PP Polymer

Polypropylene is full of tertiary carbon atoms which give oxidative and light stability problems. Stabilizer packages are therefore always included in fibers, with their small diameters and high specific surface. The polymer is hydrophobic. Special treatments or additions are required to make polypropylene dyeable. 

Polypropylene melts at about 175°C but is spun relatively hot, 75°C above its melting point. Polypropylene is often spun from large and long spinning holes (800-1500 xm, L/D = 3-5). It is evident that the low melting point is a limit for industrial applications. A further disadvantage of polypropylene is its low creep resistance. 

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One of the conveniences afforded by curing PPS is that a single uncured feedstock can give rise to an entire family of cured polymers. The flow rates, ie, the extent of cure, of the cured polymers are optimized for specific appHcations. Table 1 shows typical melt flow values of cured PPS polymers for various types of appHcations. 

Comonomers can be used to create a variety of polymer stmctures that can impart desirable properties. For example, even higher molecular weight PPS polymers can be produced by the copolymerization of a tri- or tetrafunctional comonomer (18). The resultant polymer molecules can have long-chain branching, which can be used to tailor the rheological response of the polymer to the appHcation. 

London,20th-22nd March 1991,Paper 5. 6124 NOVEL FOAMABLE PP POLYMERS Bradley M B Phillips E M HIMONT USA INC. 

Sulfar fibers are extruded from polyphenylene sulfide) or PPS by the melt-spinning process. The first PPS polymer was made in 1897 by the Friedel-Crafts reaction of sulfur and benzene. Researchers at Dow Chemical, in the early 1950s, succeeded in producing high-molecular weight linear PPS by means of the Ullmann condensation of alkali metal salts of p-bromothiophenol. 

Several Japanese and European companies have begun the production of PPS, some with a U.S. partner. The new decade should see the introduction of a number of new fibers and fiber products based on the PPS polymer. 

Fibers can be produced from a specific grade of PPS polymer. This polymer has the same outstanding heat resistance possessed by the grade of material used in injection molding compounds. As shown in Table VII, continuous filament PPS yarn has been exposed at 200°C for 60 days with only a moderate decrease in strength. 

The synthesis of PP-polymers has also been achieved by means of reductants other than those mentioned so far. For example, dialkyl hydrogen phosphonate in the presence of copper(i) chloride is an excellent reagent (Doorenbos, 1969a). 

S=0)—), but the phenyl ring appears to be unaffected. The core of the PPS polymer particles also remains unchanged under the oxidizing conditions studied, since depth profiling by Ar" " ion sputtering exhibited an increase in the sulphide concentration and a decrease in the sulphone concentration. 

FIGURE 3-4 Fast fracture strength at temperature for commercial fibers based on silicon compounds and alumina. PP = polymer pyrolysis, SG = sol gel, SS = slurry spinning, EDFG = edge defined film growth, CVD = chemical vapor deposition. Source DiCarlo and Dutta, 1995. 

Three main types of PP polymer types are used in household packaging ... 

Trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene Trioctyl phosphite Tris (dipropyleneglycol) phosphite antioxidant, PP film Tris (3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate antioxidant, PP polymers Octyl diphenyl phosphite antioxidant, pressure-sensitive adhesives BHA BHT 2,4-Bis [(octylthio) methyl]-o-cresol 4-[[4,6-Bis (octylthio)-s-triazin-2-yl] amino]-... 

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