Engineering of Poly Lactic Acids (PLAs) for melt processing: Material structure and thermal properties

Abstract

Bottles and other packaging account for approximately 70% of the global market of biopolymers, which include both biodegradable and durable materials. Durable materials account for the vast majority of the market, especially the bottles. Degradable polymers are instead refrained by the often-insufficient mechanical and thermal properties, which limit their usage to single-use packaging items at ambient temperature and in dry conditions. In this respect, the present work deals with the development and manufacturing of innovative and custom-built Poly Lactic Acids (PLAs) for injection and compression molding, which are designed to be compostable, suitable for food contact and characterized by a good compromise of mechanical properties and thermal stability. A commercial grade PLA was, therefore, compounded in a twin-screw co-rotating extruder by the addition of maleated and glycidyl methacrylate PLAs as chain extenders and micro-lamellar talc as mineral filler and nucleation promoter. Compatibilization between PLA, chain extenders and mineral filler was, therefore, investigated. Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared Spectroscopy (FTIR) were performed to evaluate the material structure and thermal response of the pellets after reactive compounding extrusion. The experimental findings show that material structure and, especially, crystallization of the PLA can be controlled by fine-tuning the compound formulation as well as by setting of the operational parameters. In addition, achievement of the appropriate crystallization degree in the polymer is found to lead to composite materials, which can boast very good thermal stability. Accordingly, the custom-built PLA formulations feature the potential to expand significantly the fields of application of non-durable polymers, thus posing a valid alternative to both durable biopolymers and conventional plastics in injection and compression molding process. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44504. © 2016 Wiley Periodicals, Inc

Engineered poly(lactic acid)‐talc biocomposites for melt processing: Effects of co‐blending with poly(butylene succinate) and poly(butylene terephthalate) on thermal and mechanical behavior

“…In fact, from both the scans, IM #3 shows a higher X c than IM #6 (from 37% and 20% to 29% and 18%), IM #2 than IM #5 (from 28% and 14% to 19% and 10%), and IM #1 than IM #4 (from 32% and 19% to 23% and 15%). In the same way, other previous works conducted on similar systems demonstrated the effect induced by the presence of MA‐PLA on the mobility of PLA chains and its capability to be organized into crystalline structures resulting in a crystallinity reduction . This was explained by supposing branching mechanisms for the PLA macromolecules due to the reaction with the maleated chain extender, that determine a macromolecular architecture of the resulting polymer characterized by a reduced mobility and, hence, a reduced self‐assembling capability into crystalline structures during the cooling process.…”

“…Maleate and glycidyl methacrylate grafted polymers, including nonacrylate and acrylate are rather typical additives employed as reactive intermediates in extrusion compounding processes of PLA, due to their affinity with the polymer matrix. To increase the affinity of the compatibilizing reactive additives with the PLA phase and to limit the use of noncompostable phases in accordance with the regulatory frame, maleate and glycidyl methacrylate grafted PLAs have been developed and previously tested, showing the possibility to effectively tune the properties of the resulting PLA compounds .…”

Improvements in mechanical strength and thermal stability of injection and compression molded components based on Poly Lactic Acids

“…[40,41] The results of such strategy, employing the reactive compatibilization of PLA with maleic anhydride (MAH) grafted PLA (PLA-MA), glycidyl methacrylate (GMA) grafted PLA (PLA-GMA), and microlamellar talc, were further investigated. [40,41] The results of such strategy, employing the reactive compatibilization of PLA with maleic anhydride (MAH) grafted PLA (PLA-MA), glycidyl methacrylate (GMA) grafted PLA (PLA-GMA), and microlamellar talc, were further investigated.…”

Poly(lactic acid)–thermoplastic starch–cotton composites: Starch‐compatibilizing effects and composite biodegradability

“…Several authors have observed that there has been an increase in studies aimed at the development of new environmentally friendly materials (ecofriendly materials). These studies have primarily focused on polymers from renewable or biodegradable sources . They have included a high use of poly(lactic acid) (PLA) because of its set of properties and applications, which are similar to those of poly(ethylene terephthalate) commodities .…”