Water resistance and biodegradation properties of conventionally-heated and microwave-cured cross-linked cellulose nanocrystal/chitosan composite films

The cross-linking of cellulose nanocrystals (CNC)/chitosan composite films with glutaraldehyde (GA) as the cross-linking agent, was carried out by using conventional heating and microwave curing, respectively. The addition of 5 wt% CNC has significantly reduced the water vapor permeability (WVP) of chitosan films by 30% compared to the neat chitosan film. The decline in the swelling and solubility were also observed in the CNC/chitosan composite films. Moreover, the cross-linking has further enhanced the water resistance by reducing the WVP, swelling and solubility of CNC/chitosan films, especially for microwave-cured GA-cross-linked CNC/chitosan films. The biodegradation testing was performed by the soil burial experiment. The cross-linked chitosan composite films were found to have a lower degradability rate compared with the uncross-linked composites especially for the microwave-cured CNC/chitosan composite films. The composite films-degrading microorganisms were identified as Ophiocordyceps heteropoda, Enterobacter kobei and E. roggenkampii, by the molecular analysis via polymerase chain reaction and DNA sequencing. This study demonstrated that the CNC/chitosan composite films especially microwave-cured composite films could be the suitable materials to be employed as the food packaging with outstanding water resistance property and moderate biodegradability. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

Cross-linking of cellulose nanocrystals/chitosan composite films using glutaraldehyde as the cross-linking agent through conventional heating and microwave curing was found to enhance water resistance properties and reduce water vapor permeability. The addition of CNC significantly decreased WVP, swelling, and solubility of chitosan films, especially for microwave-cured GA-cross-linked CNC/chitosan films. Biodegradation testing showed that cross-linked chitosan composite films had lower degradability rates compared to uncross-linked composites, particularly microwave-cured CNC/chitosan films, with identified degrading microorganisms of Ophiocordyceps heteropoda, Enterobacter kobei, and E. roggenkampii.