PP fibers

Properties. As prepared, the polymer is not soluble in any known solvents below 200°C and has limited solubiUty in selected aromatics, halogenated aromatics, and heterocycHc Hquids above this temperature. The properties of Ryton staple fibers are in the range of most textile fibers and not in the range of the high tenacity or high modulus fibers such as the aramids. The density of the fiber is 1.37 g/cm which is about the same as polyester. However, its melting temperature of 285°C is intermediate between most common melt spun fibers (230—260°C) and Vectran thermotropic fiber (330°C). PPS fibers have a 7 of 83°C and a crystallinity of about 60%. 

Fiber. High molecular weight linear PPS is weU-suited for fiber applications. The inherent properties of PPS (flame resistance, chemical resistance, and thermal stability) make PPS fiber highly desirable ia textile applications (128). PPS fiber has been designated by the U.S. Federal Trade Commission as a new generic class of materials called sulfar. Typical fiber properties are listed ia Table 7 (see High performance fibers). 

PPS fiber has excellent chemical resistance. Only strong oxidising agents cause degradation. As expected from inherent resia properties, PPS fiber is flame-resistant and has an autoignition temperature of 590°C as determined ia tests at the Textile Research Institute. PPS fiber is an excellent electrical iasulator it finds application ia hostile environments such as filter bags for filtration of flue gas from coal-fired furnaces, filter media for gas and liquid filtration, electrolysis membranes, protective clothing, and composites. 

To improve the interfacial bonding between the PP fiber and a cementitious matrix, commercially available PP fibers with different geometries were fluori-nated and the effect evaluated with regard to crack control, impact resistance (AC1 Committee 544 Report), and water absorption (ASTM C-948).M,34a In all cases, as seen in Table 16.13, fluorination improved the induced properties. 

It is well known that addition of PP fibers to concrete increases water absorption. It is, however, interesting to note that with fluorinated fibers, the water absorption is very similar to unfilled concrete, suggesting an improvement in wettability and chemical adhesion between fiber and matrix. 

Tablel6.13. Effect of Fluorinated and Unfluorinated Fibrillated PP Fibers on Certain...

A totally unexpected observation was made when the compression strength of (0.1% by volume) fluorinated fiber concrete increased from about 31 MPa (unfilled) to about 38.6 MPa (filled with fluorinated fibrillated tape). This observation is in contrast to published results31 that PP fibers do not enhance compressive strength. 

Table 16.14. Shear Bond Strengths between Concrete Matrix and Oxfluori-nated Monofilament PP Fibers with Different Oxfluorination Treatment Levels"...

Silicon-coated fiberglass Polysulfone resins Linear styrene block copolymers with butadiene/isoprene PP fibers... 

Tris(tribromoneopentyl) phosphate combines bromine and phosphorus in the same molecule it has been successfully incorporated into polypropylene. Studies have dealt with the question of synergism between bromine and phosphorus present in the same molecule.71,72 Fire-retardant efficiency without the need for antimony oxide opens the door for this product in the field of PP fibers and textiles. 

Because reactive types of flame retardants are polymer-specific, their application is limited. There are several reactive flame retardants, specifically produced and all different in composition. For example, there is a 25% pelletized concentrate of antimony pentoxide, bromine and polypropylene resin of various melt flow indices, which is geared to PP fibers for textiles and carpets,... 

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