Radiation Effects & Defects in Solids, 2013 Vol. 168, No. 4, 274–285, http://dx.doi.org/10.1080/10420150.2012.741131
Effect of electron beam irradiation on the structural, thermal and optical properties of poly(vinyl alcohol) thin film S.A. Nouha,b * and Radiyah A. Baharethc
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a Physics Department, Faculty of Science, Taibah University, Al-Madina al-Munawarah, Saudi Arabia, b Physics Department, Faculty of Science, Ain Shams University, Cairo, Egypt, c College of Science
(Girls Branch), King Abdulaziz University, Jeddah, Saudi Arabia (Received 27 September 2012; final version received 15 October 2012) Poly(vinyl alcohol) (PVA) polymer was prepared using the casting technique. The obtained PVA thin films have been irradiated with electron beam doses ranging from 20 to 300 kGy. The resultant effect of electron beam irradiation on the structural properties of PVA has been investigated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), while the thermal properties have been investigated using thermo-gravimetric analysis and differential thermal analysis (DTA). The onset temperature of decomposition T0 and activation energy of thermal decomposition Ea were calculated, results indicate that the PVA thin film decomposes in one main weight loss stage. Also, the electron beam irradiation in dose range 95–210 kGy led to a more compact structure of the PVA polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with electron beam dose has been determined using DTA. The PVA thermograms were characterized by the appearance of an endothermic peak due to melting. In addition, the transmission of the PVA samples and any color changes were studied. The color intensity E was greatly increased with increasing electron beam dose, and was accompanied by a significant increase in the blue color component. Keywords: electron beam irradiation; PVA; XRD; FTIR; thermal properties; color change
1.
Introduction
Poly(vinyl alcohol) (PVA) is an interesting material with good biocompatibility, high elasticity and hydrophilic characteristics (1). It is considered as one of the polymers that has become the center of attraction for materials scientists. On the other hand, the modification of polymers by irradiation, whether to achieve cross-linking or chain scission, is a significant industrial process throughout the world. Extensive studies have been undertaken to understand this technology and thus the effects of radiation on the most significant classes of polymers are reasonably well cataloged and understood (2, 3). It is already an established fact that the interaction of radiation with polymers leads to chain scission, chain aggregation, formation of double bonds and molecular emission. As a consequence of this, the properties of the polymer are modified (4–9). In addition, electron beam irradiation can be considered as one of the most popular and well-established processes for several applications. This technique can lead to significant alterations in the materials being treated. *Corresponding author. Email:
[email protected] © 2013 Taylor & Francis
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Ali et al. (10) studied the effect of electron beam irradiation on the structural properties of PVA/V2 O5 xerogel. They used Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques to investigate the changes in the structural properties, such as the crystallinity degree of the polymer with increasing irradiation doses. They found that the crystallinity degree of the PVA matrix decreases due to the irradiation dose. Harisha et al. (11) studied the effect of electron irradiation on the microstructural modifications in BaCl2 -doped PVA. The films were subjected to electron irradiation for different doses ranging from 0 to 400 kGy in air at room temperature. The FTIR spectral studies indicated that the electron irradiation induces chemical modifications within the doped PVA, which results in chain scission as well as cross-linking of the polymer. Ravindrachary et al. (12) studied the effect of electron irradiation on the optical properties of chalcone-doped PVA composite films using FTIR, UV–Visible, XRD techniques. The FTIR spectral study showed that the electron irradiation induces cross-linking within the polymer. The present study deals with the investigation of the effect of electron beam irradiation on the structural, thermal and optical properties of PVA polymer not only to obtain information concerning the interaction of electrons with PVA, but also to study the feasibility of enhancing its properties, improving its performance in different applications.
2.
Experimental
2.1.
Samples
PVA films were prepared using the casting technique. PVA used in the present study were supplied by BHD Chemicals, UK. The components, free from impurities, were prepared by swelling the PVA in twice-distilled water for 24 h at room temperature. The solution was then warmed to 60◦ C and stirred thoroughly for about 1 h until the PVA was completely dissolved. Appropriate amounts of PVA solution were poured onto a level glass plate, and left to dry at room temperature for about 48 h. A thin film of nearly 0.1 mm thickness was formed. The thickness was measured by a thickness gauge Model 11/2704 Ast MD 370 standard which was calibrated by Arab British Dynamics.
2.2.
Irradiation facilities
The electron beam irradiation was carried out in the electron accelerator facility of NCRRT, AEA, Cairo, Egypt (1.5 MeV and 25 kW) in which the conveyer speed was adjusted at 20 mm/min. The thickness of the sample does not exceed 1 mm to ensure complete penetration of the accelerated electrons. The dose was determined by the FWT_60-00 dosimeter that was calibrated using the CERIC/CEROUS dosimeter.
2.3. Analysis of the irradiated samples 2.3.1.
X ray diffraction (XRD)
XRD measurements were carried out with a Philips powder diffractometer-type PW 1373 goniometer. The diffractometer was equipped with a graphite monochromator crystal. The wavelength of the X-rays was 1.5405 Å and the diffraction patterns were recorded in the 2θ range (10–35◦ ) with a scanning speed of 2 degrees per minute.
