Interaction of dyes used for foods with food packaging polyester fibers

The effect of pH, temperature, dye concentration, and additives on the absorption of the dyes FD & C (Food, Drugs and Cosmetics) Blue 1 and Blue 2 upon poly(ethylene terephalate) (PET) and poly(butylene terephthalate) (PBT) subjected to different draw ratios (and, thus, resulting in different percentage crystallinities determined with DSC and wide‐angle X‐ray diffraction patterns) was investigated and a correlation between these parameters and the dye uptake was suggested. The absorption kinetics of the dyes on the polyesters were studied and a mechanism based upon the development of hydrogen bonds between the dyes and the end groups (COOH,OH) of the polyesters and the swelling of the network was proposed. Finally, an indirect measurement of the T g values of the polyesters was suggested based upon the different dyeing diffusion rates.