43561, title = {Controlling necking in extrusion film casting using polymer nanocomposites}, journal = {Journal of Macromolecular Science Part B-Physics}, volume = {56}, year = {2017}, month = {FEB}, pages = {213-233}, abstract = {The research described was concerned with the effect of layered-silicate-based organically modified nanoclay fillers on controlling the extent of necking in a polymer melt extrusion film casting (EFC) process. We show that a linear polythylene resin (such as a linear low-density polyethylene-LLDPE) filled with a very low percentage of well-dispersed (or intercalated) nanoclay displays an enhanced resistance to the necking phenomenon. In general, melt-compounded nanoclay-filled LLDPE resin formulations displayed a higher final film width (less necking), thus a lower final film thickness (greater draw down for the same draw ratio), and cooled down faster when compared to the base LLDPE resin. Incorporation of nanoclay filler in the mainly linear chain LLDPE resin led to significant modification of the melt rheological properties that, in turn, affected the melt processability of these formulations. Primarily, the intercalated nanoclay-filled LLDPE formulations displayed the presence of strain-hardening in unaxial extensional rheology. Additionally, the presence of well-dispersed nanoclay in the LLDPE resin led to a display of prominent extrudate swell indicating the presence of melt elasticity in such formulations. The presence of melt elasticity, as shown by shear rheology and strain-hardening, observed by uniaxial extensional rheology, contributed to the LLDPE nanoclay formulations displaying an enhanced resistance to necking for these films. It can be concluded that linear chain polymers susceptible to necking in an EFC process can be made more resistant to such necking by using nanoclay fillers at very low levels of loading.}, doi = {10.1080/00222348.2017.1289797}, author = {Rokade, Dhammaraj and Azad, Lal B. and Poddar, Suparna and Mishra, Satyendra and Pol, Harshawardhan V. and Shukla, Rishab} } @article {44538, title = {Non-isothermal analysis of extrusion film casting using multi-mode Phan-Thien Tanner constitutive equation and comparison with experiments}, journal = {Rheologica Acta}, volume = {57}, year = {2018}, month = {JUL}, pages = {493-503}, abstract = {

Extrusion film casting (EFC) is an industrially important process which produces thousands of tons of polymer films, sheets, and coating used for various industrial as well as household applications. In this paper, we focus on an instability which occurs during certain polymer processing operations operating under predominantly elongational flow, such as extrusion film casting and fiber spinning. This instability, called the draw resonance, occurs in the form of sustained periodic fluctuations in the film dimensions. It appears when the process goes beyond the critical line speed of the EFC process. In this work, a conventional linear stability analysis is carried out for nonisothermal EFC process to determine the onset of the draw resonance. The polymer rheology is modeled by the Phan-Thien Tanner (PTT) multi-mode constitutive equation. For the implementation, a conventional shooting method approach is used. Extrusion film casting experiments were also carried out using a conventional linear low-density polyethylene (LLDPE) by varying process parameters such as draw ratio and aspect ratio, to observe the effect on the stability of the process. Linear stability analysis results under non-isothermal conditions are compared and validated with existing results from literature and with our own experimental data. This work displays the effect of multiple relaxation modes as well as the temperature influence on the stability of EFC process. Finally, results also indicate that the temperature highly affects the stability of the EFC process and cannot be ignored from modeling of EFC process.

}, keywords = {Deborah number, Draw resonance, Film extrusion, Multi-mode, Nonisothermal, stability}, issn = {0035-4511}, doi = {10.1007/s00397-018-1095-7}, author = {Chougale, Sanket and Rokade, Dhammaraj and Bhattacharjee, Tanushree and Pol, Harshawardhan and Dhadwal, Renu} } @conference {45431, title = { Strategies to reduce necking and drawdown defects in polymer melt extrusion film casting process}, booktitle = {256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond}, year = {2018}, month = {AUG}, publisher = {AMER CHEMICAL SOC.}, organization = {AMER CHEMICAL SOC.}, address = {Boston, MA}, abstract = {256th National Meeting and Exposition of the American-Chemical-Society (ACS) - Nanoscience, Nanotechnology and Beyond}, author = {Rokade, Dhammaraj and Chougale, Sanket and Pol, Harshawardhan} } @article {46603, title = {Controlling draw resonance during extrusion film casting of nanoclay filled linear low-density polyethylene: an experimental study and numerical linear stability analysis}, journal = {Journal of Plastic Film \& Sheeting}, volume = {37}, year = {2021}, month = {JUL}, pages = {8756087920978443}, type = {Article}, abstract = {

Commercially important extrusion film casting (EFC) processes for manufacturing plastic films or sheets are hampered by several instabilities that severely limits their productivity. In this research we focussed on one important instability: the draw resonance that occurs during the EFC process mainly under extensional flow conditions. Draw resonance is the sustained periodic oscillations in the film dimensions, notably film width and thickness, when the process operates beyond a critical draw ratio (CDR). In this research our goal was to reduce this draw resonance instability by incorporating well dispersed nanoclay fillers in a base polymeric resin (such as a linear low density polyethylene - LLDPE) to determine how these nanocomposite (NC) formulations can prevent or reduce the draw resonance defect. EFC experiments were conducted on the base resin and on the NC formulations under non-isothermal conditions to determine the onset of the draw resonance experimentally. Conventional linear stability analysis was performed to determine the onset of the draw resonance defect numerically. Numerical predictions for the onset of draw resonance were in qualitative agreement with our experimental data. Our results showed that incorporating appropriate nanoclay concentrations in a base polymeric resin indeed enhanced the EFC process stability for those polymer formulations and thus can have important economic implications for processors.

}, keywords = {Draw resonance, extensional strain hardening, Extrusion, Film, hydrodynamic interactions, Nanoclay, Nanocomposites, Polyethylene, Rheology, stability}, issn = {8756-0879}, doi = {10.1177/8756087920978443}, author = {Rokade, Dhammaraj and Chougale, Sanket and Patil, Prashant and Bhattacharjee, Tanushree and Gawande, Dnyaneshwar and Pol, Harshawardhan and Dhadwal, Renu} } @article {48671, title = {Palladium-catalyzed polar solvent empowered synthesis of hyper-branched ethylene oligomers and their applications}, journal = {Polymer Chemistry}, volume = {14}, year = {2023}, month = {JUL}, pages = {3239-3251}, type = {Article}, abstract = {

In this contribution, we report the synthesis of two naphthoxy imine ligands, 2-(((2,6-dibenzhydryl-4-methoxyphenyl)imino)methyl)naphthalen-1-ol (L1) and 2-(((2,6-diisopropylphenyl)imino)methyl)naphthalen-1-ol (L2), with different steric and electronic features. L1 and L2 were treated with [(TMEDA)PdMe2] to obtain the corresponding neutral palladium(ii) complexes Cat.1 and Cat.2 in excellent yields. The identity of Cat.1 and Cat.2 was unambiguously ascertained using a combination of spectroscopic and analytical methods, including single-crystal X-ray diffraction. When exposed to 5 bar ethylene pressure, Cat.1 produced hyperbranched ethylene oligomers. The microstructure analysis of ethylene oligomers confirmed the existence of methyl, ethyl, propyl, and sec-butyl branches, with a molecular weight (M-n) of 500-1400 g mol(-1), a PDI of 1.46-2.10, and 67-106 branches per 1000 carbon atoms. The use of a polar solvent, tetrahydrofuran, led to a remarkable 3-fold increase in oligomerization activity without compromising the branching and molecular weight. The resultant hyperbranched ethylene oligomers were selectively monofunctionalized using industrially practiced hydroformylation, ozonolysis, and epoxidation, almost quantitatively. The hydroxy functionalized ethylene oligomer (F4) (5 wt\%) was melt-compounded with LLDPE and Nylon-6 to produce a tough yet flexible blend with a higher strain-to-failure as compared to an uncompatibilized blend.

}, issn = {1759-9954}, doi = {10.1039/d3py00311f}, author = {Birajdar, Rajkumar S. and Gonnade, Rajesh G. and Pol, Harshawardhan V. and Prabhu, M. Basava and Rokade, Dhammaraj and Nandimath, Sheetal and Chikkali, Samir H.} } @article {48310, title = {Rheology and processing study on controlling material and process defects in polymer melt extrusion film casting using polymer blends}, journal = {Journal of Plastic Film \& Sheeting}, volume = {39}, year = {2023}, month = {APR}, pages = {211-240}, type = {Article}, abstract = {

The primary objective of this research paper is to control the material and process defects in polymer melt extrusion film casting (EFC) process for linear chain architecture polyethylene (PE) resins through polymer blending methodology. Extrusion film casting is a well-known industrially important manufacturing process that is used to manufacture thousands of tons of polymer/plastic films/sheets and coated products. In this research, the necking defect in an EFC process has been studied experimentally for a linear low density polyethylene (LLDPE) resin and attempts have been made to control its necking by blending in a long chain branched (LCB) low density polyethylene (LDPE) resin. The blending methodology is based on the understanding that a LDPE resin displays enhanced resistance to necking as compared to the LLDPE resin. It is found that added LDPE resin enhances necking resistance for the primary LLDPE resin. Further, as the LDPE concentration increases in the blend formulation, the necking is further reduced as compared to pure LLDPE. Analogous to past studies on EFC of linear and long chain branched architecture containing PEs, it is observed that as the LDPE is increased in the blend formulations, the formulations displayed enhanced melt elasticity and extensional strain hardening in rheological studies. It is concluded from this study that polyethylene resins having linear chain architecture can be made amenable to enhanced resistance to necking using appropriate amount of a long chain branched resins. Finally, process defects such as the draw resonance onset could be shifted to higher draw ratios as the LDPE level is increased in the LLDPE-LDPE blend formulation.

}, keywords = {Draw resonance, Extrusion, Film, linear chain, long-chain branched, melt elasticity, Necking, onset, strain hardening}, issn = {8756-0879}, doi = {10.1177/87560879221150764}, author = {Rokade, Dhammaraj and Patil, Prashant and Nandimath, Sheetal and Pol, Harshawardhan} }