Special polypropylene fibers

Special types of polypropylene (PP) fibers were developed in order to widen their application. The special fibers may be ranged into the 

Blending of polymers is one of the common methods used to prepare new polymer materials with new properties. Nowadays this approach is of paramount interest from the viewpoint of both science and industry. Blending of polymers has the following technical and economic advantages  

Blending of pol)uners is practiced also in the production of synthetic (chemical) fibers. Multicomponent fibers are usually prepared by mixing more than two polymers. In this case, the ordinary spinning equipment 

The most common combinations of PP are those with polyethylene (PE), polyamide (PA) and polyethyleneterephthalate (PET). The fibers spun out of these blends find numerous practical applications, especially [1, 3]  

The polyfibrillous fibers are suitable for the preparation of microfibers, with fineness 0.1-0.5 jjim, which are easily dyeable by dye solution and possess improved elastic properties compared to PP fibers [1]. 

---

Special thanks to Peter Froehling for his help in revising the manuscript and contributing the section on dyeable polypropylene fibers. 

Meh Spinning. This process is used to produce a broad range of polypropylene fibers ranging from fine, dtex (one denier) staple coarse continuous filaments. Hoiuopolyiners are almost exclusive used to produce fibers, although copolymer blends are used in some special applications. Processing conditions and polymer melt flow vary with the desired fiber type. 

Fabrics used in the automotive industry must meet exceptionally high requirements and be subjected to nonstandard tests that simulate the high-temperature and humidity conditions of light exposure [7]. Dyed fibers cannot meet these accelerated exposure specifications, which are met by specially stabilized, pigmented polypropylene fibers. The outdoor use of polypropylene fibers is expected to grow because of improved stabilizers. It has permitted grass-substitute products to be manufactured in a variety of forms. Many of them resemble carpets, which, until 1980, were used only indoors. 

A highly crystalline, glass fiber-reinforced, speciality polypropylene, marketed under the name Polyflll PP HC, has been developed by Polykemi AB, Ystad, Sweden. The glass fiber content in the polypropylene compound can be varied and enables the wall thickness to be customized and part weights to be commensurately reduced. 

Most manufacturing methods now available are similar to this but with the following modifications in the first step, the polymers for fibers are mainly made of polyester, nylon, or thein blends. AcryUcs and polypropylene are also sometimes employed. A regular fiber as thick as 0.01—0.4 tex (0.1—4 den) may sometimes be used instead of the special fiber to imitate the hard leather. 

P.R.176 provides very lightfast polyacrylonitrile spin dyeing products. The samples equal step 6-7 on the Blue Scale. Dry and wet crocking may affect the objects to a certain extent. P.R.176 is also used in polypropylene spin dyeing, especially for coarse textiles, such as carpet fibers, split fibers, filaments, bristles, or tape, but also for finer denier yams. A special pigment preparation for this purpose is commercially available. 1/3 SD samples tolerate exposure to up to 300°C for one minute or up to 290°C for 5 minutes. In terms of lightfastness, 0.1% colorations equal step 5-6 on the Blue Scale, while 2% samples match step 7. 

P.Y.177 which was introduced to the market a few years ago, is not listed anymore as a commercial product. It was a special-purpose pigment for polypropylene and polyamide spin dyeing. As a colorant for these media, P.Y.177 has the added advantage of enhancing the stability of the fibers. 

With respect to the other fibers in Table II, glass fiber and textile-grade multifilament polypropylene came into commercial production in the United States in 1936 and 1961, respectively (4). A number of generic types have not been mentioned in this brief outline of the foundations of the man-made fiber industry since their utilization in the United States is relatively small, either because they are utilized for specialized end uses or because they have not reached their full potential as yet. 

Hollow membrane fibers are required for many medical application, e.g. for disposable dialysis. Such fibers are made by usmg an appropriate fiber spinning technique with a special inlet in the center of the spinneret through which the fiber core forming medium (liquid or gas) is injected. The membrane material may be made by melt-spinning, chemical activated spinning or phase separation. The thin wall (15-500 xm thickness) acts as a semi-permeable membrane. Commonly, such fibers are made of cellulose-based membrane materials such as cellulose nitrate, or polyacrylonitrile, polymethylmethacrylate, polyamide and polypropylene (van Stone, 1985). 

Polyolefins. Low density polyethylene and polypropylene have been developed as sheet and hollow fiber mlcroporous membranes, respectively, for use In plasmapheresis. Polyethylene Is made porous by stretching the annealed film ( ), while polypropylene la made porous by coextruding hollow fibers with a leachable plasticizer. Neither membrane has been prepared with small pore dimensions suitable for protein rejection. These polyolefin membranes are characterized by good chemical stability, but require special surfactant treatments to make them wettable. Their low deformation temperature precludes the use of steam sterilization. Because they are extruded without the usual antl-oxldants and stabilizers, their stability la lower than Injection molding formulations of the same polymer. 

---