- Email: [email protected]
Evaluation of various polyethylene as potential dosimeters by attenuated total reflectance-Fourier-transform infrared spectroscopy
Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Evaluation of various polyethylene as potential dosimeters by attenuated total reflectance-Fourier-transform infrared spectroscopy Fred Halperin n, Greta Collins, Michael DiCicco, John Logar Johnson & Johnson Sterility Assurance, 1000 US Route 202 South, Bldg. 930 East, Raritan, NJ 08869, USA
H I G H L I G H T S
Various types of PE films/sheets have been evaluated for use as a potential dosimeter. Attenuated total reflectance FTIR spectroscopy was utilized to analyze transvinylene formation in irradiated PE films/sheets. PE films/sheets were exposed to ionizing radiation using a 5 MeV high-energy electron beam accelerator. Analysis of TV peak formation at the 965 cm 1 wavenumber shows an upward trend of TV response to absorbed dose.
art ic l e i nf o
a b s t r a c t
Article history: Received 31 January 2014 Accepted 11 May 2014
Various types of polyethylene (PE) have been evaluated in the past for use as a potential dosimeter, chiefly via the formation of an unsaturated transvinylene (TV) double-bond resulting from exposure to ionizing radiation. The utilization of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy in characterizing TV formation in irradiated PE for a potential dosimeter has yet to be fully developed. In this initial investigation, various PE films/sheets were exposed to ionizing radiation in a high-energy 5 megaelectron volt (MeV) electron beam accelerator in the 10–500 kilogray (kGy) dose range, followed by ATR-FTIR analysis of TV peak formation at the 965 cm 1 wavenumber. There was an upward trend in TV formation for low-density polyethylene (LDPE) films and high-density polyethylene (HDPE) sheets as a function of absorbed dose in the 10–50 kGy dose range, however, the TV response could not be equated to a specific absorbed dose. LDPE film displayed a downward trend from 50 kGy to 250 kGy and then scattering up to 500 kGy; HDPE sheets demonstrated an upward trend in TV formation up to 500 kGy. For ultra-high molecular weight polyethylene (UHMWPE) sheets irradiated up to 150 kGy, TV response was equivalent to non-irradiated UHMWPE, and a minimal upward trend was observed for 200 kGy to 500 kGy. The scatter of the data for the irradiated PE films/sheets is such that the TV response could not be equated to a specific absorbed dose. A better correlation of the post-irradiation TV response to absorbed dose may be attained through a better understanding of variables. & 2014 Elsevier Ltd. All rights reserved.
Keywords: Attenuated total reflectance Dosimeter Electron beam irradiation FTIR Polyethylene Transvinylene
1. Introduction Historically, beginning with the work of Charlesby et al., the effects of high-energy radiation on various types of polyethylene (PE) have been studied (Charlesby et al., 1964). This includes the formation of a main-chain unsaturated transvinylene (TV) doublebond with peak at 965 cm 1 via Fourier-transform infrared (FTIR) spectroscopy (Charlesby et al., 1964; Johnson and Lyons, 1995; Muratoglu et al., 2003). The mechanism for the formation of TV n
Corresponding author. Tel.: þ 1 908 927 2805. E-mail addresses: [email protected] (F. Halperin), [email protected] (G. Collins), [email protected] (M. DiCicco), [email protected] (J. Logar).
unsaturations during irradiation using a high-energy electron beam is mainly via hydrogen abstraction and to a lesser degree by recombination of two adjacent alkyl radicals on the same chain (ASTM International F 2381-10, 2010; McLaughlin et al., 1999). Other well-known inherent effects noted from PE exposure to ionizing radiation include chain scission, cross-linking and degradation (via production of alkyl and allyl radicals), and formation of carbonyl and other oxidation products when oxygen is present (Charlesby et al., 1964; Cota et al., 2007; McLaughlin et al., 1999; Singh, 1999; Waterman and Dole, 1970a, 1970b). It has also been shown that the concentration of these TV unsaturations formed within the PE backbone as a result of exposure to ionizing radiation is dose-dependent (Charlesby et al., 1964; McLaughlin et al., 1999; Zenkiewicz et al., 2003). Furthermore, the rate of the subsequent
http://dx.doi.org/10.1016/j.radphyschem.2014.05.014 0969-806X/& 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
decay of these TV unsaturations is dependent on various factors as well (Lyons, 2004a, 2004b, 2004c). PE films have been evaluated for use as potential dosimeters in the past to varying degrees to measure the absorbed dose delivered to healthcare products. These evaluations encompassed various analytical techniques using a variety of wavelengths (Johnson and Lyons, 1995; McLaughlin et al., 1999; Wenxiu et al., 1980, 1989). [A dosimeter is a device having a reproducible, measurable response to radiation, which can be used to measure the absorbed dose in a given system (ANSI/AAMI/ISO 11137-1:2006/(R) (2010))]. The effects of electron beam processing on various PE have also been investigated (Illgen et al., 2009; Muratoglu and Harris, 2001; Muratoglu et al., 2002, 2003; Murray et al., 2012, 2013), with studies ranging from cross-linking in PE foams (Dias and de Andrade e Silva, 2007) to the effects of blending antioxidants into PE to suppress thermal oxidation (Ghaffari and Ahmadian, 2007). The utilization of attenuated total reflectance (ATR)–FTIR in characterizing TV formation in various irradiated PE films/sheets for potential dosimeters has yet to be fully developed. ASTM International F 2381-10, Standard Test Method for Evaluating TransVinylene Yield in Irradiated Ultra-High-Molecular-Weight Polyethylene Fabricated Forms Intended for Surgical Implants by Infrared Spectroscopy, compares the TV peak between 950 and 980 cm 1 to a reference band between 1330 and 1396 cm 1, and only mentions ATR-FTIR as an alternative mode of spectra collection (ASTM International F 2381-10, 2010). However, there have been a few published articles demonstrating the use of ATR-FTIR to evaluate [cross-linked] PE (Sugimoto et al., 2013) or TV formation in PE films/ sheets exposed to ionizing radiation (Murray et al., 2012, 2013). The majority of published literature reports employing conventional transmission FTIR and FTIR microscopy to investigate this TV formation in irradiated PE (Illgen et al., 2009; Johnson and Lyons, 1995; McLaughlin et al., 1999; Muratoglu and Harris, 2001; Muratoglu et al., 2002, 2003; Pinheiro et al., 2006; Zenkiewicz et al., 2003). In this initial investigation, low-density polyethylene (LDPE) films, high-density polyethylene (HDPE) sheets, and ultra-high molecular weight polyethylene (UHMWPE) sheets were exposed to different doses of ionizing radiation using a 5 megaelectron volt (MeV) [high-energy] electron beam accelerator. The different PE films/sheets were then analyzed via ATR-FTIR, and the TV peak formation at the 965 cm 1 wavenumber was assessed. Studying TV formation in irradiated PE via ATR-FTIR is of considerable interest since it offers unique sampling advantages compared to transmission FTIR, in characterizing these PE films/sheets for potential use as dosimeters in the healthcare product sterilization dose range.
2. Materials and methods 2.1. Materials Three different types of commonly available PE films/sheets were studied: LDPE film (0.004 in. thickness; McMaster Carr; Robbinsville, NJ), HDPE sheet (0.0625 in. thickness; United States Plastic Corp.s; Lima, OH); UHMWPE sheet (0.062 in. thickness; Plastics International; Eden Prairie, MN). The PE films/sheets were further prepared by cutting them into approximately 5 cm 5 cm specimens. There was neither pre- nor post-irradiation conditioning for these PE films/ sheets; all films were stored in the analytical laboratory at room conditions. 2.2. Electron beam irradiation Irradiation of the PE films/sheets was performed using a MEVEX 5 MeV, 2 kW electron beam accelerator (Model MB5000;
Kanata, Ontario). All PE films/sheets were treated at room temperature in the presence of air at Johnson & Johnson (Raritan, NJ), at two ranges of doses. The first dose range included: 10, 20, 30, 40 and 50 kilograys (kGy). The second dose range included: 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 kGy. The absorbed dose was confirmed using alanine dosimeters traceable to a national standard and measured using a Bruker e-scan electron paramagnetic resonance (EPR) spectrometer (Billerica, MA). 2.3. ATR-FTIR spectroscopy The PE films/sheets were evaluated using a Bruker ALPHA™ FT-IR spectrometer with Eco-ATR single reflection sampling module and zinc selenide (ZnSe) crystal. ATR is essentially a FTIR sampling technique that is ideal for both solids and liquids, and usually does not require any specialized sample preparation. An IR beam is transmitted through an optically dense crystal, with a high index of refraction, that is in contact with a sample which has a lower index of refraction. This results in an evanescent wave that penetrates past the sample surface, approximately 1–2 μm into the sample, and then is reflected back into the crystal for subsequent detection. ATR addresses concerns about variation in thickness, which is an influence quantity for some optical dosimeters, by examining the first 1–2 μm only. All data was recorded under ambient conditions with 32 scans per sample and at 4 cm 1 resolution: the anvil was outfitted with a slip-clutch to deliver a fixed compression of approximately 4000 psi on the sample against the ZnSe crystal. Data analysis was conducted with the Bruker OPUS IR Software (Version 7.2). The IR spectra were evaluated using the internal Integration Mode B – the software draws a straight line between two defined frequency limits and integrates the area above that line. Normalization or other transformations on the IR spectra were not performed, including comparing the area under the curve at 965 cm 1 to another reference peak.
3. Results 3.1. Evaluation of PE films/sheets irradiated in the 10–50 kGy dose range The PE films/sheets (LDPE, HDPE and UHMWPE) were irradiated at room temperature in the presence of air for the first series of target doses: 10, 20, 30, 40 and 50 kGy; only the conveyor speed was adjusted to obtain the desired target dose during a single pass. The PE films/sheets were then analyzed via ATR-FTIR to measure the area under the curve at the TV absorbance peak at 965 cm 1 wavenumber. Fig. 1 displays a box-and-whisker plot1 for the LDPE film data obtained from the median absorbance intensity (n ¼10) versus target dose (kGy), including the TV response for non-irradiated LDPE film. Although an upward trend was observed, the range and resolution of individual data points is such that a TV response could not be equated to a specific absorbed dose. Similarly, Fig. 22 displays a box-and-whisker plot for the HDPE sheet data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated HDPE sheet. Again, an upward trend was observed, with a possible outlier at 40 kGy, but the TV response is lower than that of the LDPE film. Furthermore, of the PE films/sheets exposed 1 In the box-and-whisker plots, the points coinciding with the center lines are the median absorbance intensity (n¼10) at the different absorbed doses; the boxes below and above are the ranges of the second and third quartiles (respectively), and the ‘whiskers’ are the standard error. 2 For better visualization of the data, the absorbance scale in Fig. 2 box and whisker plot is in 10 3 resolution in comparison to the other box-and-whisker plots which are in 10 2 resolution.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Fig. 1. Box-and-whisker plot for LDPE films, 0–50 kGy (single-column fitting).
Fig. 2. Box-and-whisker plot for HDPE sheets, 0–50 kGy (single-column fitting).
3
Fig. 3. Box-and-whisker plot for LDPE films, 0–500 kGy (single-column fitting).
Fig. 4. Box-and-whisker plot for HDPE sheets, 0–500 kGy (single-column fitting).
to 10 kGy, only two of the ten samples exhibited a TV response, and there was no resolution of the quartiles in the plot. Analysis of the UHMWPE sheets revealed a TV response at 965 cm 1 for the 10–50 kGy dose range (data not shown) that was equivalent to the TV response of the non-irradiated UHMWPE sheet. 3.2. Evaluation of PE films/sheets irradiated in the 50–500 kGy dose range The PE films/sheets were irradiated at room temperature in the presence of air for the second series of target doses: 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 kGy. The conveyor speed was adjusted to obtain the desired 50 kGy target dose and multiple passes through the radiation zone were used to deliver required target doses in 50 kGy fractions. The PE films/sheets were then analyzed via FTIR-ATR to measure the area under the curve at the TV 965 cm 1 wavenumber. Fig. 3 displays a box-and-whisker plot for the LDPE film data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated LDPE film. The data demonstrates an initial drop in absorbance intensity from 50 kGy up to 250 kGy, then followed by scattering up to 500 kGy. In addition, there is significant overlap in the 3rd quartile, such that a TV response could not be equated to a specific absorbed dose. Fig. 4 displays a box-and-whisker plot for the HDPE sheet data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated HDPE sheet. Although an upward trend was observed, the overlap of the 3rd quartile of the data points is such that a TV response could not be equated to a specific absorbed dose. Fig. 5 displays a box-and-whisker plot for the UHMWPE sheet data obtained from the median absorbance intensity (n¼ 10) versus target dose, including the TV response for non-irradiated UHMWPE sheet. Analysis of the UHMWPE sheets revealed that TV response up to 150 kGy was equivalent to non-irradiated UHMWPE sheet. A minimal upward trend was observed for 200 kGy to 500 kGy, but the scatter of the data is such that the TV response could not be equated to a specific absorbed dose. Lastly, the low slope of the median values of the TV response
Fig. 5. Box-and-whisker plot for UHMWPE sheets, 0–500 kGy (single-column fitting).
demonstrate that UHMWPE yielded a low sensitivity compared to the other irradiated LDPE films and HDPE sheets.
4. Discussion A general correlation of increasing TV peak formation at 965 cm 1 with increasing electron beam irradiation dose in LDPE was observed in other studies using ATR-FTIR (Murray et al., 2012, 2013). Work to develop a TV/dose calibration curve for irradiated UHMWPE was performed via FTIR microscopy (Muratoglu and Harris, 2001). These results yielded a low TV sensitivity in addition to a greater degree of variation and overlap among the different absorbed doses for both irradiated LDPE films and HDPE sheets. This is not consistent with previously reported results using transmission FTIR and FTIR microscopy for analysis where TV formation was dependent on the relatively high-dose rates as with electron beam irradiation (Charlesby et al., 1964; Johnson and Lyons, 1995; McLaughlin et al., 1999; Muratoglu et al., 2003). When analyzing the data using ATR-FTIR, there were no data normalizations or transformations performed, as indicated earlier. However, as evidenced from the variation and overlap shown in
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
4
the box-and-whisker plots of the various PE investigated, a better correlation of the post-irradiation TV response to absorbed dose may be attained through a better understanding of variables. Due to the absorbed dose build-up from the cascading effect typically experienced during electron beam processing (i.e. the well-characterized dose-depth profile), there may be more TV formed in the sub-surface regions of the PE film/sheets rather than on their surface. Since ATR-FTIR is a surface technique measuring within the first 1–2 μm of a film/sheet, this may account for the lower sensitivity that has been observed. Furthermore, the formation of TV regions is affected by temperature, and with the sharp rise in temperature experienced during high-energy electron beam irradiation, maintaining lower temperature could yield better TV formation to absorbed dose correlation (S. Spiegelberg, Pers. Comm.). In essence, there may be more TV formation in the sub-surface regions of the PE films/sheets as opposed to on the surface; thus decreased sensitivity in ATR-FTIR sampling. This may be more prominent in UHMWPE sheets, as poor TV sensitivity could be the result of high oxidation present in the sheets (Muratoglu and Harris, 2001), as evidenced from the low TV peaks obtained. It is recommended to avoid ambient oxygen, if possible during radiation processing, which will cause a drift in TV concentration over time (Johnson and Lyons, 1995). Irradiation of PE in the presence of oxygen causes macroradical formation, which in turn reacts with vinyl groups (decreasing TV concentration); this effect is enhanced by any temperature increase in the process (Pinheiro et al., 2006). Moreover, although the use of fractionated doses (electron beam processing in serial fashion) for the 100–500 kGy absorbed dose samples does not increase temperature to the same extent as dose delivered in a single pass, the time in between passes did not allow for complete cool-down of the PE films/sheets to room temperature. Therefore, as higher doses were delivered, the temperature of the PE films/sheets increased in a step-wise manner as part of the heating/cooling cycle, possibly creating an annealing effect and causing TV quenching, perhaps through cross-linking. The quality and uniformity of PE can also have an effect on the TV response at the 965 cm 1 wavenumber. Branching and the presence of crystalline lamellae regions will have a more prominent effect on the TV formation, although TV are formed randomly and distributed homogenously within the crystal matrices of PE (Marinović-Cincović et al., 2003). Some HDPE can reach as high as 95% crystallinity, whereas LDPE is on the order of 60–75% crystallinity (McLaughlin et al., 1999) and it is thought that the amorphous phase is rich in vinyl and vinylidene unsaturations (Lyons, 2004a). The low TV sensitivity observed with the UHMWPE sheets may also be related to amorphous/crystallinity differences on the film surface. Another variable of the process that is noteworthy is the energy of the electron beam system. This initial investigation used a highenergy 5 MeV electron beam irradiator, and our findings have indicated that there is low TV sensitivity on the surface of irradiated PE films/sheets as analyzed by ATR-FTIR. Maximal TV sensitivity may be the result of the well-characterized cascade effect and reside in the sub-surface region, beyond the limits of this surface analysis technique. Similar work performed with lowenergy electron beam, however, indicated that TV formation was highest at the surface of irradiated UHMWPE, when determined by FTIR microscopy (Muratoglu et al., 2002). PE irradiated using low energy electron beam and analyzed via ATR-FTIR may corroborate those findings as well.
5. Conclusions PE films/sheets were electron beam irradiated at room temperature in the presence of air to two radiation dose ranges,
followed by subsequent ATR-FTIR analysis to measure the TV absorbance peak at 965 cm 1 wavenumber. Results were somewhat promising, indicating that there was an upward trend in TV formation for LDPE films and HDPE sheets as a function of absorbed dose in the 10–50 kGy dose range, however, the range and resolution of individual data points was such that the TV response could not be equated to a specific absorbed dose. Analysis of the UHMWPE sheets revealed a TV response for the 10–50 kGy dose range that was equivalent to the TV response of the non-irradiated UHMWPE. In the 50–500 kGy dose range, LDPE film displayed a downward trend from 50 kGy to 250 kGy and then scattering up to 500 kGy. For HDPE sheets, an upward trend in TV formation was apparent, but TV response could not be equated to a specific absorbed dose. For UHMWPE sheets irradiated up to 150 kGy, TV response was equivalent to nonirradiated UHMWPE, and a minimal upward trend was observed for 200 kGy to 500 kGy. UHMWPE yielded low sensitivity compared to the LDPE films and HDPE sheets and similarly, the scatter of the data is such that the TV response could not be equated to a specific absorbed dose. FTIR analysis of PE films/sheets has been used for many years in industry to demonstrate control of irradiation processes, with the post-irradiation TV response in effect a radiation indicator. Exploiting the sampling advantage of ATR-FTIR to take measurements independent of PE film/sheet thickness, this initial investigation has focused on the utility of ATR-FTIR for analyzing various PE films/sheets as possible dosimeters in the healthcare product sterilization dose range. Given the aforementioned variables as potential influence quantities, future studies with ATR-FTIR will need to be performed to better correlate post-irradiation TV response in the PE films/sheets versus absorbed dose. These studies should include systematic characterization via a design of experiment (DOE) for maximum efficiency, as described in ISO/ ASTM 52701-13 (ISO/ASTM 52701-13, 2013).
Acknowledgments The authors would like to express their gratitude to the following individuals for providing technical guidance for this investigation: Dr. S. Spiegelberg (Cambridge Polymer Group, Inc.), R. Vetrecin (Johnson & Johnson, retired) and A. Berejka (Ionicorp, Inc., retired). References ANSI/AAMI/ISO 11137-1:2006/(R); 2010, Sterilization of Health Care Products – Radiation – Part 1: Requirements for Development, Validation, and Routine Control of a Sterilization Process for Medical Devices. ASTM International F 2381-10, Standard Test Method for Evaluating Trans-Vinylene Yield in Irradiated Ultra-High-Molecular-Weight Polyethylene Fabricated Forms Intended for Surgical Implants by Infrared Spectroscopy (2010). Charlesby, A., Gould, A.R., Ledbury, K.J., 1964. Comparison of alpha and gamma radiation effects in polyethylene. Proc. Royal Soc. Lond. A: Math. Phys. Sci. 277 (1370), 348–364. Cota, S.S., Vasconcelos, V., Senne, M., Carvalho, L.L., Rezende, D.B., Côrrea, R.F., 2007. Changes in mechanical properties due to gamma irradiation of high-density polyethylene (HDPE). Braz. J. Chem. Eng. 24 (2), 259–265. Dias, D.J., de Andrade e Silva, L.G., 2007. Polyethylene foams cross-linked by electron beam. Radiat. Phys. Chem. 76, 1696–1697. Ghaffari, M., Ahmadian, V., 2007. Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene. Radiat. Phys. Chem. 76, 1666–1670. ISO/ASTM 52701-13, Standard Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing (2013). Illgen, R.L., Bauer, L.M., Hotujec, B.T., Kolpin, S.E., Bakhtiar, A., Forsythe, T.M., 2009. High crosslinked vs conventional polyethylene particles. J. Arthroplast. 24 (1), 117–124, http://dx.doi.org/10.1016/j.arth.2008.01.134. Johnson, W.C., Lyons, B.J., 1995. Radiolytic formation and decay of trans-vinylene unsaturation in polyethylene: Fourier transform infra-red measurements. Radiat. Phys. Chem. 46 (4-6), 829–832 ([DOI:0969-806X(95)00271-5]).
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎ Lyons, B.J., 2004a. Radiolytic unsaturation decay in polyethylene. Part I – general review and analysis with additional new work. Radiat. Phys. Chem. 69, 495–502, http://dx.doi.org/10.1016/j.radphyschem.2003.10.004. Lyons, B.J., 2004b. Radiolytic unsaturation decay in polyethylene. Part II – the effect of irradiation temperature, thermal history and orientation. Radiat. Phys. Chem. 69, 503–510, http://dx.doi.org/10.1016/j.radphyschem.2003.10.005. Lyons, B.J., 2004c. Radiolytic unsaturation decay in polyethylene. Part III – the effect of certain chain transfer agents. Radiat. Phys. Chem. 70, 707–717, http://dx.doi. org/10.1016/j.radphyschem.2003.10.006. Marinović-Cincović, M., Kačarević-Popović, Z., Babić, D., 2003. Structural changes in highly crosslinked polyethylene irradiated in absence of oxygen. Radiat. Phys. Chem. 67, 425–429, http://dx.doi.org/10.1016/S0969-806X(03)00079-3. McLaughlin, W.L., Silverman, J., Al-Sheikhly, M., Chappas, W.J., Zhan-Jun, L., Miller, A., Batsberg-Pedersen, W., 1999. High-density polyethylene dosimetry by transvinylene FTIR analysis. Radiat. Phys. Chem. 56, 503–508 (PII:S0969-806X (99)00324-2). Muratoglu, O.K., Harris, W.H., 2001. Identification and quantification of irradiation in UHMWPE through trans-vinylene yield. J. Biomed. Mater. Res. A 56 (4), 584–592, http://dx.doi.org/10.1002/1097-4636(20010915). Muratoglu, O.K., O’Connor, D.O., Bragdon, C.R., Delaney, J., Jasty, M., Harris, W.H., Merrill, E., Venugopalan, P., 2002. Gradient crosslinking of UHMWPE using irradiation in molten state for total joint arthroplasty. Biomaterials 23, 717–724. Muratoglu, O.K., Delaney, J., O’Connor, D.O., Harris, W.H., 2003. The use of transvinylene formation in quantifying the spatial distribution of electron beam penetration in polyethylene. Single-sided, double-sided and shielded irradiation. Biomaterials 24, 2021–2029, http://dx.doi.org/10.1016/S0142-9612(02) 00632-4. Murray, K.A., Kennedy, J.E., McEvoy, B., Vrain, O., Damien, R., Higginbotham, C.L., 2012. The effects of high energy electron beam irradiation on the thermal and structural properties of low density polyethylene. Radiat. Phys. Chem. 81, 962–966, http://dx.doi.org/10.1016/j.radphyschem.2011.09.011.
5
Murray, K.A., Kennedy, J.E., McEvoy, B., Vrain, O., Ryan, D., Cowman, R., Higginbotham, C.L., 2013. The effects of high energy electron beam irradiation in air on accelerated aging and on the structure property relationships of low density polyethylene. Nucl. Instrum. Methods Phys. Res. B 297, 64–74, http://dx.doi.org/ 10.1016/j.nimb.2012.12.001. Pinheiro, L.A., Chinelatto, M.A., Canevarolo, S.V., 2006. Evaluation of Philips and Ziegler-Natta high-density polyethylene degradation during processing in an internal mixture using the chain scission and branching distribution function analysis. Polym. Degrad. Stab. 91, 2324–2332, http://dx.doi.org/10.1016/j. polymdegradstab.2006.04.005. Singh, A., 1999. Irradiation of polyethylene: some aspects of crosslinking and oxidative degradation. Radiat. Phys. Chem. 56, 375–380 (PII:S0969-806X(99) 00328-X). Sugimoto, M., Shimada, A., Kudoh, H., Tamura, K., Seguchi, T., 2013. Product analysis for polyethylene degradation by radiation and thermal ageing. Radiat. Phys. Chem. 82, 69–73, http://dx.doi.org/10.1016/j.radphyschem.2012.08.009. Waterman, D.C., Dole, M., 1970a. Ultraviolet and infrared studies of free radicals in irradiated polyethylene. J. Phys. Chem. 74 (9), 1906–1912. Waterman, D.C., Dole, M., 1970b. The radiation chemistry of polyethylene. X. Kinetics of the conversion of alkyl to allyl free radicals. J. Phys. Chem. 74 (9), 1913–1922. Wenxiu, C., Haishen, J., Xiangdi, L., Dongyuan, L., Huaying, B., 1980. On polyethylene film dosimeter. Radiat. Phys. Chem. 16, 195–199. Wenxiu, C., Haishun, J., Gongxu, L., 1989. The minimum range of dose measurement on polyethylene film dosimeter. Radiat. Phys. Chem. 33 (5), 417–420. Zenkiewicz, M., Rauchfleisz, M., Czupryńska, J., 2003. Comparison of some oxidation effects in polyethylene film irradiated with electron beam or gamma rays. Radiat. Phys. Chem. 68, 799–809, http://dx.doi.org/10.1016/S0969-806X(03) 00368-2.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
Contents lists available at ScienceDirect
Radiation Physics and Chemistry journal homepage: www.elsevier.com/locate/radphyschem
Evaluation of various polyethylene as potential dosimeters by attenuated total reflectance-Fourier-transform infrared spectroscopy Fred Halperin n, Greta Collins, Michael DiCicco, John Logar Johnson & Johnson Sterility Assurance, 1000 US Route 202 South, Bldg. 930 East, Raritan, NJ 08869, USA
H I G H L I G H T S
Various types of PE films/sheets have been evaluated for use as a potential dosimeter. Attenuated total reflectance FTIR spectroscopy was utilized to analyze transvinylene formation in irradiated PE films/sheets. PE films/sheets were exposed to ionizing radiation using a 5 MeV high-energy electron beam accelerator. Analysis of TV peak formation at the 965 cm 1 wavenumber shows an upward trend of TV response to absorbed dose.
art ic l e i nf o
a b s t r a c t
Article history: Received 31 January 2014 Accepted 11 May 2014
Various types of polyethylene (PE) have been evaluated in the past for use as a potential dosimeter, chiefly via the formation of an unsaturated transvinylene (TV) double-bond resulting from exposure to ionizing radiation. The utilization of attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy in characterizing TV formation in irradiated PE for a potential dosimeter has yet to be fully developed. In this initial investigation, various PE films/sheets were exposed to ionizing radiation in a high-energy 5 megaelectron volt (MeV) electron beam accelerator in the 10–500 kilogray (kGy) dose range, followed by ATR-FTIR analysis of TV peak formation at the 965 cm 1 wavenumber. There was an upward trend in TV formation for low-density polyethylene (LDPE) films and high-density polyethylene (HDPE) sheets as a function of absorbed dose in the 10–50 kGy dose range, however, the TV response could not be equated to a specific absorbed dose. LDPE film displayed a downward trend from 50 kGy to 250 kGy and then scattering up to 500 kGy; HDPE sheets demonstrated an upward trend in TV formation up to 500 kGy. For ultra-high molecular weight polyethylene (UHMWPE) sheets irradiated up to 150 kGy, TV response was equivalent to non-irradiated UHMWPE, and a minimal upward trend was observed for 200 kGy to 500 kGy. The scatter of the data for the irradiated PE films/sheets is such that the TV response could not be equated to a specific absorbed dose. A better correlation of the post-irradiation TV response to absorbed dose may be attained through a better understanding of variables. & 2014 Elsevier Ltd. All rights reserved.
Keywords: Attenuated total reflectance Dosimeter Electron beam irradiation FTIR Polyethylene Transvinylene
1. Introduction Historically, beginning with the work of Charlesby et al., the effects of high-energy radiation on various types of polyethylene (PE) have been studied (Charlesby et al., 1964). This includes the formation of a main-chain unsaturated transvinylene (TV) doublebond with peak at 965 cm 1 via Fourier-transform infrared (FTIR) spectroscopy (Charlesby et al., 1964; Johnson and Lyons, 1995; Muratoglu et al., 2003). The mechanism for the formation of TV n
Corresponding author. Tel.: þ 1 908 927 2805. E-mail addresses: [email protected] (F. Halperin), [email protected] (G. Collins), [email protected] (M. DiCicco), [email protected] (J. Logar).
unsaturations during irradiation using a high-energy electron beam is mainly via hydrogen abstraction and to a lesser degree by recombination of two adjacent alkyl radicals on the same chain (ASTM International F 2381-10, 2010; McLaughlin et al., 1999). Other well-known inherent effects noted from PE exposure to ionizing radiation include chain scission, cross-linking and degradation (via production of alkyl and allyl radicals), and formation of carbonyl and other oxidation products when oxygen is present (Charlesby et al., 1964; Cota et al., 2007; McLaughlin et al., 1999; Singh, 1999; Waterman and Dole, 1970a, 1970b). It has also been shown that the concentration of these TV unsaturations formed within the PE backbone as a result of exposure to ionizing radiation is dose-dependent (Charlesby et al., 1964; McLaughlin et al., 1999; Zenkiewicz et al., 2003). Furthermore, the rate of the subsequent
http://dx.doi.org/10.1016/j.radphyschem.2014.05.014 0969-806X/& 2014 Elsevier Ltd. All rights reserved.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
2
decay of these TV unsaturations is dependent on various factors as well (Lyons, 2004a, 2004b, 2004c). PE films have been evaluated for use as potential dosimeters in the past to varying degrees to measure the absorbed dose delivered to healthcare products. These evaluations encompassed various analytical techniques using a variety of wavelengths (Johnson and Lyons, 1995; McLaughlin et al., 1999; Wenxiu et al., 1980, 1989). [A dosimeter is a device having a reproducible, measurable response to radiation, which can be used to measure the absorbed dose in a given system (ANSI/AAMI/ISO 11137-1:2006/(R) (2010))]. The effects of electron beam processing on various PE have also been investigated (Illgen et al., 2009; Muratoglu and Harris, 2001; Muratoglu et al., 2002, 2003; Murray et al., 2012, 2013), with studies ranging from cross-linking in PE foams (Dias and de Andrade e Silva, 2007) to the effects of blending antioxidants into PE to suppress thermal oxidation (Ghaffari and Ahmadian, 2007). The utilization of attenuated total reflectance (ATR)–FTIR in characterizing TV formation in various irradiated PE films/sheets for potential dosimeters has yet to be fully developed. ASTM International F 2381-10, Standard Test Method for Evaluating TransVinylene Yield in Irradiated Ultra-High-Molecular-Weight Polyethylene Fabricated Forms Intended for Surgical Implants by Infrared Spectroscopy, compares the TV peak between 950 and 980 cm 1 to a reference band between 1330 and 1396 cm 1, and only mentions ATR-FTIR as an alternative mode of spectra collection (ASTM International F 2381-10, 2010). However, there have been a few published articles demonstrating the use of ATR-FTIR to evaluate [cross-linked] PE (Sugimoto et al., 2013) or TV formation in PE films/ sheets exposed to ionizing radiation (Murray et al., 2012, 2013). The majority of published literature reports employing conventional transmission FTIR and FTIR microscopy to investigate this TV formation in irradiated PE (Illgen et al., 2009; Johnson and Lyons, 1995; McLaughlin et al., 1999; Muratoglu and Harris, 2001; Muratoglu et al., 2002, 2003; Pinheiro et al., 2006; Zenkiewicz et al., 2003). In this initial investigation, low-density polyethylene (LDPE) films, high-density polyethylene (HDPE) sheets, and ultra-high molecular weight polyethylene (UHMWPE) sheets were exposed to different doses of ionizing radiation using a 5 megaelectron volt (MeV) [high-energy] electron beam accelerator. The different PE films/sheets were then analyzed via ATR-FTIR, and the TV peak formation at the 965 cm 1 wavenumber was assessed. Studying TV formation in irradiated PE via ATR-FTIR is of considerable interest since it offers unique sampling advantages compared to transmission FTIR, in characterizing these PE films/sheets for potential use as dosimeters in the healthcare product sterilization dose range.
2. Materials and methods 2.1. Materials Three different types of commonly available PE films/sheets were studied: LDPE film (0.004 in. thickness; McMaster Carr; Robbinsville, NJ), HDPE sheet (0.0625 in. thickness; United States Plastic Corp.s; Lima, OH); UHMWPE sheet (0.062 in. thickness; Plastics International; Eden Prairie, MN). The PE films/sheets were further prepared by cutting them into approximately 5 cm 5 cm specimens. There was neither pre- nor post-irradiation conditioning for these PE films/ sheets; all films were stored in the analytical laboratory at room conditions. 2.2. Electron beam irradiation Irradiation of the PE films/sheets was performed using a MEVEX 5 MeV, 2 kW electron beam accelerator (Model MB5000;
Kanata, Ontario). All PE films/sheets were treated at room temperature in the presence of air at Johnson & Johnson (Raritan, NJ), at two ranges of doses. The first dose range included: 10, 20, 30, 40 and 50 kilograys (kGy). The second dose range included: 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 kGy. The absorbed dose was confirmed using alanine dosimeters traceable to a national standard and measured using a Bruker e-scan electron paramagnetic resonance (EPR) spectrometer (Billerica, MA). 2.3. ATR-FTIR spectroscopy The PE films/sheets were evaluated using a Bruker ALPHA™ FT-IR spectrometer with Eco-ATR single reflection sampling module and zinc selenide (ZnSe) crystal. ATR is essentially a FTIR sampling technique that is ideal for both solids and liquids, and usually does not require any specialized sample preparation. An IR beam is transmitted through an optically dense crystal, with a high index of refraction, that is in contact with a sample which has a lower index of refraction. This results in an evanescent wave that penetrates past the sample surface, approximately 1–2 μm into the sample, and then is reflected back into the crystal for subsequent detection. ATR addresses concerns about variation in thickness, which is an influence quantity for some optical dosimeters, by examining the first 1–2 μm only. All data was recorded under ambient conditions with 32 scans per sample and at 4 cm 1 resolution: the anvil was outfitted with a slip-clutch to deliver a fixed compression of approximately 4000 psi on the sample against the ZnSe crystal. Data analysis was conducted with the Bruker OPUS IR Software (Version 7.2). The IR spectra were evaluated using the internal Integration Mode B – the software draws a straight line between two defined frequency limits and integrates the area above that line. Normalization or other transformations on the IR spectra were not performed, including comparing the area under the curve at 965 cm 1 to another reference peak.
3. Results 3.1. Evaluation of PE films/sheets irradiated in the 10–50 kGy dose range The PE films/sheets (LDPE, HDPE and UHMWPE) were irradiated at room temperature in the presence of air for the first series of target doses: 10, 20, 30, 40 and 50 kGy; only the conveyor speed was adjusted to obtain the desired target dose during a single pass. The PE films/sheets were then analyzed via ATR-FTIR to measure the area under the curve at the TV absorbance peak at 965 cm 1 wavenumber. Fig. 1 displays a box-and-whisker plot1 for the LDPE film data obtained from the median absorbance intensity (n ¼10) versus target dose (kGy), including the TV response for non-irradiated LDPE film. Although an upward trend was observed, the range and resolution of individual data points is such that a TV response could not be equated to a specific absorbed dose. Similarly, Fig. 22 displays a box-and-whisker plot for the HDPE sheet data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated HDPE sheet. Again, an upward trend was observed, with a possible outlier at 40 kGy, but the TV response is lower than that of the LDPE film. Furthermore, of the PE films/sheets exposed 1 In the box-and-whisker plots, the points coinciding with the center lines are the median absorbance intensity (n¼10) at the different absorbed doses; the boxes below and above are the ranges of the second and third quartiles (respectively), and the ‘whiskers’ are the standard error. 2 For better visualization of the data, the absorbance scale in Fig. 2 box and whisker plot is in 10 3 resolution in comparison to the other box-and-whisker plots which are in 10 2 resolution.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
Fig. 1. Box-and-whisker plot for LDPE films, 0–50 kGy (single-column fitting).
Fig. 2. Box-and-whisker plot for HDPE sheets, 0–50 kGy (single-column fitting).
3
Fig. 3. Box-and-whisker plot for LDPE films, 0–500 kGy (single-column fitting).
Fig. 4. Box-and-whisker plot for HDPE sheets, 0–500 kGy (single-column fitting).
to 10 kGy, only two of the ten samples exhibited a TV response, and there was no resolution of the quartiles in the plot. Analysis of the UHMWPE sheets revealed a TV response at 965 cm 1 for the 10–50 kGy dose range (data not shown) that was equivalent to the TV response of the non-irradiated UHMWPE sheet. 3.2. Evaluation of PE films/sheets irradiated in the 50–500 kGy dose range The PE films/sheets were irradiated at room temperature in the presence of air for the second series of target doses: 50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 kGy. The conveyor speed was adjusted to obtain the desired 50 kGy target dose and multiple passes through the radiation zone were used to deliver required target doses in 50 kGy fractions. The PE films/sheets were then analyzed via FTIR-ATR to measure the area under the curve at the TV 965 cm 1 wavenumber. Fig. 3 displays a box-and-whisker plot for the LDPE film data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated LDPE film. The data demonstrates an initial drop in absorbance intensity from 50 kGy up to 250 kGy, then followed by scattering up to 500 kGy. In addition, there is significant overlap in the 3rd quartile, such that a TV response could not be equated to a specific absorbed dose. Fig. 4 displays a box-and-whisker plot for the HDPE sheet data obtained from the median absorbance intensity (n ¼10) versus target dose, including the TV response for non-irradiated HDPE sheet. Although an upward trend was observed, the overlap of the 3rd quartile of the data points is such that a TV response could not be equated to a specific absorbed dose. Fig. 5 displays a box-and-whisker plot for the UHMWPE sheet data obtained from the median absorbance intensity (n¼ 10) versus target dose, including the TV response for non-irradiated UHMWPE sheet. Analysis of the UHMWPE sheets revealed that TV response up to 150 kGy was equivalent to non-irradiated UHMWPE sheet. A minimal upward trend was observed for 200 kGy to 500 kGy, but the scatter of the data is such that the TV response could not be equated to a specific absorbed dose. Lastly, the low slope of the median values of the TV response
Fig. 5. Box-and-whisker plot for UHMWPE sheets, 0–500 kGy (single-column fitting).
demonstrate that UHMWPE yielded a low sensitivity compared to the other irradiated LDPE films and HDPE sheets.
4. Discussion A general correlation of increasing TV peak formation at 965 cm 1 with increasing electron beam irradiation dose in LDPE was observed in other studies using ATR-FTIR (Murray et al., 2012, 2013). Work to develop a TV/dose calibration curve for irradiated UHMWPE was performed via FTIR microscopy (Muratoglu and Harris, 2001). These results yielded a low TV sensitivity in addition to a greater degree of variation and overlap among the different absorbed doses for both irradiated LDPE films and HDPE sheets. This is not consistent with previously reported results using transmission FTIR and FTIR microscopy for analysis where TV formation was dependent on the relatively high-dose rates as with electron beam irradiation (Charlesby et al., 1964; Johnson and Lyons, 1995; McLaughlin et al., 1999; Muratoglu et al., 2003). When analyzing the data using ATR-FTIR, there were no data normalizations or transformations performed, as indicated earlier. However, as evidenced from the variation and overlap shown in
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎
4
the box-and-whisker plots of the various PE investigated, a better correlation of the post-irradiation TV response to absorbed dose may be attained through a better understanding of variables. Due to the absorbed dose build-up from the cascading effect typically experienced during electron beam processing (i.e. the well-characterized dose-depth profile), there may be more TV formed in the sub-surface regions of the PE film/sheets rather than on their surface. Since ATR-FTIR is a surface technique measuring within the first 1–2 μm of a film/sheet, this may account for the lower sensitivity that has been observed. Furthermore, the formation of TV regions is affected by temperature, and with the sharp rise in temperature experienced during high-energy electron beam irradiation, maintaining lower temperature could yield better TV formation to absorbed dose correlation (S. Spiegelberg, Pers. Comm.). In essence, there may be more TV formation in the sub-surface regions of the PE films/sheets as opposed to on the surface; thus decreased sensitivity in ATR-FTIR sampling. This may be more prominent in UHMWPE sheets, as poor TV sensitivity could be the result of high oxidation present in the sheets (Muratoglu and Harris, 2001), as evidenced from the low TV peaks obtained. It is recommended to avoid ambient oxygen, if possible during radiation processing, which will cause a drift in TV concentration over time (Johnson and Lyons, 1995). Irradiation of PE in the presence of oxygen causes macroradical formation, which in turn reacts with vinyl groups (decreasing TV concentration); this effect is enhanced by any temperature increase in the process (Pinheiro et al., 2006). Moreover, although the use of fractionated doses (electron beam processing in serial fashion) for the 100–500 kGy absorbed dose samples does not increase temperature to the same extent as dose delivered in a single pass, the time in between passes did not allow for complete cool-down of the PE films/sheets to room temperature. Therefore, as higher doses were delivered, the temperature of the PE films/sheets increased in a step-wise manner as part of the heating/cooling cycle, possibly creating an annealing effect and causing TV quenching, perhaps through cross-linking. The quality and uniformity of PE can also have an effect on the TV response at the 965 cm 1 wavenumber. Branching and the presence of crystalline lamellae regions will have a more prominent effect on the TV formation, although TV are formed randomly and distributed homogenously within the crystal matrices of PE (Marinović-Cincović et al., 2003). Some HDPE can reach as high as 95% crystallinity, whereas LDPE is on the order of 60–75% crystallinity (McLaughlin et al., 1999) and it is thought that the amorphous phase is rich in vinyl and vinylidene unsaturations (Lyons, 2004a). The low TV sensitivity observed with the UHMWPE sheets may also be related to amorphous/crystallinity differences on the film surface. Another variable of the process that is noteworthy is the energy of the electron beam system. This initial investigation used a highenergy 5 MeV electron beam irradiator, and our findings have indicated that there is low TV sensitivity on the surface of irradiated PE films/sheets as analyzed by ATR-FTIR. Maximal TV sensitivity may be the result of the well-characterized cascade effect and reside in the sub-surface region, beyond the limits of this surface analysis technique. Similar work performed with lowenergy electron beam, however, indicated that TV formation was highest at the surface of irradiated UHMWPE, when determined by FTIR microscopy (Muratoglu et al., 2002). PE irradiated using low energy electron beam and analyzed via ATR-FTIR may corroborate those findings as well.
5. Conclusions PE films/sheets were electron beam irradiated at room temperature in the presence of air to two radiation dose ranges,
followed by subsequent ATR-FTIR analysis to measure the TV absorbance peak at 965 cm 1 wavenumber. Results were somewhat promising, indicating that there was an upward trend in TV formation for LDPE films and HDPE sheets as a function of absorbed dose in the 10–50 kGy dose range, however, the range and resolution of individual data points was such that the TV response could not be equated to a specific absorbed dose. Analysis of the UHMWPE sheets revealed a TV response for the 10–50 kGy dose range that was equivalent to the TV response of the non-irradiated UHMWPE. In the 50–500 kGy dose range, LDPE film displayed a downward trend from 50 kGy to 250 kGy and then scattering up to 500 kGy. For HDPE sheets, an upward trend in TV formation was apparent, but TV response could not be equated to a specific absorbed dose. For UHMWPE sheets irradiated up to 150 kGy, TV response was equivalent to nonirradiated UHMWPE, and a minimal upward trend was observed for 200 kGy to 500 kGy. UHMWPE yielded low sensitivity compared to the LDPE films and HDPE sheets and similarly, the scatter of the data is such that the TV response could not be equated to a specific absorbed dose. FTIR analysis of PE films/sheets has been used for many years in industry to demonstrate control of irradiation processes, with the post-irradiation TV response in effect a radiation indicator. Exploiting the sampling advantage of ATR-FTIR to take measurements independent of PE film/sheet thickness, this initial investigation has focused on the utility of ATR-FTIR for analyzing various PE films/sheets as possible dosimeters in the healthcare product sterilization dose range. Given the aforementioned variables as potential influence quantities, future studies with ATR-FTIR will need to be performed to better correlate post-irradiation TV response in the PE films/sheets versus absorbed dose. These studies should include systematic characterization via a design of experiment (DOE) for maximum efficiency, as described in ISO/ ASTM 52701-13 (ISO/ASTM 52701-13, 2013).
Acknowledgments The authors would like to express their gratitude to the following individuals for providing technical guidance for this investigation: Dr. S. Spiegelberg (Cambridge Polymer Group, Inc.), R. Vetrecin (Johnson & Johnson, retired) and A. Berejka (Ionicorp, Inc., retired). References ANSI/AAMI/ISO 11137-1:2006/(R); 2010, Sterilization of Health Care Products – Radiation – Part 1: Requirements for Development, Validation, and Routine Control of a Sterilization Process for Medical Devices. ASTM International F 2381-10, Standard Test Method for Evaluating Trans-Vinylene Yield in Irradiated Ultra-High-Molecular-Weight Polyethylene Fabricated Forms Intended for Surgical Implants by Infrared Spectroscopy (2010). Charlesby, A., Gould, A.R., Ledbury, K.J., 1964. Comparison of alpha and gamma radiation effects in polyethylene. Proc. Royal Soc. Lond. A: Math. Phys. Sci. 277 (1370), 348–364. Cota, S.S., Vasconcelos, V., Senne, M., Carvalho, L.L., Rezende, D.B., Côrrea, R.F., 2007. Changes in mechanical properties due to gamma irradiation of high-density polyethylene (HDPE). Braz. J. Chem. Eng. 24 (2), 259–265. Dias, D.J., de Andrade e Silva, L.G., 2007. Polyethylene foams cross-linked by electron beam. Radiat. Phys. Chem. 76, 1696–1697. Ghaffari, M., Ahmadian, V., 2007. Investigation of antioxidant and electron beam radiation effects on the thermal oxidation stability of low-density polyethylene. Radiat. Phys. Chem. 76, 1666–1670. ISO/ASTM 52701-13, Standard Guide for Performance Characterization of Dosimeters and Dosimetry Systems for Use in Radiation Processing (2013). Illgen, R.L., Bauer, L.M., Hotujec, B.T., Kolpin, S.E., Bakhtiar, A., Forsythe, T.M., 2009. High crosslinked vs conventional polyethylene particles. J. Arthroplast. 24 (1), 117–124, http://dx.doi.org/10.1016/j.arth.2008.01.134. Johnson, W.C., Lyons, B.J., 1995. Radiolytic formation and decay of trans-vinylene unsaturation in polyethylene: Fourier transform infra-red measurements. Radiat. Phys. Chem. 46 (4-6), 829–832 ([DOI:0969-806X(95)00271-5]).
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i
F. Halperin et al. / Radiation Physics and Chemistry ∎ (∎∎∎∎) ∎∎∎–∎∎∎ Lyons, B.J., 2004a. Radiolytic unsaturation decay in polyethylene. Part I – general review and analysis with additional new work. Radiat. Phys. Chem. 69, 495–502, http://dx.doi.org/10.1016/j.radphyschem.2003.10.004. Lyons, B.J., 2004b. Radiolytic unsaturation decay in polyethylene. Part II – the effect of irradiation temperature, thermal history and orientation. Radiat. Phys. Chem. 69, 503–510, http://dx.doi.org/10.1016/j.radphyschem.2003.10.005. Lyons, B.J., 2004c. Radiolytic unsaturation decay in polyethylene. Part III – the effect of certain chain transfer agents. Radiat. Phys. Chem. 70, 707–717, http://dx.doi. org/10.1016/j.radphyschem.2003.10.006. Marinović-Cincović, M., Kačarević-Popović, Z., Babić, D., 2003. Structural changes in highly crosslinked polyethylene irradiated in absence of oxygen. Radiat. Phys. Chem. 67, 425–429, http://dx.doi.org/10.1016/S0969-806X(03)00079-3. McLaughlin, W.L., Silverman, J., Al-Sheikhly, M., Chappas, W.J., Zhan-Jun, L., Miller, A., Batsberg-Pedersen, W., 1999. High-density polyethylene dosimetry by transvinylene FTIR analysis. Radiat. Phys. Chem. 56, 503–508 (PII:S0969-806X (99)00324-2). Muratoglu, O.K., Harris, W.H., 2001. Identification and quantification of irradiation in UHMWPE through trans-vinylene yield. J. Biomed. Mater. Res. A 56 (4), 584–592, http://dx.doi.org/10.1002/1097-4636(20010915). Muratoglu, O.K., O’Connor, D.O., Bragdon, C.R., Delaney, J., Jasty, M., Harris, W.H., Merrill, E., Venugopalan, P., 2002. Gradient crosslinking of UHMWPE using irradiation in molten state for total joint arthroplasty. Biomaterials 23, 717–724. Muratoglu, O.K., Delaney, J., O’Connor, D.O., Harris, W.H., 2003. The use of transvinylene formation in quantifying the spatial distribution of electron beam penetration in polyethylene. Single-sided, double-sided and shielded irradiation. Biomaterials 24, 2021–2029, http://dx.doi.org/10.1016/S0142-9612(02) 00632-4. Murray, K.A., Kennedy, J.E., McEvoy, B., Vrain, O., Damien, R., Higginbotham, C.L., 2012. The effects of high energy electron beam irradiation on the thermal and structural properties of low density polyethylene. Radiat. Phys. Chem. 81, 962–966, http://dx.doi.org/10.1016/j.radphyschem.2011.09.011.
5
Murray, K.A., Kennedy, J.E., McEvoy, B., Vrain, O., Ryan, D., Cowman, R., Higginbotham, C.L., 2013. The effects of high energy electron beam irradiation in air on accelerated aging and on the structure property relationships of low density polyethylene. Nucl. Instrum. Methods Phys. Res. B 297, 64–74, http://dx.doi.org/ 10.1016/j.nimb.2012.12.001. Pinheiro, L.A., Chinelatto, M.A., Canevarolo, S.V., 2006. Evaluation of Philips and Ziegler-Natta high-density polyethylene degradation during processing in an internal mixture using the chain scission and branching distribution function analysis. Polym. Degrad. Stab. 91, 2324–2332, http://dx.doi.org/10.1016/j. polymdegradstab.2006.04.005. Singh, A., 1999. Irradiation of polyethylene: some aspects of crosslinking and oxidative degradation. Radiat. Phys. Chem. 56, 375–380 (PII:S0969-806X(99) 00328-X). Sugimoto, M., Shimada, A., Kudoh, H., Tamura, K., Seguchi, T., 2013. Product analysis for polyethylene degradation by radiation and thermal ageing. Radiat. Phys. Chem. 82, 69–73, http://dx.doi.org/10.1016/j.radphyschem.2012.08.009. Waterman, D.C., Dole, M., 1970a. Ultraviolet and infrared studies of free radicals in irradiated polyethylene. J. Phys. Chem. 74 (9), 1906–1912. Waterman, D.C., Dole, M., 1970b. The radiation chemistry of polyethylene. X. Kinetics of the conversion of alkyl to allyl free radicals. J. Phys. Chem. 74 (9), 1913–1922. Wenxiu, C., Haishen, J., Xiangdi, L., Dongyuan, L., Huaying, B., 1980. On polyethylene film dosimeter. Radiat. Phys. Chem. 16, 195–199. Wenxiu, C., Haishun, J., Gongxu, L., 1989. The minimum range of dose measurement on polyethylene film dosimeter. Radiat. Phys. Chem. 33 (5), 417–420. Zenkiewicz, M., Rauchfleisz, M., Czupryńska, J., 2003. Comparison of some oxidation effects in polyethylene film irradiated with electron beam or gamma rays. Radiat. Phys. Chem. 68, 799–809, http://dx.doi.org/10.1016/S0969-806X(03) 00368-2.
Please cite this article as: Halperin, F., et al., Evaluation of various polyethylene as potential dosimeters by attenuated total reflectanceFourier-transform infrared spectroscopy. Radiat. Phys. Chem. (2014), http://dx.doi.org/10.1016/j.radphyschem.2014.05.014i