YELLOWING OF TEXTILES DUE TO ATMOSPHERIC POLLUTANTS

Over the past two three decades the problem of yellowing of textiles has become progressively more widespread.

It would be wrong to regard yellowing as a phenomenon arising from a single cause.

There are more than 20 different ways in which white or pale-coloured textiles can undergo this undesirable change in appearance.

The critical factors identified are:Access to hindered phenolAccess to air and NOx

pHAuxiliaries MoisturePackaging

In the case of indigo-dyed textiles there is the risk of the dyestuff being destroyed due to environmental influences. This irreversible destruction of the dyestuff is caused, amongst others, by an interaction of ultraviolet radiation, ozone & nitrogen oxide -“photochemical smog”. However, noxious gases may effect a destruction of the dyestuff even without ultraviolet radiation being involved. The degradation products of the indigo are usually yellow; therefore we also speak of yellowing during storage of the indigo.

The critical factors identified are:

The interior of the pile is protected against detrimental influences by its relative inaccessibility.

Due to the extreme ring dyeing of the warp yarn, the indigo dyestuff situated on the surface is highly accessible to noxious gases, such as NOx and O3.

This phenomenon is, for instance, observed when looking at the folded edges of made-up jeans. In a pile of folded jeans, the folded edges are particularly affected since they are especially exposed to light & air.

ATTACKING AGENTSOzone O3 :

Ozone is the strongest oxidizing agent after fluorine. In organic chemistry it serves to detect C-C double bonds. The general bleaching effect of ozone on indigo is well-known. Therefore the indigo dyestuff is also used as an indicator dyestuff in detection systems (e.g. Drager) which serve to measure the ozone concentration.

Nitrogen oxides Nox :

Nitrogen oxides are also referred to as “nitrous gases”. Nitrogen oxides are mainly composed on nitrogen monoxide & nitrogen dioxide. They are known to be highly aggressive agents.

PROBLEMS CAUSED, AMONGST OTHERS, BY NOXIOUS GASES :

Yellowing of optical brighteners due to

nitrogen oxides / ozone.

Destruction of natural rubber by ozone

Changes of shade caused by nitrogen oxides

Yellowing of polyurethane fibres due to

nitrogen oxides & sulphur dioxide

Destruction of indigo by ozone and nitrogen

COUNTER - MEASURES :

Storage of the textiles in a controlled environment.

Optimum ventilation of the store rooms (circulating air). Nox is heavier than air and accumulates on the ground.

Packing e.g. in polyethylene foil that does not contain any migrating, light-inhibiting stabilizers.

Do not expose goods to sunlight.

Protective finishing with

AQUASORB-OZ & Powersil-NOZ

MECHANISM OF YELLOWING OF INDIGO-DYED TEXTILES DUE TO AIR POLLUTANTS, SUCH AS OZONE & NITROGEN OXIDES  Ultraviolet radiation UV ozone O3 nitrogen oxides Nox. Short wavelength portion partly formed

of the sunlight by UV & Nox e.g. from the combustion of  fossil fuels

photochemical smog formation of aggressive radicals

Radical attack against the double-bonded, conjugated indigo system

H

H

Indigo

Formation of peroxide & other radicals destruction of the C-C double bond formation of mostly yellow degradation products are

N

COOH

HH

N

O

O

Phenylglycine(Colourless)

Isatine(Yellow)

N

NO

O

It is a quaternary ammonium softener used to protect indigo dyed fabric against ozone & NOx fading .

Economical & Ecofriendly.

Stable silicone emulsion

Imparts excellent softness and better softening effect than conventional amino fluid

Protect Indigo Dye from Ozone fading

Eco friendly

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