Colour Fixative: Keeping Colour Fresh and Long-Lasting

A good fabric is inseparable from a good colour fixative. The colour fixative is the key agent that ensures the colour of dyed fabric remains vibrant and long-lasting. This article will detail the principles of how colour fixative works and how to select the right one.

Principles of Colour Fixative Action

Formation of Insoluble Colour Precipitate

Some colour fixative, such as small molecular quaternary ammonium salts and polyamine resins, has cationic groups in its molecule that can form ionic bonds with the water-soluble anionic groups in the dye, much like two complementary puzzle pieces fitting together. This tight bond closes off the water-soluble groups in the dye, forming an insoluble colour precipitate. These precipitates then settle onto the fibre, like a strong armour surrounding the dye, greatly enhancing the colour fastness of the dyed fabric.

Film Formation and Encapsulation

Water-based polyurethane colour fixative acts like a considerate guardian. When adsorbed onto the surface of the fabric, under high heat, the fixative molecules undergo a self-crosslinking reaction to form a tough polymeric film on the surface of the fabric. This film acts as a dense protective layer, tightly encapsulating the dye on the fibre surface, preventing the dye from falling off through physical means, thus significantly improving the colour fastness of the dyed fabric. For silk fabric, the film formed by water-based polyurethane colour fixative stabilizes the colour of the silk, keeping it vibrant even after repeated washes.

Covalent Crosslinking Fixation

Epichlorohydrin derivatives, organosilicon-based and other reactive colour fixative works in a more direct manner. The reactive groups on this colour fixative act like magical glue, reacting with the active groups on the fibre and the dye, and through a "bridging" action, covalently bond the dye molecules securely to the fabric. This tight connection enhances the interaction between the dye and the fibre, making it more difficult for the dye to detach from the fibre, thereby improving the colour fastness of the dyed fabric. In cellulose fibre fabrics dyed with reactive dyes, reactive colour fixative can form stable covalent bonds between the dye and the fibre, effectively improving wash fastness and abrasion resistance.

How to Choose a Colour Fixative?

Green and Environmentally Friendly

For many years, resin-based colour fixative formed by the condensation of dicyandiamide and formaldehyde has been commonly used. However, research from the last century has revealed that such fixatives often contain high levels of free formaldehyde after finishing, which can cause skin irritation and ulcers when used in children's clothing. This has raised awareness and led to research into greener, more environmentally friendly colour fixatives. Many countries have strict regulations on both the environmental impact of additives and the formaldehyde content in textiles. Thus, colour fixative must not only be effective but also formaldehyde-free.

Effectiveness

Colour fixative is an indispensable auxiliary in textile processing, and the demand for it is huge, which unfortunately provides opportunities for subpar products to enter the market. The quality of these products may be unreliable, and using ineffective one can waste time, money, and resources, which could ultimately disrupt production schedules and cause unnecessary trouble.

Cost-effectiveness

Those in the textile industry know that the usage and demand for colour fixative is massive. A high cost-performance product can truly save costs and significantly reduce the financial burden on enterprises. When purchasing, it's advisable to choose products directly from manufacturers, ensuring both product quality and competitive pricing, which can greatly reduce operational costs.