Abstract
Chitosan films containing citric acid were prepared using a multi-step process called heterogeneous crosslinking. These films were neutralized first, followed by citric acid addition, and then heat treated at 150 °C/0.5 h in order to potentially induce covalent crosslinking. The viscoelastic storage modulus, E′, and tanδ were studied using dynamic mechanical analysis, and compared with neat and neutralized films to elucidate possible crosslinking with citric acid. Films were also prepared with various concentrations of a model crosslinker, glutaraldehyde, both homogeneously and heterogeneously. Based on comparisons of neutralized films with films containing citric acid, and between citric acid films either heat treated or not heat treated, it appeared that the interaction between chitosan and citric acid remained ionic without covalent bond formation. No strong evidence of a glass transition from the tanδ plots was observable, with the possible exception of heterogeneously crosslinked glutaraldehyde films at temperatures above 200 °C.
Highlights
While chitosan films have advantages, such as high anti-microbial and low oxygen-permeability properties [3], their high moisture affinity and relatively poorer mechanical properties compared to common plastics, such as polyethylene terephthalate, low density polyethylene, and polypropylene, limit their packaging applications
The viscoelastic properties, namely the E, E, and tanδ of chitosan films were investigated to gain insights on the presence of potential covalent crosslinking between citric acid and chitosan
While the effect of crosslinking for the model GTA films was demonstrated with respect to E, no statistical difference was observed for E between citric acid (CA), CA-HT, and neutralized chitosan films near 200 ◦C suggesting that the post thermal treatment of CA films did not induce covalent crosslinking and the interaction between the chitosan amine and CA remained ionic
Summary
While chitosan films have advantages, such as high anti-microbial and low oxygen-permeability properties [3], their high moisture affinity and relatively poorer mechanical properties compared to common plastics, such as polyethylene terephthalate, low density polyethylene, and polypropylene, limit their packaging applications. The water vapor permeability (WVP) of chitosan films is typically a magnitude higher than that of thermoplastics. Their tensile strength (TS) is in the same range as some plastics; their elongation capacities and elastic moduli are lower. Improving mechanical properties and reducing hydrophilicity of chitosan films has been attempted by several methods, including (i) composite formation with fatty acids [6,7] and other polysaccharides [8], (ii) grafting hydrophobic compounds [9,10] or phenolics [11,12], and (iii) crosslinking the polymer chains [8]. A st3uodf y18on the effect of heating chitosan films has shown amidization reactions occur with the acids used in the preppraerpaatiroantio[3n6[]3.6H].oHwoewverv,eart, 6a0t 6◦0C°, Cci,trcictraicciadciddodesoensont oatpappepareator troearcetawctiwthitthhethaemaimneinoef ocfhicthoistaonsa[n36]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
