The disposal of large amounts of waste from daily use polymers is among one of the foremost concerns in the current era. Effective utilization of bio-renewable materials procured from natural sources has been proposed as a potential solution to this problem. Among such different polymers, Poly lactic acid (PLA) which is a bio-degradable polymer, resembles quite promotable features, which can be polymerized from sustainable sources as chips sugarcane, starch and corn. Ring-opening polymerization (ROP) of Lactide (LA) monomer considering catalysts such as Al, Sn or Zn is one of the efficient methods for the PLA synthesis. However, the PLA polymerized through this type of catalysts may contain trace elements of the catalyst. Due to their carcinogenic nature, the traces of such catalysts should be (ideally) removed from the synthesis process. The use of alternative energy (AE-UV, Microwave) sources could be a potential route. Alternative development of non-metal catalysts is best alternatives for the processing of PLA through ROP. PLA layer based composite materials are gaining huge interest due to their multiple application (food, medical etc.) as eco-friendly material. In this article, we review on the implementation of AE sources for PLA processing and to populate the current state-of-the-art associated with the PLA research, especially application in nanocomposite materials field. A C C E P T E DACCEPTED MANUSCRIPT 2 ROP of Monomers through Metal/ ROP of Monomers through Metal/ ROP of Monomers through Metal/ ROP of Monomers through Metal/metal metal metal metal----free free free free Catalyst Catalyst Catalyst CatalystThe basis of the ROP process starts with opening the cyclic ring of monomers like amides (lactams), esters (lactones) and a cyclic ether. Then the opened ring acts as an active centre where other monomers join to create a longer polymer chain via ionic propagation consisting of initiation/ propagation as well as termination reactions [12]. In last two decades, several different classes of catalysts were implemented to synthesis PLA however, metal-based catalysts are the most common [7][8][9][10][11]. Apart from metal, organic and enzyme-based catalysts were also tried but with regards to the efficiency and reaction time, metal based catalysts show a more promising effect than non-metal based catalysts. Among many, Sn(Oct) 2 was a highly approved catalyst by United State food and drugs association (USFDA) for catalysis of LA. Once the monomer gets activated by the initiator (catalyst), the active site attracts other monomers to attach and increase the chain length. Thermodynamic and reaction kinetic are key factors for the suitability of polymerization of cyclic monomers [12], [13].

In this study, a novel kind of hybrid pigment based on nanoclays and dyes was synthesized and characterized. These nanoclay-based pigments (NCPs) were prepared at the laboratory with sodium montmorillonite nanoclay (NC) and methylene blue (MB). The cation-exchange capacity of NC exchanged with MB was varied to obtain a wide color gamut. The synthesized nanopigments were thoroughly characterized. The NCPs were melt-mixed with linear low-density polyethylene (PE) with an internal mixer. Furthermore, samples with conventional colorants were prepared in the same way. Then, the properties (mechanical, thermal, and colorimetric) of the mixtures were assessed. The PE-NCP samples developed better color properties than those containing conventional colorants and used as references, and their other properties were maintained or improved, even at lower contents of dye compared to that with the conventional colorants.

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The reported research work was a multi-disciplinary, collaborative effort. Author SPD is the lead researcher and author of this manuscript. A detailed literature review and information regarding the ROP of lactide in the literature was conducted by author SPD as part of his doctoral thesis. Authors SPD, VM, HAA, JLB and KB contributed to the development of detailed study for the state-of-the art in the field of chronological development in the field of PLA processing. The author's contributed equally for making the manuscript more scientific and meaningful in terms of English language.

In this study, a new type of nanopigment, obtained from a nanoclay (NC) and a dye, was synthesized in the laboratory, and these nanopigments were used to color an ethylene vinyl acetate (EVA) copolymer. Several of these nanoclay-based pigments (NCPs) were obtained through variations in the cation exchange capacity (CEC) percentage of the NC exchanged with the dye and also including an ammonium salt. Composites of EVA and different amounts of the as-synthesized nanopigments were prepared in a melt-intercalation process. Then, the morphological, mechanical, thermal, rheological, and colorimetric properties of the samples were assessed. The EVA/NCP composites developed much better color properties than the samples containing only the dye, especially when both the dye and the ammonium salt were exchanged with NC. Their other properties were similar to those of more conventional EVA/NC composites.

PLA is one of the most promising bio-compostable and bio-degradable thermoplastic polymers made from renewable sources. PLA is generally produced by ring opening polymerization (ROP) of lactide using the metallic/bimetallic catalyst (Sn, Zn, and Al) or other organic catalysts in a suitable solvent. In this work, reactive extrusion experiments using stannous octoate Sn(Oct) 2 and tri-phenyl phosphine (PPh) 3 were considered to perform ROP of lactide. Ultrasound energy source was used for activating and/or boosting the polymerization as an alternative energy (AE) source. Ludovic ® software, designed for simulation of the extrusion process, had to be modified in order to simulate the reactive extrusion of lactide and for the application of an AE source in an extruder. A mathematical model for the ROP of lactide reaction was developed to estimate the kinetics of the polymerization process. The isothermal curves generated through this model were then used by Ludovic software to simulate the "reactive" extrusion process of ROP of lactide. Results from the experiments and simulations were compared to validate the simulation methodology. It was observed that the application of an AE source boosts the polymerization of lactide monomers. However, it was also observed that the predicted residence time was shorter than the experimental one. There is potentially a case for reducing the residence time distribution (RTD) in Ludovic ® due to the 'liquid' monomer flow in the extruder. Although this change in parameters resulted in validation of the simulation, it was concluded that further research is needed to validate this assumption.

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