High-temperature polymer poly sulfide

Over the past 20 years a considerable chemical research effort was devoted to developing new high temperature polymers. It is interesting to note that some of these materials are now finding new applications and solutions to old problems of processing through blending. A commercial series of products trade-named Tribolon XT has been announced which are based on an aromatic polymide (Upjohn s 2080) with Phillips poly(phenylene sulfide), trade-named Ryton. A recent publication (88) describes some of the unique characteristics of this new family of materials. 

The field of step-growth polymers encompasses many polymer structures and polymerization reaction types. This chapter attempts to cover topics in step-growth polymerization outside of the areas reviewed in the other introductory chapters in this book, i.e., poly(aryl ethers), dendritic polymers, high-temperature polymers and transition-metal catalyzed polymerizations. Polyamides, polyesters, polycarbonates, poly(phenylene sulfides) and other important polymer systems are addressed. The chapter is not a comprehensive review but rather an overview of some of the more interesting recent research results reported for these step-growth polymers, including new polymerization chemistries and mechanistic studies. 

Because the chemical stmcture of poly(phenylene sulfide) [9016-75-5] (PPS) does not fall into any of the standard polymer classes, the Federal Trade Commission granted the fiber the new generic name of Sulfar. The fiber has excellent chemical and high temperature performance properties (see... 

Montaudo and co-workers have used direct pyrolysis mass spectrometry (DPMS) to analyse the high-temperature (>500°C) pyrolysis compounds evolved from several condensation polymers, including poly(bisphenol-A-carbonate) [69], poly(ether sulfone) (PES) and poly(phenylene oxide) (PPO) [72] and poly(phenylene sulfide) (PPS) [73]. Additionally, in order to obtain data on the involatile charred residue formed during the isothermal pyrolysis process, the pyrolysis residue was subjected to aminolysis, and then the aminolyzed residue analysed using fast atom bombardment (FAB) MS. During the DPMS measurements, EI-MS scans were made every 3 s continuously over the mass range 10-1,000 Da with an interscan time of 3 s. 

The preparation of the related high molecular weight poly-1.4-phenylene sulfide has been accomplished by heating />-bromothio-phenolate salts in pyridine at 250° C (57). The commercially available polyethersulfones are reported to be prepared by condensation of 4.4 -dichlorodiphenyl sulfone with salts of biphenols in solvents such as dimethylsulfoxide at 150° C. The work of Bacon and Hill would suggest that both of these reactions might be carried out at considerably lower temperatures with copper (I) salts as catalysts. In addition, it has been demonstrated that copper (I) acetylides react quantitatively with aromatic iodides to yield tolanes (15, 77) therefore this reaction should also be the basis for a similar polymer forming reaction. 

Poly sulfide compounds that are compatible with epoxy resins are liquid elastomers at room temperature. The most significant commercial resin of this type is LP-3 from Toray. The predominant product is a mercaptan-terminated liquid polymer (LP) that contains approximately 37% bound sulfur (see Fig. 7.2). It is the high concentration of sulfur linkages that provides these products with their unique chemical properties. A sulfur odor is noticeable during processing, making ventilation important. 

Poly(ethylene oxide) is a linear polymer containing the donor oxygen atoms in the main backbone. Some other similar systems known to function as polymer electrolytes include simple poly ethylene glycol (PEG) [145], end acetylated PEG [146], poly propylene oxide (PPO) [ 147-148], poly(/ -propiolactone) [149], polyethylene succinate) [150-151],poly (ethylene adipate) [152],poly (ethylene imine) [153] and poly (alkylene sulfide) [154], Many of these form metal salt complexes. However, conductivities of the order of 10 s S cm are observed only at high temperatures. Table 5 summarizes this data. 

Poly(phenylene sulfide), prepared by the Phillips process, is a highly crystalline polymer that can be used for long times at high temperatures... 

A series of high molecular weight poly(thioether ketone)s (M = 55,000-100,000), eg, (24) and (25), have successfully been prepared from bis(4-mercaptophenyl) ether (4,4 -dimercaptodiphenyl ether) or bis(4-mercaptophenyl) sulfide (4,4 -dimercaptodiphenyl sulfide) by reaction with a series of ketone-activated aromatic fluoro-compoimds in the presence of anhydrous K2CO3. The polymers are amorphous and soluble in common organic solvents. They show TgS from 154 to 251°C and excellent thermal stability [temperatures of 5% weight loss (Tds) even above 500°C] (65). 

There are many polymers with high-temperature resistant fibers, most of them with textile properties (low tenacity, high elongation) (see Table 17.7). Their application is in insulation, hot gas filtration, and suchlike. Large products are meta-meta aramid (Nomex, Teijin-Conex) and polybenzimidazole (PBI). Smaller products are poly(phenylene sulfide) (PPS), several aromatic polyketones (for example poly(ether ether ketone), PEEK) and aromatic polysulfones see Reference 9, Chapters 8 and 9. 

The material can be melt processed because of the ether linkages present in the backbone of the polymer, but it stiU maintains properties similar to those of the polyimides. The high-temperature resistance of the polymer allows it to compete with the polyketones, polysulfones, and poly(phenylene sulfides). The glass transition temperature of PEI is 215°C. The polymer has very high tensile strength, a UL temperature index of 170°C,... 

Because of good thermal and hydrolytic stability, excellent mechanical and chemical stability, low cost, and commercial availability of sulfonated aromatic hydrocarbon polymers, recent research has focused on the synthesis and development of sulfonated aromatic hydrocarbon polymers specifically for high-temperature PEMFCs. Typical examples include sulfonated poly(ether ether ketone) (SPEEK) or poly(ether ketone ketone) (SPEKK) [1,2], sulfonated poly(ether sulfone) (SPSE) [3], alkyl sulfonated polybenzimidazole (PBI), sulfonated naphthalenic polyinrides (sNPl) [4-6], sulfonated polyCphenylene sulfide) [7,8]. Both post- and pre-sulfona-tion methods have been used in the past. Other than the post-sulfonation modification of aromatic polymers, recently, efforts have been dedicated to direct polycondensation from sulfonic acid containing monomers to synthesize sulfonated polymers [9]. The latter approach, namely pre-sulfonation, is widely applied because of the ease of controlling sulfonation degree and deactivated sites in the arylene backbones, which further avoid side reactions such as decomposition and hydrolysis of polymers resulted from the post-sulfonation method. 

Poly(phenylene sulfide) has been commercial since 1973 (Ryton Phillips Petroleum Go.) and as a crystalline polymer offers excellent chemical resistance [99]. It also offers good flammability resistance and high temperature resistance and stability. The major deficiency is the poor toughness and commercial products are fiberglass reinforced to counteract this... 

High-performance engineering thermoplastics have recently assumed increasing importance due to their exceptional properties at elevated temperatures. A number of such specialty polymers has been introduced into the market for high-temperature applications and examples of some of the outstanding ones are poly phenylene oxide (PPO), poly phenylene sulfide (PPS), polyether sulfone (PES), polyaryl sulfone (PAS), polyether ether ketone (PEEK), polyetherimide (PEI), and polyarylate (PAi). 

The most widely used and least expensive polymer resins are the polyesters and vinyl esters. These matrix materials are used primarily for glass fiber-reinforced composites. A large number of resin formulations provide a wide range of properties for these polymers. The epoxies are more expensive and, in addition to commercial applications, are also used extensively in PMCs for aerospace applications they have better mechanical properties and resistance to moisture than the polyesters and vinyl resins. For high-temperature applications, polyimide resins are employed their continuous-use, upper-temperature limit is approximately 230°C (450 F). Finally, high-temperature thermoplastic resins offer the potential to be used in future aerospace applications such materials include polyetheretherketone (PEEK), poly(phenylene sulfide) (PPS), and polyetherimide (PEI). 

Increased efficiency, including the need to more tightly pack the engine compartments, are driving the evaluations of high-temperature plastics for underhood applications, including poly(phenylene sulfide) (PPS), liquid-crystal polymers, and acetal copolymers. 

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