Recent Advances in the Investigation of Poly(lactic acid) (PLA) Nanocomposites: Incorporation of Various Nanofillers and their Properties and Applications

Abstract

Poly(lactic acid) (PLA) is considered the most promising biobased substitute for fossil-derived polymers due to its compostability, biocompatibility, renewability, and good thermomechanical properties. However, PLA suffers from several shortcomings, such as low heat distortion temperature, thermal resistance, and rate of crystallization, whereas some other specific properties, i.e., flame retardancy, anti-UV, antibacterial or barrier properties, antistatic to conductive electrical characteristics, etc., are required by different end-use sectors. The addition of different nanofillers represents an attractive way to develop and enhance the properties of neat PLA. Numerous nanofillers with different architectures and properties have been investigated, with satisfactory achievements, in the design of PLA nanocomposites. This review paper overviews the current advances in the synthetic routes of PLA nanocomposites, the imparted properties of each nano-additive, as well as the numerous applications of PLA nanocomposites in various industrial fields.

Keywords: applications; nano-additives; nanocomposites; poly(lactic acid) (PLA); properties; synthesis.

Figure 4

Biological resources for the green synthesis of metal-oxide NPs [65].

Figure 1

Synthetic routes employed for the preparation of PLA nanocomposites.

Figure 2

Top and cross-sectional microstructure of (a) neat PLA and (b) PLA-graphene filaments [57].

Figure 3

Top-down and bottom-up approaches for the fabrication of metal-based nanoparticles [62].

Figure 5

Biosynthesis of ZnO NPs using L.specioca leaves [72].

Figure 6

SEM analysis of ZnO-NPs: (a) 200 °C (spherical shape) and (b) 800 °C (nanorods) [72].

Figure 7

Carbon-based nano-additives. Three-dimensional presentation of (a) SWCNTs and (b) MWCNTs [110]; (c) schematic representation of a graphene sheet [111] and (d) 2D and 3D illustration of the fullerene C60 structure [112].

Figure 8

Chemical structure of lignin (Major monolignol units are colored: sinapyl alcohol—red, guaiacyl alcohol—blue, and p-coumaryl alcohol—green) [135].

Figure 9

Chemical structure of tannin [137].

Figure 10

Reaction kinetics and % of inhibition of the PLA-based (a) TANN and (b) KL composites film evaluated with DPPH radical scavenging in the methanol solution indicated after 24 h [144].

Figure 11

Commonly employed preparation routes for nano-biochar from biomass feedstock [159].

Figure 12

Schematic overview of the numerous applications involving PLA nanocomposites.

Figure 13

Industrial scale setup of the film blowing process: (a) Calendaring of the neat PLA film and (b,c) the blown film of the 1% PLA/MgO nanocomposite [194].

Figure 14

Subdermal implants of F1, F2, F3, and F4 at 60 days: (A) Formulations from the 4 X HE technique, (B) formulations from the 10 X GT technique, and (C) formulations from the 100 X HE technique. Yellow oval: Implantation zone. D: Dermis. M: Muscle. Fc: Fibrous capsule. IZ: Implantation zone. Col III: type III collagen. Yellow arrows: Fragments of materials. Red arrows: Inflammatory cells. Blue arrows: Blood vessels. HE: Hematoxylin and Eosin technique. GT: Gomori technique [199].

Figure 15

Images of skin wound healing process in mice after 0, 7, and 14 days of treatment with the PLA/ZnO/TXA nanocomposites [203].

Figure 16

Filtration performance of FM1 (containing 0 wt.% TiO₂ prepared at a relative humidity of 45%), FM2 (containing 1 wt.% TiO₂ prepared at a relative humidity of 45%), FM3 (containing 1.75 wt.% TiO₂ prepared at a relative humidity of 45%), FM4 (containing 1.75 wt.% TiO₂ prepared at a relative humidity of 15%), and FM5 (containing 1.75 wt.% TiO₂ prepared at a relative humidity of 60%) at various face velocities: (a) filtration efficiency, pressure drop, and quality factor of FM1, FM2, and FM3 at a face velocity of 5.3 cm/s and 14.1 cm/s, respectively and (b) filtration efficiency, pressure drop, and quality factor of FM3, FM4, and FM5 at a face velocity of 5.3 cm/s and 14.1 cm/s, respectively [213].

Figure 17

SEM micrographs of the micro needle surfaces of PLA/MWCNTs nanocomposites [232].

Figure 18

(a) SEM micrograph of the developed MTX microspheres and (b) in vitro release profiles of MTX from microspheres within 15 days of study [237].

Figure 19

Effects of the c-CNT and f-CNT addition on the (a) tensile strength, and (b) Young’s modulus [238].

Figure 20

(a) Storage modulus (E′) and (b) Tan δ of pure PLA, PLA/c-CNT, and PLA/f-CNT obtained from DMA [238].

Figure 21

(a) Tensile strength variation pf PLA/lignin and nanolignin composites, (b) TEM micrographs of PLA/nanolignin containing 1 wt.% nanolignin and Reaction kinetics of the free radical DPPH during immersion of PLA–Lignin, (c) and PLA-Nanolignin (d) films in ethanol solution [260].

Figure 22

(A) Optical observation of prepared films before and after different incubation days under composting conditions and (B) % disintegrability degree under composting conditions [129].

Figure 23

(A) Visual observation of PLA and PLA/PEG/LCNF nanocomposites after different days under composting environment and (B) disintegration degree under composting conditions as a function of time [263].

Figure 24

Three-dimensional-printed scaffolds destined for tissue engineering applications. The top view shows the schematic drawing from Solidworks 2016 (Dassault Systèmes, Vélizy-Villacoublay, France). The bottom view shows the original SEM image of the 3D-printed scaffold (MakerBot Z18 3D printer, New York City, New York, USA) [291].

Figure 25

Schematic illustration of preparation and application of PLA/n-HA scaffolds for bone regeneration. The PLA/n-HA composite material was prepared by the wet mixing method, and the 3D-printed composite scaffold was made by PLA/n-HA filament. The material characterization and in vivo and in vitro experiments of the composite materials successively verified the sufficient mechanical strength and non-toxicity suitable for the promotion of the repair of bone defects [55].