Radiation Effects & Defects in Solids Vol. 167, No. 5, May 2012, 352–360
Structural and optical investigation of the effect of electron beam irradiation in a PM-355 nuclear track detector S.A. Nouha,b * and S. Bahammamc
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a Faculty of Applied Science, Applied Physics Department, Taibah University, Al-Madina al-Munawarah, Saudi Arabia; b Faculty of Science, Physics Department, Ain Shams University, Cairo, Egypt; c College of Science, Princess Nora Bint Abdul Rahaman University, Riyadh, Saudi Arabia
(Received 15 November 2011; final version received 23 November 2011) The effect of electron beam irradiation on the structure and optical properties of a PM-355 solid-state nuclear track detector has been investigated. Samples from PM-355 were irradiated with electron beams with different doses ranging from 20 to 250 kGy. The structural and optical modifications in the electron beam-irradiated PM-355 samples have been studied as a function of dose using different characterization techniques such as Fourier transform infrared spectroscopy, Vickers hardness, refractive index and color difference measurements. The Commission International de E’Claire (CIE units x, y and z) methodology was used in this work for the description of colored samples. In addition, the color differences between the non-irradiated sample and those irradiated with different electron beam doses were calculated. The results indicate that the PM-355 detector acquires color changes under electron beam irradiation. Keywords: electron beam irradiation; FTIR spectroscopy; Vickers hardness; refractive index; color changes; PM-355
1.
Introduction
Due to the vast area of interest covered by polymers, they obviously become the center of attraction for material scientists (1). The polymer PM-355 having the same chemical composition as the solid-state nuclear track detector CR-39, it finds diverse applications in physical and technological sciences (2). Numerous publications investigated that PM-355 (Supergrade PM-355, Pershore Mouldings Ltd, UK) is of specific interest (3–6). Nowadays, the modification of polymers by radiation whether to achieve crosslinking 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 (7). 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 optical and structural properties of the polymer are modified (8–13). In addition, electron beam irradiation can *Corresponding author. Email:
[email protected]
ISSN 1042-0150 print/ISSN 1029-4953 online © 2012 Taylor & Francis http://dx.doi.org/10.1080/10420150.2011.644553 http://www.tandfonline.com
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be considered as one the most popular and well-established processes for several applications. This technique can lead to significant alterations in the materials being treated. On the other hand, the study of color changes in irradiated polymers is an important technique that has been used to assess physical changes in polymers (14). Factor et al. (15) studied the color changes in gamma-irradiated polycarbonate. They reported that polycarbonate turns to moderately intense yellow color due to gamma irradiation, while when it is irradiated with electron beam it acquires a green color. Various authors have ascribed the color in irradiated polycarbonate to substituted benzophenones, radical species, highly conjugated compounds or rearranged isopropylidene radicals (16). The present study deals with the investigation of the effect of electron beam irradiation on the structural and optical properties of the PM-355 polymer not only to obtain information concerning the interaction of electrons with PM-355, but also to study the feasibility of enhancing its properties, improving its performance in different applications.
2. 2.1.
Experimental Irradiation facilities
Electron beam irradiation was carried out in the electron accelerator facility of the ICT-type 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 PM-355 films is 250 μm which ensures complete penetration of the accelerated electrons so that the transferred energy density is still in an acceptable range. Anyhow, the conveyer was attached to a cooling system to avoid heating of the samples. The dose was adjusted frequently using a FWT’60-00 dosimeter that was calibrated by irradiation in a gamma facility against a Ceric/Cerous dosimeter supplied by Nordion, Canada. It is recognized that transfer of the calibration from gamma to 1.5 MeV electron beam irradiation involves an added uncertainty which was estimated to be less than 5%. The same irradiation facility is described in references (16, 17). 2.2. Analysis of the irradiated samples Fourier transform infrared (FTIR) spectroscopic measurements were carried out using a spectrophotometer of Type Shimadzu, Model 8201 PC. This instrument measures in the wavenumber range 400–4000 cm−1 , with an accuracy better than ±4 cm−1 . The hardness measurements were performed with a Shimadzu HMV-2000 microhardness tester which uses a Vickers diamond pyramid indenter having a square base and 136◦ pyramid angle to measure the Vickers hardness (Hv ). The hardness indentations were carried out on the surfaces of the pristine and irradiated PM-355 at room temperature at the load range 50–700 mN. For each load, five indentations were performed at several points of the sample and the average values were considered. The duration of the indentations was 10 s. The refractive index measurements were carried out using an Abbe refractometer (Type Reichert; mark II, Model-10480, New York, USA). The accuracy of measuring the values of refractive indices, surface temperature of the prism and the wavelength of the light used were ±0.0001, 18.3–20.5◦ C and 5893◦A, respectively. Several values were measured to the same sample and the average values were considered. The transmission measurements were carried out at room temperature using a Shimadzu UV– Vis–NIR scanning spectrophotometer, type 3101 PC. This unit measures in the wavelength range from 200 to 3200 nm, with wavelength accuracy better than ±3 nm over 200–2000 nm and better than ±9 nm over 2000–3000.
