Presented by Prakash Arun Khude PhD Research Scholar IIT Delhi Indian Institute of Technology Delhi Department of Textile Technology Introduction Light is very essential on earth Source of light on earth is SUN ID: 613670
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Slide1
Engineering of Fabrics for UV Protection
Presented byPrakash Arun KhudePhD Research Scholar, IIT Delhi
Indian Institute of Technology, Delhi
Department of Textile TechnologySlide2
Introduction
Light is very essential on earth.Source of light on earth is SUNSlide3
U.V
RadiationsUltraviolet Radiations are electromagnetic rays with a wavelength between 100-400nm.Solar UVR that reaches earth have wavelength between 290-400nm.Slide4
Classification Of U.V Rays
U.V rays has three regions depending upon wavelength:Ultraviolet region – A (UVA) (320-400nm)Ultraviolet region – B (UVB) (290-320nm)Ultraviolet region – C (UVC) (100 nm and 290 nm)
UV-C completely
absorbed by the ozone layer
UV-B and UV-A reach the earth’s surface and cause serious health problems, particularly skin cancer.Slide5
MelanomaThe most dangerous form of skin cancer, these cancerous growths develop when unrepaired DNA damage to skin cells (most often caused by ultraviolet radiation from sunshine or tanning beds) triggers mutations (genetic defects) that lead the skin cells to multiply rapidly and form malignant
tumors.Slide6
Erythemasuperficial reddening of the skin, usually in patches, as a result of injury or irritation causing dilatation of the blood capillaries
.Slide7
Characteristics Of U.V regions
Region
Wavelength
(nm)
Relative Intensity(%)
Av. Photon Energy(kj/mol)
UV-A
315-400
3.2
315
UV-B
280-315
2.4
350
UV-C
100-280
0.5
400Slide8
Factors
Affecting Solar U.V LevelSun angleGeographical PositionSeasonal EffectsCloudsOzoneScattering
AltitudeTime of daySlide9
Why UV protection’s necessary ?Slide10
PreventionSlide11
Effects Of U.V
radiationsHuman SkinThe major effects of UV are SunburnErythema(skin reddening) S
kin cancer (Melanoma)DNA damage.Acceleration of Skin Ageing
Eye damage.
DNA d
amageSlide12
Protection Factor
Protection factor is used to quantify the protective effect of material.SPF/UPF is the ratio of actual potential erythemal effect to the erythemal effect transmitted through the fabric.Larger the UPF/SPF, the more protective the fabric to UV radiation.Slide13
where
Sλ is Solar spectral irradiance in Wm-2nm-1 Eλ is relative erythemal spectral effectiveness
T
λ
is spectral
transmission of object
∆
λ
is band
width in nm
λ is
wavelength in nm
ED is effective dose of UVR for unprotected skin
ED
M
is the effective dose of UVR for protected skinSlide14
Ultraviolet protection factor
Classification UPFApproximate % UV blocked Good UV protection 15-2493.3%-95.8%
Very good UV protection25-39
96%-97.4%Excellent
UV protection
40-50
97.5%-98%
Textile’s UV protection performance is determined by ultraviolet protection factorSlide15
When light falls on a fabric or fiber
it will either reflected, transmitted or absorbed.The UV protection by textile is a function of the physio-chemical characteristics.
Mechanism of UV transmittance Slide16
Factors of UV protection
Fibre ChemistryFabric Construction, Porosity, Thickness and Weight.Dye Concentration, Whitening agents, UV absorbersMoisture contentFinishing chemicalsSlide17
UPF F
actorsCover FactorTo optimize the fabric construction so as to increase the skin cover by fibers, which can be achieved by spacing the yarns as closely as possible. UV transmittance can also be reduced by improving the absorption & reflection properties.
The more the cover factor, high is UPF.
Color (Dye)
Humidity
The
UPF
increased as the relative humidity increased, but this increase is fibre dependent, more pronounced in viscose & silk Slide18
Polyester, silk and wool fabrics are better UV blockers than cotton or
rayonPolyester fibers show a better absorption-due their aromatic natureFACTORS
INFLUENCING THE UV PROTECTION OFFERED BY TEXTILES
Fiber
typeSlide19
Fabric construction
Tighter the weave, the greater is protection as the transmission is reduced.With the same weave structure, the UPF of the fabric increases with its thicknessClosed textured (have low porosity)hence low transmission of UVR.
Cover factor-UPF increases with the cover factorSlide20
UPF increases as the relative humidity is raised
The effect of relative humidity is strongly dependent on the fiber type(natural swelling behaviour of fibers)Swelling-reduces space between ends and picks
Moisture contentSlide21
Dyes have a considerable influence on UV permeability.
They absorb light in the UVR spectral regionAbsorbing property of each dye is unique to that dyestuffTheir UV protection power is dependent on concentration. Binary mixture of monochlorotriazine dyes provide higher UPF than the individual ones.
Lengthening of the chromophoric
chain of two linked dyes owing to their interaction leads to an increase of the UPF of fabric.
DyesSlide22
ColorThe effect of colour on the UPF of samples with identical weaves and weights
ColorsPolyester
White
16
Pink
19
Green
19
Dark Red
29
Black
34
Color
Cotton
White
12
Azure
18
Royal
27
Black
32
Navy
37Slide23
U.V Absorbers
UV absorbers are colorless compounds with very strong absorption in the UV range of 290-400nm.UV Absorbers incorporated into fibres convert electronic excitation energy into thermal energy.They function as radical scavengers and oxygen scavengers.Slide24
UV Absorbers
Selectively absorb UVR and convert it in to heat.Cibatex UPFIt is UV
absorber with two reactive groups It is stable to repeated washing due to bi-reactive structure
Applied to cotton and cotton blend fibers
.
Cibafast
W
a
monosulphonated
benotriazole
derivative
Applied
to wool, silk, polyamide
fibers
and their blends
.
Are joined to the
fiber
by covalent bond in order to improve UV protection permanently.Slide25
UV absorption of synthetics can be modified by pigmentation
This results in scattering of UV raysThey are wrapped up in the fiber and are fast to washing.leads to a permanent improvement of UV protection
Special Finishing Agents
TiO
2
particles
Rayosan
finish
Rayosan
is a commercial UV-absorber
React with
fibers
like reactive dyes
Rayosan
C paste and CO liquid products
Used for finishing cellulose; polyamide
The
Rayosan
finish has a good washing fastnessSlide26
Standards of Measuring Of
UPFUV Standard 801AS/NZS 4396/1996
EN
13578-1Slide27
American Association of Textile Chemists and
Colorists (AATCC) Test Method 183 and American Society for Testing and Materials (ASTM) D 6544 for the rigorous evaluation of a fabric’s life cycle UV protection. Australian/New Zealand Standard 4399-which is the original globally recognized standard for sun protective clothing.
In addition,
American Society for Testing and Materials D 6603 for labelling
sun protective clothing. Slide28
BRIEFING
:Slide29
29