Chemical process of covalent bonding Science of Tie Dye Chemical process of covalent bonding

History of Tie Dye Techniques Bandhani—from India; oldest tie-dye tradition still known to be practiced. The design is dots tied with thread before immersion dyeing. Shibori—Japanese used to elaborate kimonos African Tie Dye 1950’s USA

Chemical Bonds The types of bonds directly determine the properties of the dyes. The most permanent, wash-fast dyes are the most tightly attached to the fiber molecules. The requirements for forming chemical bonds are what determines the ingredients and method for each recipe for dyeing.

Types of Chemical Bonds Fiber Reactive Dyes (brighter, longer-lasting) --attach to fiber by the same strong covalent bonds that hold atoms within the dye molecule together. The dye actually becomes one molecule with the cellulose fiber molecule to which it attaches. Covalent bonds are formed by electron sharing between atoms.

What is a covalent bond? Covalent bonding is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds. In short, attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding.

Types of Chemical Bonds Direct Dyes includes “all purpose” dyes that are left in cotton that has been dyed with them; loosely associated with the fiber molecule through the property called substantivity, which is the tendency of the dye to associate with the dye without strong bonds. Substantivity is said to result from a combination of the relatively weak Van der Waals forces and some hydrogen bonding and colors tend to be not as bright.

van der Waals forces The van der Waals equation is an equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion and R-6 van der Waals attraction). In chemistry and physics, the name van der Waals force is used as a synonym for the totality of intermolecular forces. These forces, which act between stable molecules, are weak compared to those appearing in chemical bonding. Historically, the use of the name for the total force is correct, because the Dutch physicist J. D. van der Waals, who lent his name to these forces, considered both the repulsive and the attractive component of the intermolecular force.

Types of Chemical Bonds Disperse Dyes Used for synthetic fibers such as polester and work by being vaporized by the heat of an iron or heat transfer press and then condensing onto and into the fiber. They can also be induced to migrate into the fiber by boiling with a special carrier. Dye tends to rub off, though no visibly so, making it more allergenic than other types of dye.

Types of Chemical Bonds Vat Dyes such as indigo are trapped within the fiber by having been converted to a form that is insoluble in water. The vat dye is insinuated into the fiber while in a water-soluble form—a physical form of attachment and not a chemical bond. Blue jeans are vat dyed so fading happens.

Types of Chemical Bonds Naphthol Dyes held in fiber in a water insoluble form; widely used for Batik. This dye does not react to the heat of the wax however it is quite toxic and not commonly used.

Types of Chemical Bonds Natural Dyes these are an acid dye, which is why they will bond to wool and other animal fibers, but not to cotton. To improve attachments use metal ions to form a bridge between the dye and fiber; this is called mordanting. Cotton is typically mordanted with tannins in addition to metal ions.

To learn more… Cellulosics Dyeing by John Shore