The influence of electron and gamma irradiation on the properties of starch:PVA films – the effect of irradiation dose

The paper discusses the effect of ionizing radiation on the functional properties of the biodegradable starch:PVA films. The analysis is related to the possible use of the material for packing the products (particularly, food) that are predicted for radiation decontamination and to the potential modification of the material by radiation treatment. Our previous results have shown that the influence of ionizing radiation on the films’ properties varied for the specific compositions (differing in starch:PVA ratio or the type of substrates) and depended on irradiation conditions. However, these studies considered only the irradiation performed in gamma chamber or in e-beam using a dose of 25 kGy. Therefore, the present study deals with the effect of the irradiations performed using various doses on the selected promising starch:PVA composition. The films characterized by starch:PVA weight ratio of 45:55 was obtained by solution casting and irradiated with fast electrons in air and with 60Co gamma rays in nitrogen applying the doses of 5, 10, 20, 25, 30, 50, and 75 kGy. No regular dependence has been noticed between the composition of films (differing in the starch and PVA content) and the intensities of the particular bands in the UV-VIS DRS spectra after irradiation. The results indicated strong interaction of the starch and PVA components in the films and the occurrence of specific reactions in each composition upon irradiation. No special differences were observed between tensile strength and Young’s modulus of the non-irradiated films characterized by the starch:PVA ratio equal to 45:55 and the samples irradiated using doses in the range of 5–75 kGy. Similarly, no differences were observed in both cases between the swelling capability of the non-irradiated and the irradiated films. However, it can be deduced that solubility in water increased when the radiation dose increased. The results show that using the doses till the range 25 kGy does not cause an essential change of all the examined properties of the starch:PVA (45:55) films. Accordingly, starch:PVA (45:55) films might be considered suitable for packing food predicted for radiation decontamination

The influence of ionizing radiation on the properties of starch-PVA films

The cornstarch: poly(vinyl alcohol) (PVA) films characterized by the alternating ratio of starch:PVA (100:0, 80:20, 60:40, 40:60, 20:80, and 0:100) and containing 30% of glycerol were prepared by solution casting. The films were irradiated with an absorbed dose of 25 kGy with gamma rays in a vacuum and with fast electrons in the air. The films characterized by a high content of starch appeared stiff, while the films characterized by a high content of PVA were highly flexible. The tensile strength and flexibility, as well as swelling and hydrophilicity, increased with the increase in the PVA content in the films. However, the tensile strength and wetting angle values achieved a minimum at an intermediate composition. It was found that irradiation enables to reduce hydrophilicity of the films accompanied by a decrease in their flexibility. No general conclusion concerning the effect of irradiation on tensile strength and swelling behavior can be derived. An increase in the homogeneity of the films and an increase in the compatibility of their components was found by scanning electron microscopy (SEM). Strong interactions of the starch and the PVA components were discovered by diffuse reflectance spectroscopy. Degradation was found to be the prevailing process occurring in the films under the influence of irradiation. The possible accompanying crosslinking is discussed in terms of the gel content in the samples. Creation of various oxidation products in the films characterized by the modified composition was observed under the influence of irradiation carried out in the air. Basing on the obtained results it can be supposed that the selected starch-PVA compositions might appear useful as packagings of the products predicted for radiation decontamination