Explain why some fabrics get dyed very well while others do not. Cite specific t

Question

Explain why some fabrics get dyed very well while others do not. Cite specific types of non-covalent interactions. Explain why some fabrics get dyed very well while others do not. Cite specific types of non-covalent interactions. 2c. Explain why some of the fabrics get discussion should be based on the chemical strue specific ypes of non-sovalent interactions.that are relevant. Although you do not know the exact structure of the dye that came from your plant, you can speculate that it is polar becauss it is soluble in water, and that it probably has lots of oxygen atoms and possibly nitrogen atoms ( bonding), and that it may be ionic. dyed (no mordants) very well while others do not. Your tures of the fibers and dye and should cite the 3 nlon 6.6 (polyamide) PETE (polyester) orlon: (poly(acrylonitrile)) rayon) Note: viscose rayon comes from trees 8.wool (polypepti HOCHz CELLULOSE TRIACETATE CELLULOSE Polylpropylene) Poly (ethylene terephthalate) Polyester PETE most 0 O R carbo Poly(peptide) R is variable by amino acid Polyamide Poly(acrylonitrile) Nylon6,6 Polyamide 150 mL alun

Explanation / Answer

The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction. The reaction between dyes and fibres must take into account the various types of forces exerted by one molecule upon another. All dyeing mechanisms can be divided into following three groups.

Van der Waals’ forces:

Individually these are very weak forces, but collectively they are considered to be of sufficient strength to be the most important attractive forces between dye and fibre. These forces of attraction are known as Van der Waals’ forces. Disperse dyes are held in a polyester fibre by means of Van der Waals’ forces.

Hydrogen bond:

These forces of attraction are weak forces set up between certain atoms in the dyestuff molecule when they are close enough to other atoms in the fibre. One of these atoms is the hydrogen atom, hence the term “hydrogen bond”. Some direct and vat dyes are “hydrogen bonded” in cellulose fibres.

Hydrophobic bonding:

The hydrophobic groups, especially alkyl chains, tend to associate together and escape from aqueous environment. The effect due to two simultaneous causes-the Van der Waals’ forces between the hydrogen groups and the hydrogen bonds between water molecules. Each set of forces causes respective assembly of molecules or groups to associate together and to exclude the other. Hydrophobic bonds occur when both the fibre and dye contain a considerable portion of purely hydrocarbon, aliphatic or aromatic, as with some dyes applied on wool or most dyes applied on polyester. It is strictly not a new type of bond or intermolecular force.

Ionic bonding:

These bonds play an important part in dyeing fibre containing amino groups, i.e. wool, silk and nylon with anionic dyes. In the presence of water or dilute acids the amino groups become protonated:

NHCHCOOH      NHCHCOO

Acid dyes, being anionic in solution, are attracted at the positive site of the fibre. As the fibre forms zwitterions on ionization, a negative charge is also created on the fibre. This negative charge is responsible for attraction towards basic dyes which forms cationic dye ions in solution. However, basic dyes are now mostly applied on acrylic fibres which contain strong acidic sites. Due to ionization in acidic medium, negative charged sites are created in fibre which attracts cationic dye ions.

Covalent Bonding

Bonds resulting in very strong chemical forces that are not easy to break expect under serve conditions are called covalent bonds. The classic example is that of the combination of cellulose fibres with reactive dyestuffs, where the hydroxyl group in the cellulose is covalently bonded to a suitable atom in the reactive dye.

Comparision of relative dye fiber bonds:

Bonds type

Relative strength

Van der Waals’ force

1.0

Hydrogen bond

3.0

Ionic bond

7.0

Covalent bond

30.0

Table for fiber, dyes, dye-fiber bonds:

Fibre

Dye class having affinity

Types of dye-fibre bonds

Cellulosic: cotton, jute, rayon, etc.

Direct, vat, solublised vat and sulphur dye

Van der Waals’ forces and hydrogen bonding

Reactive dye

Covalent bonds

Protein/polyamide: wool, silk, nylons

Direct, acid,metal complex and basic dye

Ionic bond or electrostatic bonds

Reactive dye

Covalent bonds

Polyester

Disperse dye

Van der Waals’ forces and hydrogen bonding

Acrylic

Cationic

Ionic bond or electrostatic bonds

Disperse dye

Van der Waals’ forces and hydrogen bonding

Bonds type

Relative strength

Van der Waals’ force

1.0

Hydrogen bond

3.0

Ionic bond

7.0

Covalent bond

30.0

Related Questions

Navigate

• Browse (All)
• Browse E
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.