Natural fibres cannot be dyed with solvents. Man made fibres especially polyester is now-a-days
dyed with solvents. In case of polyester dyeing, it is seen that water is not attracted to both dye
molecules and fibre polymer. Because they are hydrophobic, so in polyester dyeing solvent can be
conventionally used as dyeing media. The dye is attracted to fibre surface and forms a layer on it.
When at high temperature the gap between polymeric chains in polyester fibre is increased the dye
molecules enter inside the fibre polymer system. It occurs at about 1300C temperature in case of
high temperature dyeing. We can reduce the temperature by using carriers. But, carriers are
phenolic compounds which may dissolve the polyester fibre. So, carrier is not used.
