Source: New Cloth Market
Many attempts to use water dyeing polypropylene (PP) fibers have not resolved the undyeability of the fibers very successfully. Because of the success of dyeing polyester with disperser dyes in supercritical fluid many attempts to apply this technique to dyeing PP fibers have been made. This paper discusses the advantages and feasibility of dyeing PP in supercritical fluid instead of water. Approaches of dyeing PP fibers in supercritical fluid and the dyes used in supercritical fluids are also reviewed.
Keywords: supercritical fluid, polypropylene fibers, dyeing
The worldwide consumption of polyolefin fibers, mainly PP has grown rapidly in the polymer market since 1980s. The growing demand for PP fibers can be explained by their several intrinsic, advantageous properties, namely easy process ability, low specific gravity, almost zero water adsorption, good chemical resistance, good antistatic character as well as wide availability and low cost.
PP fiber has a non-polar, aliphatic structure with its high crystallinity and high stereo-regularity which are responsible for the good physical properties of the material. PP fibers are difficult to dye since their structure does not contain dye sites to which certain kinds of dyes will bind. To improve the dyeability of PP fibers, the primary mission is to investigate the solvents capable of penetrating the PP structure so as to carry a dyestuff into the penetrated fibers. Since conventional dyeing medium---water does not resolve this successfully.
Fiber modifications without deterioration of the positive characteristics of PP fibers have been tried to make conventional water-dyeing possible, but most of them have not been successful till now. The application of new polymer additives changed the positive characteristics of PP fibers. The high cost of blending PP fibers with other fibers made the technology unsuitable for commercial use.
Originally published in New Cloth Market, March-2011