Synthesis, properties, and applications of polylactic acid‐based polymers

Abstract

Polylactic acid (PLA) is known as one of the greatest promising bioabsorbable and compostable polyesters with the capability of high molecular weight synthesis. Lactic acid condensation, azeotropic dehydration, and condensation ring‐open polymerize of lactide are three methods for PLA polymerization. Comprehension of material properties is critical for choosing the right processing method and adjusting PLA characteristics. A variety of mechanical properties of this material, from soft and elastic to stiff and high strength makes PLA suitable for a wide range of applications. Besides, PLA can be blended or copolymerized with other polymeric or non‐polymeric substances. Thus, this polymer can achieve suitable chemical, mechanical, and rheological properties. Understanding the role of these properties and selecting a suitable processing technique is necessary for its intended consumer and various applications. This study elaborated a general summary of the polymerization, processing, and characteristics of PLA (i.e., structural diversities, rheological performances, mechanical properties, and permeability). Besides, this work presented some information regarding essential factors that can be used for modifying PLA properties to address the requirements for various applications such as biomedical, food packing, biocomposite, and additive manufacturing.

Hybrid manufacturing of mixed‐material bilayer parts via injection molding and material extrusion three‐dimensional printing

“…These results indicated that the varied combinations of parameters would affect the tensile performances of finished specimens. In addition, low standard deviations of maximum tensile strength and Young's Modulus can be found in Table 4, which agrees with the tensile behaviors of half thickness series samples in previous publications both for ABS samples and PLA specimens 40,41 . This indicates a superior flexibility in these samples, 46 making overmolding technique popularized in manufacturing industry, such as aerospace products and electronic components.…”

“…Regarding the manufacturing time for the FDM and IM specimens, Gong et al shows it takes 6 min to fabricate one PLA specimen using FDM only. In converse, two IM specimens can be fabricated in 90 s 41 …”

“…Infill density indicates the quantity of material used for the internal structure of FDM specimens, with a higher value enhancing properties of FDM specimens, such as mechanical properties and fire properties 47,48 . However, a different phenomenon can be found that a 50% infill density of substrate results in greater tensile performance for ABS pieces but a 75% infill density of substrate can be attributed to higher tensile stress for PLA pieces, 40,41 which emphasizes the importance to figure out the real explanation conforming to the greater tensile performances of finished specimens.…”

“…The tensile performances of these mixed‐material specimens were compared to those fabricated using ABS and PLA material only, in which around 2% lower value of tensile strength can be determined if compared to samples fabricated using ABS only, 40 but a clear deviation (20%) can be found in comparison to those PLA specimens 41 . The phenomenon can primarily be ascribed to insufficient contact between the two materials, leading to weak sections in the finished specimens.…”

“…ABS and PLA are two popular thermoplastics right now because they have high mechanical properties and processability but low melting temperatures 39–41 . Some previous publications have fabricated batches of overmolded samples with varied joint configurations using ABS 42 and PLA, 43 respectively, to determine the effect of overmolding technique on their tensile performances and found a higher tensile performance in specimens with female joint configurations.…”