A pair of white polyester Ladies trousers which had been packed with polypropylene film had partly changed to yellow on storage in the warehouse in Turkey.
What could be the reason? And what could be done to prevent it?
The yellowing has possibly been caused by a constituent of the packaging film which has leaked out onto the fabric during storage and which can turn yellow under the conditions of storage ; most likely gaseous oxides of nitrogen. Similar effects can be seen on packaged articles stored in a shop window due to light fading of the leached constituent. This article discusses about the latter stages of the supply chain and concerns the packaging of dyes textiles / garments in plastic or polypropylene bags.
2. Full Article
2.1 Offending Component.
The offending component is the anti oxidant BHT (Butylated Hydroxy Toluene). The problem has also been observed on Cellulosic fabrics, where direct contact with BHT can destroy some reactive dye chromophores giving a severe shade change or bleaching effect.
The problem is well known, and has been investigated, in Japan.
2.2 Yellowing by BHT
The yellowing usually occurs on folded parts of the goods whose surfaces are exposed.
The problem does not just occur on white goods; but also on pastel coloured yarns, fabrics and finished goods.
To a certain degree, the yellowing is pH dependent. Alkaline finishes make the problem worse. Acidic finishes are recommended. Acid counteracts yellowing.
2.3 Diagnostic Test
As a diagnostic test, BHT can be removed from the fibre by dissolution in an organic solvent, such as DMF (dimethyl formamide).This is a useful test, but not a practical solution to the problem. BHT can also be detected by Gries reagent, which produces a red colouration in the presence of BHT.
The Gries reagent is a. 1:1 mixture of 1% (w/v) sulphanilamide in 2.5% (w/v) phosphoricacid .