Evaluation of the Thermal and Morphological Properties of γ-Irradiated Chitosan-Glycerol-Based Polymeric Films

Abstract

Industry-sponsored research has intensified to find suitable substitutes for synthetic polymers. For this purpose, biopolymers are promising materials that are extracted from renewable resources. However, there are areas of concern (biopolymers are mostly brittle in the dry state) that require further research before they are used in advanced applications. To overcome this, plasticizers are often added to biopolymers to enhance their physicochemical properties. In this study, chitosan (CH)-glycerol (GL)-based polymeric films were prepared by a simple drop-casting technique, and the influence of a plasticizer (GL) on the properties of chitosan films was analyzed. Additionally, the as-prepared samples were irradiated with γ-rays (60Co γ rays with a dose of 102 kGy) to study the effect of γ-irradiation on the properties of polymeric composites. To achieve this, different samples were prepared by varying the amount of GL. FT-IR analysis revealed the interruption of hydrogen bonding in chitosan by the incorporation of GL. This led to the chain-spreading of CH, which ultimately increased the flexibility of the composite films (CH-GL). The DSC of the CH film showed two peaks: one endothermic peak below 100 °C (due to water vapor) and a second exothermic peak that appeared between 130 and 360 °C (degradation of the amino group). Plasticization of CH films with GL was confirmed by DSC, where the exothermic degradation was converted into an endothermic peak. Depending upon the amount of GL, γ-irradiation considerably affected the chemical structure of CH by breaking the carbohydrate and pyranose rings; this led to a decrease in the crystallinity of the composite films. The changes studied in the DSC and TGA analysis complemented each other. γ-irradiation also affected the morphology of the films, which changed from smooth and homogeneous to roasted structures, with random swelling on the surface of the films. This swelling reflected the degradation of the surfaces into thin layers. Considering the changes that occurred in the films post-γ-irradiation, it can be inferred that the irradiation dose of 102 kGy is sufficient to degrade as-prepared biopolymer composites.