UV Protective Textile Material

7/28/2019 UV Protective Textile Material

1/30

Page | 1

1.Introduction:An appropriate amount of sun bath promotes the circulation of blood, invigorates the

metabolism and improves resistance to various pathogens. Penetration of UVR into the top

layer of the skin leads to damage in the lower layer and produces premature ageing of skin and

other effects including roughening, blotches, sagging, wrinkles, squamous cells and basal cell

cancer. Many people love sunbathing, thereby extending the long term risk to their health.

Persons working in the open atmosphere are also prone to keratose, the precursor of skin

cancer. Australia has high levels of solar UV radiation, mainly because of its geographical

position; New Zealand, USA, Switzerland, Norway, Scotland, Britain and Scandinavian countries

also have high melanoma rates.

The principal role of ultraviolet (UV) protective clothing is to protect the skin against the

harmful effects of the sun, notably skin cancer. This is one of the most prevalent forms of

cancer but, fortunately, it is also one of the most preventable. Public awareness about the

dangers of excessive exposure to the sun has grown considerably in recent years. However,

large sections of the public remain unaware that UV protective clothing exists or that UV

resistance in conventional clothing can be increased. Consequently, they rely on sunscreen for

UV protection. The slow and limited adoption of UV protection in clothing by mainstream

consumers may be partly due to the fact that it can not be seen or feltunlike other

performance features such as moisture management and stretch.

2.UV radiation:Ultraviolet radiation is electromagnetic radiation or light having a wavelength greater than 10nm but less than 400 nm. Ultraviolet radiation has a wavelength longer than that of x-rays but

shorter than that of visible light. Ultraviolet is energetic enough to break some chemical bonds.Unravelling the mysteries related to ultraviolet rays, their properties, and their effects on

various living creatures has been a gradual process spanning to the duration of almost three

centuries starting from the seventeenth century. Terms such as near UV (290 400 nm), far UV

(180 290 nm) and vacuum UV (below 180 nm) have been coined by physicists based on the

properties of the radiation. The term UVA represents the region 320 400 nm, the term UVB

represents the region between UVC and UVA, i.e. 290 320 nm, and UVC region represents the

region below 290 m . The order of potency has been decided as UVC > UVB >UVA >. The

proportion of the UV region is about 5 6 % of the total incident radiation, and the quantumenergy of UVR is similar to the bond energies of organic molecules.

Fig (1): Electromagnetic radiation.


2/30

Page | 2

Fig (2): Different types of UV radiation and their potency.

Light comparison:

Electromagnetic radiation as well as the light can be classified in to different sections according

to their wavelength. In that classification only visible light (wavelength 380nm-750nm) we can

observe in open eyes. Except visible light other light are invisible, to see those light or observe

their presence we need to follow some special procedure.

Name Wavelength Frequency (Hz) Photon Energy (eV)

Gamma ray less than 0.01 nm more than 10 EHz 124 keV - 300+ GeVX-Ray 0.01 nm to 10 nm 30 EHz - 30 PHz 124 eV to 124 keV

Ultraviolet 10 nm - 400 nm 30 PHz - 790 THz 3.3 eV to 124 eV

Visible 380 nm - 750 nm 790 THz - 405 THz 1.7 eV - 3.3 eV

Infrared 750 nm - 1 mm 405 THz - 300 GHz 1.24 meV - 1.7 eV

Microwave 1 mm - 1 meter 300 GHz - 300 MHz 1.24 eV - 1.24 meV

Radio 1 mm - 100,000 km 300 GHz - 3 Hz 12.4 feV - 1.24 meV

Table (1): Light comparison.
http://en.wikipedia.org/wiki/Millihttp://en.wikipedia.org/wiki/Micro-http://en.wikipedia.org/wiki/Extremely_high_frequencyhttp://en.wikipedia.org/wiki/Extremely_low_frequencyhttp://en.wikipedia.org/wiki/Femto-http://en.wikipedia.org/wiki/Femto-http://en.wikipedia.org/wiki/Extremely_low_frequencyhttp://en.wikipedia.org/wiki/Extremely_high_frequencyhttp://en.wikipedia.org/wiki/Micro-http://en.wikipedia.org/wiki/Milli


3/30

Page | 3

Visible light:Visible light waves are the only electromagnetic waves we can see. We see these waves as the

colors of the rainbow. Each color has a different wavelength. Red has the longest wavelength

and violet has the shortest wavelength. When all the waves are seen together, they makewhite light.

Fig(3): Visible light region.

When white light shines through a prism, the white light is broken apart into the colors of the

visible light spectrum. Water vapor in the atmosphere can also break apart wavelengths

creating a rainbow. Each color in a rainbow corresponds to a different wavelength of

electromagnetic spectrum.

Fig(4): Wavelength of different visible light

Infared light:Infrared (IR) light is electromagnetic radiation with longer wavelengths than those of visible

light, extending from the nominal red edge of the visible spectrum at 0.74 micrometres (m) to
http://en.wikipedia.org/wiki/Micrometrehttp://en.wikipedia.org/wiki/Micrometre


4/30

Page | 4

300 m. This range of wavelengths corresponds to a frequency range of approximately 1 to

400 THz,and includes most of the thermal radiation emitted by objects near room

temperature. Infrared light is emitted or absorbed by molecules when they change their

rotational-vibrational movements. The existence of infrared radiation was first discovered in

1800 by astronomer William Herschel.

Fig(5): An image of two people in mid-infrared thermal light (false-color).

Much of the energy from the Sun arrives on Earth in the form of infrared radiation. Sunlight at

zenith provides an irradiance of just over 1 kilowatt per square meter at sea level. Of this

energy, 527 watts is infrared radiation, 445 watts is visible light, and 32 watts is ultravioletradiation. The balance between absorbed and emitted infrared radiation has a critical effect

on the Earth's climate.

Infrared light is used in industrial, scientific, and medical applications. Night-vision devices

using infrared illumination allow people or animals to be observed without the observer being

detected. In astronomy, imaging at infrared wavelengths allows observation of objects

obscured by interstellar dust. Infrared imaging cameras are used to detect heat loss in

insulated systems, to observe changing blood flow in the skin, and to detect overheating of

electrical apparatus.

The UV Component of Sunlight:Ultraviolet (UV) radiation is part of the solar electromagnetic spectrum, with wavelengths

shorter than those of visible light, but longer than X-rays. It is an essential factor for many

global biological and environmental phenomena. There are three major subtypes of UV rays,

namely, UVA (320400 nm), UVB (280320 nm) and UVC (100280 nm). UVA accounts for

about 95% of the total UV energy that reaches the Earths surface, the remaining 5% being

UVB. Seeing that the shorter the wavelength, the greater the absorption by the atmosphere,

UVC, being totally absorbed by stratospheric gases, mainly oxygen and ozone, fails to reach thetroposphere. Furthermore, since UVB is very effectively screened out by ozone molecules, only
http://en.wikipedia.org/wiki/Irradiancehttp://en.wikipedia.org/wiki/Kilo-http://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/File:Ir_girl.pnghttp://en.wikipedia.org/wiki/Climatehttp://en.wikipedia.org/wiki/Ultraviolethttp://en.wikipedia.org/wiki/Visible_lighthttp://en.wikipedia.org/wiki/Kilo-http://en.wikipedia.org/wiki/Kilo-http://en.wikipedia.org/wiki/Irradiance


5/30

Page | 5

a small fraction actually reaches the surface, contrary to most of UVA. In the face of global

efforts to diminish ozone-depleting substances, it can be said that, given the recent measures

of increasing ozone levels worldwide, the Montreal Protocol on Substances That Deplete the

Ozone Layer is really working.

Fig (6): Year-round (2009) solar UVA (blue) and UVB (red) doses measured in So PauloSP

(2332'S, 4638'W), Brazil.

Furthermore, apart from the ozone-depleting gases policy, continuous efforts are under way to

monitor the yearly incidence of surface UV radiation. Our research group has been dedicatingspecial attention to the measurement of solar-UV rays in the city of So Paulo (2332'S;

4638'W), the largest in Brazil, and one of the most populous in the World. The incidence of

solar UVB and UVA radiation has been measured throughout the day, over the last two years.

In the year-round graph presented in Figure 1, the winter (June to August) reduction in UV

levels (although lower than in higher latitudes) is more pronounced in UVB daily doses, mainly

due to the solar-angle effect at this latitude, as UVB is more absorbed by the atmospheric air

mass, whereas UVA practically freely passes through.

Data of UVA and UVB doses for an entire day, at different latitudes in Brazil are presented inFigure 2 for comparison. The results show that the daily flow of UVA, besides being remarkably

greater than UVB, is comparably more constant and detectable earlier in the day. Nevertheless,

and as expected, at a lower latitude (Natal) UVB incidence is higher and can be detected earlier

in the morning (around 6:00 a.m.), when compared to the other mid-latitudes (around 7:00

a.m.). Ozone concentration, although important, is not the only factor exerting an influence on

the incidence of UV radiation. The solar zenith angle, which varies according to the time of day,

day of the year and latitude, also contributes enormously.


6/30

Page | 6

Fig (7): Solar UVA (blue) and UVB (red) irradiation profiles at (a) So Martinho da SerraRS

(2944'S, 5382'W), (b) So PauloSP (2332'S, 4638'W), and (c) NatalRN (547'S, 3512'W),Brazil.

3.UV Effects on the Biosphere and Human Health:The biological consequences arising from increased UV irradiance are numerous. In terrestrial

ecosystems, these affect plants, pathogens, herbivores, soil microbes and other basic

processes. As each type of organism reacts to induced UV damage in a different manner, the

eventual changes in balance can possibly lead to significant alterations in carbon and nitrogen

cycling. Furthermore, apart from ozone concentration dependence, UV irradiance is also

affected by climate change factors, thus complex interactions are expected to occur, therebydiversely affecting terrestrial ecosystems. The effects of UV radiation on human health are

better defined. Besides producing vitamin D, UVB radiation itself is correlated with skin cancer,

photo aging, immune supression and cataracts, to mention just a few of the harmful effects. It

is widely known that in humans the most important benefit derives from the production of

vitamin D. Nevertheless, there is a limit in this production, which, when passed, leads to the

degradation of already formed vitamins, thereby attaining toxic levels, whereby the efforts

concentrated on determining the optimal level of production. It has been shown that

casual, and little daily UV doses are sufficient to prevent the lack of vitamin D. However, there

is evidence that modern lifestyles can be held responsible for the increasing levels of

melanoma among indoor-workers. It is speculated that windows and sunscreens, which blockmainly UVB and facilitate UVA penetration, give rise to a reduction in cutaneous vitamin D


7/30

Page | 7

levels, possibly inversely correlated to the increase in the incidence of melanoma.

Mechanistically, UV irradiance is the cause of many deleterious effects, such as the induction of

DNA damage, inseparable from those beneficial. Furthermore, various UV wavelengths exhibit

different skin-penetration capabilities, with diversification in carcinogenesis as the outcome.

Obviously, both ecosystems and the human population are always much more exposed to UVA

than UVB irradiance, in absolute flow terms. Nevertheless, these values require weighting,using action spectra involving the relative biological effectiveness for various endpoints. With

this in mind, knowledge on the UV pattern at different sites is of vital interest for determining

the potential risks arising from local UV radiation worldwide. Thus, the development of

appropriate biological sensors assumes an important role in a scenario of increasing UV

incidence.

Fig(8): UV rays effect on skin.

Factors that affect solar UVR include cloud cover, the suns altitude, geographical position,

altitude, ozone layer, scattering in the atmosphere, environmental and related conditions.

Much research has been carried out to assess the impact of the UV rays on various living

organisms, especially humans and the relationship between skin cancer and UV dosage is well

correlated. Changes in leisure behaviour, which has led to more frequent sun exposure, are

one of the major reasons for malignant cutaneous melanoma. Skin cells that receive sunlight

absorb harmful UV radiation, and slough off to excrete harmful UV from the body. But theabsorption of too much UVR leads to scars that can induce diseases like skin cancer. Excessive

UV radiation leads to cell damage and causes inflammation of human skin, the obvious

consequences of which are erythema or sunburn.

The reciprocal value of these cuticle radiation doses is called erythema effectiveness whose

maximum occurs at 308 nm. The total UVR dose reaching the skin is an important factor in the

occurrence of both erythema and skin cancer, although there is no proven link between

erythema and skin cancer. In terms of sensitivity to light and tendency to pigmentation, there

are 6 basic types of skin that demand different levels of UV protection as shown in Table 2.


8/30

Page | 8

Skin type

(Appearance

unexposed)

Critical dose

mJ/cm

Self protection

time (min)

Risk level

I - White 15 30 5 - 10 Burns easily, has the

highest risk of

prematureskin ageing and

greatest risk of

developing

skin cancer

II - White 25 35 8 - 12 Burn and only rarely

tan

III - Brownish 30 50 10 - 15 Tan and occasionally

burn

IV - Brown 45 60 15 - 20 Tan and occasionally

burnV - Brown 60 100 20 - 35 Sufficient levels of

melanin and rarely

burns,

easily tan

VI Dark Brown -

Black

100 200 35 - 70 Sufficient levels of

melanin pigment

provide

protection. Very rarely

burns, easily tan

Table (2): Effect of UV rays on different types of skin.

The minimal erithemal dose (MED) is apparently consistent with a fair complexion, but shows

variations among people of types III and IV. For practical purposes, the population could be

classified into two main groups, sensitive and less sensitive individuals.

4.The DNA molecule as the main target of UV light in the cells:The most important cellular effects induced by UV radiation (cell-death and mutagenesis) are

directly related to a chain of events that primarily involve the induction of DNA lesions.

Notwithstanding, the chemical nature and efficiency in the formation of DNA lesions greatly

depend on the wavelength of incident UV photons as well as on the base composition of the

DNA molecule, as previously demonstrated. In fact, the absorption spectra of DNA from various

species for wavelengths greater than 300 nm clearly indicated that its relative absorption

increases as a function of guanine-cytosine content. Therefore, as the maximum of light

absorption by DNA molecules is 260 nm, UVC is revealed as being the most effective

wavelength for the induction of DNA photoproducts. The absorption spectrum of a purified

plasmid DNA sample is presented in Figure 3, as a demonstrative example.


9/30

Page | 9

Fig (9): The absorption spectrum for the DNA molecule. A sample of purified plasmid DNA(pCMUT vector), diluted in a TE buffer (10 mMTris-HCl [pH 8.0], 1 mM EDTA [pH 8.0]) at the

indicated concentration, was used to obtain this spectrum, with an Evolution 300 UV-Vis

Spectrophotometer (ThermoFisher Scientific, USA).

The different wavelengths of UV light induce different types of DNA damage. The direct

excitation of the DNA molecule by UV sunlight (mainly by UVB wavelengths) results in well-

known modifications that trigger off dimerization reactions between adjacent pyrimidines. The

main products resulting from these photochemical reactions are cyclobutanepyrimidine dimers

(CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs). In addition, upon further

irradiation with UVA wavelengths (around 320 nm), the normal isomers of 6-4 PPs can beconverted to their Dewar valence isomers. However, in certain dormant life-forms produced by

bacteria, such as Bacillus subtilis, the only DNA photoproduct produced upon exposure to UV

light corresponds to two thymines linked by the methyl group of one of the bases.

The formation of this specific lesion, viz., 5-thyminyl-5,6-dihydrothymine (spore photoproduct,

SP), is possibly due to specific features of the spores, these including DNA conformation (A

form), dehydration, the presence of dipicolinicacid in the core, and the binding of small acid-

soluble proteins to DNA . Apart from direct induction of DNA lesions, UV radiation can also

cause DNA damage indirectly, following photon absorption by chromophores other than DNA

itself, thereby generating reactive oxygen species.

Oxidatively generated DNA damage, mostly in the form of 7, 8-dihydro-8-oxoguanine

(considered a marker for this type of damage), and which occurs more effectively with UVA

than UVB, has often been proposed as a pre-mutagenic lesion in UVA mutagenesis. Another

type of UV-induced DNA lesion, although rather inefficiently so, is the single-strand break. It

has also been suggested that this is probably an innocuous lesion with little involvement in the

formation of mutations.


10/30

Page | 10

Fig (10): The main DNA lesions induced by UV light: CPD-cyclobutane pyrimidine dimer; 6-4PP-

pyrimidine (6-4) pyrimidone photoproduct; DewarPP-Dewar valence isomer; Single strand

breaks; 8-oxoG-7, 8-dihydro-8-oxoguanine; Spore photoproduct.

It is well-known that solar UV radiation can generate chemical modifications in the DNA

structure, leading to several biological consequences. Thus, in the evolution of life on Earth,

cells have developed specific DNA repair mechanisms capable of dealing with different types of

lesions. In both prokaryotes and eukaryotes, these biochemical pathways are indispensable for

maintaining genomic integrity by removing damaged DNA bases or short fragments ofnucleotides containing UV photoproducts. However, through inadequate repair, unremoved

UV-induced DNA damage possibly interferes with basic cellular processes, such as transcription

and DNA replication, thereby leading to mutations and/or cell-death.

5.Solar UV index, UV protection factor and solar protection factor:The effect of ultraviolet radiation on living biological organisms has been extensively studied,

and various reporting methods such as UV index, UV protection factor (UPF) and solar

protection factor (SPF) have been adopted to create awareness among the general public of

the deleterious effects of UV radiations. At a given wavelength, electromagnetic radiation maybe reflected, absorbed or transmitted by any given object. If the response of the system at

each wavelength is a linear function of the dose, then the response (R) by a broad spectrum is

given by the following formula:

()()

where I ( , t) is the irradiance at wavelength , t is time and () is the cross-section foreliciting this response at wavelengths . The changes in the spectrum have been covered by

including time as an argument of the irradiance function and as a variable of integration.


11/30

Page | 11

The UV index is designed to provide the public with a numerical indication of the maximum

potential solar UVR level during the day; the higher the number, the higher the solar UVR

hazard. The global solar UV Index is a measure of the highest level of UVR every day, and the

UVI is calculated using various input parameters such as the ozone level, potential cloud cover,

water vapour and aerosols. The UV index is reported as the maximum biologically effective

solar average UVR (UVReff) for the day, and is an average taken over either 10 or 30 minutes.The UVR is usually highest around midday but the temperature is often highest later in the

afternoon. UVR index values are grouped into five exposure categories, from low to extreme

with different colour codes.

6.UV protection factor:The protection extended by the textile materials, accessories and sun screen lotions are

denoted by different terminologies known as UPF and SPF. Risk estimates of unprotected skin,

protected skin and UPF are given by the following formulae:

risk unprotected = SA

risk protected = SAT

UPF = risk unprotected / risk protected

Where S is the source spectrum (Wm2 nm-1), T is the transmittance, A is the action

spectrum for measured response and is the bandwidth in nm. Since the relative erythemal

spectral effectiveness is higher in the UVB region compared to the UVA region, the UPF values

depend primarily on the transmission in the UV B region. UV rays falling on textiles are partly

reflected, absorbed and partly transmitted through the fibres& interstices, and the optical

porosity of a fabric limits its potential to provide protection against UVR.The solar protection

factor (SPF) is defined as a quotient from a harmful dose without, and a harmful dose with, sunprotection. This can be calculated from erythemal effectiveness (EW ()), (P()) and from the

wavelength dependent transmission of the sun protection agent. The difference between the

values of UPS and SPF arises mainly because of the hole effect in the fabrics.

7.Effect of UV radiation on textile materials:UV radiation is one of the major causes of degradation of textile materials, which is due to

excitations in some parts of the polymer molecule and a gradual loss of integrity, and depends

on the nature of the fibres. Because of the very large surface volume ratio, textile materials are

susceptible to influences from light and other environmental factors. The penetration of UVR in

nylon causes photo oxidation and results in decrease in elasticity, tensile strength and a slight

increase in the degree of crystallinity. In the absence of UV filters, the loss in tensile strength

appears to be higher in the case of nylon (100% loss), followed by wool, cotton and polyester,

with approximately 23%, 34% and 44% respectively after 30 days of exposure. Elevated

temperature and UVB radiation on cotton plants result in severe loss of bolls. Naturally-

coloured cottons contain pigmentranges from light green to tan, brown and inherent long-term UV protection properties with a

UPF of 64 and 47, whereas normal cotton shows a UPF of 8.


12/30

Page | 12

8.UV absorbers:UV absorbers are organic or inorganic colourless compounds with strong absorption in the UV

range of 290 360 nm. UV absorbers incorporated into the fibres convert electronic excitation

energy into thermal energy, function as radical scavengers and ?singlet oxygen quenchers. The

high-energy, short-wave UVR excites the UV absorber to a higher energy state; the energyabsorbed may then be dissipated as longer-wave radiation. Alternately,isomerisation can occur

and the UV absorber may then fragment into non-absorbing isomers. Sunscreen lotions contain

UV absorbers that physically block UVR. The most widely used UVB screens, 2-ethyl hexyl-4-

methoxy cinnamate with high RI, make a substantial contribution to the RI matching of skin, i.e.

refractive index matching. An effective UV absorber must be able to absorb throughout the

spectrum, to remain stable against UVR, and to dissipate the absorbed energy to avoid

degradation orloss in colour.

Organic UV absorbers are mainly derivatives of o-hydroxybenzophenones, o-hydroxy phenyl

triazines, o-hydroxy phenyl hydrazines. The orthohydroxyl group is considered essential forabsorption and to make the compound soluble in alkaline solution. Some of the substituted

benzophenones penetrate into synthetic fibres much like disperse dyes. Commonly-used UV

absorbers are 2-hydroxy benzophenones, 2-hydroxy phenyl benzotriazoles, 2-hydroxy phenyl-

Striazinesand chemicals such as benzoic acid esters, and hindered amines. The strong

absorptionin the near UV of 2, 4 dihydroxybenzophenone is attributed to conjugating chelation

between theorthohydroxyl and carbonyl groups. Organic products like benzotriazole, hydro

benzophenone and phenyl triazine are primarilyused for coating and padding processes in

order to achieve broad protection against UV rays. Suitable combinations of UV absorbers and

antioxidants can yield synergistic effects. Benzophenone derivatives have low energy levels,

easy diffusibility and a low sublimation fastness. Orthohydroxy phenyl and diphenyltriazinederivatives have an excellent sublimation fastness, and a self-dispersing formulation can be

used in high temperature dyeing in padbathsand also in print pastes.

UV absorbers incorporated into the spinning dope prior to the fibre extrusion and dye bath in

bath dyeing improve the light fastness of certain pastel shades and the weatherability of spun-

dyed fibres. UV absorbers to the extent of 0.6 2.5% are sufficient enough to provide UVR

protection fabrics. The presence of UV absorbers in PET, nylon, silk and wool protects the fibres

against sunlight-induced photo degradation. On wool, UV absorbers can retard the photo-

yellowing that occurs upon exposure to sunlight. Triazine class-hindered amine light stabilisers

are used in PP to improve the UV stability. The addition of HALS to 0.15% weight is sufficient toimprove stability substantially. Even pigmented PP requires UV stabilisers if the fibres are

exposed to UV during their services [43]. High-energy UV absorbers suitable for PET include

derivatives of o-hydroxyphenyldiphenyltriazine, suitable for dye baths, pad liquor or print

paste.

UV absorbers have refractive indices of about > 2.55, by means of which maximum covering

capacity and opacity is achieved. The presence of inorganic pigments in thefibres results in

more diffuse reflection of light from the substrate, and provides better protection. TiO2 added

in the spinning dope for matt effects in the fibres also acts as a UV absorber. Titanium dioxide

and ceramic materials have an absorption capacity in the UV region between 280 and 400 nm,

and reflects visible and IR rays; these absorbers are also added as dope additives [53]. For

maximum effect, the particles have to be monomolecularly distributed, and are often applied


13/30

Page | 13

in one bath. Nanoscale titanium gel particles strongly bound to the cotton fabrics can give a

UPF 50 without impairing the tensile properties. Brighter viscose yarns provide the highest

UV transmittance compared to the dull pigmented viscose yarns, modal yarns. Zinc oxide

nanoparticles, which have a very narrow size distribution (20-40 nm) and minimal aggregation,

can result in higher levels of UV blocking [51]. Use of TiO2, ZnO alone produces less absorption

of UVR than a mixture of (67/33) titanium dioxide and zinc oxide on cotton and nylon fabrics[32]. Microfine nylon fabrics with a porosity of 0.1% are capable of giving UPF > 50 with 1.5%

TiO2. Incorporating UV absorber in dyeing decreases the dye uptake slightly, except in post-

treatment application.

Many commercial products and processes have been developed to produce fabrics with a high

level of UPF using various dope additions and topical applications for almost all types of fabrics

produced from cellulosic fibres, wool, silk and synthetic fibres. Most of the commercial

products are compatible with the dyes and other finishing agents applied to the textile

materials, and these agents can be applied using simple padding, the exhaust method, the

padthermofix and the pad-dry-cure methods.

9.Textile materials and UV protection:Sun protection involves a combination of sun avoidance and the use of protective garments &

accessories. Reducing the exposure time to sunlight, using sunscreens and protective clothes

are the three ways of protection against the deleterious effects of UV radiation. Apart from

sunscreen lotions, textile materials and accessories made of textile materials are largely used

for UV protection. UV protection through textiles include various apparels, accessories such as

hats, shoes, shade structures such as umbrellas, awnings, and baby carrier covers and the

fabric materials to produce these items.

Fig (11): Relationship between percentage reduction of UV radiation by textile.


14/30

Page | 14

Nature of fibres & fabric:In textiles, UPF is strongly dependent on the chemical structure of the fibres. The nature of the

fibres influences the UPFs as they vary in UV transparency. Natural fibres like cotton, silk, and

wool have a lower degree UVR absorption than synthetic fibres such as PET. Cotton fabric in a

grey state provides a higher UPF because the natural pigments, pectin, and waxes act as UV

absorbers, while bleached fibres have high UV transparency. Raw natural fibres like linen and

hemp possess a UPF of 20 and 10 to 15 respectively, and are not perfect UV protectors even

with lignin content. However, the strong absorption of jute is due to the presence of lignin,

which acts as a natural absorber. Protein fibres also have mixed effects in allowing UV

radiation. Dyed cotton fabrics show higher UPF, and undyed, bleached cotton yields very poor

UPF values. Wool absorbs strongly in the region of 280 400 nm and even beyond 400 nm.

Exposure to sunlight damages the quality of silks colour, strength and resiliency in both dry

and wet conditions. Mulberry silk is deteriorated to a greater extent than muga silk. Bleached

silk and bleached PAN show very low UPFs of 9.4 and 3.9 respectively. Polyester fibres absorb

more in the UV A& UV B regions than aliphatic polyamide fibres.

Moisture and swelling:The ability of textile fibres to provide UV protection varies depending upon the structure and

other additives present in the fibres. Besides, the construction parameters and wear conditions

of the textile materials, moisture and additives incorporated in processing also affect the UPF

of the textile material. In the case of moisture, the influence largely depends on the type and

hygroscopicity of fibres, as well as conditioning time, which result in swelling phenomena. The

RH and/or moisture content affect the UPF of the fabric in two ways, namely the swelling of

fibres due to moisture absorption, which reduces the interstices, and consequently the UVtransmittance. On the other hand, the presence of water reduces scattering effects, as the

refractive index of water is closer to that of the textile polymer, and hence there is a greater

UV transmission vis- vis a lower UPF.A typical cotton fabric could transmit 15-20% UVR, rising

to more than 50% if the garment is wet. Foradequate protection, the UVR transmission should

be lower than 6% and 2.5% for extremely good protection. Dependence of humidity is more

pronounced in silk and viscose, of which viscose has a higher water absorption and swelling

capacity, while silk has poor swelling properties. Even though silk has poor swelling properties,

its very fine nature and a greater number of fibres in the crosssectionof yarn results in higher

swelling due to capillary absorption, and in turn less UV transmittance. Finishing treatments

given to the fabrics to reduce swelling reduce the transmittance of UV rays. In general,hygroscopic fibres and their UPF show better correlation.

Fabric construction factors:When the ultraviolet radiation hits the textile materials, different types of interactions occur

depending upon the substrate and its conditions. The UV protection by textile materials and

apparel is a function of the chemical characteristics, physico-chemical type of fibre, presence of

UV absorbers, construction of fabric, thickness, porosity, extension of the fabric, moisture

content of the fabrics, colour and the finishing given to the fabric. A part of the radiation is

reflected at the boundaries of the textile surface. The UVR transmitted through textile fabricsconsists of the unchanged waves that pass through the interstices of the fabrics as well as


15/30

Page | 15

scattered waves that have interacted with the fabrics. Another part is absorbed when it

penetrates the sample, and is converted into a different energy form. The portion of radiation

that travels through the fabric and reaches the skin is appropriately referred to as the

transmission component.

The UPF increases with fabric density and thickness for similar construction, and is dependenton porosity (UPF = 100 / porosity). A high correlation exists between the UPF and the fabric

porosity but is also influenced by the type of fibres. The relative order of importance for the UV

protection is given by % cover >fibre type > fabric thickness. Cloth cover does not consider the

flatness of the yarns, which might result in a higher cloth cover than the calculated value. A

UPF with fabric weight and thickness shows better correlation than cloth cover. Therefore

fabrics with themaximum number of yarns in warp and weft give high UPFs. UPF values of 200,

40, 20 and 10 can be achieved with the percentage cover factors of 99.5, 97.5, 95 and 90

respectively. The percentage UVR transmission of a fabric is related to the fabric cover factor

by (100 cover factor) and the UPF is given by UPF = 100 / (100-CF). To achieve a minimum

UPF rating of 15, the cover factor of the textile must be greater than 93%, and a very smallincrease in CF leads to substantial improvements in the UPF of the textiles above 95% cover

factor. In the case of terry cloth, a high variability in UPF exists due to irregularities in the fabric

construction. Woven fabrics usually have a higher cover factor than knits due to the type of

construction. Thick rib structures of hemp and linen can allow 10.52 12.70% and 9.03

11.47% of UV A and UV B respectively . However, knitted structure made from a blend of

synthetic fibres with Lycra offers the best protection against solar radiation, and warp-knitted

blinds are capable of screening up to 80% of the solar radiation and bright glares.

Stretching reduces the UPF rating of the fabric during wear, as the effective cover factor is

reduced. However, the cover factor can be modified through many dry finishing processes

through overfeed on the stenter, compressive shrinkage processes such as compacting and

sanforising, whichare normally used to obtain dimensional stability, incidentally increasing the

cover factor and hencethe UPF. Gentle milling employed in the case of lightweight wool fabrics

can also enhance the cover factor and the UPF.

Dyeing and finishing:Depending upon the type of dye or pigment, the absorptive groups present in the dyestuff,

depth after dyeing, the uniformity and additives, the UV protection abilities of the textile

materials are considerably influenced. In a given fabric, higher transmission of UV radiation is

observed in the case of bright fibres (viscose) than dull fibres. A protective effect can be

obtained by dyeing or printing, which is better than using heavyweight fabrics which are not

suitable for summer conditions. Darker colours of the same fabric type (black, navy, dark red)

absorb UVR much more strongly than the light pastel colours for identical weave with UPF, in

the ranges of 18 37 and 19 34 for cotton and polyester respectively [3, 35]. Some direct,

reactive and vat dyes are capable of giving a UPF of 50+. Some of the direct dyes substantially

increase the UPF of bleached cloth, which depends on the relative transmittance of the dyes in

the UV B region. In many cases, a UPF calculated using a direct dye solution appears to be

higher than that of the fabric after dyeing, mainly because the actual concentrations are mostly

less than the theoretical concentration. Dyes extracted from various natural resources also

show the UPF within the range of 15 45 depending on the mordant used. Cellulosic fabrics

transmit UV A and UV B equally with the transmittance ratio (TA/TB) 0.9. When dyed with the

reactive dyes, the UPF increases from 4.7 to 5.0 14.0 depending upon the concentration,


16/30

Page | 16

which is not sufficient to satisfy the minimum requirements. Some of the vinyl sulphone dyes

and monochlorotriazine dyes possess UVR absorption characteristics, which also increase with

theconcentration. Cellulosic fabrics dyed with these dyes show reduced UVR transmission from

24.6% to 10-20% and 27.8% to 8-22% for UV A and UV B respectively. When mixtures of these

dyes are used, the UPF increases synergistically. Some combinations of disperse reactive mix

can give prolonged UV protection with a UPF of 50+ for P/C blends. Optical brightening agentsor fabric whitening agents are used at the finishing operations, as well as in the wash cycles,

and their effect on UPFs has been demonstrated extensively in the past. Optical brightening

agents are often applied to enhance the whiteness of textiles by UV excitation and visible blue

emission. The phenomenon of excitation and emission is caused by the transition of electrons

involving p-orbitals from either conjugated or aromatic compounds. Most optical brighteners

have excitation maxima within the range of 340 400 nm. OBA can improvethe UPF of cotton

and cotton blends, but not of fabrics that are 100% polyester or nylon. The presence of OBA in

the P/C blends (67/33) to the extent of 0.5% can improve the UPF from 16.3 to 32.2, which is

more or less closer to that obtained using the UV absorbers with 0.2% (UPF 35.5). Washing the

fabrics leads to a loss of UPF in the case of OBA-treated fabrics, and the UPF reaches the levelof that in untreated fabric after 10 washes, which shows the semi-permanent nature of the

finish and protection. Another limitation of many OBAs is that they mostly absorb in the UVA

part of the day light spectrum (93%) but have a weak absorption in UV absorption around 308

nm (92%), which plays an important role in skin disease.

Protection factor of fabrics:The ability of fabrics to protect against UV radiation can be tested by two major methods: in

vitro method (or instrumental / spectrophotometric method) and in vivo method (or

laboratory / human skin method). Both methods assess the amount/degree of sunburnprotection provided by the fabrics with so called term UPF by in vitro method and SPF by in

vivo method. Theoretically, the UPF and SPF value for any fabrics should be the same.

However, some studies indicated that the results of UPF and SPF values are not statistically

identical; never the less both values are in a good correlation (Hatch &Osterwalder, 2006).

10. How Sun Protection Clothing Works:

Fig(12): Clothing ofAstronauts
http://astronauts.nasa.gov/http://astronauts.nasa.gov/http://astronauts.nasa.gov/http://astronauts.nasa.gov/


17/30

Page | 17

There are a variety of factors:

Construction: Dense, tight construction (either weaves or knits) minimizes the spacesbetween yarns, which in turn minimizes the amount of UV light that can pass through.

Some tightly constructed UPF-rated garments use vents to boost air circulation and help

the wearer stay cool. Thicker fabrics also help reduce UV transmission. Dyes: It is the specific type of dye (and the concentration in which it is used) that

impacts a fabric's UV transmission, not its color. Some dyes deflect more UV radiation

than others, and some absorb none at allincluding black dyes. How can one know

what kind of dyes are used in individual garments? The only tip-off is if the garment

carries a UPF rating. Clothing engineered for UV protection may use high concentrations

of premium dyes that disrupt UV light. Such dyes include "conjugated" molecules that

disrupt UV radiation. The higher the concentration of such dyes, the darker the garment

becomes. But ultimately color has no influence on UV rays. Note: Pigment-dyed fabrics,

which include a resin that creates a powdery look and feel, get high marks for UV

protection. Treatments: Chemicals effective at absorbing UV light may be added during

processing. Specialized laundry additives, which include optical brightening agents and

newly developed UV-disrupting compounds, can boost a garment's UPF rating.

Fiber type: Polyester does an excellent job at disrupting UV light (due to hydrogen-and carbon-based benzene rings within the polymer). Nylon is good. Wool and silk are

moderately effective. Cotton, rayon, flax and hemp fabrics (natural fibers composed of

cellulose polymers) often score low without added treatments. However, unbleached

or naturally colored cotton performs better at interacting with UV light than bleached

cotton.

Stretch: If a garment is stretched 10% or more beyond its normal dimensions, spacesbetween yarns are widened and its effectiveness against UV light may be reduced up to

40%.

Wetness: A fabric's ability to disrupt UV radiation is usually reduced when wet,though the reasons why are not completely understood. Wetness may cause a 30% to

50% reduction in a fabric's UPF rating.

Condition: Worn or faded fabrics are less effective against UV light.11. Factors which effects the UV protection:

There are several reasons or factors available which effects the protection factor of UV

protective textile. Those factors are so important for the better performance to that textile.

Those factors are -

Effects of yarn structure on UV protection Effects of fabric geometry on UV protection Effect of cover factor or open porosity Effect of fabric tightness Effect of volume porosity Effects of colour on UV protection Effects of maintenance and usage on UV protection Effects of additives on UV protection


18/30

Page | 18

Effects of yarn structure on UV protection:Woven fabrics are made from different types of yarns. Raw material of yarn or fibre

composition is the initial yarn parameter which has an effect on UVR protection. Fibres have

different ability to absorb UV radiation and to block most of the incident radiant energy and

those prevent it from reaching the skin. There is a lack of studies dealing with the effect of

fibre composition only. The reason is that yarn colour, additives and coatings have much

more significant impact on UV transmission properties rather than fibre composition itself.

Never less, Crews et al. (Hatch &Osterwalder, 2006) conducted a comparison of undyed

woven fabrics and determined how fibre composition ranked relative in regard to UV

absorbance. They established three distinct groups regarding the decreasing ability of fibre

UVR absorbance: 1.group includes polyester, 2. group includes wool, silk and nylon and 3.

group includes cotton and rayon fibres. Natural fibres have lower UV blocking properties

regarding the synthetic ones, but from the thermo-physiology point of view there are more

suitable in hot wearing conditions. Hustvedt et al. (2005) found that naturally-pigmented

cotton fabrics have excellent sun protective properties, which are far superior to conventional,bleached or unbleached cotton fabrics. Stankovic et al. (2009) conducted a

study of yarn twist effect on UPF of cotton knitted fabric and found that yarn twist to a great

extent influenced the UV protection properties through the influence on yarn compactness

and surface properties, which in turn influenced the open porosity of the fabric.

Effects of fabric geometry on UV protection:UV light passes direct through the macropores or fabric open area (direct UV transmittance)

and also through the yarns, where changes the direction before leaving the fabric (scattered

UV transmittance). Numerous studies focused on different fabric constructional parameterswhich represent the fabric structure the best and have direct and significant effect on UV

protection. Such role has been given to fabric cover factor, fabric open porosity, fabric mass,

fabric thickness etc. (Gies et al., 1998; Dimitrovski et al., 2009; Gabrijeliet al., 2009; Hatch

&Osterwalder, 2006).

Effect of cover factor or open porosity:To evaluate only the influence of fabric cover factor (or its complementary relationshipopen

porosity) on UPF and eliminate other significant factors such as colour and additives, the set of

fabrics should be precisely prepared. Our experiment (Dubrovski&Golob, 2009) was focused on

100% cotton woven fabrics in a grey state with the same yarn fineness (14 tex) and different

thread densities to achieve fabric cover factor between 59% and 87%. This was possible by

introducing different types of weave (plain, twill, satin), while it is known that by plain weave

lower densities are achieved due to the high number of thread passages regarding to the twill

and satin weaves. Fabric cover factor and open porosity were calculated according to Eq. (15)

to Eq. (18). While also cotton yarns absorb some of the incident UVR we could not focuse only

on the UVR that goes through the macropores.

To eliminate the influence of raw material, yarns with 100% absorption of UV light that strikes

them should be used but this is not usually the case. From the Fig. 5 it can be seen that higher

cover factor (or lower open porosity) means better UV protection and that cover factor shouldbe at least 80% (or open porosity lower than 20%) to achieve good UV protection according to


19/30

Page | 19

AS/NZ standard. This is possible only by higher thread densities and definitely not by plain

weaves in our case. Even if the plain fabric would have the 0highest cover factor it would not

reach the UPF 15. The results of mentioned study refer to

the theoretical values of open porosity and cover factor.

In real fabric open porosity is much lower, especially in the case of fabrics made from thestaple-fibre yarns, where the phenomenon of latticed pores, the phenomenon of changing the

position of warp threads according to the longitudinal axis and the phenomenon of thread

spacing irregularity occur.

In this case the correlation between the measured open porosity/cover factor (image analysis)

and UPF is not so good and should be treated regarding the type of weave (Fig. 6).

Fig (13): The influence of theoretical values of open porosity or cover factor on UV protectionof

cotton fabrics in a grey state.

The plain-weave fabric includes the maximum percentage of weave passages (67%) and it is

reasonable to assume that all the threads are more or less equidistant and that the effect of

fully latticed pores is reduced to its minimum, whereas by satin weave the effect of fully

latticed pores is very high those reducing open area for UV transmission. If we observe

measured values of open porosity, the limit values to reach good UV protection of fabrics is12% or lower without taking into account the type of weave. Further observation regarding the

type of weave shows that by plain and twill weave it is not possible to reach UPF 15 neither by

12% of open porosity, while by satin weaves this is possible. The results clearly

indicate that theoretically defined open porosity/cover factor is not satisfactory parameter

toasses its influence on UPF because of the absence of weave influence. In real fabrics,

especially in fabrics with staple-fibre yarns, different types of pores regarding the type of

weave and other phenomenon are involved, which all reduce the fabric open area in

comparison with theoretically calculated values of open porosity. On the other hand, open

porosity/cover factor could be a good parameter showing the influence on UPF if the set of

fabrics with the same type of weave, raw material and yarn fineness is observed. In our

previous research (Dubrovski&Brezocnik, 2002) we also proposed the predictive model of open

porosity which is in better correlation with measured values than theoretical ones.


20/30

Page | 20

Fig (14): The influence of measured values of open porosity and cover factor on UV protection

of cotton fabrics in a grey state (a without weave influence, b with the weave influence).

Effect of fabric tightness:Fabric tightness or relative fabric density is another parameter which represents the fabric

structure or how tight the fabric is woven, similar as cover factor. Advantage of fabric tightness

is the consideration of weave by its calculation (Eq. (8) to Eq. (11)). It is known that by satin

weave it is possible to achieve higher warp/weft density than with twill or plain weaves, so the

limit density as well as actual density will be higher. Consequently, the macropores will be

smaller and UV radiation will have less free space to pass through thanin twill or plain weaves.

The fabric tightness is relative term and according to previous mentioned experiment


21/30

Page | 21

(Dubrovski&Golob, 2009), the following decreasing rate of UPF values could be seen within the

same fabric tightness: satin twill plain

Fig(15): The influence of fabric tightness on UV protection of cotton fabrics in a grey state.

The macropores in plain fabrics have very stable and uniform form as a consequence of more

thread passages. On the other hand, the pores in satin fabrics are not as stable due to few

thread passages, and tend to group together which further reduces the free space area. By

fabrics made from staple-fibre yarns macropores are further reduced because of the

phenomenon of latticed pores. Nerveless higher actual warp/weft density by each weavemeans higher fabric tightness and consequently higher UV protection. Results for fabrics in a

grey state show that none of the plain fabrics offered minimum UV protection, even if they

were tightly woven. Twill fabrics had good UV protection if they were woven with tightness

above 70%, while satin fabrics offered good UV protection already by 60% tightness.

Effect of volume porosity:Thicker and heavier fabrics minimize UVR transmission (Scott, 2005). While some of the

researchers focused on fabric mass and thickness, we decided to include volume porosity as a

parameter influencing UPF, while it includes fabric mass and thickness through the fabric

volume fraction according to the Eq. (19), Eq. (20) and Eq. (25). Results for grey fabrics (Fig. 8)

show that there is no direct correlation between volume porosity and UPF. Moreover, results

indicate that volume porosity depends on the type of weave and affects UPF as well.

This is in accordance with previous mentioned discussion about the macropores. The

macropores as three-dimensional forms are bigger, more stable and uniform in plain fabrics

compared with macropores in twill or satin fabrics at the same volume porosity. Lower volume

porosity means higher UPF. Plain fabrics did not offer any UV protection, while twill and satin

fabrics offered good UV protection when volume porosity was less than 64%

and 66%, respectively.


22/30

Page | 22

Fig(16):The influence of fabric volume porosity on UV protection of cotton fabrics in a greyState.

Effects of colour on UV protection:Undyed or bleached fabrics offer much lower protection against UV radiation if any in

comparison with dyed fabrics. Dyes react like additives; they improve UV protection abilities,

because they absorb UV radiation in the visible and UV radiation band. By bleaching process

the naturally occurring pigments and lignin which act as UV absorbers are removed those

affect UV absorber ability of cotton fabrics. Hypothesis that the hue of dye is responsible for

UV protection of fabric is a matter to discuss.Gatewood (Scott, 2005) noted that

transmission/absorption characteristics of dyes in the UV band were a better predictor of UV

protection than thecolour of the dyestuff itself. Srinivasaen et al. (Hatch &Osterwalder, 2006)

who studied the effect of fourteen direct dyes on the UPF of cotton fabrics, concluded that

colour (hue) is not related to UPF, while fabrics dyed with the dyestuff with the same hue (red

28, red 24, red 80) and identical oncentration had different UPF values. Also the black fabric in

this study did not have the highest UPF

despite the common fact that darker colours (such as black, navy blue, dark green, red) of the

same fabric type absorb UVR more strongly than light pastel shades (Yallambie, 2003; Wilson et

al., 2008b).Neverless, the results of mentioned study indicate that higher dye concentration

means higher UPF. Wilson et al. (2008a) concluded that black fabrics generally transmitted 20%

less UVR than their matched white quivalent.

In another study Wilson et al. (2008b) examined the relationship between UV transmittance

and colour and found that depth of colour, rather than colour per se is the principal aspect of

colour affecting UV transmittance. The best description of the relationship between colour and

UVR transmission was provided by the L*, and L* and b* components of the LAB system. He

suggested that by developing fabrics for UV protection, selection of dyes that generate colours

with CIE Y or L* values of less than pproximately 28 or 38, respectively is recommended. Our

study (Dubrovski&Brezocnik, 2009) focused on the effect of woven construction and colour ofcotton woven fabrics dyed with the same concentration (1%) of reactive dyestuffs Cibacron LS


23/30

Page | 23

(red, blue marine and black), bleached fabrics (white) and naturally pigmented abrics (dirty

white).

The comparison of UPF of fabrics with the same construction but different colour was made for

fabrics in plain, twill and satin weave and by three different levels of fabric tightness (55-65%,

65%-75%, 75%-85%). By satin and twill fabrics at third level of fabric tightness, where higherdensities can be achieved and those the influence of open porosity is set to its minimum, the

results show that all dyed fabrics posses excellent UV protection (UPF=1000), while naturally

pigmented twill and satin fabric had UPF 25 and 50, respectively. UPF of bleached twill and

satin fabric was 10 and 15, respectively. The L* component of fabric colour was around 93, 86,

44, 31 and 17 for white, dirty white, red, blue marine and black fabric, respectively. The

previous mentioned recommendation that L* value of the dyed fabrics should be less than 38

to develop fabric with good UV protection, could not be generalized, while in our case also

white satin fabric with L* of 93 showed good UV protection at third level of fabric tightness.

Our results show that there were no big differences between red, blue and black coloured

fabrics UPF at higher thread densities by twill and satin fabrics, but there was a huge differencebetween uncoloured and bleached fabrics UPF on one side and coloured fabrics UPF on

another.

The general conclusion of mentioned research was that UPF of cotton fabrics dyed with direct

dyestuffs is influenced by the colour components (L*, a*, b*), fabric tightness and type of

weave so we proposed a prediction model of UPF based on CIELAB colour components, weave

factor, and warp/weft density. Riva et al. (2009) analyzed the influence of the shade and colour

intensity of the dyeing as well as their interaction with the initial UPF of the uncoloured cotton

fabrics. They proposed UPF prediction model for cotton fabrics dyed with direct dyestuffs

(yellow 98, blue 77, red89) on the basis of the initial UPF of fabrics before dyeing, standard

depth of colour, the corrected standard depth of colour and two categorical qualitative

variables that define colour hue of dyestuffs.

Effects of additives on UV protection:During the fibre/yarn/fabric processes there is a possibility to include additives like a dye,

pigment, delusterant, optical brighteners and UV absorbers, which have the ability to absorb

UV radiation and those improve UV protection properties of fabrics with little UV protection

like cotton, rayon, silk, wool, nylon and undyed fabrics. Besides dying, other techniques areknown to incorporate additives in fabric structure: 1. addition of additives duringfibre/yarn

manufacturing, 2. addition of additives during fabric surface treatments or special treatments.

Pigments found in naturally-pigmented cotton are naturally UV absorbers and produce shades

ranging from tan to green and brown. According to the study of Hustvedt& Crew (2005), fabrics

from naturally pigmented cotton have excellent sun protection properties, which are far

superior to conventional, bleached and unbleached cotton fabrics (green UPF=30-50+, tan

UPF=20-45, brown UPF=40-50+, bleached conventional UPF=4, unbleached conventional

UPF=8). Their UV protection properties remain high enough even after 80 AFUs light exposure.

its effect is permanent. Optical brighteners convert a portion of incident UV radiation near 360

nm to the visible blue wavelengths about 430 nm and reflect it. UV absorbers are colourless

additives having chromophore system that absorbs very effectively in the UV band. Optical

brightness and UV absorbers are recently added to commercial laundry detergents (Yallambie,


24/30

Page | 24

2003). Varga et al. (2009) introduced a nanoparticle coating on yarns. They applied

anoZnOfinish on undyed and reactive dyed cotton yarns with the aim of studying the effect of

the knitting operation on the durability of the coated nanoparticles and found that such yarns

withstand the knitting process. They also performed sol-gel finishing of cotton fabrics, coated

with TiO2 nanoparticles and found that such fabrics are durable to domestic washing, and even

there was a reduction in the load of nanoparticles on the fabric surface after washing, the UPFvalues were not affected. Abidi et al. (2009) reported that titania or titania-silicianonosol

treatment in the form of thin film at cotton fabric surface offer excellent UV

protection.Gorensek et al. (2007) treated cotton fabrics with nanosilver, which was in the form

of nano powder added in the dyebathat two concentration (5 mg/L and 20 mg/L) and found

that a noticeable increase of UPF was recorded by the 5% mock dyed sample with 20 mg/L

nanosilver as well as by pale dyed fabrics in comparison with bleached and dyed cotton fabrics,

respectively. Grancaric et al. (2009) treated PET fabrics for summer clothing with ultrasound

(US), ethylene-diamine (EDA), fluorescent whitening agents Uvitex ERN based on

benzoxazolederivate (FWAs) and Tinofast PES UV absorbers based ontriazine derivate and

compared their UPF values. Untreated PET fabrics did not have any UV protection (UPF=5),while all other treatments lead to very good UV protection. EDA treated fabric resulted in

better UV protection than US treated fabrics.

Effects of maintenance and usage on UV protection:When the fabrics for clothing are in use, their initial UPF of fabric is modified by laundering as

well as by wearing conditions connected with the tension produced in contact with the body

(fabric stretch) and with an exposure to the UV radiation in wet state (swimsuit). Stretching is

more common in knitted rather than woven fabrics, with exception of elasticised wovenfabrics. Most fabrics shrink when they are laundered which lead to significant improvement in

the UPF of fabrics because of the open area reduction (Hatch & Osterwalder, 2006). Another

reason of UPF improvement by laundering is optical whiteners whichare added to laundry

detergent. Due to the effect of wetness and the effect of opening of the fabrics caused by the

tension on tightened and/or elasticized garments, the initial UPF of unstretched and dry fabric

does not have proper meaning. European standard EN 13758-1 in annex C considers

measurements under stretched and wet conditions informatively, while ASTM D 6544 refers to

the preparation of textiles prior to ultraviolet transmission testing which includes exposure

conditions (laundering, simulated sunlight and chlorinated pool water). Algaba et al. (2007)

conducted a study on undyed woven fabrics made with three different cellulose fibres (cotton,modal and modal sun fibresthat contain UV absorber in the spinning bath) which were exposed

to the simulation of the wearing conditions of the clothing. Samples were stretched with a

tension of 2, 4, and 6 N and the measurements were carried out after maintaining the samples

(unstretched or stretched) in water until saturation. The UPF of fabrics decreased significantly

when tension increased. The sign of the influence of the wetness on UPF depended on the

fibretype. The UPF of wet cotton and modal fabrics was lower, while modal sun fabrics had

higher UPF regarding the dry fabrics. Osterwalder et al. (Scott, 2005) concluded that UV

absorbance is independent from environment and therefore treating cotton with UV absorber

will afford complete protection when the fabric is wet. Wilson et al. (2008a) reported that by

10 x 20% extension UPF of cotton woven and knitted fabrics were decreased by -30% to -75%.


25/30

Page | 25

12. History & development of UV protecting textile:In the early 1990s UV protective clothing was considered to be a niche market as it comprised

mainly swimwear for children and babywear. Its lack of popularity among adults was due to its

relatively high cost, and the perception that it was heavy, hot and uncomfortable to wear.

However, in the past decade, a number of companies have introduced UV protective fabrics

and garments which do not sacrifice comfort, breathability or other desirable characteristics

commonly associated with good performance apparel. Furthermore, high quality UV protective

clothing today is both functional and fashionable. It is typically made from lightweight,

breathable fabrics, and can provide as much protection from UV radiation as heavyweight

denim.

Looking ahead, it has been projected by some authorities that consumers will come to expect

their outdoor apparel to offer UV protectionin the same way as they expect it to be

waterproof or insulating today. Others in the industry are less optimistic, and believe that it willtake some time before garment manufacturers and consumers fully understand the benefits of

UV protective clothing.

Although clothing has been used for protection against solar exposure for thousands of years,

in modern times sun protective clothing was popularized (but not exclusively used) in Australia

as an option or adjunct to sunscreen lotions and sunblock creams. Sun protective clothing and

UV protective fabrics in Australia now follow a lab-testing procedure regulated by a federal

agency: ARPANSA. This standard was established in 1996 after work by Australian swimwear

companies. The British standard was established in 1998. The NRPB (National Radiological

Protection Board) forms the basis of the British Standards Institute standard. Using theAustralian method as a model, the USA standard was formally established in 2001, and now

employs a more stringent testing protocol: This method includes fabric longevity,

abrasion/wear and washability. (To date, the focus for sun protection is swimwear, appropriate

hats, shade devices and sunglasses for children.) UPF testing is now very widely used on

clothing used for outdoor activities.

The original UPF rating system was enhanced in the United States by the ASTM (American

Standards and Testing Methods) Committee D13:65 at the behest of the U.S. Federal Trade

Commission (FTC) to qualify and standardize the emerging sun protective clothing and textile

industry. The FDA had reviewed clothing making sun protection claims (SPF, % UV blockage, orskin cancer prevention claims) in 1992. Only one brand of sun protective clothing, Solumbra ,

was reviewed and cleared under medical device regulations. The FDA initially regulated sun

protective clothing as a medical device, but latter transferred oversight for general sun

protective clothing to the FTC. The UPF rating system may eventually be adopted by interested

apparel and domestic textile/fabric manufacturers in the industry at large as a "value added"

program strategic to complement consumer safety and consumer awareness.


26/30

Page | 26

Solumbra:Solumbra is a line of sun protection clothing and a patented fabric. Introduced in 1992,

Solumbra was reviewed under medical device regulations by the U.S. (FDA) and by Health

Canada. This was revolutionary; no sun protective clothing had previously been reviewed as a

medical device in the U.S. or Canada.]

Solumbra offered improved and superior (UV) protectionwhen compared to a conventional 30 SPF sunscreen and typical summer clothing. Solumbra

sun protective clothinghats, shirts, pants and accessoriesis now rated at 100+ SPF.

Solumbra was developed as a personal sun protection clothing solution by Shaun Hughes, who

was diagnosed and treated for malignant melanoma, a potentially deadly form of skin cancer,

at age 26 during a visit to Memorial Sloan-Kettering Cancer Center in 1983. After two surgeries,

he found that traditional UV protection was not sufficient: he would sun tan through his

sunscreen and sunburn through his summer clothing. Based upon medical research and

involvement of UV and medical experts, Hughes developed the Solumbra line of fabric and

clothing. Solumbra was reviewed under medical device regulations. Solumbra entered the U.S.marketplace soon after May 13, 1992. The Solumbra logo is a depiction of the suns rays

eclipsed by effective sun protection that, in turn, provides an area of safe shade.

Solumbra has been used by highly sun sensitive patients as well as by world-class athletes

participating in international competition. Sun protection clothing can offer superior

photoprotection because of typical sunscreen shortcomings: not equally broad spectrum,

misapplication, low durability, allergic reaction, poor reapplication behavior, and poor cosmetic

elegance. Sun protection clothing has become a choice of patients with skin cancer, lupus,

vitiligo, porphyria, XP, and sun allergies.
http://en.wikipedia.org/wiki/Memorial_Sloan-Kettering_Cancer_Centerhttp://en.wikipedia.org/wiki/Sunscreenhttp://en.wikipedia.org/wiki/Sunburnhttp://en.wikipedia.org/wiki/Sunburnhttp://en.wikipedia.org/wiki/Sunscreenhttp://en.wikipedia.org/wiki/Memorial_Sloan-Kettering_Cancer_Center


27/30

Page | 27

Technology: Solumbra sun protection fabrics rely on four methods to achieve sunprotection: fiber content, weaving methods, fabric dyeing process and finishing process.

The key concept is to prevent UV from transmitting through the fibers and apertures

(holes between the fibers). Solumbra I fabric is protected by U.S. and international

design and process patents.Hughes developed the technology without treatments or

coatings that could lose their effectiveness and photoprotection after use, laundering

and exposure to environmental factors. Solumbra clothing designs are based upon

published medical guidelines.] Designs are typically long sleeved, long legged and wide

brimmed, all to provide maximum UV protection against both direct and indirect UV

exposure.

Research: Solumbra fabrics were at the forefront of in vitro and in vivo research into UVprotection offered by fabrics. This research revealed that traditional summer clothing in

North America offered less than 15 SPF protection, the minimum level recommended

by doctors. R Sayre was the lead researcher of in vitro SPF testing for regular summer

fabrics, which tested between SPF 5 to 9 when dry and SPF 3-9 when wet.Nicholas

Lowe and R Sayre followed this up with in vivo research. They found that Solumbra

offered over 50 SPF when dry or wet. In vivo research spearheaded by J Menter and

Sayre, published in the Journal of the American Academy of Dermatology, showed that

most mice contracted squamous cell carcinoma (scc) skin cancers through typical

summer fabrics and mice protected by Solumbra fabrics did not incur skin cancers.

Subsequent research by Menter and Sayre found that specific Solumbra fabrics

provided photoprotection for mice against injury from visible light when sensitized with

the photosensitizer, ALA, compared to insufficient protection by typical summer fabric.

Research was just presented by an independent researcher in March 2012 that showed

that Solumbra fabrics now offer 100+ SPF even after 500 durability cycles.

Innovation: The New York Times declared Sun Precautions was the innovator, with itsSolumbra line, which blocks more than 97 percent of UVA and UVB. Solumbra has

been featured in other leading publications and national media, including Time, U.S.

News and World Report, People, MSNBC, The Today Show, The Los Angeles Times,

Vogue, and Health. In October 2011, Travel and Leisure magazine found that Solumbra

was one of the 'The Game Changers'--Worlds Most Important Travel Innovations. The

American Academy of Dermatology recognized Solumbra and Sun Precautions with a

Gold Triangle Award for assisting with skin cancer awareness and prevention.

Recent invention of NCSU researcher :Designing affordable, ultraviolet-resistant clothing that lessens wearers' risk of skin cancer is

the goal of North Carolina State University researchers.The researchers began by imagining

clothing that acts like a computer. They developed clothing fibers with a microscopic coating ofthe same conductive material found on computer chips. The team discovered another

potential benefit "to be able to impart UV protection on different fabrics," NCSU textile
http://en.wikipedia.org/wiki/SPFhttp://en.wikipedia.org/wiki/Photosensitizerhttp://en.wikipedia.org/wiki/Aminolevulinic_acidhttp://en.wikipedia.org/wiki/Aminolevulinic_acidhttp://en.wikipedia.org/wiki/Photosensitizerhttp://en.wikipedia.org/wiki/SPF


28/30

Page | 28

engineering researcher Chris Oldham said.The fabric coating resists the sun's UV rays, which

can prevent fading of outdoor materials such as flags. It might also be used on clothing to

reduce the risk of skin cancer.UV-resistant fabrics already on the market can be

expensive."They are looking for a more affordable product that will protect them in the

sunlight," Oldham said rather than dipping fabrics in an oil-based liquid solution, NCSU

researchers heated chemicals into gas form that deposits a coating 1,000 times thinner ahuman hair. The process might work on a wide range of lightweight, summer-time fabrics.

"What we're trying to do is use greener materials like cotton and recycled polyesters and make

those feel the same and also act the same as some of these high-end, UV-resistant fabrics,"

NCSU textile engineering researcher Jesse Jur said. In addition to protecting people from the

sun, the clothing could be used as a sensor to track heart rate and body temperature in real

time.The NCSU Chancellor's Innovation Fund recently awarded a $75,000 grant to get the

technology into the market more quickly.

13. UPF measurement systems & test:Appropriate precaution which were applied while carrying out the measurement should be

sufficient to collect all the scattered and transmitted lights through an integrating sphere, to

include all the erythemal active wavelengths (UVA & UVB) spectral measurements without any

influence of fluorescence from FWA, if it is present in the fabric. There are currently 12 sites in

Australia and Antarctica installed with broadband UVR detectors to measure the total energy

received over a range of wavelength in UVR region in both direct and diffuse radiation.

Polysulphone films have been widely used in the construction of personal dosimeters, which

absorb strongly in the UV B region.

The instrument for measuring fabric transmission includes broadband radiometers,

spectroradiometers, or spectrophotometers, and Xenon lamps. Filters are placed next to the

test specimen to prevent the effects of fluorescence reaching the integrating sphere. The

spectral response of the detector is also important in determining system performance, and it

must be capable of detecting UVR accurately and linearly over a very large rangeof intensities

and discriminating the signal from the detector dark current.

Many commercial systems have difficulty in measuring UPFs above 100 due to dynamic range,

dark current discrimination at lower wavelengths of 380 nm. Low light levels in the UVR source used for measurement can also lead to difficultyin distinguishing between the transmitted UVR and the natural dark current of the

detector.The measurement of UPF on a clothing material can be carried out by measuring the

diffuse spectraltransmittance in vitro or by measuring the increase in exposure time required

to induce erythema or sun burn in vivo.

The preparation of the fabric prior to the UV transmission test includes the exposure of

specimen to laundering, simulated sunlight and chlorinated pool water, and to present in a

state that simulate the conditions at the end of two years of normal seasonal use, so that the

UV protection level finally stated on the label estimates the maximum transmittance of the

garment fabric during a two-year life cycle.


29/30

Page | 29

14. UV protection care labeling:Initiatives for developing standards related to UV protection started in the 1990s, and

standards related to the preparation of fabrics, testing and guidance for UV protection labelling

have been formulated by different agencies. Care labelling similar to fabric andgarment care

labels has been developed for UV protection, and standard procedures have been established

for the measurement, calculation, labelling methods and comparison of label values of textile

products.

Since 1981, the Skin Cancer Foundation, an international body, has offered a Seal of

Recommendation for the photo-protective products which includes sunscreens, sunglasses,

window films and laundry detergent additives, in accordance with AATCC TM 183 or AS/NZS

4399; the products recommended are reviewed annually.

UPF Transmission (%) Classification Grade

> 40 < 2.5 Excellent protection III

30-40 3.3 2.5 Very good protection II

20-29 5.0 2.4 Good protection I

Table(3): Grades and classification of UPF

UV labelling is an additional requirement besides other labelling requirements of garments

including Permanent Care Labels and Fibre Content labels. Apart from the UPF label, block

numbers can also be used based on the UV transmittance value in their respective UVR range.

Table 2 shows the various grades and the related protection factors for the textile materials.

The UPF value to be placed on the label is that of the sample, reduced by its standard error of

UPF values, and then rounded down to the nearest multiple of 5 but not greater than 50. A UPF

of 20 means that 1/20th, i.e. 5%, of the biologically effective UV radiation striking the surface

of the fabric actually passes through it.

15. Conclusion:The best technique for reducing UV exposure is to avoid sun exposure, but this is an

unacceptable solution to all. Recreational exposure accounts for most of the significant UVR

exposures of the population, and occupational exposure is also significant. However, there is

growing interest in reducing the UVR exposure of outdoor workers. This necessitates the

development of stronger UV absorbers which will be especially suitable for low UPF fibres,

which are highly preferred by the consumers. UVR exposure can be reduced by implementing

by behavioural changes such as avoiding sunlight at its maximum, using protection such as

hats, sunscreens, sun glasses, and clothing.


30/30

Woven fabrics can provide simple and convenient protection against harmful effects of UV

radiation if the necessary attention is paid to their engineering in the phase of a new product

development. There are several factors influencing UV protection properties of woven fabrics

like yarn construction (fibre type, twist, yarn packing factor), fabric construction with its

primary (type of weave, yarn fineness, warp/weft density, relative fabric density or fabric

tightness) and secondary (cover factor, open porosity, mass, thickness, volume porosity)parameters of fabric geometry, additives (dye, pigment, delusterant, optical brighteners, UV

absorbers), laundering and wearing conditions (stretch, wetness). The proper combination of

mention factors allows production of passive woven fabrics with high UV protection properties,

which may reduce risk associated with UV overexposure. For subject wearing garment made

from UV protected fabrics the information about how long he/she could be exposed to the

harmful UV rays before the serious skin damage occur, will be more useful, instead of knowing

UPF value of garment. UV exposure time is affected by several factors like subject skin type,

geographic position of subject, daily time or the sun position, the presence of clouds, altitude,

portion of skin covered by fabric, etc. However, nowadays, there is a trend to develop smart

textiles or active intelligent fabrics which, for example, could change their own colour independence on external stimulus like UV light (Vikova, 2004). Soon such smart textiles will be

developed which will warn the subject how long he/she could be on the sun, what is the

average UV index in a particular position, what is the UPF of wearing fabric in a particular

moment, when subject should use the shadow, etc.

16. References:1. D. Saravanan, UV PROTECTION TEXTILE MATERIALS2. Perkin S.W., Functional Finishes and High Performance Textiles3. Mallik S.K., Arora T., UV Radiations: Problems and Remedies4. Hatch K.L., Making a Claim that a Garment Fabric is UV Protective5. Anon, UPFAnalysis of Textile6. Achwal W.B., UV Protection by Textiles7. Polona Dobnik Dubrovski Woven Fabrics and Ultraviolet Protection8. http://en.wikipedia.org/wiki/Space_suit9. http://www.rei.com/learn/expert-advice/sun-protection.html
http://en.wikipedia.org/wiki/Space_suithttp://en.wikipedia.org/wiki/Space_suit

UV Protective Textile Material

Documents

Transcript of UV Protective Textile Material