High oxygen barrier chitosan films neutralized by alkaline nanoparticles

Urška Jančič,Tamilselvan Mohan,Karin Stana Kleinschek,Selestina Gorgieva,Silvo Hribernik,Mojca Božič,Rupert Kargl

doi:10.1007/s10570-021-04195-w

Urška Jančič, Tamilselvan Mohan + Show 5 more

Open Access

https://doi.org/10.1007/s10570-021-04195-w

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Journal: Cellulose	Publication Date: Sep 21, 2021
Citations: 10	License type: open-access

Affiliation: University of Maribor, Graz University of Technology

Abstract

The most frequent neutralisation procedure, applied on chitosan (CS) films includes treatment with NaOH base. Such treatment endows CS films with stability in water, yet, same can significantly decrease the film performance. In the present paper, we investigate Mg(OH)2 nanoparticles as a neutralisation agent for CS solutions followed by casting into films. This is combined and compared with classical casting and film drying from non-neutralized solutions followed by NaOH treatment after film formation. The influence on the properties of resulting films is investigated in detail and large differences are found for structure and barrier properties. The stable, opaque-to-transparent CS films (depending on Mg(OH)2 content and post-treatment) were obtained by facile casting method of neat CS or CS–Mg(OH)2 dispersions, in the complete absence of cross-linkers and plasticizers. FTIR data demonstrate the Mg(OH)2 and NaOH deprotonation effect, and strongly suggest intensive H-bonding interaction between CS and Mg(OH)2. X-ray photoelectron spectroscopy showed differences in the hydroxide content and protonation of CS nitrogen. The reduction of surface roughness and increase of homogeneity, the tensile strength and elongation, as well as thermal stability and excellent oxygen barrier properties were measured for CS enclosing the Mg(OH)2 nanoparticles. Further treatment with 1 M NaOH causes re-packing of CS polymer chains, improving the crystallinity and water vapour barrier properties, degrading the mechanical properties by increasing the films brittleness and increasing the char formation due to reduced thermal stability.Graphic abstract

Highlights

IntroductionChitosan (CS) is a pseudo-natural, deacetylated chitin product, originated from exoskeletons of arthropods (including crustaceans and insects), marine diatoms and algae, as well as some fungal cell walls
Chitosan (CS) is a pseudo-natural, deacetylated chitin product, originated from exoskeletons of arthropods, marine diatoms and algae, as well as some fungal cell walls
Aqueous acidic—CS solutions can be efficiently neutralized by the addition of alkaline Mg(OH)2 nanoparticles, without causing inhomogeneous gelation of the polymer

Summary

Introduction

Chitosan (CS) is a pseudo-natural, deacetylated chitin product, originated from exoskeletons of arthropods (including crustaceans and insects), marine diatoms and algae, as well as some fungal cell walls. CS possesses the excellent capacity to form microspheres, membranes and fibres, mainly using acetic acid as solvent, or other alternative solvents, such as lactic (Niamsa and Baimark 2009), tartaric (Cui et al 2018), maleic, hydrochloric and nitric acid, adipic, and citric acid (Hejazi et al 2018) as well as inorganic AlCl3Á6H2O(Hu et al 2018) all of which influence final mechanical properties. The solubility in such, semiaquatic environments and diluted acidic solutions, contributes to high moisture absorption, diminishing the mechanical properties as well, for which different plasticizers, fillers, or cross-linking agents have been used (Hejazi et al 2018; Gorgieva et al 2018)

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