@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} } @article {49528, title = {Electrochemical deconstruction of waste polyvinylidene chloride (PVDC) to value-added products in batch and flow}, journal = {Chemistry-A European Journal}, volume = {31}, year = {2025}, month = {FEB}, type = {Article}, abstract = {

Chlorinated polymers have made enormous contributions to materials science and are commercially produced on a large scale. These chlorinated polymers could be recycled as chlorine sources to efficiently produce valuable chlorinated compounds owing to their facile release of HCl. Although the thermal stability of PVDC is low compared to PVC, this can be advantageous in terms of easy and fast dehydrochlorination. Herein, we report an efficient electrochemical chlorination using poly(vinylidene chloride) (PVDC) as a chlorine source that works in an undivided cell and applies to a good number of examples. This method works on commodity polymers such as waste PVDC-PVC pharma blister film, PVDC-PO multilayer food packaging, and compression molded sheets of Ixan PVDC (with heat stabilizer) with similar efficiency. Furthermore, this method also provides the dechlorination of PVDC up to 98 \%, leading to unsaturated dechlorinated material. Converting PVDC into more stable unsaturated compounds, the release of harmful chlorine-containing gases during incineration can be minimized. Additionally, this method is not only restricted to batch processes but an electroflow process for PVDC dechlorination and electrosynthesis has also been demonstrated.

}, keywords = {chlorination, Electrochemical recycling, Electroflow-synthesis, Graphitic material, Polyvinylidene chloride}, issn = {0947-6539}, doi = {10.1002/chem.202403980}, author = {Mishra, Subhadip and Kar, Sourav and Rangappa, Raghavendrakumar and Patil, Prashant and Kadam, Vijay and Chikkali, Samir H. and Samanta, Ramesh C.} } @article {49685, title = {Upcycling of postconsumer recyclate polypropylene into low warping and high toughness 3D printable filaments}, journal = {ACS Applied Polymer Materials}, volume = {7}, year = {2025}, month = {JUN }, pages = {7373-7381}, type = {Article}, abstract = {

Polypropylene (PP) is widely used in commodity applications owing to its chemical stability, mechanical properties and low cost. However, almost 50\% of the produced PP ends up as postconsumer waste (PCW) within a short period of usage. Being a non-biodegradable polymer, recycling PCW PP is important to mitigate plastic waste in landfills. Nonetheless, recycling or upcycling postconsumer recyclate (PCR) PP into valuable resources without deterioration in physical and mechanical properties is a challenge. This report presents an approach to upcycle PCR polypropylene (rPP) into high quality 3D printing filament that not only prints with very low warpage but with significantly high elongation at break and toughness. Incorporation of poly(butylene adipate-co-terephthalate) (PBAT) along with maleic anhydride grafted polypropylene (MAPP) in specific proportions led to a significant enhancement in mechanical properties, miscibility, crystallization behavior, and 3D printability. rPP/PBAT blends with 20 wt \% PBAT and 10 wt \% MAPP exhibited a 62-fold enhancement in elongation at break over rPP (from 1.88 to 118.29\%) and a 72-fold increase in toughness (from 2 to 143.60 kJ/m3) with almost similar tensile strength. The final printed components had better layer adhesion and structural stability with a dramatic decrease in warpage, from 25.82\% for pristine rPP to only 7.86\% for rPP/PBAT blend. Isothermal crystallization studies and data analysis using the Avrami equation showed that crystallization half-time (t 1/2), which measures the duration needed for half of the total crystallinity to form, increased from 12.6 s for rPP to 66 s for the rPP/PBAT blend. This report demonstrates an approach to upcycle PCR PP, a positive step toward realizing the goals of circular economy and sustainable additive manufacturing.

}, keywords = {Crystallization, FFF 3D printing, polypropylene/poly(butylene adipate-co-terephthalate)blends, toughness, warpage}, issn = {2637-6105}, doi = {10.1021/acsapm.5c00942}, author = {Gopal, Animesh and Patil, Prashant and Pol, Harshawardhan and Shanmuganathan, Kadhiravan} }