After printing the printed fabric is dried at for minute in a dryer. Remark: Our naphtholation process was not so sufficient. So printing becomes uneven. But we learn about the printing of cotton fabric with azoic dye.
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Classes[ edit ] Many kinds of azo dyes are known, and several classification systems exist. Some classes include disperse dyes, metal-complex dyes , reactive dyes , and substantive dyes. Also called direct dyes, substantive dyes are employed for cellulose-based textiles, which includes cotton.
The dyes bind to the textile by non-electrostatic forces. In another classification, azo dyes can be classified according to the number of azo groups. Trypan blue is an example of a direct dye , used for cotton. Physical properties, structure, and bonding[ edit ] As a consequence of п- delocalization , aryl azo compounds have vivid colors, especially reds, oranges, and yellows. An example is Disperse Orange 1. Some azo compounds, e. Most are salts, the colored component being the anion usually, although some cationic azo dyes are known.
The anionic dye adheres to these articles through electrostatic forces. Cationic azo dyes typically contain quaternary ammonium centers. Preparation[ edit ] Most azo dyes are prepared by azo coupling , which entails an electrophilic substitution reaction of an aryl diazonium cation with another compound, the coupling partner. Typical aniline partners are shown below. Since anilines are prepared from nitro compounds, some azo dyes are produced by partial reduction of aromatic nitro compounds.
Typical reactions include metal complexation and acylation. Illustrative azo dyes or their precursors Direct Brown
They are a commercially important family of azo compounds. Azoic dye is produced by the reaction of coupling component and diazo component. The procedure of producing azoic dye is different from that of producing other dyes. Azoic dye is also called ice color because it needs low temperature after the dye is produced. Preparation Most azoic dyes are prepared by azo coupling, which requires an electrophilic substitution reaction of an aryl diazonium cation with another compound-coupling partner. Azo coupling is an organic reaction between a diazonium compound and another aromatic compound that produces azo compound. In this electrophilic aromatic substitution reaction, the aryldiazonium cation is an electrophile and the aromatic compound is a nucleophile.
Azobenzene is the prototypical aromatic azo compound. It exists mainly as the trans isomer, but upon illumination, converts to the cis isomer. Typical aniline partners are shown below. Therefore, they are used as dyes , and are commonly known as azo dyes , an example of which is Disperse Orange 1.
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