Functional Nanocomposite Films of Poly(Lactic Acid) with Well-Dispersed Chitin Nanocrystals Achieved Using a Dispersing Agent and Liquid-Assisted Extrusion Process

Mitul Patel,Giorgia Spigno,Shiyu Geng,Kristiina Oksman,Linn Berglund,Daniel Schwendemann

doi:10.3390/molecules26154557

Abstract

The development of bio-based nanocomposites is of high scientific and industrial interest, since they offer excellent advantages in creating functional materials. However, dispersion and distribution of the nanomaterials inside the polymer matrix is a key challenge to achieve high-performance functional nanocomposites. In this context, for better dispersion, biobased triethyl citrate (TEC) as a dispersing agent in a liquid-assisted extrusion process was used to prepare the nanocomposites of poly (lactic acid) (PLA) and chitin nanocrystals (ChNCs). The aim was to identify the effect of the TEC content on the dispersion of ChNCs in the PLA matrix and the manufacturing of a functional nanocomposite. The nanocomposite film’s optical properties; microstructure; migration of the additive and nanocomposites’ thermal, mechanical and rheological properties, all influenced by the ChNC dispersion, were studied. The microscopy study confirmed that the dispersion of the ChNCs was improved with the increasing TEC content, and the best dispersion was found in the nanocomposite prepared with 15 wt% TEC. Additionally, the nanocomposite with the highest TEC content (15 wt%) resembled the mechanical properties of commonly used polymers like polyethylene and polypropylene. The addition of ChNCs in PLA-TEC15 enhanced the melt viscosity, as well as melt strength, of the polymer and demonstrated antibacterial activity.

Highlights

PLA is a member of the aliphatic polyester family produced from renewable resources and has recently gained attention due to its biocompatibility, biodegradability, transparency, high modulus and strength
An optical microscopy (OM) image of chitin and isolated chitin nanocrystals (ChNCs) dispersed in water is shown in Figures 1a and S1
The results show that the addition of 1 wt% ChNCs slightly decreased the transparency of the PLA-triethyl citrate (TEC) films; the increasing content of the dispersing agent improved the transmittance of the nanocomposites from 82% to 88.5%, indicating a better dispersion of

Summary

Introduction

PLA is a member of the aliphatic polyester family produced from renewable resources and has recently gained attention due to its biocompatibility, biodegradability, transparency, high modulus and strength. The conventional extrusion process for the preparation of PLA nanocomposites is challenging due to the feeding of dried nano-sized materials. To improve the dispersion of nano-sized reinforcements in PLA polymer matrices, different approaches have been attempted, including surface modifications by acylation and polymer grafting, as well as the coupling agent, which enhance the compatibility between the nanomaterial and polymers [9,10,11]. These strategies, are expensive, complex, time-consuming and do not solve all of the problems described above

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Conclusion