Applied Radiation and Isotopes 86 (2014) 21–27
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Dosimetric characteristics of a Radiochromic polyvinyl butyral film containing 2,4-hexadiyn-1,6-bis(n-butyl urethane) A.A. Abdel-Fattah a, Y.S. Soliman a,n, A.M.M. Bayomi a, A.A. Abdel-Khalek b a b
National Center for Radiation Research and Technology (NCRRT), Atomic Energy Authority, P. O. Box 8029, Nasr City, Cairo 11787, Egypt Faculty of Science, Chemistry Department, Beni-Suef University, Beni-Suef City, Egypt
H I G H L I G H T S
A new thin film based on 2,4-hexadiyn-1,6-bis(n-butyl urethane) is developed. The film is suitable for industrial dosimetry in the 3–150 kGy range. Overall uncertainty of dose measurements does not exceed 6.9% (2s).
art ic l e i nf o
a b s t r a c t
Available online 31 December 2013
A radiation-sensitive compound 2,4-hexadiyn-1,6-bis(n-butyl urethane) (HDDBU) was synthesized, characterized by FTIR spectroscopy, and introduced into a thin polyvinyl butyral film to form a radiation dosimeter for industrial irradiation facilities. The monomer polymerizes under gamma radiation, inducing change in the film spectrum in the range of 200–400 nm. According to XRD spectroscopy, the film contains monomeric HDDBU in a non-crystalline state. The dose response function, radiation sensitivity, and dependences of the response on environmental factors were studied. Uncertainty of dose measurements with the proposed dosimetry system was analyzed in detail. & 2013 Elsevier Ltd. All rights reserved.
Keywords: Dosimetry Radiochromic film Industrial irradiations
1. Introduction Conjugated diacetylene monomers are radiation-sensitive materials. When irradiated in the crystalline state, they undergo a topochemical polymerization (1,4-addition reaction) to form intensely colored fully conjugated polydiacetylenes (Wegner, 1972; Cao and Mallouk, 1991). The color of polydiacetylenes stems from the extensive delocalization of π-electrons along π-conjugated polymer chains. The color intensifies progressively with increasing absorbed dose (Patel, 1979, 1981). Fig. 1 (a–c) shows a diagram of topochemical polymerization of diacetylene units into π-conjugated polydiacetylene under ionizing radiation in the crystalline state (Janzen et al., 2006; Hu and Li, 2002). However, there is also crosslinking in the non-crystalline state, as shown in Fig. 1 (d and e) (Hu and Li, 2002). Conjugated diacetylenes have been extensively investigated as dosimetric materials for industrial irradiation processes (Patel, 1981, 2009; Soliman et al., 2013). They are commonly used as radiation-sensitive components in Gafchromic film formulations (Butson et al., 2001; Cheung et al., 2005; Vandana et al., 2011).
n
Corresponding author. Tel./fax: þ 2 02 2671 4166. E-mail address:
[email protected] (Y.S. Soliman).
0969-8043/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apradiso.2013.12.023
Generally, conjugated diacetylenes are synthesized by oxidative coupling of the corresponding acetylenes (Hay, 1962). This method is commonly used to prepare diacetylene diol compounds from acetylenic alcohols, such as propargyl alcohol (Hu and Li, 1999). Diacetylene diols can undergo an addition reaction to produce highly πconjugated and highly radiation-sensitive monomers of diacetylene diurethane (Wegner, 1972; Patel, 1981; Shchegolikhin et al., 2003). A thin solid film with diacetylene polyester of poly(hexa-2,4diynylene adipate) as a radiation-sensitive component was proposed for monitoring doses in the range of 0.5–60 kGy (Soliman, 2007). Under gamma rays, this component undergoes crosslinking polymerization and changes the color of the solid film from faint yellowishorange to deep orange. The spectrum of the irradiated film features an absorption band in the vicinity of 500 nm with a shoulder near 465 nm. The expanded uncertainty of dose measurements based on this phenomenon was reported to be less than 5.6% at the confidence level 95%. A conjugate diacetylene-diol monomer of 2,4-hexadiyn-1,6diol was synthesized by oxidative coupling of propargyl alcohol and incorporated into a thin polyvinyl butyral (PVB) film for dosimetry in the dose range of 0.5–65 kGy (Abdel-Fattah et al., 2009). The reported overall uncertainty of dose measurements at 273 nm was under 5% (2s), provided that the contributions from the temperature and humidity effects were not included. A conjugated monomer of 10,12pentacosadiynoic acid (PCDA) undergoes topochemical solid-state
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Fig. 1. Possible reactions of conjugated diacetylene molecules under ionizing radiation (Hu and Li, 2002). Diacetylene units in a stack in a crystal (a) react via topochemical solid-state polymerization to form polydiacetylene chains (b) and (c). By contrast, conjugated diacetylene units in a non-crystalline environment (d) crosslink via random reactions of C0 C triple bonds to form polymer (e).
polymerization by the gamma and UV radiations, which makes it possible to prepare a very thin film using the Langmuir–Blodgett technique; the films thus obtained can be used for dosimetry in various dose ranges (Ali et al., 1996). PCDA was recently added to solutions of PVB in low (3–10%) (Soliman et al., 2013) and high (20–50%) (Abdel-Fattah et al., 2012) concentrations to manufacture thin film dosimeters. The thin film dosimeters containing PCDA at the lower concentrations were found to be useful for spectrophotometric measurements of high doses (3–100 kGy). On the other hand, the dosimeters with the higher PCDA concentrations enable one to measure doses in the 15–2500 Gy range using spectral reflectance colorimetry. Upon gamma-ray exposure, films with the lower PCDA concentrations remained colorless, while the films with the higher monomer concentrations developed a deep blue color. These results suggest that PVB films with PCDA can be used as dosimeters in various radiation processing technologies, such as sterilization of medical devices, food irradiation, insect population control, and blood irradiation. Additionally, the films can be used as detectors of irradiated blood and food (Abdel-Fattah et al., 2012). The spectrum of the unirradiated thin film of lower PCDA amount exhibits four absorption bands, namely, at 216, 227, 241, and 256 nm (Soliman et al., 2013). Upon gamma-ray exposure, two new bands appear at 271 nm and 286 nm, and their intensities grow with the absorbed dose. The expanded uncertainty of dose measurements with both the dosimeters was approximately 6% (2s). The objective of the present study was to synthesize radiationsensitive monomer 2,4-hexadiyn-1,6-bis(n-butyl urethane) (HDDBU), to characterize it with FTIR spectroscopy, and to study the dosimetry potential of PVB films containing this substance. The prepared films were characterized by the UV-visible and XRD spectroscopies before and after gamma-ray exposure. The radiation sensitivity of the dosimeters was characterized, and the uncertainty of doses measured with them was calculated and discussed.
2. Experimental 2.1. Synthesis of 2,4-hexadiyn-1,6-diol Conjugated diacetylenes are usually synthesized by oxidative coupling of acetylenes (Hay, 1962). This monomer was synthesized by oxidative coupling of propargyl alcohol (99%, Aldrich) in the presence of cuprous chloride (97%, Nice Chemicals, India) and N,N, N0 ,N0 -tetramethyl ethylenediamine (98%, Fluka) under oxygen bubbling (Shchegolikhin et al., 2003; Abdel-Fattah et al., 2009; Hu and Li, 1999). Fig. 2a shows the reaction of synthesis of 2,4hexadiyn-1,6-diol. The product was recrystallized from ethyl acetate (99.5%, Sigma-Aldrich) and stored in a sealed bottle wrapped in aluminum foil in a desiccator in a cool and dark place. The obtained 2,4-hexadiyn-1,6-diol had pale yellow color; the yield was about 67%; and the melting point was 110–112 1C. The compound is highly sensitive to UV light, and it is strongly recommended to put it into a dark and cool place immediately after crystallization and drying. A polymeric film with this monomer was previously investigated as a dosimeter in the dose range of 0.5–65 kGy (Abdel-Fattah et al., 2009). 2.2. Synthesis of 2,4-hexadiyn-1,6-bis(n-butyl urethane (HDDBU) HDDBU was synthesized by adding freshly-prepared monomer 2,4-hexadiyn-1,6-diol to an anhydrous THF (Aldrich) solution of butyl isocyanate (98%, Aldrich), di-n-butyltin bis(2-ethylhexanoate) (Alfa-Aesar) and triethylamine (99%, Merck) (Wegner, 1972; Patel, 2009; Shchegolikhin et al., 2003). Fig. 2b shows the synthesis of HDDBU. The product was recrystallized from acetone (99.5%, Merck) twice and kept in a dark, cool, and dry place. It was faint blue with the melting point at 74–76 1C. Gamma rays readily polymerized the monomer, making it deep blue.
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temperature of the sample and the temperatures at both sides of the peltier junction. The thermistors had been calibrated at NPL, and their calibration was periodically verified during the study against another calibrated thermometer. The absorption spectra of the film dosimeters irradiated to doses between 3 kGy and 150 kGy were recorded with a UV–vis spectrophotometer Evolution 500 (Thermo Electro Corp., UK) in the range 200–400 nm. The optical density at the wavelength λmax of the most intense peak was plotted vs. the absorbed dose. The film thicknesses were measured with a Digitrix-Mark II thickness gauge (precision71 mm). The x-ray diffraction (XRD) patterns of pure solid HDDBU, pure PVB film, and the compound PVB film with HDDBU before and after irradiation were recorded at room temperature with a Shimadzu x-ray diffractometer (Model XRD-6000, 40 kV, 30 mA) equipped with an x-ray tube containing a Cu target. A continuous scanning mode at the scanning speed 8 deg min-1 in the range of 4–90o (2θ) was used. Fig. 2. Syntheses of 2,4-hexadiyn-1,6-diol (a) and HDDBU (b).
3. Results and discussion The intensity of the color grew with the absorbed dose, in line with the results by Patel (1981). A FTIR analysis of the monomer (spectrometer ATI Mattson, Genesis Series, Unicam, UK) revealed two absorption bands, namely, at 3329 and 1545 cm-1, which indicated N–H stretching and bending vibrations of a secondary amine, respectively. In addition, the absorption band of diacetylenes (C C, medial alkyne) around 2149 cm 1 was observed. The spectrum also featured absorption bands in the range 2956– 2872 cm 1 (C–H stretching of aliphatic hydrocarbons), a band at 1707 cm 1 (C ¼O), and another band at 1647 cm 1 (C ¼C). 2.3. Preparation of the thin-film dosimeter Three batches of thin films with different concentrations of HDDBU in PVB (pioloform BR18, average MW 50–60 103, Wacker Co., USA) were prepared. Three solutions containing 20% PVB along with 5, 10, or 15 phr (parts per a hundred parts of the resin) of HDDBU in a mixture of butanol and acetone (1/2 v/v) were stirred for about 24 h at room temperature in the dark. Then the mixtures were put onto polyester sheets (size A4) using an Automatic Film Applicator System (Braive Instrument, Belgium) adjusted to 250 mm. The coated polymer films thus obtained were dried in a dark place at room temperature for 72 h. Finally, the thin films were stripped from the polyester sheets, cut into 1 1 cm2 pieces and stored in a tightly enclosed envelop at 10 1C and normal humidity. The thickness of the obtained dry films was found to be 0.032 70.004 mm (1s).
3.1. Effect of gamma rays on the HDDBU/PVB films Fig. 3 shows absorption spectra of the films irradiated to various doses. In this study, we focused only on the radiationinduced changes of the spectrum in the UV range (200–400 nm). The spectrum of unirradiated films featured three absorption bands at 233, 245, and 259 nm, which are characteristic of the diacetylene chromofore (Soliman et al., 2013; Kühling et al., 1990). These bands grow in intensity with the radiation dose without any shifts. In addition, two new absorption bands, namely, at 273 and 285 nm, which are characteristic of a diacetylene polymer, develop upon irradiation, and their intensities increase proportionally to the absorbed dose. Additionally, the band initially located at 273 nm shifts gradually to higher wavelengths as the absorbed dose grows. We selected the 259-nm band to study the dose response because its radiation sensitivity was similar to the
2.4. Radiation source and measurement instruments The manufactured films were irradiated to 3–150 kGy in a Gamma Cell GC-220 Excel, (MDS Nordion, Canada) using a specially designed polystyrene holder to ensure electron equilibrium. The dose rate to water in the center of the sample holder was calibrated by the National Physical Laboratory (NPL) in the UK using the alanine dosimetry system according to the standard ISO/ ASTM 51261 (2004). During the period of the study, the dose rate was approximately 2.50 kGy h 1. The radiation source was equipped with a temperature control unit manufactured and installed in the cavity of the GammaCell by NPL. The temperature system made use of an oven comprising a cross-linked polystyrene shell with aluminum lining. Heating and, to a lesser extent, cooling were provided by means of a peltier junction mounted in the base of the oven. Platinum thermistors were used to measure the
Fig. 3. Absorption spectra of the PVB films with 10 phr of HDDBU irradiated to various doses.
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Fig. 5. Dose response of the HDDBU/PVB films at 259 nm in the full dose range of 3–150 kGy. ΔA ¼(Ai Ao) / f, where Ai and Ao are absorbances of the irradiated and unirradiated films, respectively, and f is the film thickness. Error bars represent 2s.
Fig. 4. XRD patterns of unirradiated solid pure HDDBU, an unirradiated PVB film without additives, and a PVB film containing HDDBU before and after irradiation.
sensitivities of the other bands, its position in the spectrum was stable, and its peak was sharp. Irradiation makes the film faint yellow, in accordance with the absorption band developing around 440 nm (inset in Fig. 3). Pure HDDBU in the solid state polymerizes under gamma irradiation topochemically, which makes it blue. However, when irradiated as a low-concentration additive in the PVB film, like in this study, it changes its color only to faint yellow (inset in Fig. 3). This can be attributed to a lower probability of formation of long πconjugated polymer chains in the polymer matrix, a high degree of conjugation of which would produce the blue color. Also, in the polymer matrix, the monomer molecules are not in the crystalline state (Fig. 4), which would enable them to polymerize topochemically, but in the amorphous state, where they can polymerize only randomly (Wegner, 1972; Janzen et al., 2006; Hu and Li, 2002). The transformation of the monomer from the crystalline to the amorphous state in the process of the film preparation is evidenced by the very broad diffraction bands of HDDBU in PVB, which overlap with the bands of the matrix. These are different from the sharp diffraction bands of HDDBU in the pure solid state.
3.2. Dose response Fig. 5 shows dose response functions of the films with various concentrations of HDDBU. Each dose point corresponds to four replicate films. The dose dependences are linear up to 50 kGy (Fig. 6): the linear correlation coefficients were found to be 0.997, 0998, and 0.995 for the films with the HDDBU concentrations of 5, 10, and 15 phr, respectively. The sensitivity of the films to radiation doses, expressed as the slope of the dose response curve, increases linearly with the HDDBU concentration (Fig. 7). The film with 15 phr of HDDBU is approximately 2.4 times more sensitive than the film with 5 phr of HDDBU.
Fig. 6. Dose response of the HDDBU/PVB films at 259 nm in the low-dose range of 3–50 kGy. Error bars represent 2s.
3.3. Effect of the pre-irradiation storage conditions on the dose response To investigate possible effects of preirradiation storage on the manufactured films, we monitored absorbances of unirradiated films stored under different conditions. Three groups of films manufactured approximately one month before the start of the experiment were stored under different conditions, and their absorbances at 259 nm were monitored for 85 days. One of the groups was stored at room temperature in the dark; another group was stored at room temperature exposed to laboratory fluorescent light; and yet another group was stored at 4 1C in the dark. The relative humidity of the air was (42 73)% in all the cases. As one can see from Fig. 8, the absorbances of the films stored in the dark at 4 1C remained essentially unchanged during the whole period of the observations. The absorbances of the films stored at room temperature in the dark changed about 3% over the same period of time. However, the absorbances of the films stored at room temperature under fluorescent light increased approximately 8% by the end of the observation. So, storage of unirradiated films in the dark at 4 1C is recommended.
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Fig. 7. Radiation sensitivity of the HDDBU-containing PVB films as a function of the HDDBU concentration in the film.
Fig. 9. Absorbances of the PVB films with 10 phr of HDDBU stored under different conditions after the irradiation to 25 kGy.
Fig. 8. Pre-irradiation stability of the absorbances of the PVB films with 10 phr of HDDBU stored under different conditions.
Fig. 10. Response of the PVB films with 15 phr of HDDBU to 10 kGy as a function of the relative humidity of the air during the irradiation. Error bars represent 2s. The absorbances were measured after the irradiation.
3.4. Effect of the post-irradiation storage conditions on the dose response Multiple HDDBU/PVB films with 10 phr of HDDBU were irradiated to 25 kGy approximately one month after their manufacturing. After the irradiation, they were stored under different conditions. One group was stored at room temperature in the dark; another group was stored at room temperature under laboratory fluorescence light; and yet another group was stored at 4 oC in the dark. The relative air humidity was always (42 73)%. The absorbances of the films at 259 nm were measured periodically over 85 days of storage (Fig. 9). The signals of the films stored at 4 1C were very stable over the whole observation period. On the contrary, the responses of the films stored at room temperature, either in the dark or under fluorescent light, increased rapidly during the first week of storage and then grew more slowly until the end of the observation period. The responses of the films stored in the dark grew roughly 1.5%, 9%, and 13% during the first 1, 8, and 24 days of storage, respectively. Thus, to minimize the systematic errors from the absorbance change during the post-irradiation storage, it is recommended to keep the films between the irradiation and absorbance measurements in a dark cool place or to standardize the period between
irradiations and measurements in both calibrations and routine dose determinations. 3.5. Effect of the air humidity during irradiation on the dose response Several films were irradiated simultaneously to 10 Gy in air atmospheres with different relative humidities to investigate the effect of humidity levels on the dose response function (Fig. 10). The following exactly known relative humidities were achieved in the air above saturated salt solutions in tightly closed jars at 25 1C (Greenspan, 1977) 33% (magnesium chloride), 53% (magnesium nitrate), 75% (sodium chloride), and 94% (potassium nitrate). The relative humidity, (RH) in an additional jar with dry silica gel was assumed to be 0%. The films were stored in the jars for 72 h before the irradiation and remained in the jars during the irradiation itself. The dose response increases slightly (within 5%) with increasing RH from 0% to 33% and then tends to be stable in the RH range of 33–75%. However, if RH increases further, the dose response grows dramatically. So, in order to minimize the effect of the RH of the environment during irradiations, it is advisable to pack the
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Table 1 Uncertainties of dose measurements in the range of 3–50 kGy with PVB films containing 15 phr HDDBU. Source of uncertainty
Type of uncertainty
Standard uncertainty, %
Calibration of the radiation sourcea Process of irradiation of calibration filmsb Variations of the sensitivity of the spectrophotometerc Reproducibility of the absorbance measurementsd Uniformity of the dosimeter batch Uncertainty of the calibration curve fit Irradiation temperature variations Post-irradiation variations of the response Irradiation temperature effect Combined standard uncertainty (uc), 1s Expanded uncertainty (2r)
B B A
1.145 0.44 0.035
A
0.38
A A B A
1.20 1.55 0.20 0.43
A
2.47 3.42 6.84
a
Taken from the NPL calibration certificate. Includes geometry imperfections, source decay correction, timer setting and nonuniformity of the gamma field (Mehta, 2006). c Estimated from 100 replicate measurements of the absorbance of irradiated film to 25 kGy while the film was immobile in the sample holder. d Estimated from 100 replicate measurements of the absorbance of an irradiated film with film reinserted into the holder after each measurement. b
Fig. 11. Response of the PVB films with 15 phr of HDDBU to 10 kGy as a function of the irradiation temperature. Error bars represent 2s.
films into sealed aluminum pouches in an atmosphere with the RH in the range of 33–75%. 3.6. Effect of irradiation temperature on the dose response Sets of the film with 15 phr of HDDBU were irradiated to the same dose 10 kGy in a temperature-controlled environment provided by the temperature controller described in the experimental section. The film had been kept in the environment with the desired temperature for 5 min before the irradiation and remained their during the irradiation. Fig. 11 shows that there is a steep increase in the response with increasing irradiation temperature in the range of 30–50 1C. The temperature dependence can be described with a polynomial function ΔA mm 1 ¼ 7:857–0:271 T þ 6:891 10 3 T 2 with the correlation coefficient r2 ¼ 0.9995 in the entire studied temperature range of 20–50 1C. The average temperature coefficients in the ranges 20–30 1C and 30–50 1C are approximately 1.22 and 4.29%/oC, respectively. To eliminate systematic errors resulted from the irradiation temperature variations, it is strongly advised to construct a calibration curve using dosimeters irradiated at the temperature to be used in irradiations of future routine dose measurements (Sharpe and Miller, 2009).
4. Estimated overall uncertainty of determined doses Uncertainty of a dose measurement can be defined as a parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand (ISO/ASTM 51707, 2004). Contributions to the overall uncertainty can be classified into two categories, namely, Type A (uA, evaluated by statistical methods from a series of repeated observations) and Type B (uB, evaluated by nonstatistical methods, for example, based on manufacturer–supplied information) (ISO/ASTM 51707, 2004). Sources of uncertainty in dose measurements with the proposed film system can be summarized as follows: calibration of the radiation source used for film calibration; irradiation itself (geometric factors, source decay correction, timer setting); batch nonuniformity; measurement of absorbance; environmental factors (temperature and humidity during the irradiation and
post-irradiation changes of the response); and the calibration function fit. Table 1 presents the uncertainty budget for measurements in the dose range between 3 kGy and 50 kGy, which is suitable for sterilization and food irradiation. Some of these components are explained in the footnotes to Table 1, while the others are discussed below. The uncertainty resulted from the batch nonuniformity (lot heterogeneity) was investigated by irradiating different sets of films to different doses and analyzing them at 259 nm immediately after irradiation. The following equation can be used to estimate this parameter (ISO/ASTM 51707, 2004; Sharpe and Miller, 2009): u¼
sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi Σ i ðni 1Þðsi Þ2 ; Σ i ðni 1Þ
where ni and si are the number of dosimeters and the coefficient of variation of the measured doses at a given dose level, respectively. The uncertainty was found to be 1.2%. This value inevitably includes, in addition to the the batch heterogeneity, effects of the variation of the actual absorbed doses given to the dosimeters and of the variability in the performance of the measurement instrument and analysis procedures (Mehta, 2006). The uncertainty of the analytical function chosen to fit the responses of the calibration dosimeters will affect the overall uncertainty. The standard uncertainty of the fit was calculated using the following formula (Sharpe and Miller, 2009): sffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ΣðresidualsÞ2 u¼ ; nd nc where nd is the number of dosimeters and nc is the number of variable paramaters in the selected function. The values of the residuals were provided by the commercial program TableCurve 2D (Version 5.01, Jandel Scientific Software), which was used to find the best function to fit the responses of the calibration films. The uncertainties of the fit were found to be 1.5% and 1.3% for the low (3–50 kGy) and high (50–150 kGy) dose ranges, respectively. Absorbances of all individual calibration films, rather than their averages, were used in the uncertainty estimation. The standard
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uncertainty can be reduced by increasing the number of doses given to the calibration films. The temperature of the film dosimeter during the irradiation will affect its dose response and, accordingly, the determined dose. Assuming that the dosimeters are used within the temperature range of 30–50 1C, the temperature coefficient is approximately 4.29%/1C. If the uncertainty in the difference between the irradiation temperatures during the calibration and the dose measurement is 71 1C and the temperature effect has a rectangular probability distribution (divisor √3Þ (IAEA, 2013), the standard uncertainty related to the temperature effect will be u ð1sÞ ¼
ð1 4:29Þ pffiffiffi ¼ 2:47 %: 3
If the dosimeters are used at lower temperatures (20–30 1C), the uncertainty will decrease down to 0.71%. This component of the uncertainty can by smaller if the dosimetry system is calibrated at irradiation temperatures close to those actually used in the irradiation facilities (ISO/ASTM 51261, 2004). The instability of the absorbance of the film after irradiation is yet another factor that contributes to the uncertainty of the resulted dose (Soliman and Abdel-Fattah, 2012). Here, we assume that the absorbance measurements in calibration and routine dose determinations are performed in similar periods of time after irradiation. The study of the post-irradiation color stability showed that the variations of the absorbances during 24 h after irradiation are within 1.5%. So, if the periods between the absorbance measurements in calibration and dose determination are within 712 or 724 h, the standard uncertainties will equal 0.43% and 0.87%, respectively, provided that the divisor √3 is used (ISO/ ASTM 51707, 2004). A similar analysis showed that the overall uncertainties of doses measured in the ranges of 3–50 and 50–100 kGy would be about 6.845% and 6.34%, respectively (2s). These uncertainties are acceptable for dose measurements in radiation process control. The uncertainties go down to less than 5% if the dosimeters are used within the temperature range 20–30 1C and the absorbances are measured in similar periods of time after the irradiations in the calibration and dose determinations. It is assumed that calibration films have been irradiated under radiation conditions very similar to those used in the irradiation of the test films. If this assumption is wrong, an unknown error in the determined dose may occur. The standard uncertainty of the measured dose can be reduced by increasing the number of replicate films at each dose point and by correcting the dosimeter response for irradiation temperature (Sharpe and Miller, 2009). 5. Conclusion A radiation-sensitive compound HDDBU was synthesized by the reaction of butyl isocyanate with freshly prepared 2,4-hexadiyn-1,6-diol. The compound, characterized with FTIR spectroscopy, was introduced into a PVB film to prepare a radiation dosimeter suitable for a wide range of applications in radiation processing. XRD diffraction showed that HDDBU in PVB was in a non-crystalline form and radiation-induced polymerization was random rather than topochemical. The spectrum of HDDBU/PVB films undergoes a change upon gamma irradiation. Two new bands, at 273 nm and 285 nm, appear, and their intensities increase with the radiation dose, as do intensities of the bands at 233, 245, and 259 nm originally present in the spectrum of HDDBU. The dosimeters with appropriate concentrations of HDDBU can be used for dose measurements in the range 3– 150 kGy. They are suitable for use in monitoring various industrial
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processes, such as food irradiation, radiation sterilization of medical devices, and polymer modification. The response of the film was not affected by variations of relative humidity of the air in the range of (33–75)%; however, it was significantly affected by variations of the irradiation temperature in the range of 30–50 1C. To minimize the environmental effects, it is strongly recommended to calibrate the dosimeters under actual radiation processing conditions in the production facility using an independent reference dosimetry system. The overall uncertainty of absorbed dose determined with this system is below 6.2% (2s). References Abdel-Fattah, A.A., Abdel-Rehim, F., Soliman, Y.S., 2009. Synthesis of diacetylene diol and its possible use for high-dose dosimetry. Arab J. Nucl. Sci. Appl. 42, 4. Abdel-Fattah, A.A., Abdel-Rehim, F., Soliman, Y.S., 2012. A new label dosimetry system based on pentacosa-diynoic acid monomer for low dose applications. Radiat. Phys. Chem. 81, 70–76. Ali, N.M., Tucker, C.E., Smith, F.A., 1996. Consideration of radiation-induced polymerization of diacetylene LB films for dosimetry. Thin Solid Films 289, 267–271. Butson, M.J., Chueng, T., Yu, P.K.N., 2001. Radiochromic film dosimetry in water phantoms. Phys. Med. Biol. 46, N27–N31. Cao, G., Mallouk, T.E., 1991. Topochemical diacetylene polymerization in layered metal phosphate salts. J. Solid State Chem. 94. (95–71). Cheung, T., Butson, M.J., Yu, P.K.N., 2005. Reflection spectrometry analysis of irradiated GAFCHROMIC XR type R radiochromic films. Appl. Radiat. Isot. 63, 127–129. Greenspan, L., 1977. Equilibrium relative humidity of some saturated salt solutions at 25 1C. J. Res. Nat. Bur. Stand. 81A, 89. Hay, A.S., 1962. Oxidative coupling of acetylenes. J. Org. Chem. 27, 3320–3321. Hu, X., Li, X., 1999. Preparation and structural/property relationships of polyester containing conjugated diacetylene groups. J. Polym. Sci. Part B Polym. Phys. 37, 965–974. Hu, X., Li, X., 2002. Reaction and structural change during thermal annealing in a semicrystalline, aromatic diacetylene-containing polyester. J. Polym. Sci. Part B Polym. Phys. 40, 2354–2363. IAEA, 2013. Guidelines for the Development, Validation and Routine Control of Industrial Radiation Processes, IAEA Radiation Technology Series no. 4. International Atomic Energy Agency, Vienna, Austria. (STI/PUB/1581). ISO/ASTM 51261, 2004. Guide for selection and calibration of dosimetry systems for radiation processing, Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA. ISO/ASTM 51707, 2004. Standard guide for estimating uncertainties in dosimetry for radiation processing, Annual Book of ASTM Standards. ASTM International, West Conshohocken, PA. Janzen, M.C., Ponder, J.B., Bailey, D.P., Ingison, C.K., Suslick, K.S., 2006. Colorimetric sensor arrays for volatile organic compounds. Anal. Chem. 78, 3591–3600. Kühling, S., Helmut, K., Höcker, H., 1990. Poly(2,4-hexadiyn-1,6-ylene carbonate) synthesis and topochemical cross-linking reaction. Macromolecules 23, 4192–4195. Mehta, K., 2006. Radiation Processing Dosimetry—A Practical Manual. GEX Corporation, Centennial, CO, USA. Patel, G.N., 1979. Acceleration of radiation-induced crosslinking in polyethylene by diacetylenes. Radiat. Phys. Chem. 14, 729–735. Patel, G.N., 1981. Diacetylenes as radiation dosage indicators. Radiat. Phys. Chem. 18, 913–925. Patel, G.N., 2009. Self-indicating radiation alert dosimeter. US Patent no. 7476874 B2. Sharpe, P., Miller, A., 2009. Guidelines for the Calibration of Routine Dosimetry Systems for Use in Radiation Processing. National Physical Laboratory, NPL Rep. CIRM 29. Shchegolikhin, A.N., Lazareva, O.L., Mel0 nikov, V.P., Ozeretski, V.Y., Small, L.D., 2003. Ramman-active Taggants and their Recognition. US Patent no. 6610351B2. Soliman, Y.S., Beshir, W.B., Abdel-Fattah, A.A., 2013. Ultraviolet spectral analysis of polyvinyl (butyral) film incorporating 10,12-pentacosadiynoic acid monomer for application in radiation processing dosimetry. Int. J. Polym. Mater. 62, 203–208. Soliman, Y.S., 2007. Development of some dyed polymeric materials for application in radiation dosimetry. Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt. (Ph.D. thesis). Soliman, Y.S., Abdel-Fattah, A.A., 2012. Magnesium lactate mixed with EVA polymer/paraffin as an EPR dosimeter for radiation processing application. Radiat. Phys. Chem. 81, 1910–1916. Vandana, S., Shaiju, V.S., Sharma, S.D., Mhatre, S., Shinde, S., Chourasiya, G., Mayaa, Y.S., 2011. Dosimetry of gamma chamber blood irradiator using Gafchromic EBT film. Appl. Radiat. Isot. 69, 130–135. Wegner, G., 1972. Topochemical polymerization of monomers with conjugated triple bonds. Macromol. Chem. 154, 35–48.
