Thermal behavior of injection‐ and compression‐molded custom‐built polylactic acids

Abstract

In recent time, the quest for renewable materials for the development of packaging items is constantly increasing. The class of polylactic acids (PLAs) is the most promising one, although a broader scale commercial expansion of these polymers cannot leave unceasing enhancement of their functional properties aside, especially toughness and thermal stability. Similarly, continuous innovation in prototyping competitive easy-route solutions for material processing is another key to successful industrial applications of PLAs. In this respect, this study deals with the design and formulation of innovative custom-built PLAs for injection and compression molding, which are compostable, suitable for food contact, and characterized by a good compromise of mechanical properties and thermal resistance. Therefore, a commercial grade PLA was modified by reactive compounding extrusion with maleic anhydride (MAH)-grafted PLA (PLA-MA) and glycidyl methacrylate (GMA)-grafted PLA (PLA-GMA) and micro-lamellar talc. Material structure and thermal response of the compounds were evaluated by differential scanning calorimetry (DSC) and Fourier transform-infrared spectroscopy (FTIR). The experimental findings show that material structure and, especially, crystallization of the PLA can be controlled by fine-tuning the compound formulation. In addition, achievement of the appropriate crystallization degree in the polymer can lead to compostable composite materials with good thermal stability. Accordingly, the custom-built PLA formulations feature the potential to expand significantly the fields of application of compostable biopolymers, thus posing a valid alternative to both durable not compostable bioplastics and conventional plastics in injection and compression molding process

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

“…% range 21-49) materials. Melt processing by both injection and compression molding increases the weight crystallinity degree of the formulations compared to the pristine extrusion products, [40,41] as it can be argued by comparing the data in Table 2, first scan, with the corresponding data in Table 3 referring to the extruded pellets. Compression molding causes the greatest increase in the crystallinity of the material.…”

“…[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.…”

“…The present research effort deals with the characterization of custom‐built compostable and food grade PLAs obtained by injection and compression molding from an innovative engineered formulation . 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.…”