Procedure
2.2.1. Procedures of manufacturing cellulose acetate
Colors, dusts, and fats were removed from flax fibers and cotton
linters by washing with water and bleaching with 120 mL
of household bleaching agent (5% NaOCl & 5% NaOH), thoroughly
washing and, then, was followed by drying. A sample
of 35 g of each raw material was used. Acetic anhydride
(100 mL), glacial acetic acid (100 mL) and sulfuric acid
(10 mL) were mixed and the mixture was cooled to 7 C.
Flax fibers or cotton linters were added slowly to the previous
mixture with agitation to bring about the acetylation process;
this step produced the primary CA. Hydration of the primary
CA (viscous fluid) was achieved by diluting with 30 mL of
equal parts of concentrated acetic acid (99.8%) and sulfuric
acid (98%) and, then, the primary CA was allowed to age
for 15 h. The resulting viscous fluid was centrifuged in order
to separate the final product. Plasticizer (polyethylene glycol
600) was added as 25% by volume of the viscous CA with agitation;
this formed the final product which was dried in an
oven at 60 C until a constant weight in order to get the product
ready for use. Before being shaped, the product was
diluted with acetone to bring it into the form of a viscous fluid
which could be poured in a mold or on a smooth surface for
shaping.