The UVR ( ultra violet radiation ) protective’s of sunscreens, sunglass, hats and clothing
have been subjected to considerable research for some time and in recent years extended to
the protection provided by shade strures.
In recent years, there has been an increasing interest in this protective properties of
clothing against the harmful effects of ultra violet(UV)radiation. This stems primarily from
the fact that the intensity and frequency of the UV radiation has increased over the last few
years due to rapid industrialization all over the world, indirectly affecting the ozone
protective layer…..
Ultra violet radiation
Sunlight consists of a wide range of different wavelengths of radiation. Sunrays reach the
surface of the earth at a wavelength between190-300nm.radition between190-400nm is
called a UVR consisting of three ranges of rays differing in their wavelengths i.e., UV-A rays,
UV-B Rays and UV-C rays.

Sun protection properties depend on the extent to which a woven or knitted fabric transmits absorbs or reflects UV radiation.

  • UV-C (100-280nm): it doesn’t have significant effects on the skin health since it has
    very shortest wavelength.
  • UV-B (280-380nm): these rays have shorter &high energy rays which effect the
    melanin in deeper layer of skin& causes skin thickening, sun-burnt and also skin
    cancer.
  • UV-A (320-400NM):ITS Longer energy radiation penetrates deeper into skin
    &damages DNA that result in sink cancer.

 

LABELING OF SUN PROTEACTIVE CLOTHING
UPF range UV protective category Protective time

15-24 Good protection 4-5 hrs
5-39 Very good protection 5-7 hrs
40-,50 Excellent protection More than 5 hrs

Incidence of damage to skin is further expected to increase by an annual rate of 7-10 per cent per
annum. However, this can be avoided by the use of sun protective textiles.
UPF (ultra violet protection factor ) concept
UPF is the measure of ability of the textile fabric to block UVR from passing through it and reaching
the skin. It is the safety factor of the fabric. Higher the UPF value, more the protection. Table1 gives
the rating scheme for the purpose of labeling the sun protective clothing capacity of garments.A
person wearing a garment with higher UPF can be exposed to direct sunlight for longer periods
without any UVR effect on the skin.

UV PROTECTION BY TEXTILES
Sun protection properties depend on the extent to the which a woven or knitted fabric transmits,
absorbs or reflects UV radiation. But the transmission, absorption and reflection are turn
dependent on the *fiber, fabric construction (thickness and porosity) and finish. Following figure
shows a number of factors that play a key role in the transmission and absorption of UVR by fabrics.

 

There are two possibilities of reducing UV transmittance by fabrics:

  • By reducing porosity through modification of construction.
  • By improving the absorption and reflection properties of fabric.

Factors affecting UPF of sun textiles some parameters that effects the UV-absorption
characteristics are :

  • Fiber properties
  • Fabric characteristics
  • Chemical processing

FIBER PROPERTIES
Among the natural fibers, grey cotton shows good protection as the natural pigments, waxes and
pectin act as UVR absorbers. In comparison, scoured and bleached cotton offer poor protection.
Wool provides maximum protection, while silk is intermediate between the two fibers. Synthetic
fibers I general are all the better UV Absorbers. By the same logic, aromatic due to its aromatic
structure. By the same logic, aromatic polyamides show better absorption than aliphatic
polyamides. Acrylic show low UPF due to the Di-pole Interaction of the nit rile group , pigmented
viscose fibers show better absorption & lower transmittance than lustrous fibers.

Among the natural fibers, grey cotton shows good protection as the natural pigments, waxes and pectin act as UVR absorbers.

FABRIC CHARACTERISITICS

Usually lightweight and loosely woven fabrics are preferred in hot outdoor situations; but these
provide minimum protection. UPF improves as the weave becomes tighter; weight goes upper and
with more thickness. Porosity and cover factor of the fabric have been shown to be the important
factors in sun protection.

FABRIC CHEMICAL PROCES

Absorption of the fabrics ca be efficiently increased by use of selected dyes, fluorescent-
whitening agents and by means of UV absorbers. These products have chromospheres
systems that absorb very effectively, in the UV region, enabling them to maximize the
absorption of UV radiation & minimize the transmittance of UV radiation on textiles.
Dyes used: as the spectral region of all dyes extends to the UV region (9290-400nm), all dyes acts
UV absorbers. Studies show that for a given color, darker the shade (navy blue, black, olive shades),
higher the protection. Recent research works report an increase in UV protection of cotton textiles,
when dyed with selected reactive, direct &vat dyes. Since all these dyes consist of aromatic
structure, it shows good UPF range.
FWA(florescent whitening agent): FWA’S are applied to fabric during laundering to enhance
whiteness of textiles by including fluorescence by UV excitation & visible blue emmsion. FWA’S
have excitation maxima in the range of 340-400nm and hence have been known to improve UPF of
textiles in case of white fabrics.
Finishing with UV absorbs: UV absorbers include all organic and inorganic compounds, which
preferentially absorb UV radiation. Besides, they should meet other criteria such as:

  • Absorb effectively throughout the UV region(280-400nm).
  • Be UV stable itself
  • Dissipate the absorbed energy in such a way so as to cause no degradation (or) color change
    in the medium it protects. E.g. titanium-dioxide deserves special mention.

UV absorbers are the derivatives of one of the thee different structure given below:

  • O-hydroxyl benza phenone
  • O-hydroxyl phenyl benzotriazole
  • 0-hydropzy phenyl triazine.

UV absorbers are now available that are like colorless dyes & are applicable with dyes by most
of the usually methods such as exhaust or pad batch method.
E.g.: commercialized UV absorbers include raysoan, tinofastcel, and ciba geigy.

TESTING OF SUN PROTECTIVE TEXTILES
Testing for the UV protection factors (UPF) enables retailers and manufacturers to determine
how much protection their clothing provides. The higher the factor , the greater the protection
it offers. Australian and new Zealand standard associations are defined as show in the table(1)

Test method: in vitro testing involves the use os a spectrophotometer in the rage of 280-400nm
to calculate the UPF of the fabric & rating is given as shown in table (1)
Application : the area of most apid consumption of sun protective textiles has been reports in
geo-textiles, packaging tsxtiles, protection textiles and agricultural textiles. Textiles such as
awnings, tents, hats, umbrellas, shoes ,baby-carrier covers,beach cannabis provide simple and
protective textiles include various articles in the field of protective purpose, medical texiles and
geo-textiles.

CONCLUSION
The various features discussed above show that it is possible to engineer textiles with the
required degree of protection depending on the end use requirements. Using the correct fiber,
fabric weave, construction and right finish, it is now possible to make UV safe materials, hence
,apart from sun protective clothing, the other innovative textile products will be able to open
up new markets and new horizons for the textile industry.