**3.2.2 Properties of acetate fibres**

#### **Physical properties**

These fibres in no way resemble fibres of cellulose. Both cellulose diacetate and triacetate are relatively hydrophobic and thermoplastic. The standard regains of cellulose di – and triacetate are 5.0 and 2.5%, respectively. They hardly swell in water(Broadbent, 2001).

Cellulose diacetate is thermoplastic in the hot dyebath and care should be taken to ensure the goods are not subjected to stretching. They are approximately 40% weaker wet than dry, and their extensibility is increased by about 40% when wet. They are permanently glazed at temperatures above approximately 175C, soften at 205C and melt at approximately 230C. The low temperature of softening may be of advantage for embossed finishing (Trotman, 1984).

The mechanical properties of triacetate fibres are close to those of the secondary acetate but they do not lose a great deal of strength when wet. It gives fabrics with a firm crisp handle, less soft than that of the diacetate (Broadbent, 2001)..

#### **Chemical properties**

Both cellulose acetates are resistant to dilute solutions of acids but are sensitive to alkaline solution, which cause hydrolysis of the acetate ester to hydroxyl groups, especially at higher temperatures. The triacetate is more hydrophobic and more compact and crystalline than the diacetate and has better resistance to alkaline solutions and to solvents (Broadbent, 2001).
