c-Irradiation effects on the thermal and optical properties of undoped and eosin doped 70/30 (wt/wt%) PVA/glycogen films F.H. Abd El-kader b , S.A. Gaafar a , K.H. Mahmoud b, * , S.I. Bannan a , M.F.H. Abd El-kader a a Department of Biophysics, Faculty of Science, Cairo University, Giza, Egypt b Department of Physics, Faculty of Science, Cairo University, Giza, Egypt Received 31 January 2007; received in revised form 16 April 2007; accepted 18 May 2007 Available online 8 June 2007 Abstract Differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), UV/visible spectra and colour detection of pristine and c- irradiated undoped and eosin-doped 70/30 (wt/wt%) PVA/glycogen has been measured. The kinetic parameters such as the activation energy, entropy, enthalpy and free energy for all investigated samples were determined using Coats–Redfern relation. The shift of T g position towards lower temperatures with increasing c-doses reflect that the degradation process is the predominant one. The values of absorbance and optical parameters in UV/visible range for c-irradiated blend sample doped with eosin showed no significant variation with increasing c-doses. This reflects that the addition of eosin to 70/30 (wt/wt%) PVA/glycogen makes it more resistant to c-radiolysis. The calculated colour parameters such as L * , U * , V * , C * , hue and Y e were found to be dependent on addition of eosin and c-irradiation. Ó 2007 Elsevier B.V. All rights reserved. Keywords: PVA/glycogen; c-Irradiation; Thermal properties; Optical parameters; Colour detection 1. Introduction The effect of c-irradiation on polymeric materials is the destruction of the chemical bonds and linkages as well as creation of highly energetic electrons, ions and radicals. These highly energetic species migrate in the polymer net- work causing further damages to the adjacent macromole- cules through their track. These highly active groups may recombine again at random leading to crosslinks. The pres- ence of oxygen enhances such recombination through it interactions with these active macromolecules. In aliphatic alcohol the hydrogen atom is removed by interaction of radiation yielding a-hydroxy alkyl and hydrogen atom. Polyvinyl alcohol on irradiation yields a-hydroxy alkyl radical which has been investigated previously [1–3]. Accordingly, c-irradiation of polymers has become one of the most common processes producing modifications in their physical, chemical and morphological structure [4–6]. Polyvinyl alcohol is highly elastic in spite of its semi- crystalline feature and has different commercial applica- tions, such as paper and textile sizing, adhesive and emulsifiers. All of the common polysaccharides contain glucose as the monosaccharide unit. Polysaccharides of various composition are being increasingly used in medi- cine and biology, e.g. as a suitable materials for human bodies or protective coating for drugs. Glycogen is the storage form of glucose in animals and humans which is analogous to starch in plants. Glycogen is synthesized and stored mainly in the liver and muscles. Glycogen still has some extent of rigidity and brittleness. However, due to its narrow processing window, relatively low impact resistance and high cost, its application is limited now. These shortcoming could be overcome by blending it with 1567-1739/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2007.05.004 * Corresponding author. E-mail address: cairounil@yahoo.com (K.H. Mahmoud). www.elsevier.com/locate/cap www.kps.or.kr Current Applied Physics 8 (2008) 78–87