Polypropylene fibers, coloration

Polypropylene fibers. A small part of the total fibers market (and therefore at the tail end of this section on fibers) is fiber grade polypropylene. The chemistry for polypropylene fibers is the same as for thermoplastics. The spinning mechanics are the same as that for nylon. Polypropylene fibers are particularly resistant to abrasion and chemicals, and they are lightweight. However, they dont take colors very well, and the materials have low softening points and low resilience (they wrinkle). The major applications for polypropylene fibers are carpet-face fiber and backing (because its tough) and rope (because it is strong and floats in water). 

Contrary to other synthetic fiber materials, polypropylene fibers cannot be colored by contacting them with an aqueous solution or dispersion of organic dyes. Due to its highly apolar nature, polypropylene is not able to interact with conventional dye molecules, so that it cannot take up any dye from the dye bath. 

A pertinent example of the application of Werner s coordination complexes to the coloring of synthetic fibers is exhibited in the case of polypropylene fibers containing nickel. The minute nickel particles have been evenly dispersed throughout the fiber by a chelate stabilizer/ so that upon dyeing with azo disperse dyes bearing the same o-substituents, as noted above, a fast deep color is formed (4)- This example,... 

Benzothiazines have been used in industry as dyes and as antioxidants of rubber and natural elastomers. They have been used widely to prepare azodye compounds with specific properties, such as water insolubility, which is useful in the dyeing of polypropylene fibers, and increased stability to gas fading.72,73 Several reports are concerned with the antioxidant properties of benzothiazines,74-77 and their use as color photography developers.78... 

The use of polypropylene fibers will grow depending on the ability of the textile industry to take advantage of properties that can be built into polypropylene. Some of these properties, such as toughness, low density, chemical stability, etc., are inherent to all polypropylene products. Others, like color stability and UV and thermal stability, are built into the product by additives. Still others, such as improved uniformity due to low-temperature extrusion of modified polymers, open new areas of use. The future growth of polypropylene in textiles depends on the ability of the suppliers and users to take advantage of all the properties to make unique products from polypropylene. 

In recent years, the quality of polypropylene fiber has been improved to enhance such properties as light weight, moldability, light stability, coloration, recovery feasibility, flame resistance, and antistatic propensity. It is increasingly used for automotive interior furnishing and parts. 

Because polypropylene contains no polar groups, it contains no dye sites capable of reacting permanently with dye molecules. Since monomers containing polar groups react with the catalysts used to make polypropylene, it has thus far proven difficult to incorporate dye sites during polymerization. Therefore, coloration of polypropylene fibers has been accomplished either by (1) modification of polypropylene as part of the fiber-manufacturing process to render the resultant fiber dyeable or by (2) the addition of pigments. 

There are many options and elegant methods for the dyeability modification of polypropylene fiber. The key to success is the cost, fiber properties, and color durability. With further research and market evaluation, it is quite hopeful that the dyeing problem of polypropylene fiber will be successfully resolved in the near future. 

Fiber finishes are normally added as lubricants or as antistats to the surface of fibers to facilitate fiber production and subsequent processing. Finishes are additives that may not achieve exactly what is intended. Low-molecular-weight mineral oils dissolve readily in polypropylene as do other materials added to the surface. It has been proposed that finishes may cause softening of the polymer surface [178], particularly at higher temperatures. Since polypropylene fibers are produced in colored form, the producer finish is not necessarily scoured off because it is for a dyeable fiber. The finish used by the fiber producer most frequently remains as part of the final product—for better or worse. Thus, the fiber finish must be considered not only as a processing aid but also as an additive. 

Mitsubishi Corp. has developed a Rovalpolypropylene fiber with good antistatic, anticorrosive, and color properties. It can be woven into carpet for computer rooms. Courtaulds Corp. invented an electrically conductive polypropylene fiber that has excellent chemical resistance. Unlike surface-treated conductive fibers, this polypropylene fiber provides uniform electrical conductivity across its filament. These conductive fibers are now offered in multifilament and monofilament forms at 12 and 18 tex. An antistatic polypropylene fiber of fine denier was also invented by researchers at East China University of Science and Technology, Shanghai, China. It can be used in domestic polypropylene carpets. With hypothermal agglomerates, it can be prepared in partially oriented polypropylene filament yarn for use in antipollution, antistatic applications such as work clothes for operating personnel in oil, chemical, and electronics industries [230,231]. 

Broda, J. (2004c). Polymorphic composition of colored polypropylene fibers. Crystal Groivth Design, Vol.4, Issue 6, pp. 1277- 1282. 

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