1. Engineering of Fabrics for UV Protection
Presented by
Prakash Arun Khude
PhD Research Scholar, IIT Delhi
Department of Textile Technology
Indian Institute of Technology, Delhi

2. Introduction Light is very essential on earth.
Source of light on earth is SUN

3. U.V Radiations
Ultraviolet Radiations are electromagnetic rays with a wavelength between nm.
Solar UVR that reaches earth have wavelength between nm.

4. Classification Of U.V Rays
U.V rays has three regions depending upon wavelength:
Ultraviolet region – A (UVA) ( nm)
Ultraviolet region – B (UVB) ( nm)
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.

5. Melanoma
The 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.

6. Erythema
superficial reddening of the skin, usually in patches, as a result of injury or irritation causing dilatation of the blood capillaries.

7. Characteristics Of U.V regions
Wavelength
(nm)
Relative Intensity(%)
Av. Photon Energy(kj/mol)
UV-A
3.2
315
UV-B
2.4
350
UV-C
0.5
400

8. Factors Affecting Solar U.V Level
Sun angle
Geographical Position
Seasonal Effects
Clouds
Ozone
Scattering
Altitude
Time of day

9. Why UV protection’s necessary ?

10. Wearing sun protective clothing
Prevention
Using
umbrella,
hat
Applying sunscreen
Wearing sun protective clothing

11. Effects Of U.V radiations
Human Skin
The major effects of UV are
Sunburn
Erythema(skin reddening)
Skin cancer (Melanoma)
DNA damage.
Acceleration of Skin Ageing
Eye damage.
DNA damage

12. 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.

13. 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
EDM is the effective dose of UVR for protected skin

14. Ultraviolet protection factor
Textile’s UV protection performance is determined by ultraviolet protection factor
Classification
UPF
Approximate % UV blocked
Good UV protection
15-24
93.3%-95.8%
Very good UV protection
25-39
96%-97.4%
Excellent UV protection
40-50
97.5%-98%

15. Mechanism of UV transmittance
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.

16. Factors of UV protection
Fibre Chemistry
Fabric Construction, Porosity, Thickness and Weight.
Dye Concentration, Whitening agents, UV absorbers
Moisture content
Finishing chemicals

17. UPF Factors Cover Factor
To 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

18. FACTORS INFLUENCING THE UV PROTECTION OFFERED BY TEXTILES
Fiber type
Polyester, silk and wool fabrics are better UV blockers than cotton or rayon
Polyester fibers show a better absorption-due their aromatic nature

19. 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 thickness
Closed textured (have low porosity)hence low transmission of UVR.
Cover factor-UPF increases with the cover factor

20. Moisture content
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

21. Dyes Dyes have a considerable influence on UV permeability.
They absorb light in the UVR spectral region
Absorbing property of each dye is unique to that dyestuff
Their 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.

22. Color
The effect of colour on the UPF of samples with identical weaves and weights
Colors
Polyester
White 16
Pink 19
Green
Dark Red 29
Black 34
Color
Cotton
White 12
Azure 18
Royal 27
Black 32
Navy 37

23. U.V Absorbers
UV absorbers are colorless compounds with very strong absorption in the UV range of nm.
UV Absorbers incorporated into fibres convert electronic excitation energy into thermal energy.
They function as radical scavengers and oxygen scavengers.

24. UV Absorbers Selectively absorb UVR and convert it in to heat.
Cibatex UPF
It 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.

25. Special Finishing Agents
TiO2 particles
UV absorption of synthetics can be modified by pigmentation
This results in scattering of UV rays
They are wrapped up in the fiber and are fast to washing.
leads to a permanent improvement of UV protection
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 fastness

26. Standards of Measuring Of UPF
UV Standard 801
AS/NZS 4396/1996 EN

27. 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.

28. BRIEFING: