Vat dye displays no substantivity towards cellulose but with the help of suitable reducing agent and alkali convert the insoluble vat dye to its soluble leuco form results in change of colour – it is ture.
vat dye displays no substantivity towards cellulose but with the help of suitable reducing agent and alkali convert the insoluble vat dye to its soluble leuco form results in change of colour. it is
a – true,
b – false?
Yes, it is absolutely true, because vat dye are not proper substantivity towards cellulosic materials. but some reducing agent or alkali are used to convert proper soluble leco form. as a results it gives even dyeing in case of cellulosic (cotton) materials. therefore, option (a) is correct✅.
It can be converted insoluble to soluble form with the help of vatting process. so, this is the reasons, vatting process is required and it is very important before dyeing. vat dye have good affinity specially for a cellulose (cotton) materials. vatting process is very necessary steps to required before dyeing.
You know that, vat dye are substantively for (cotton) cellulosic materials. thats why, reducing agent are used in vat dyeing. most commonly reducing agent such as, sodium dithionite (Na2S2O4) it’s helps to easily convert insoluble vat dye to soluble leuco form.
these type of dyes is used from very long time in textile process house or plant, specially for dyeing of cellulose materials. vat dye is windly used for colouration of denim, jeance and cotton materials. vat dyeing process is very complex and costly as compared with other dyeing methods such as reactive dyes, basic dyes, and disperse dye.
Properties of vat dye
first properties of vat dye is, it is insoluble in water. if I m taking about about the particle size of vat dye, you know that it is very small particle size. vat dyeing process is done, in alkaline condition, it is maintain PH [12-14]. vat dye mostly belong to indigo, and anthraquinone class. vat dyes can’t be directly applied on cotton material for dyeing. in vat dyeing process, first need vatting process. and after vatting process is done then it can apply on textile cellulosic materials for colouration. after dyeing it gives different shade. wet fastness is very good but rubbing fastness is not proper. wet fastness is very good around [4-5]. rubbing fastness is not proper. Sometimes, this dyes are also apply on wool and silk material for colouration and for printing. after this dyeing, dye are entrapped inside the fiber and it is not easy to come out during any process and any treatment. this type of dyeing process is very expensive.