Surface Modification of Cellulose Acetate with Cutinase and ...

Surface Modification of Synthetic Fibres - Introduction
In the laboratory, nylon 6,6 can also be made using adipoyl chloride instead of adipic. It
is difficult to get the proportions exactly correct, and deviations can lead to chain
termination at molecular weights less than a desirable 10,000 Daltons. To overcome this
problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an
exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C, the
salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the
chains into yarn, so to combat this, acetic acid is added to react with a free amine end
group during polymer elongation to limit the molecular weight. In practice, and
especially for 6,6, the monomers are often combined in a water solution. The water used
to make the solution is evaporated under controlled conditions, and the increasing
concentration of "salt" is polymerized to the final molecular weight (Kohan, 1992).
3.2. Polyamide 6,6 fibres properties
Despite of all the excellent properties exhibited, nylon fibers present low hydrophylicity
and low reactivity with the most usual finishing and colouring agents. Coating finishing
effects are difficult to obtain when hydrophobic polyamide fabrics are used. Recent
studies clearly indicate that the modification of synthetic polymers with enzymes is an
effective and environmentally friendly alternative to chemical methods using alkaline
products (Silva et al., 2004).
4. Acrylic
Acrylic fibers are synthetic fibers made from a polymer (polyacrylonitrile) with an
average molecular weight of approximatly 100,000 Dalton. To be called acrylic the
polymer must contain at least 85% acrylonitrile monomer (Greenley, 1989). Typical
comonomers are vinyl acetate or methyl acrylate. The polymer is formed by free-radical
polymerization. The fiber is produced by dissolving the polymer in a solvent such as
N,N-dimethylformamide or aqueous sodium thiocyanate, metering it through a multihole
spinnerette and coagulating the resultant filaments in an aqueous solution of the
same solvent. Washing, stretching, drying and crimping complete the processing.
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