@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} } @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 {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} }