Engineering of Fabrics for UV Protection

Presentation on theme: "Engineering of Fabrics for UV Protection"— Presentation transcript:

Engineering of Fabrics for UV Protection

Presented byPrakash Arun KhudePhD 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

U.V Radiations

Ultraviolet Radiations are electromagnetic rays with a wavelength between 100-400nm.Solar UVR that reaches earth have wavelength between 290-400nm.

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.

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.

Erythema

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

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

400

Factors Affecting Solar U.V Level

Sun angleGeographical PositionSeasonal EffectsCloudsOzoneScatteringAltitudeTime of day

Why UV protection’s necessary ?

Prevention

Effects Of U.V radiations

Human SkinThe major effects of UV are SunburnErythema(skin reddening) Skin cancer (Melanoma)DNA damage.Acceleration of Skin AgeingEye damage.

DNA d

amage

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.

where

S

λ

is Solar spectral irradiance in Wm

-2

nm

-1

E

λ 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 skin

Ultraviolet protection factor

Classification UPFApproximate % UV blocked Good UV protection 15-2493.3%-95.8%Very good UV protection25-3996%-97.4%Excellent UV protection 40-5097.5%-98%

Textile’s UV protection performance is determined by ultraviolet protection factor

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

Factors of UV protection

Fibre Chemistry

Fabric Construction, Porosity, Thickness and Weight.

Dye Concentration, Whitening agents, UV absorbers

Moisture content

Finishing chemicals

UPF Factors

Cover 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

Polyester, silk and wool fabrics are better UV blockers than cotton or rayonPolyester fibers show a better absorption-due their aromatic nature

FACTORS INFLUENCING THE UV PROTECTION OFFERED BY TEXTILES

Fiber

type

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 factor

UPF increases as the relative humidity is raisedThe effect of relative humidity is strongly dependent on the fiber type(natural swelling behaviour of fibers)Swelling-reduces space between ends and picks

Moisture content

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.

Dyes

Color

The effect of colour on the UPF of samples with identical weaves and weights

ColorsPolyesterWhite 16Pink19Green19Dark Red29Black34

Color

Cotton

White

12

Azure

18

Royal

27

Black

32

Navy

37

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.

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.

UV absorption of synthetics can be modified by pigmentationThis 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

TiO2 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 fastness

Standards of Measuring Of UPF

UV Standard 801

AS/NZS

4396/1996

EN

13578-1

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.

BRIEFING:

29