Ind. Eng. Chem. Res. 2007, 46, 2677-2682
2677
APPLIED CHEMISTRY Modelization of the Influence of the Treatment with Two Optical Brighteners on the Ultraviolet Protection Factor of Cellulosic Fabrics Ine´ s M. Algaba,† Montserrat Pepio´ ,‡ and Ascensio´ n Riva*,† Instituto de InVestigacio´ n Textil de Terrassa (INTEXTER), UniVersidad Polite´ cnica de Catalun˜ a (UPC), Colo´ n 15, 08222 Terrassa, Spain, and Departamento de Estadı´stica e InVestigacio´ n OperatiVa, UniVersidad Polite´ cnica de Catalun˜ a (UPC), Colo´ n 11, 08222 Terrassa, Spain
The objective of this paper is the modelization of the influence that the treatment with optical brighteners has on the ultraviolet protection factor (UPF) of fabrics whose composition and structure are appropriate for use in summer garments. Following an experimental design, the study has been conducted with fabrics composed of three different cellulosic fibers (cotton, Modal, and Modal Sun) and with three different structures. The fabrics have been treated with two optical brighteners at several concentrations. A statistical model has been formulated for each fiber type, which allows estimation of the UPF, with regard to the type of optical brightener and its concentration and the initial UPF of the untreated fabric. Introduction The protection against ultraviolet (UV) radiation has been considered for many years as one of the most appropriate means to avoid damage of the skin. People are increasingly concerned about the health risk posed by overexposure to UV radiation. The advice of the World Health Organization (WHO) is to protect the skin from the sun, and, among other protection measures, the WHO recommends the use of loose-fitting, fulllength clothes with a high protection factor. Although there is a general misconception that the protection provided by any textile is appropriate, numerous studies have concluded that most sport clothing and light garments worn in the summer do not provide sufficient protection. In the protection against UV radiation, which is provided by every textile article, there are several influencing factors: the fiber type; the structural characteristics of the fabrics; the color; the presence of optical brightening agents, resins, or UV absorbers applied in the finishing process; the wearing conditions of the garments (stretched, wet); etc.1-8 Optical brightening agents are organic chemicals, uncolored or slightly colored, that have the capability of absorbing UV radiation and emitting it as visible light of a determined wavelength that, in most cases, corresponds to the spectral band of blue. For this reason, they cause an increase of the amount of spectral energy on the corresponding band, with a consequent increase in the visual perception of whiteness.9 The capability of the optical brightening agent to absorb UV radiation and reflect it as visible radiation leads to the theoretical conclusion that they could increase the protection that the fabrics provide against UV radiation. * To whom correspondence should be addressed. E-mail: ariva@ intexter.upc.edu. † Instituto de Investigacio ´ n Textil de Terrassa (INTEXTER), Universidad Polite´cnica de Catalun˜a (UPC). ‡ Departamento de Estadı´stica e Investigacio ´ n Operativa, Universidad Polite´cnica de Catalun˜a (UPC).
The present paper shows the results of the study of the improvement of the ultraviolet protection factor (UPF) by the application of two optical brightening agents, with a different chemical structure, on cellulosic fabrics made with cotton, Modal, and Modal Sun fibers. Both products were used in their commercial form and applied on three original fabrics for each fiber, with the same construction (plain weave) but different structures (weight per surface unit and coverage factor), so that their initial protection factor could be classified as low, medium, and high. The influence of the chemical structure and the concentration of both products has been evaluated, as well as the influence of the initial structure. For this purpose, the UPF of the untreated and treated fabrics has been calculated and statistical models that relate the UPF with the different variables have been estimated. The models demonstrate if the effects of the different variables and their interactions are significant in the value of the response UPF. Experimental Section Materials. The study has been performed on fabrics composed of cotton, Modal, and Modal Sun. Three different fabrics have been used for the treatments to determine if the influence of the products is dependent on the structure of the original fabric. Their initial UPF (UPFi) has been taken as the variable that represents the structure of the original fabrics, with three different levels, designated as low, medium, and high UPFi. Table 1 shows the characteristics of each fabric. The initial UPF of the fabrics has a correlation with the weight per surface unit and the coverage factor. In previous research, the authors studied these correlations and established statistical models that define them.2 However, the UPF also is dependent, and to a very important extent, on the type of fiber used in the manufacturing of the fabrics. Fabrics with the same weight per surface unit or the same coverage factor, but made with different raw materials, present very different UPF values. The coverage factor was determined by image analysis:2 the microscopic image of the fabric was obtained using a light microscope and a video
10.1021/ie060723c CCC: $37.00 © 2007 American Chemical Society Published on Web 03/29/2007
2678
Ind. Eng. Chem. Res., Vol. 46, No. 9, 2007
Table 1. Characteristics of the Original Cotton, Modal, and Modal Sun Fabrics at Various Levels of the Variable UPF Cotton medium UPFi
high UPFi
low UPFi
medium UPFi
high UPFi
low UPFi
medium UPFi
high UPFi
4.06 94.93 0.318 89.42
4.78 122.09 0.339 93.96
6.92 180.04 0.400 97.86
5.12 106.63 0.292 85.12
11.39 192.75 0.367 92.46
15.53 216.09 0.402 94.20
12.66 102.43 0.273 87.75
17.61 129.02 0.290 91.29
27.54 156.24 0.346 94.75
14.3 14.3
14.3 20
25 25
14.3 14.3
20 25
25 25
14.3 14.3
14.3 20
14.3 29.4
40 25
40 27
40 27
40 25
40 27
40 25
40 25
40 27
40 25
Table 2. Chemicals and Concentrations Concentration, C (% o.w.f.) concentration term low medium high
C.I. Fluorescent Brightener 252
C.I. Fluorescent Brightener 351
0.300 0.525 0.750
0.200 0.450 0.700
camera; the microscope image was magnified and, using image analysis software, converted to pixels on the computer screen; the area of fabric occupied by yarns was considered to be those area represented by black pixels. The cover factor is calculated as follows:
Coverage (%) )
Modal Sun
low UPFi
parameter value of the initial UPF weight per surface unit (g/m2) thickness (mm) coverage factor, via image analysis (%) yarn number (tex) warp weft thread count (yarns/cm) warp weft
Modal
number of black pixels × 100 total number of pixels
Products and Concentration. The fabrics have been treated with two optical brightening agents with different chemical structures. C.I. Fluorescent Brightener 252 is a derivative of the stilbene disulfonic acid, which chemical structure is the stilbyl-s-triazine.
quantitative variables, which are the initial UPF of the fabrics (UPFi) and the concentration of the optical brightener in each treatment (C, expressed in units of % owf). The qualitative variable has two different levels: C.I. Fluorescent Brightener 252 or C.I. Fluorescent Brightener 351. The quantitative variable initial UPF of the fabrics has the three levels shown in Table 1: low, medium, and high. The variable concentration has four different levels, including the untreated fabric and the fabrics treated at the concentrations shown in Table 2. The combination of the variables and their levels results in 24 different experiences for each fiber, providing three sets of fabrics with a gradation in their compactness and the concentration of the products with which they have been treated. Method for the Determination of the Ultraviolet Protection Factor (UPF). The UPF of the fabrics has been determined using the in vitro method, according to the indications of the Australian/New Zealand Standard AS/NZ 4399.12 A Labsphere UV-1000F ultraviolet transmitance analyzer, with a xenon flash lamp and polychromatic illumination, has been used. The UPF of each specimen is calculated as follows: 400
∑
UPFi )
Eλ × Sλ × ∆λ
λ)290 400
∑
Eλ × Sλ × Tλ × ∆λ
λ)290
C.I. Fluorescent Brightener 351 is a derivative of the distyrylbiphenyl (the 4,4′-bis(2-sodium sulfonate styryl)biphenyl).
where Eλ is the CIE relative erythemal spectral effectiveness, Sλ the solar spectral irradiance, Tλ the spectral transmittance of the fabric, ∆λ the wavelength step (in nanometers), and λ the wavelength of radiation (also given in nanometers). The rated UPF of the sample is calculated introducing a statistical correction. Starting from the standard deviation of the mean UPF, the standard error in the mean UPF is calculated for a 99% confidence level. The rated UPF will be the mean UPF value minus the standard error, rounded down to the nearest multiple of 5:
UPF ) UPF - tR/2,N-1
The optical brightening agents were applied at three different concentrations, chosen according to the recommendations of the technical brochure of the chemicals.10,11 The levels of the variable concentration are shown in Table 2. Experimental Plan. For each set of fabrics made with a different fiber, the system consists of a first qualitative variable, which is the type of optical brightener used (Q2), and two
( ) SD xN
where UPF is the mean UPF, tR/2,N-1 the t variate for a confidence level of R ) 0.005, and SD the standard deviation of the mean UPF. If the rated UPF determined using the aforementioned formula is less than the lowest individual UPF measurement for that sample, then the rated UPF shall be the lowest UPF measured for the specimens, rounded down to the nearest multiple of 5. The rated UPF is always a multiple of 5. For UPF ratings of 51 or greater, the term “50+” shall be used.
Ind. Eng. Chem. Res., Vol. 46, No. 9, 2007 2679 Table 3. UPF Classification System of Sun Protective Clothing, for the Purposes of Labelinga UPF range
UV radiation protection category
UV radiation transmission (%)
UPF rating
15-24 25-39 40-50, 50+
good very good excellent
6.7-4.2 4.1-2.6 e2.5
15, 20 25, 30, 35 40, 45, 50, 50+
a
Using Standard AS/NZ 4399 (1996).12
Table 4. Formulas for the Pseudo-codification of the Variables cUPFi and cC, from the Original Variables UPFi and C Codified Variables material cotton modal modal sun
cUPFi cUPFi ) cUPFi ) cUPFi )
UPFi - 5.491 1.43 UPFi - 10.328
cC C - 0.375 cC ) 0.375 cC )
C - 0.375 0.375
cC )
C - 0.375 0.375
5.204 UPFi - 20.975 7.4385
The Australian/New Zealand Standard establishes, in addition, a classification system of the fabrics, according to their sun protective properties. For the purpose of labeling, sun protective clothing shall be categorized according to its rated UPF, as shown in Table 3. Statistical Data Analysis: Codification of the Variables. The statistical analysis and modelization of the UPF was performed using codified variables. If the model, together with the effects of the factors, includes the quadratic effects and interactions, it is almost certain that there will be problems during the matrix calculations. These problems are due to the higher or lower numerical value of one variable, relative to another, and to the fact that the quadratic effects and interactions can reach numerical values much lower or higher than the simple effects. Hence, the use of original variables can lead to a model that, although perfectly valid to describe the response value, makes the significance of quadratic effects and interactions bigger and masks the significance of the simple effects. From the technical viewpoint, this is not useful when looking for the optimization of the system. To avoid these problems and obtain reliable statistical models, the data analysis should be always performed with codified variables. When the variables are codified, the levels of all of them are converted into values of -1, 0, and +1, and, hence, all have the same weight in the analysis of their effects. In addition, the weight of every level of the variables with the codification is the same in the simple effects, quadratic effects, and in the interactions, because multiplying by -1, 0, or +1 will always give, as a result, -1, 0, or +1. However, one requirement to codify the variables is that their levels be equidistant.13 In our system, the levels of the variables are not and, thus, a real codification of the variables is not possible. The adopted solution is to perform a pseudo-codification of these variables, applying to each level the formulas shown in Table 4. Statistical Data Analysis: Initial Model and Estimation of the Significant Coefficients. The statistical data analysis was performed using the lineal model method. The results corresponding to each fiber (cotton, Modal, and Modal Sun) were analyzed separately; however, conjointly, the results obtained in the treatment with the two optical brighteners to elucidate if the differences between them are significant. The type of optical brightener is then a qualitative variable with two levels and is
incorporated in the model by the definition of the categorical variable Q2. This variable acquires different levels, depending on the qualitative characteristic in each experience: 0 for the treatment with C.I. Fluorescent Brightener 252 (samples 1-12) and 1 for the treatment with C.I. Fluorescent Brightener 351 (samples 13-24). The initial model includes the terms corresponding to the simple effects cUPFi and cC, as well as their interaction and quadratic terms. The categorical variable is introduced alone and multiplied by all the terms in the model, to evaluate if the behavior of the response in front of the factors varies with the level of the categorical:
UFP ) β0 + β1cUPFi + β2cC + β3‚cUPFicC + β4cUPFi2 + β5cC2 + β6cUPFi2cC + β7cUPFicC2 + β8Q2 + β9Q2cUPFi + β10Q2cC + β11Q2cUPFicC + β12Q2cUPFi2 + β13Q2cC2 + β14Q2‚cUPFi2cC + β15Q2cUPFicC2 + The estimation of the significant coefficients of the model was conducted using the forward stepwise regression method. The significance of the coefficients and the complete model is checked for an R error prefixed in 5%. With these analyses, the significant coefficients βi of the model are obtained. The model must be later separate in two models, according to the levels of the categorical variables Q2. The model corresponding to the fabrics treated with the C.I. Fluorescent Brightener 252 then is obtained, substituting in the model Q2 ) 0, and the model corresponding to the treatment with C.I. Fluorescent Brightener 351 is obtained substituting Q2 ) 1. Results Ultraviolet Protection Factor (UPF). The results obtained in the measurement of the UPF of the untreated and treated fabrics are shown in Table 5. According to the results shown in the table, the application of any of the studied optical brighteners produces an improvement in the UPF of the fabrics. The UPF increase is greater for higher concentrations. However, when the lightest fabrics are treated (low initial UPF), in most cases, the improvement in the UPF is insufficient to allow a classification of the treated fabrics as protective against ultraviolet protection. When more-compacted fabrics are used as a basis (higher initial UPF), the treatment with the optical brighteners is more effective and it is possible to obtain several light fabrics that can provide all levels of protection. Modelization of the UPF. The obtained models (in codified variables) and their correaltion coefficient (R2) values are shown in Table 6. Also are shown the separated models to reflect the UPF achieved in the treatment with C.I. Fluorescent Brightener 252 and C.I. Fluorescent Brightener 351. Figure 1 shows the response surfaces, according to the estimated model for the cotton, Modal, and Modal Sun fabrics, treated with the optical brighteners C.I. Fluorescent Brightener 252 and C.I. Fluorescent Brightener 351, versus the initial UPF (UPFi) and concentration (C). The curves show the combination of the variables that provides UPF values in multiples of 5 until reaching a UPF value of 50 and multiples of 25 for higher values. According to the UPF intervals for classification and labeling indicated by the standard AS/NZ 4339, the different gray intensities distinguish the zones with UPF that do not provide protection (UPF < 15) and the zones that provide good
2680
Ind. Eng. Chem. Res., Vol. 46, No. 9, 2007
Table 5. Ultraviolet Protection Factor (UPF)a UPF sample
characteristics of the sample
qualitative UPFi
concentration, C
cotton
Modal
Modal Sun
1 2 3 4 5 6 7 8 9 10 11 12
untreated C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252 untreated C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252 untreated C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252 C.I. Fluorescent Brightener 252
low low low low medium medium medium medium high high high high
0.000 0.300 0.525 0.750 0.000 0.300 0.525 0.750 0.000 0.300 0.525 0.750
4.06 7.83 8.62 11.29 4.78 13.90 21.66 27.33 6.92 46.67 89.03 147.01
5.12 8.32 10.63 11.94 11.39 35.29 43.25 52.40 15.53 43.59 71.93 82.88
12.66 23.72 24.19 27.47 17.61 47.86 59.48 54.41 27.54 74.89 81.54 89.14
13 14 15 16 17 18 19 20 21 22 23 24
untreated C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351 untreated C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351 untreated C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351 C.I. Fluorescent Brightener 351
low low low low medium medium medium medium high high high high
0.000 0.200 0.450 0.700 0.000 0.200 0.450 0.700 0.000 0.200 0.450 0.700
4.06 6.77 9.03 9.37 4.78 10.82 17.92 24.17 6.92 27.23 61.12 112.58
5.12 7.98 11.16 13.56 11.39 26.04 44.25 60.66 15.53 31.07 56.53 83.36
12.66 22.02 23.21 23.21 17.61 54.42 60.00 60.40 27.54 80.48 82.66 87.40
a
Legend: UPF < 15, no protection; 15 e UPF < 25, good protection; 25 e UPF < 40, very good protection; UPF g 40, excellent protection.
Table 6. Estimated Models of the Response UPF, Depending on the Variables parameter R2 ) 99.90%
C.I. Fluorescent Brightener 252: Q2 ) 0 C.I. Fluorescent Brightener 351: Q2 ) 1
R2 ) 99.37% C.I. Fluorescent Brightener 252: Q2 ) 0 C.I. Fluorescent Brightener 351: Q2 ) 1
R2 ) 95.68%
model description/formula Cotton Fabric UPF ) 24.3565 + 25.0927cUPFi + 24.0722cC + 33.0262(cUPFi)cC + 10.36392cUPFi2 + 6.76952cC2 + 9.6130cUPFicC2 + 12.5714cUPFi2cC - 4.5780(Q2)cUPFi - 4.85072(Q2)cUPFicC 5.55182(Q2)cUPFi2 - 6.3309(Q2)cUPFi2‚cC UPF ) 24.3565 + 25.0927cUPFi + 24.0722cC + 33.0262cUPFicC + 10.3639cUPFi2 + 6.7695cC2 + 9.6130cUPFicC2 + 12.5714cUPFi2cC UPF ) 24.3565 + 20.5147‚cUPFi + 24.0722cC + 28.17545cUPFi‚cC + 4.8121cUPFi2 + 6.7695cC2 + 9.6130cUPFicC2 + 6.2405cUPFi2cC Modal Fabric UPF ) 32.8562 + 20.8255cUPFi + 18.3409cC + 15.9999cUPFicC 4.3705cC2 + 3.2462(Q2)cC - 3.2782(Q2)cUPFi2 + 5.6254(Q2)cC2 UPF ) 32.8562 + 20.8255cUPFi + 18.3409cC + 15.9999cUPFi‚cC 4.3705cC2 UPF ) 32.8562 + 20.8255cUPFi + 21.5871cC + 15.9999cUPFi‚cC 3.2782cUPFi2 + 1.2550cC2 Modal Sun Fabric UPF ) 65.5109 + 28.95399cUPFi + 18.0367cC + 9.9889cUPFi‚cC 10.6345cUPFi2 - 17.8778cC2 - 9.1746cUPFi‚cC2
protection (15 e UPF < 25), very good protection (25 e UPF < 40), and excellent protection (UPF g 40). Table 6 shows that very elevated R2 values are obtained (99.9% for cotton, 99.4% for Modal, and 95.8% for Modal Sun), which means that, with a few terms, an elevated percentage of the response value is explained by the model and, consequently, there is a high security over the values estimated with the models. The influence of the type of optical brightener is more or less significant, depending on the type of fiber. The absence of a term with Q2 in the model for Modal Sun indicated that the type of product is not a variable with a significant influence when the treatment is performed on the fabrics made in this study with this fiber. In contrast, the type of optical brightener is a significant variable in the treatment of the cotton and Modal fabrics. For the cotton fabrics, the treatment with C.I. Fluorescent Brightener 252 is more effective to increase the UPF, whereas for the Modal fabrics, the treatment with C.I. Fluo-
rescent Brightener 351 has greater effectiveness. However, the differences between both optical brighteners do not cause a noticeable change in the final classification of the fabrics, according to the UPF rating of the AS/NZ 4399 standard. In Table 6 and Figure 1, a great influence of the other two variables (UPFi and C) can be observed, independent of the type of fiber. An increase in the value of one variable or another produces an increase in the value of the response, as demonstrated by a positive sign of the coefficients of these variables in the models. In addition, the tendency of the curves allows one to deduce that there is a very important contribution of the interaction of C and UPFi on the increase in the UPF. For fabrics with low UPFi (a less-compacted structure), the increase in C promotes small increments in the response UPF. However, when the UPFi is higher (more-compacted fabrics), the effect of C is more perceptible and small increments produce very noticeable improvements of the protection against ultraviolet radiation.
Ind. Eng. Chem. Res., Vol. 46, No. 9, 2007 2681
Figure 1. Response surfaces estimated according to the models that correlates the response UPF of the fabric, as a function of the initial UPF (UPFi) of the fabric and the concentration (C) of the optical brighteners.
Also remarkable is the significance of the quadratic terms of the concentration that produce a perceptible curvature in the response surfaces. In the treatment with the cotton fabrics, the quadratic terms of the concentration have positive coefficients, which are indicative of acceleration in the improvement of the UPF when the value of the concentration increases. Something similar occurs, although less perceptible, in the treatment of the Modal fabrics with C.I. Fluorescent Brightener 351, whereas when C.I. Fluorescent Brightener 252 is used, the opposite effect is observed. A negative sign of the coefficients indicates a deceleration of the increase in the response when the concentrations are higher. The coefficients of the quadratic terms of the concentration in the model for the Modal Sun fabrics also have
negative signs. In this case, in addition, the values of these coefficients are quite elevated, producing a very marked curvature and a tendency to reach a saturation point (a concentration of C ≈ 0.55% owf of the products). When the objective is the optimization of the treatment conditions to reach a fixed level of protection, an adjustment of both the product concentration and the fabric compactness is needed. The treatment of any fabric with a sufficient concentration of the optical brighteners may not be sufficient to reach a high protection; hence, the appropriate amount of the product must be applied on a fabric with minimum compactness.
2682
Ind. Eng. Chem. Res., Vol. 46, No. 9, 2007
Conclusions A finishing treatment with optical brightening agents is an efficient means to improve the protection provided by cotton, Modal, and Modal Sun fabrics against the damaging effect of ultraviolet (UV) radiation. Using statistical data analysis, a model for each fiber type was obtained, which quantifies the ultraviolet protection factor (UPF) of the fabrics, as a function of the initial UPF (UPFi) of the fabrics and the type and concentration of optical brightener. The models prove that the application of the optical brighteners significantly increases the UPF of the fabrics and allows one to obtain light fabrics that, in regard to exposure to UV radiation, can provide levels of good protection (15 e UPF < 25), very good protection (25 e UPF < 40), and excellent protection (UPF g 40). The attained level of protection is dependent, nevertheless, on all the variables considered in this study. For the optical brightening agents used and inside the experimental range of this study, the models demonstrate that the type of product does not have a significant influence on the UPF values of the treated Modal Sun fabrics. However, the type of optical brightener is a significant variable in the treatment of the cotton and Modal fabrics. Greater improvement in the UPF is attained in the treatment of the cotton fabrics with C.I. Fluorescent Brightener 252 and in the treatment of the Modal fabrics with C.I. Fluorescent Brightener 351. The increase in the concentration of the products in the treatment generally produces a significant improvement in the protection provided by the fabrics against UV radiation. In the cotton fabrics treated with any of the studied optical brighteners and in the Modal fabrics treated with C.I. Fluorescent Brightener 351, the relationship between the response UPF and the variable concentration is quadratic and positive; hence, the same increment in the concentration produces higher and higher increments in the UPF when the value of the variable is higher and higher. In the Modal fabrics treated with C.I. Fluorescent Brightener 252 and in the Modal Sun fabrics, the relationship is also quadratic but negative and, consequently, the same increment in the concentration produces higher increments in the UPF for lower concentrations and smaller variations when the concentration is higher. The improvement in the UPF produced by the increase of the concentration of the optical brighteners is strongly influenced by the fabric compactness, which is dependent on both the weight per surface unit and the coverage factor. There is a remarkable interaction between the UPFi of the fabrics and the concentration (C) of the products. For fabrics with low UPFi, the increase in the concentration promotes small increments in the response UPF. However, when the UPFi is higher, the effect of the concentration is more perceptible and small increments produce very noticeable improvements in the UPF. The models allow the estimation, a priori, of the UPF, according to the variables of the system, although always inside the experimental range (that is, with values of the variables between the levels minimum and maximum that were used to estimate the model). The models also ease the selection of the
values of the variables, with a great number of different combinations, to obtain a predefined UPF. One must take into account that the optical brighteners can lose effectiveness along the life cycle of the textile articles. Their loss of effectiveness as barrier products against UV radiation is being studied by the authors and will be the objective of a future publication. Acknowledgment The authors thank the Spanish “Comisio´n Interministerial de Ciencia y Tecnologı´a (CICYT)” for the funding of the research projects MAT 99-0996 and MAT 2003-04853, under which this study was conducted. They also thank the Spanish “Ministerio de Educacio´n, Cultura y Deporte”, for the concession of a grant of its programme of “Formacio´n de Profesorado Universitario”, to develop a doctoral thesis. They express their special gratitude to the company Hilaturas Llaudet S.A. for the fibre supply and spinning of the yarns used in this study and the company Ciba Especialidades Quı´micas for the supply of the finishing product, as well as to Mrs. R. Prieto and P. Ferrer for their co-operation in the laboratory preparation and treatment of the fabrics. Literature Cited (1) Pailthorpe, M. Sun Protective Clothing. Text. Horiz. 1996, 16 (5), 11. (2) Algaba, I.; Riva, A.; Crews, P. C. Influence of fiber type and fabric porosity on the Ultraviolet Protection Factor provided by summer fabrics. AATCC ReV. 2004, 4 (2), 26. (3) Crews, P.; Kachman, S.; Beyer, A. Influences on UVR transmission of undyed woven fabrics. Text. Chem. Color. 1999, 31 (6), 17. (4) Hilfiker, R.; Kaufmann, W.; Reinert, G.; Schmidt, E. Improving Sun Protection Factors of Fabrics by Applying UV-Absorbers. Text. Res. J. 1996, 66 (2), 61. (5) Haerri, H. P.; Haenzi, D.; Donze´, J. J. The application of ultraviolet absorbers for sun protective fabrics. Presented at the 39th International ManMade Fibres Congress, Dorbirn, Austria, September 13-15, 2000. (6) Reinert, G.; Fuso, F.; Hilfiker, R.; Schmidt, E. UV-protecting properties of textile fabrics and their improvement. Text. Chem. Color. 1997, 29 (12), 36. (7) Srinivasan, M.; Gatewood, B. Relationship of dye characteristics to UV protection provided by cotton fabrics. Text. Chem. Color. Am. Dyest. Rep. 2000, 32 (4), 36. (8) Zhou, Y.; Crews, P. C. Effect of OBAs and Repeated Launderings on UVR Transmission through Fabrics. Text. Chem. Color. 1998, 30 (11), 19. (9) Cegarra, J. Fundamentos y Tecnologı`a a del Blanqueo de Materias Textiles; Universitat Polite`cnica de Catalunya: Terrassa, Spain, 1997. (10) Fluorescent Whitening Agents for Textiles: Ciba UVITEX BHT liq.; Ciba Specialty Chemicals, Inc.: Basel, Switzerland, 2000; 10 pp. (11) Fluorescent Whitening Agents for Textiles: Ciba UVITEX NFW liq.; Ciba Specialty Chemicals, Inc.: Basel, Switzerland, 2000; 11 pp. (12) Australian/New Zealand Standard AS/NZS 4399, Sun protective clothingsEvaluation and classification, 1996. (ISBN 0-7337-0573-1.) (13) Pepio´, M.; Polo, C. Disseny i optimitzacio´ de processos; Laboratori d’Estadı´stica ETSEIT-UPC: Terrassa, Spain, 1996.
ReceiVed for reView June 7, 2006 ReVised manuscript receiVed February 27, 2007 Accepted March 3, 2007 IE060723C
