Basic Dye/Cationic Dyes | Properties of Basic Dyes | Dyeing of Acrylicwith Basic Dyes

Basic Dye

Basic dyes, these dyes are also known as cationic dyes.This a class of synthetic dyes , that act as bases and when made soluble in water , they form a colored cationic salt , which can react with the anionic sites on the surface of the substrate. The basic dyes produce bright shades with high tinctorial values, on textile materials.

Properties of Basic Dyes
Basic Dyes are cationic soluble salts of coloured bases. Basic dyes are applied to substrate with anionic character where electrostatic attractions are formed. Basic dyes are not used on cotton as the structures are neither planar nor large enough for sufficient substantivity or affinity. Basic dyes are called cationic dyes because the chromophore in basic dye molecules contains a positive charge. The basic dyes react on the basic side of the isoelectric points. Basic dyes are salts, usually chlorides, in which the dyestuff is the basic or positive radical. Basic dyes are powerful colouring agents.It’s applied to wool, silk, cotton and modified acrylic fibres. Usually acetic acid is added to the dyebath to help the take up of the dye onto the fibre. Basic dyes are also used in the coloration of paper.

Ionic nature:-The ionic nature of these dyes is cationic.

Shade range:-These dyes exhibit an unlimited shade range with high tinctorial strength, brightness and many colors are having fluorescent properties.

Solubility:-The solubility of these dyes is very good in water ,in the presence of glacial acetic acid.

Leveling properties:- These dyes have a very high strike rate , therefore leveling is poor.

Exhaustion :- cationic dyes exhaust at a variable rates, K values are used to define the exhaustion characteristics of the cationic dyes. K=1 means the fastest exhaustion , while K=5 means the slowest exhaustion. So while making the combination shades the dyes of similar K values must be used.

Affinity:- These dyes shows a very affinity towards wool , silk and cationic dye able acrylic, but have no affinity towards cellulosics. To dye cellulosics with basic dyes the material must be treated with suitable mordanting agents.

Fastness Properties:-
The light fastness is poor to moderate , but wet fastness is good.

Dyeing of Acrylic with Basic Dyes
The most common anionic group attached to acrylic polymers is the sulphonate group, -SO3-, closely followed by the carboxylate group, -CO2-. These are either introduced as a result of co-polymerisation, or as the residues of anionic polymerisation inhibitors. It is this anionic property which makes acrylics suitable for dyeing with cationic dyes, since there will be a strong ionic interaction between dye and polymer (in effect, the opposite of the acid dye-protein fibre interaction).

Advantages of Basic Dyes
•High Tinctorial strength
•Moderate substantivity
•Relatively economical
•Wide shade range
•Includes some of the most brilliant synthetic dyes
•Shows good brightness

Limitations of Basic Dyes
*Poor shade stability
*High acid content
*Coloured backwaters
*Very poor lightfastness
*Preferential dyeing

Modified Basic Dyes
These dyes, generally based on the chemistry of basic dyes, have longer molecular structures than traditional basic dyes, and thus have significantly improved properties.

Though still cationic in nature, modified basic dyes exhibit improved fibre coverage and substantivity on many furnishes,making them ideal for dyeing applications. Lightfastness is also improved considerably over traditional basic dye.

Key advantages over conventional basic dyes:-
•Excellent substantivity
•Better Lightfastness
•Covers all fibres
•Clear backwaters

What is Serviceability? | Factors of Serviceability

Serviceability
Serviceability is a relative term which is serviceable of performing useful service.A garment is considered to be serviceable when it is fit for its particular end use. After being used for a certain length of time the garment ceases to be serviceable when it can no longer fill its intended purpose in the way that it did when it was new. The particular factors that reduce the service life of a garment are heavily dependent on its end use. For instance overalls worn to protect clothing at work would be required to withstand a good deal of hard usage during their lifetime but their appearance would not be considered important. However, garments worn purely for their fashionable appearance are not required to be hard wearing but would be speedily discarded if their appearance changed noticeably. An exception to this generalisation is found in the case of denim where a worn appearance is deliberately strived for.

Factors of Serviceability:

If asked, many people would equate the ability of a fabric to ‘wear well’ with its abrasion resistance, but ‘wear’, that is the reduction in serviceable life, is a complex phenomenon and can be brought about by any of the following factors:

1. Changes in fashion which mean that the garment is no longer worn whatever its physical state.
2. Shrinkage or other dimensional changes of such a magnitude that the garment will no longer fit.
3. Changes in the surface appearance of the fabric which include: the formation of shiny areas by rubbing, the formation of pills or surface fuzz, the pulling out of threads in the form of snags.
4. Fading of the colour of the garment through washing or exposure to light. The bleeding of the colour from one area to another.
5. Failure of the seams of the garment by breaking of the sewing thread or by seam slippage.
6. Wearing of the fabric into holes or wearing away of the surface finish or pile to leave the fabric threadbare. Wearing of the edges of cuffs, collars and other folded edges to give a frayed appearance.
7. Tearing of the fabric through being snagged by a sharp object.