Elsevier

Polymer Testing

Volume 84, April 2020, 106380
Polymer Testing

Preparation, characterization, mechanical and barrier properties investigation of chitosan-kaolinite nanocomposite

https://doi.org/10.1016/j.polymertesting.2020.106380Get rights and content

Highlights

  • Preparation of a novel Clay Bio-Polymer Nanocomposite (CBPN) films by mixing polymer (chitosan, C) with exfoliated nanoclay (kaolinite, k).

  • Mechano-chemical treatment of kaolinite allows its exfoliation and the significant reduction of its particles size.

  • Study of physicochemical properties namely thickness, water solubility, color, light transmission and transparency of the films.

  • Determination of antimicrobial activities against gram-positive and gram-negative bacteria (strain) of CBPN films.

Abstract

The purpose of this study was to prepare a novel Clay Bio-Polymer Nanocomposite (CBPN) films by mixing polymer (chitosan, C) with exfoliated nanoclay (kaolinite, k). DRX has shown that the mechano-chemical treatment of kaolinite allows its exfoliation and the significant reduction of its particles size. Physicochemical properties namely thickness, water solubility, color, light transmission and transparency of the films were studied. Fourier transform infrared analysis (FTIR) was to study the interaction between chitosan and kaolinite. Differential scanning calorimetry (DSC) scans showed that the transition temperature (Tg) of films depends on the film's composition. The surface morphology of the films was also studied by scanning electron microscopy (SEM). Results showed that water solubility (Ws) decrease with the increase of the amount of clay. In addition, the presence of clay in the said films increases the mechanical strength. All prepared films were tested for their antimicrobial activities against gram-positive and gram-negative bacteria (strain). It was found that all CBPN films showed good inhibitory activity against all the tested bacteria. The above analysis suggested that the CBPN films could be used as potential candidates for therapeutic application.

Introduction

Chitosan is a natural cationic polysaccharide derived from chitin through a deacetylation process. Due to its extensive properties, such as biocompatibility, biodegradability, antimicrobial activity, non-toxicity and chelation with metal. Chitosan finds a wide variety of applications in the agricultural, food, industrial, and cosmetic. Also, it is considered as an excellent choice for many therapeutic applications [[1], [2], [3]]. It is easily molded into a variety of forms like gels, membranes, beads, nanoparticles (NPs), sponges and scaffolds [[4], [5], [6], [7], [8], [9]]. In addition, this polymer also has excellent film forming ability as described by Jridi et al. [2]. However, chitosan films showed a poor mechanical (elasticity) and barrier properties as well as limited water resistant. Therefore, to improve these basic characteristics, it is necessary to combine chitosan with nanofillers such as fibers, nanotubes, layered [[10], [11], [12]]. Among them, layered nanosheet clays are a special type of nanofillers in order to obtain clays biopolymer nanocomposites (CBPN). Many researchers have extensively studied to introduce clay in the polymer due to their easy availability in nature, low cost, environmental friendliness, their special three dimensional 3D layered structure, excellent surface interaction due to its smaller particle size, high mechanical strength, stiffness, high surface area, high aspect ratio and cation exchange characteristics, etc [13,14]. Besides clay minerals possess, some excellent properties such as good biocompatibility and non-toxicity which make grounds for their applications in food, medicine, pharmacy, cosmetics etc [[15], [16], [17], [18], [19]]. Among various clay minerals, kaolinite is one of the most abundant clay minerals on earth [20] and it is relatively inexpensive. However, to the very best of our knowledge, a few numbers of scientific publications of kaolinite based on chitosan bionanocomposite have been cited [21,22]. There are a number of methods used for the exfoliation of clay that involve intercalation, ion exchange, ultrasonic waves or mechano-chemical treatment [8,13,14]. The exfoliation of kaolinite can dramatically increase the cation exchange capacity and specific surface area values of lamellar kaolinite. Exfoliated kaolinite nanosheets can be incorporated into polymer/kaolinite nanocomposites to form an innovative class of materials that have a great of potential as superabsorbent, drug delivery system, tissue scaffolds, rheological modifier, wound dressing, and biosensors. To achieve exfoliation directly without using liquid media is desired but it is a big challenge. Some recent studies have showed that grinding of kaolinite powder in high-energy ball milling is conducive to exfoliating kaolinite [23]. During high-energy ball milling, impact force and friction force of the grinding ball can destabilize the structure of kaolinite, promoting its exfoliation [24]. With the ball milling, the ordered structure of kaolinite turns disordered and some layers are finally peeled off kaolinite particles.

Thus, the aim of the current study is to prepare a bio-nanocomposite films based on chitosan and exfoliated kaolinite. All films were tested for their physicochemical, mechanical and structural properties. Thereafter, the antioxidant and the antimicrobial properties were investigated in order to obtain a potential nanocomposite film as an advanced therapeutic product.

Section snippets

Chemicals

Low molecular weight chitosan with viscosity of20–300 cP,(Cat. No. 448869) with a deacetylation degree 75–85% and the kaolinite powder (Cat. No. 03584) were purchased also from Sigma Aldrich Company Ltd, Darmstadt, Germany. The glacial acetic acid (HAc) was bought from Gifrer Barbezat. Glycerol used as plasticizer was purchased from Loba Chemie, Mumbai, India.

Preparation of CBPN film

To prepare film forming solution (FSS), chitosan powder was dissolved in acetic acid solution (2%, w/v) under gently stirring. In

X-ray diffraction analysis

The clay dispersion within chitosan has been characterized by XRD which is one of the most frequently used methods to study the structure of nanocomposite and identify successfully the character of the dispersion of the clay within the polymer matrix.

As it can be seen in Fig. 3, the diffraction patterns for the mechanically treated kaolinites consistent with the deterioration of its structure during the grinding process. The diffractograms indicate that kaolinite suffers significant structural

Conclusion

In the current study, a clay biopolymer nanocomposites films were made from chitosan and kaolinite. Mixing polymer and clay improve greatly its physical and mechanical characteristics. XRD, FTIR spectra and DSC demonstrated good interaction between chitosan and clay. The addition of the clay had a clear effect on the solubility, the film thickness, the transmittance, the transparency, and the color of all films. The values of TS strength of chitosan/nanoclay films increased significantly with

CRediT authorship contribution statement

Amina Baccour Neji: Investigation, Writing - original draft. Mourad Jridi: Methodology, Validation. Hela kchaou: Formal analysis. Moncef Nasri: Supervision. Rym Dhouib Sahnoun: Conceptualization, Validation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was funded by the Ministry of Higher Education and Scientific Research, Tunisia.

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