X-ray shielding by a novel garment woven with melt-spun monofilament weft yarn containing lead and tin particles

Abstract

Conventional lead aprons are rather heavy and uncomfortable for the wearer and also crack easily due to bending during both usage and storage. Coating of textiles with certain compounds provides protection against ionizing radiation. However, coated garments may have reduced flexibility and breathability. The principle aim of this study is development of a lightweight textile-based X-ray radiation shielding. The shielding fabric, while capable of significantly attenuating X-rays, relative to current conventional aprons is more intrinsically flexible, breathable, economical, easy to maintain, and crack resistant. Samples of fabrics were woven using melt-spun polypropylene monofilament yarns containing lead and tin particles. Shielding properties of the samples was measured using a high-purity germanium detector. Results showed that the samples composed of higher metal particles concentration and higher metal density and atomic number exhibited higher attenuation capability. Mechanical properties of the samples were evaluated. Furthermore, insignificant changes in the attenuation capability of samples due to abrasion and laundering processes occurred.

Keywords

X-ray shielding protective garment attenuation coefficient high-purity germanium detector lead tin

Radioactive sources are used in medical diagnostics, therapy, natural science, and technology. In medicine alone, more than 3 billion X-ray exposures are made every year.^1–3 X-rays are employed in numerous fields, ranging from computed tomography scans, phase-resolved medical imaging, and material surface research to security checkpoints in airports.⁴ Uncontrolled radiations or frequent exposure to X-rays is associated with damage to human cells, tissues, and organs.⁵ Therefore, protection against radiation is of paramount importance in the medical imaging field and other associated industries.^2,4

Generally, high atomic number materials, such as bismuth, tungsten, lead, and tin, are capable of attenuating X-rays via the photoelectric effect.⁵ Lead, due to its high density and atomic number, is considered to provide the most effective protection against X-ray radiation. Therefore, it forms the backbone of the structures used in radiological facilities.^2,6–8

Radiation shielding materials have been historically constructed from rubber, polymer, elastomeric polymer, or vinyl binders with an elastic matrix embedded with tiny lead particles or lead oxide.^9–11 Conventional protective lead aprons are made from lead sheets that are integrated into a textile-based apparel casing.² These aprons are very heavy and uncomfortable for the wearer, particularly when worn for long periods, which can result in orthopedic problems.^4,12–15 In addition, bending of the aprons during usage and storage can crack the lead sheets.¹⁶

In order to reduce the weight of protective garments, while maintaining their shielding performance, lead is replaced by bismuth, tin, antimony, or their mixture.^7,17–20 Incorporation of metal powder into polymeric yarns and formation of fabric-like protective garments is a challenge yet to be addressed. Effective attenuation can be achieved if the metal powder fraction in the polymer is adequately high. Such a fabric must be so robust that it can withstand forces during use and maintenance without occurrence of characteristic deterioration.⁸

Schlattl et al.²¹ evaluated and compared the shielding effectiveness of different protective clothing containing materials such as lead, tin, and a compound of 80% tin and 20% bismuth. It was found that light tin and tin/bismuth apron provide less protection than lead aprons. Schmid et al.²² compared the effectiveness of different shielding materials, included lead, tin/antimony, and bismuth barrier/tin/tungsten, and deduced that the latter, while more expensive, is more protective than the others. Qu et al.⁴ prepared a composite of BaSO₄ particles and regenerated cellulose at various proportions. Aral et al.²³ used cotton fabrics coated with silicone rubber containing equal amounts of tungsten, bismuth, or barium sulfate powders. The bismuth–silicone rubber blend yielded higher attenuation ratios per thickness. Maghrabi et al.² examined the suitability of bismuth oxide (Bi₂O₃) as an alternative to lead for coating of textiles. It was found that coating of polyester fabrics with coating paste containing over 50% Bi₂O₃ enhances shielding effectiveness against transmitted X-rays. Despite the shielding effectiveness of the coating formulations used, coating generally tends to make the fabric less breathable and less resistant to laundry.⁴

Comfort of X-ray protective garments is of paramount importance, especially during long use by the wearers. Comfort of protective garments is related to factors such as weight, flexibility, and the extent of X-rays attenuation. In addition, these garments are expected to be economical, easy to fabricate, and resistant to abrasion, laundering, and cracking.^4,8,21 Thus, production of protective garments encompassing the above criteria must be considered as a new phenomenon in garment engineering.

In this study, samples of woven fabrics using polypropylene (PP) monofilament yarns containing lead and tin particles were produced. The monofilament yarns were produced via the melt spinning process on a laboratory-scale melt spinning machine. A high-purity germanium (HPGe) detector was used to evaluate the shielding capability of the samples. An up to date and profound literature survey indicated that no attempt has so far been made to provide protection against X-rays using a textile-based protective barrier containing melt-spun monofilament yarns. Moreover, this study pioneers the use of a highly accurate HPGe detector and a ¹³³Ba radioactive source, which emits low-energy γ-rays with well-defined energies, in measuring X-rays transmitted through textile fabrics.

Experimental details

Sample preparation

Lead (Pb) and tin (Sn) metal particles were purchased from Pourian Chemical Company. PP granules were obtained from Navidzar Shimi Petrochemical Company. Pb/PP and Sn/PP masterbatches were produced by the compounding facilities of Iran Diba Company. Table 1 shows the specification of the material used.

Table 1.

Metal particle specifications

Metal	Density (g/cm³)	Atomic number	Particle size (µm)	Purity (%)
Lead	11.34	82	≤45	>99
Tin	7.31	50	≤45	>99

Monofilament yarns containing various types of particles at different wt% levels were spun on a Fourne laboratory-scale melt spinning machine. Mixtures of PP granules and masterbatches at the desired proportions were used and seven different monofilament yarns, as described in Table 2, were produced. For comparison purposes, a pure PP monofilament yarn was produced as a control sample. The temperature of the five heating zones of the single screw extruder was set at 210℃, 210℃, 205℃, 200℃, and 195℃, respectively. A draw ratio of 5:1 was used to draw the monofilaments after the melt-spinning operation. The diameter of the monofilament yarns was measured using a microscope using Motic software.

Table 2.

Monofilament yarn specifications

Monofilament code	Polypropylene (wt %)	Lead particles (wt %)	Tin particles (wt %)	Diameter (µm)	Diameter CV%
L30	70	30	0	190	7.78
L40	60	40	0	191	8.83
L50	50	50	0	189	9.98
LT30	70	15	15	191	7.57
T30	70	0	30	190	7.45
T40	60	0	40	190	8.62
T50	50	0	50	191	9.33
R^a	100	0	0	190	5.14

^aControl sample

Samples of fabrics were woven on a Smit rapier weaving machine (TP 422, 220 cm, Staubli Dobby, Italy). Weft backed weave fabrics (face weave 7/1 satin and back weave 1/7 sateen) were produced using the melt-spun monofilament yarns as the weft with 20/2 Ne polyester/viscose as the warp. The use of the laboratory-scale melt spinning machine prevented production of an adequate amount of yarns. Thus, warp composing of polyester/viscose yarns was used and the produced monofilament yarns were used as weft yarns. Figure 1 shows the weave pattern used. This pattern results in enhancement of fabric weft density and consequently reduction in fabric porosity and increase in particle concentration of the samples.²⁴

Figure 1.

Weft backed weave: (a) weave pattern; (b) fabric image.

The porosity of the layered sample fabric was measured by an SDL Atlas Air Permeability Tester according to ASTM D 737-96 at a pressure differential of 100 Pa and test area of 78.5 mm². The air permeability of the sample was found to be 2.29 ml/s.cm². This rather low air permeability value points to the correct selection of the weave pattern used for weaving of the samples. This also vividly calls for other weave patterns to be considered in future researches.

Fabric weight and thickness

Fabric mass per unit area (weight) was measured according to ASTM D3776. Samples of 10 cm × 10 cm were cut and weighed.

Sample thickness was measured according to ASTM D1777. Ten measurements were taken and the average thickness of samples was calculated. Sample specifications are given in Table 3.

Table 3.

Sample specifications

Sample code	Warp density (thread/cm)	Weft density (thread/cm)	Sample weight (g/m²)	Sample thickness (mm)
L30	20	80	367.09 (4.76)^a	0.513 (7.65)
L40	20	80	388.62 (4.82)	0.540 (7.72)
L50	20	80	420.40 (4.98)	0.475 (7.98)
LT30	20	81	364.48 (4.63)	0.531 (7.67)
T30	20	81	361.38 (5.09)	0.509 (8.03)
T40	20	81	382.85 (5.18)	0.518 (8.23)
T50	20	81	417.71 (5.27)	0.549 (8.39)
R	20	80	308.23 (4.10)	0.525 (6.91)

^aDenotes CV%.

Field emission scanning electron microscopy

The surface morphology of the monofilament yarns was analyzed using an HITACHI S4160 field emission scanning electron microscope (FESEM). Samples were prepared using a DSR1 gold sputter coater (Nano-structured Coatings Co., Iran) for 100 s. The longitudinal surface and cross-section of specimens were observed at 20 kV.

Measurement of X-ray attenuation

The radiation shielding capabilities of the samples were measured in the low-energy X-ray region using a HPGe detector at 30, 35, 53, and 80 keV radiation energy levels produced by a ¹³³Ba source. The HPGe detector (GMX40P4, ORTEC) was a coaxial n-type detector with a 0.05 cm beryllium window that has a resolution (FWHM) of 760 eV at 5.9 keV ⁵⁵Fe. The distance between the source and the sample was set at 12 cm and the samples were positioned between the detector and the source. Figure 2 shows the schematic of the measurement method.

Figure 2.

Schematic of the X-ray measuring set-up.

The X-ray attenuation capability of materials is described by the exponential attenuation law as follows

\frac{I}{I_{0}} = e^{- μ x}

(1)

where I, I₀, e, μ, and x denote the intensity of the attenuated beam, initial intensity, natural logarithm base, linear attenuation coefficient (1/cm), and thickness of the material (cm), respectively. Thus, the linear attenuation coefficient of materials can be obtained from equation (2)

μ = - \frac{Ln (I / I_{0})}{x}

(2)

The attenuation coefficient can also be calculated by the XCOM database. XCOM is a web database that can be used to calculate the attenuation coefficients of elements, compounds, or mixtures with an atomic number less than 100 at energies from 1 keV to 100 GeV.²⁵

The X-ray attenuation percentage (XAP) is calculated by equation (3)

XAP (%) = \frac{(I_{0} - I)}{I_{0}} \times 100

(3)

In order to calculate the attenuation coefficient for each sample at each energy, the intensity of the attenuated beam (I) should be measured at different thicknesses of samples, while maintaining the same initial intensity (I₀). Testing samples with different thicknesses were prepared by superimposing layers of the same fabric on top of each other. According to Figure 3, samples were superimposed on each other by aligning the weft yarns of each layer with respect to the underneath layer. A sample represented by (0°) code is a sample in which all layers forming the test sample have weft yarns aligned in the exactly same direction. A sample represented by (45°) code is a sample in which each layer has weft yarns aligned at 45° to the left or right with respect to the weft yarn of the underneath layer. A sample represented by (90°) code is a sample in which each layer of weft yarns is aligned at 90° with respect to the weft yarn of the underneath layer. The effect of weft yarn alignment of the stacked test sample on the radiation attenuation was also investigated.

Figure 3.

Schematic representation of weft yarn alignments in the samples.

Tensile properties

The tenacity and breaking elongation at of each monofilament yarn were measured in accordance with ASTM D 3822, at a speed of 15 mm/min with a gauge length of 25 mm. In addition, the tenacity and breaking elongation of fabrics were evaluated according to ASTM D5035 with a gauge length of 75 mm at a speed of 150 mm/min. Monofilament yarns and fabrics were tested 10 and five times, respectively. All experiments were carried out under standard laboratory conditions of 20 ± 2℃ and 65 ± 2% relative humidity using a Zwick universal testing machine 1446-60.

Abrasion resistance measurement

A Martindale abrasion test was performed according to ASTM D4966 with a Nu-Martindale Abrasion Tester 406. The circular fabric samples with 38 mm diameter were mounted on a dynamic disk to be abraded under constant pressure of 9 kPa. The abrading face was a standard wool fabric. The average of five percentage weight losses (WL%) based on equation (4) were calculated after 10,000 abrasion cycles using an A&D Weighing balance (±10^–4 g)

WL % = \frac{w_{0} - w_{1}}{w_{0}} \times 100

(4)

where w₀ and w₁ are sample weights before and after abrasion, respectively.

Laundering resistance measurement

The laundering resistance of samples was evaluated using an Ahiba AG CH-8305 laboratory dyeing machine (Datacolor, Switzerland) based on ISO 105-C06. Washing solution was prepared by dissolving 4 g/l of detergent in 60℃ water. Solution pH was adjusted at 10.5 ± 0.1 by adding 1 g/l of sodium carbonate. Rectangular samples of 4 cm × 10 cm together with 25 spherical steel balls of 6 mm diameter were placed in containers and washed for 30 minutes at 60℃. The specimens at the end of wash were rinsed twice for 1 min in two separate 100 ml of water at 40℃ and dried in air.

Results and discussion

Field emission scanning electron microscopy

Figure 4 depicts the FESEM images of all monofilament yarn cross-sections. The bright points and regions represent the dispersed metal particles embedded in the dark PP matrix. Ignoring the slight particle agglomerations, the images vividly confirm uniform dispersion of the metal particles in the polymer matrix despite particle shape and size unevenness. Samples containing higher particle concentrations have more bright regions. Figure 4(a₁) is the magnified FESEM image of sample L30 in which the invisible tiny particles in the unmagnified images are visible. The deformities visible on the samples are caused during cutting of the monofilament yarns using a microtome. Figure 5 depicts longitudinal views of samples. Based on the information given in Table 2, the diameter of the monofilament yarns can be considered to be uniform. Considering the increase in the CV% of the monofilament yarn diameters, it can be stated that an increase in metal particle concentration adversely affects yarn uniformity. Deterioration of yarn diameter uniformity is due to the creation of high stressed points along the yarn axis during the melt spinning process.²⁶ Table 3 points to a slight variation in the thickness of the layered samples. This can be attributed to monofilament yarn diameter CV%, errors during superimposing of the layers and, to some extent, inevitable difficulty associated with fabric thickness measurement.

Figure 4.

Monofilament yarn cross-section field emission scanning electron microscope images: (a)–(g) samples L30, L40, L50, LT30, T30, T40, T50.

Figure 5.

Monofilament yarn longitudinal field emission scanning electron microscope images: (a)–(g) samples L30, L40, L50, LT30, T30, T40, T50.

X-ray attenuation

The radiation attenuation coefficient of the 0°, 45°, and 90° superimposed samples was measured at 30, 35, 53, and 80 keV energy levels. The attenuation coefficients of samples at the 30 keV energy level with respective alignments are shown in Figures 6. The attenuation coefficient is the gradient of the best fitted line through the data. The intercept of the fitted line is due to measuring device noises. The weft yarn alignment is shown in parentheses adjacent to the energy level. The pictorial representations of attenuation coefficients at other energy levels are not shown. This is due to the fact that these coefficients were obtained using the same method. The calculated sample attenuation coefficient (μ) and the R² values of the best fitted lines are presented in Table 4. The calculated μ is the average of five repeated experiments. Attenuation of X-ray radiation is dependent on the energy level as the beam-related parameter and density, atomic number and electrons per gram are material-related parameters.⁵ According to Table 4, the attenuation coefficient of all samples decreases with an increase in X-ray energy levels. The increase in radiation energy level tends to increase the number of transmitted photons, which in turn reduces the attenuation coefficient.⁵ The X-ray attenuation level also increases with metal particle concentration. Therefore, higher ratios of metal to PP results in a higher attenuation coefficient.¹⁷ This is due to the superior shielding properties of lead and tin in comparison to PP. The shielding superiority of these metal particles is due to their higher density and atomic number. Moreover, a higher concentration of metal particles results in a higher sample weight and consequently higher density. Therefore, the attenuation coefficient of fabric samples increases with increasing fabric density.^5,25

Figure 6.

Attenuation coefficients at 30 keV.

Table 4.

Attenuation coefficient of samples (1/cm)

Energy level (keV)	L30	L40	L50	LT30	T30	T40	T50	R
30 (0°)	8.80	9.89	12.87	8.40	8.35	9.32	10.67	0.21
30 (0°)	(0.996)^a	(0.970)	(0.995)	(0.992)	(0.992)	(0.987)	(0.992)	(0.995)
30 (45°)	9.07	10.38	13.85	8.23	8.44	9.96	11.30	0.21
30 (45°)	(0.995)	(0.996)	(0.992)	(0.996)	(0.997)	(0.995)	(0.993)	(0.994)
30 (90°)	9.55	10.79	14.35	9.10	9.48	10.17	11.61	0.21
30 (90°)	(0.998)	(0.996)	(0.994)	(0.998)	(0.997)	(0.998)	(0.996)	(0.992)
35 (0°)	7.72	8.38	11.08	7.01	6.99	8.08	9.05	0.18
35 (0°)	(0.997)	(0.978)	(0.995)	(0.991)	(0.991)	(0.987)	(0.991)	(0.989)
35 (45°)	8.18	8.94	12.04	7.44	7.51	8.77	9.81	0.19
35 (45°)	(0.988)	(0.995)	(0.990)	(0.992)	(0.994)	(0.999)	(0.991)	(0.993)
35 (90°)	8.38	9.40	12.54	7.76	8.02	8.84	9.93	0.19
35 (90°)	(0.988)	(0.994)	(0.993)	(0.998)	(0.998)	(0.995)	(0.995)	(0.996)
53 (0°)	5.66	5.78	7.54	4.33	4.06	5.31	6.06	0.10
53 (0°)	(0.985)	(0.984)	(0.980)	(0.970)	(0.925)	(0.989)	(0.982)	(0.994)
53 (45°)	5.78	5.91	8.47	4.55	4.89	6.02	6.59	0.12
53 (45°)	(0.977)	(0.986)	(0.977)	(0.944)	(0.984)	(0.990)	(0.982)	(0.941)
53 (90°)	6.16	6.51	9.10	5.05	5.03	6.22	6.93	0.12
53 (90°)	(0.994)	(0.990)	(0.989)	(0.989)	(0.988)	(0.992)	(0.991)	(0.951)
80 (0°)	4.46	4.55	6.04	3.42	3.11	3.61	4.84	0.08
80 (0°)	(0.992)	(0.991)	(0.989)	(0.979)	(0.942)	(0.990)	(0.987)	(0.978)
80 (45°)	4.78	4.83	7.22	3.98	3.96	4.07	5.51	0.09
80 (45°)	(0.980)	(0.980)	(0.972)	(0.979)	(0.975)	(0.988)	(0.978)	(0.938)
80 (90°)	5.30	5.45	7.67	4.48	4.31	4.75	5.76	0.09
80 (90°)	(0.988)	(0.989)	(0.977)	(0.985)	(0.987)	(0.979)	(0.989)	(0.927)

^aDenotes R².

The effect of energy level and metal particle concentration on μ is also shown in Table 4. For a given energy level, samples L30, L40, and L50 have a higher attenuation coefficient than their counterpart samples T30, T40, and T50. While the first three samples, as shown in Table 2, contain lead particles, the second three samples contain tin particles. Lead particles have a higher density and atomic number compared to tin particles. The higher attenuation coefficient of samples containing lead particles compared to those containing tin particles is due to differences in the density and atomic number of lead and tin. The higher density and atomic number result in reduction of the transmitted photons, and thus the observed increase in attenuation coefficient.⁵

The attenuation coefficients of lead and tin at all energy levels, extracted from the XCOM database, are presented in Table 5. It can be seen that the attenuation coefficient values of lead are higher than those of tin at all energy levels. This trend is also observable in measured experimental results, thus confirming the validity of the measured experimental data in Table 4.

Table 5.

Attenuation coefficients extracted from the XCOM database

Element	Attenuation coefficient (1/cm)
Element	30 keV	35 keV	53 keV	80 keV
Pb	3.44 × 10⁺²	2.53 × 10⁺²	8.39 × 10⁺¹	2.74 × 10⁺¹
Sn	3.01 × 10⁺²	2.22 × 10⁺²	6.92 × 10⁺¹	2.22 × 10⁺¹
C	5.80 × 10⁻¹	5.20 × 10⁻¹	4.10 × 10⁻¹	3.60 × 10⁻¹
H	3.21 × 10⁻⁵	3.16 × 10⁻⁵	2.99 × 10⁻⁵	2.78 × 10⁻⁵

For experimental purposes, the LT30 sample was selected due to its low cost in comparison to tin samples and also due to the fact that it is lighter than lead samples. According to Table 4, μ of LT30 sample more or less lies between the μ of samples T30 and L30. This is because sample LT30 contains a mixture with equal proportions of lead and tin particles. The control sample R at all energy levels exhibits the lowest μ. This is due to the fact that sample R contains C and H elements, which have lower density, atomic number, and attenuation coefficient in comparison to Pb and Sn, as shown in Table 4.²⁵ The L50 sample exhibits the highest μ at all energy levels due to higher lead concentration.¹⁷

Changing weft yarn alignment from 0° to 90°, as shown in Table 4, increases the value of μ, which peaks at 90° weft yarn alignment at all energy levels. Since monofilament weft yarns alone contain metal particles, the contribution of particle free warp yarns in the shielding effect provided by the fabric is zero. Thus, variation in weft yarn alignment during preparation of the layered samples results in the availability of the shielding effect in other directions as well as the weft direction. The observed maximum value of μ at 90° alignment at all energy levels vividly points to the fact that protection is provided along the principle axes of the fabric by the weft yarns. At 45° alignment the protective weft yarns cannot fully cover the principle axes of the layered fabric, and thus the higher protection achieved at 90°. Reduction from the maximum value of μ is solely due to deviation from the transverse direction to the weft yarn direction in the superimposed samples. Figure 7 denotes the effect of superimposing weft yarn alignments on the attenuation coefficient at all energy levels.

Figure 7.

Variation of the attenuation coefficient with weft yarn alignment at different energy levels.

The XAP of samples with five different thicknesses was calculated by equation (3). The results confirm the fact that an increase in samples thickness enhances sample XAP at all energy levels.²³ The XAP was calculated for samples with the highest thickness, as shown in Table 6, where the existence of a reverse relationship between the XAP and energy level is detectable. In addition, the XAP increases by changing the weft yarn alignment from 0° to 90°. Thus, it can be stated that the highest protection and XAP is offered by sample L50 at all energy levels and weft yarn alignments.

Table 6.

X-ray attenuation percentage of the thickest samples

Sample code	Sample thickness (cm)	0°				45°				90°
Sample code	Sample thickness (cm)	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV
L30	0.49	97.96	96.37	90.78	83.53	98.29	97.37	91.88	85.39	98.61	97.45	93.09	88.38
L40	0.53	99.19	98.22	91.84	86.04	99.40	98.67	93.38	88.90	99.50	98.91	95.02	91.54
L50	0.44	99.40	98.67	93.73	89.35	99.61	99.14	96.04	93.20	99.68	99.30	96.87	94.36
LT30	0.52	98.04	96.11	86.69	76.50	98.00	96.94	89.58	81.21	98.59	97.22	89.97	84.73
T30	0.50	97.73	95.57	85.35	73.06	97.83	96.57	88.31	79.91	98.59	97.14	88.81	82.18
T40	0.49	98.44	97.18	89.28	77.82	98.84	97.87	92.14	80.93	99.15	98.27	93.19	85.36
T50	0.51	99.28	98.40	92.48	87.22	99.49	98.87	94.40	90.39	99.51	98.95	95.31	91.55
R	0.52	10.49	09.39	06.05	05.24	10.73	09.45	07.50	05.93	10.93	09.67	07.60	06.16

The shielding capability of fabric is directly related to fabric porosity. Low fabric porosity results in reduction of the probability of X-ray transmission through the fabric. Thus, low fabric air permeability, which corresponds to low fabric porosity, confirms the strong effect of the fabric structure and weave pattern on X-ray shielding capability.

An attenuation performance of over 90% is required in most medical and industrial applications of X-rays protection.²³ Based on this fact, the fabric thicknesses required for 90%, 95%, and 99% XAP at different energy levels were calculated using equation (1), as are depicted in Tables 7 –9.

Table 7.

Required thicknesses for 90% X-ray attenuation percentage (calculated, cm)

Sample code	0°				45°				90°
Sample code	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV
L30	0.26	0.30	0.41	0.52	0.25	0.28	0.40	0.48	0.24	0.27	0.37	0.43
L40	0.23	0.27	0.40	0.51	0.22	0.26	0.39	0.48	0.21	0.24	0.35	0.42
L50	0.18	0.21	0.31	0.38	0.17	0.19	0.27	0.32	0.16	0.18	0.25	0.30
LT30	0.27	0.33	0.53	0.67	0.28	0.31	0.50	0.58	0.25	0.30	0.46	0.51
T30	0.28	0.33	0.57	0.74	0.27	0.31	0.47	0.58	0.24	0.29	0.46	0.53
T40	0.25	0.28	0.43	0.64	0.23	0.26	0.38	0.57	0.23	0.26	0.37	0.48
T50	0.22	0.25	0.38	0.48	0.20	0.23	0.35	0.42	0.20	0.23	0.33	0.40
R	11.11	12.69	24.14	30.02	10.87	12.43	18.67	26.02	10.83	12.17	18.49	25.41

Table 8.

Required thicknesses for 95% X-ray attenuation percentage (calculated, cm)

Sample code	0°				45°				90°
Sample code	30 KeV	35 KeV	53 KeV	80 KeV	30 KeV	35 KeV	53 KeV	80 KeV	30 KeV	35 KeV	53 KeV	80 KeV
L30	0.34	0.39	0.54	0.67	0.33	0.37	0.52	0.63	0.31	0.36	0.49	0.57
L40	0.30	0.36	0.52	0.66	0.29	0.34	0.51	0.62	0.28	0.32	0.46	0.55
L50	0.23	0.27	0.40	0.50	0.22	0.25	0.35	0.41	0.21	0.24	0.33	0.39
LT30	0.36	0.43	0.69	0.88	0.36	0.40	0.65	0.75	0.33	0.39	0.59	0.67
T30	0.36	0.43	0.74	0.96	0.35	0.40	0.61	0.76	0.32	0.37	0.60	0.69
T40	0.32	0.37	0.56	0.83	0.30	0.34	0.50	0.74	0.29	0.34	0.48	0.63
T50	0.28	0.33	0.49	0.62	0.27	0.31	0.45	0.54	0.26	0.30	0.43	0.52
R	14.45	16.51	31.40	39.06	14.14	16.17	24.30	33.85	14.08	15.83	24.06	33.07

Table 9.

Required thicknesses for 99% X-ray attenuation percentage (calculated, cm)

Sample code	0°				45°				90°
Sample code	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV	30 keV	35 keV	53 keV	80 keV
L30	0.52	0.60	0.83	1.03	0.51	0.56	0.80	0.96	0.48	0.55	0.75	0.87
L40	0.47	0.55	0.80	1.01	0.44	0.52	0.78	0.95	0.43	0.49	0.71	0.85
L50	0.36	0.42	0.61	0.76	0.33	0.38	0.54	0.64	0.32	0.37	0.51	0.60
LT30	0.55	0.66	1.06	1.35	0.56	0.62	1.00	1.16	0.51	0.59	0.91	1.03
T30	0.55	0.66	1.13	1.48	0.55	0.61	0.94	1.16	0.49	0.57	0.92	1.07
T40	0.49	0.57	0.87	1.28	0.46	0.52	0.77	1.13	0.45	0.52	0.74	0.97
T50	0.43	0.51	0.76	0.95	0.41	0.47	0.70	0.84	0.40	0.46	0.66	0.80
R	22.22	25.39	48.27	60.04	21.74	24.85	37.35	52.04	21.65	24.34	36.99	50.83

Considering the above, it can be seen that sample L50 has the least thickness necessary to provide 90%, 95%, and 99% protection at all energy levels and weft yarn alignments. This is confirmed by the L50 sample, which provides X-ray attenuation at 80 keV at 90° weft yarn alignment, at 3, 4, and 6 mm thickness for 90%, 95%, and 99% XAP, respectively. The corresponding thicknesses in the case of control sample R under identical conditions are about 25, 33, and 51 cm. The higher metal particle concentrations of the L50 and T50 samples have enabled these samples to provide higher shielding properties.¹⁷

The weight of conventional 0.5 mm lead equivalent aprons with a thickness of 1.5 mm is about 8–9 kg.m^–2. The difference in weight is due to the cover and the rubber or polymer imbedding material.^8,17 The X-ray transmission value for these aprons is about 5% at 100 kVp energy level, which is equivalent to a mean energy of 53 keV.⁸ At the same energy level, the required thickness of the L50 sample for 5% X-ray transmission value is about 3.3 mm. Therefore, at this thickness, the gross weight of this sample is about 5 kg.m^–2. This is 44% lighter than a conventional lead apron with the same radiation attenuation capability. It must be emphasized that Pb is a significantly cheaper element than the materials such as Ba, W, Bi, and Sb used in other aprons.²⁷

Tensile properties

The tenacity and breaking elongation of textile fabrics are generally tested along two principle directions. Sample tensile properties were only tested along the weft direction, that is, the direction along which the protective monofilament yarn lies. Table 10 shows that an increase in the metal particles concentration reduces tenacity and breaking elongation of the monofilament yarns as well as those of the fabric samples. The reduction in tensile properties of the monofilament yarns may be due to an increase in yarn diameter variation as the direct consequence of an increase in metal particle concentration, as is shown in Table 2.²⁸

Table 10.

Tensile properties of monofilament yarns and fabrics

Sample code	Monofilament		Fabric (weft direction)
Sample code	Tenacity (cN/tex)	Breaking elongation (%)	Tenacity (MPa)	Breaking elongation (%)
L30	22.88 (5.34)^a	28.64 (6.27)	61.54 (7.03)	12.54 (7.33)
L40	21.80 (6.08)	26.34 (6.89)	59.44 (7.51)	12.17 (7.45)
L50	20.78 (6.31)	23.81 (7.12)	58.39 (7.79)	11.96 (7.61)
LT30	22.50 (5.76)	27.38 (6.37)	60.93 (7.13)	12.30 (7.37)
T30	22.64 (5.84)	27.95 (6.43)	61.24 (7.21)	12.39 (7.56)
T40	21.60 (6.24)	25.54 (6.96)	58.88 (7.57)	12.02 (7.67)
T50	20.64 (6.82)	22.89 (7.34)	57.89 (7.87)	11.81 (7.85)
R	25.77 (4.98)	33.47 (5.51)	65.12 (6.77)	13.98 (6.96)

Denotes CV%.

Comparing samples R and L50, it can be seen that while the former has tenacity and breaking elongation of 25.77 cN/tex and 33.47%, respectively, the corresponding values of these parameters for the L50 sample are 20.78 cN/tex and 23.81%, respectively. Moreover, the addition of metal particles reduces the tenacity and breaking elongation of the L50 sample by 19.36% and 28.86%, respectively. This trend is also valid when considering tensile properties of the fabrics.

Abrasion resistance analysis

The percentage weight loss of abraded samples after 10,000 abrasion cycles is shown in Table 11. Subscript A in the sample codes indicates the sample is abraded by the Martindale abrasion tester.

Table 11.

Percentage weight losses (WL%) and attenuation coefficient of abraded samples

Sample code	Weight loss (%)	CV%	Attenuation coefficient (1/cm)
Sample code	Weight loss (%)	CV%	30 keV	35 keV	53 keV	80 keV
L30_A	2.46	9.17	9.52	8.34	6.13	5.26
L40_A	2.56	8.37	10.75	9.36	6.48	5.41
L50_A	2.47	9.27	14.30	12.50	9.05	7.63
LT30_A	2.59	8.31	9.06	7.73	5.02	4.44
T30_A	2.52	8.95	9.44	7.98	4.99	4.28
T40_A	2.47	9.55	10.13	8.80	6.18	4.71
T50_A	2.39	9.08	11.58	9.89	6.89	5.72
R_A	2.48	9.07	0.21	0.19	0.12	0.09

The results show a maximum weight loss of approximately 2.5% after abrasion. This renders the samples as highly hard wearing. This phenomenon is not only due to the use of highly abrasion resistant PP yarns but also is a consequence of the selected weave pattern. This weave pattern tends to place the weft yarn predominantly on the surface. Thus, the prepared sample fabric surfaces are mainly covered by highly abrasion resistant PP weft yarns containing metal particles.²⁹ The radiation attenuation capability of abraded samples was measured at all energy levels. The attenuation coefficients of abraded samples with 90° weft yarn alignment are presented in Table 11. Statistical analysis did not point to a significant difference between the attenuation coefficient of samples before and after abrasion test at the 5% significance level. Similar results were observed for weft yarn alignments at 0° and 45°. Considering the facts that insignificant changes occurred in attenuation coefficients and weight lost is fractional, then it can be concluded that metal particles are firmly adhered to the monofilament yarns and remain so during abrasion. This is confirmed by the images shown in Figure 5, which vividly confirm the embedment of the metal particles in the polymer matrix of the monofilament yarns.

Laundering resistance analysis

In order to evaluate the shielding capability of samples after severe laundering, samples were washed under the defined condition. The attenuation coefficient of samples with 90° weft yarn alignment after laundering is presented in Table 12. The subscript W denotes washed sample. Statistical analysis shows that laundering cannot significantly affect the attenuation coefficient of samples at the 5% significance level. Similar results were observed for 0° and 45° weft yarn alignments. Considering the insignificant changes in attenuation coefficients, it can be stated that metal particles cannot be separated from monofilament yarns during laundering.

Table 12.

Attenuation coefficient of samples after laundering

Sample code	Attenuation coefficient (1/cm)
Sample code	30 keV	35 keV	53 keV	80 keV
L30_W	9.53	8.36	6.14	5.28
L40_W	10.77	9.38	6.49	5.43
L50_W	14.32	12.52	9.07	7.65
LT30_W	9.08	7.75	5.03	4.46
T30_W	9.46	8.00	5.01	4.30
T40_W	10.15	8.82	6.20	4.73
T50_W	11.59	9.91	6.91	5.74
R_W	0.21	0.19	0.12	0.09

The P-values obtained by analysis of the variance for the attenuation coefficient of samples before and after abrasion and laundering tests at 80 keV energy level are reported in Table 13. The reported data confirm the ineffectiveness of the abrasion and laundering operation on the shielding properties of the samples.

Table 13.

Statistical analysis of variance for µ of the samples after abrasion and laundering at 80 keV energy level

Sample code	P-value
Sample code	L30	L40	L50	LT30	T30	T40	T50	R
L30_A	0.066
L30_W	0.066
L40_A		0.066
L40_W		0.066
L50_A			0.646
L50_W			0.646
LT30_A				0.052
LT30_W				0.052
T30_A					0.052
T30_W					0.052
T40_A						0.646
T40_W						0.646
T50_A							0.646
T50_W							0.646
R_A								1.000
R_W								1.000

Conclusion

The main aim of this study was to develop a textile-based garment that can replace other X-ray radiation shielding garments. The measurement of X-ray attenuation pointed to the usefulness of adding lead and tin particles to polymer melt during the melt spinning of monofilament yarns. Therefore, the effects of metal particle types and concentration in PP monofilament weft yarns on shielding properties against X-rays were examined.

The results showed that yarns with higher metal particle concentrations provide a higher attenuation coefficient. In addition, a similar effect was observed when metal particles of higher density and atomic number were used. It was found that 90° weft yarn alignment results in the highest attenuation coefficient. Among the samples, L50 was found to provide the most effective shielding properties. Furthermore, it was concluded that as far as sample thickness is concerned, the L50 sample is capable of providing an XAP of 0.99% at the lowest thickness of 6 mm.

Tensile properties of the yarns and fabrics were also evaluated and it was found that the addition of metal particles tends to increase the yarn unevenness due to the formation of highly stressed points along the yarn axis. The formation of highly stressed points tends to reduce tenacity and breaking elongation of the yarns. It was found that the tensile properties of the fabrics tend to follow the same trend.

The effect of abrasion and laundering operations on the attenuation coefficient was also examined. Statistical analysis pointed to the insignificant effect of these operations on the shielding properties of the fabrics.

It is concluded that the developed fabrics are potentially suitable to be used in garment forms in applications where protection against X-rays is required. In addition to their technical function, such textile-based item enjoys merits such as low costs, comfort, and ease of maintenance in comparison to conventional X-ray protective garment currently in use.

Footnotes

Acknowledgement

The authors would like to express their sincere thanks to Eng. Kh. Rahmani for their invaluable assistance throughout of conduction of this work.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

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