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 7C. 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 agi-tation; this formed the final product which was dried in an oven at 60C until a constant weight in order to get the pro-duct 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.