Polyphenylene sulfide structure

As regards the general behaviour of polymers, it is widely recognised that crystalline plastics offer better environmental resistance than amorphous plastics. This is as a direct result of the different structural morphology of these two classes of material (see Appendix A). Therefore engineering plastics which are also crystalline e.g. Nylon 66 are at an immediate advantage because they can offer an attractive combination of load-bearing capability and an inherent chemical resistance. In this respect the arrival of crystalline plastics such as PEEK and polyphenylene sulfide (PPS) has set new standards in environmental resistance, albeit at a price. At room temperature there is no known solvent for PPS, and PEEK is only attacked by 98% sulphuric acid. 

The palladium-catalyzed formation of sulfides can generate polyphenylene sulfide from a dithiol and a dibromoarene, or from 4-bromobenzenethiol (Equation (38)).17 In 1984 Asahi Glass obtained patents for the formation of this polymer in the presence of palladium and nickel catalysts.125,126 In addition, Gingras reported palladium-catalyzed couplings of aryl halides and thiols to form discrete phenylene sulfide oligomers.127,128 A number of polyphenylene sulfide wires, ranging from dimeric to pentameric structures, were prepared by the palladium coupling, albeit in modest yields ... 

Synthesis conditions and analytical results (Table II) are consistent with the hypothetical structures of sulfur lignin shown in Figure 2. Sulfur lignin is an aromatic thioether and it resembles polyphenylene sulfide derivatives (8). 

Polyphenylene sulfide parts are commonly bonded together with adhesives. A suggested surface preparation method is to solvent-degrease the substrate in acetone, sandblast, and then repeat the degreasing step with fresh solvent. The polyphenylene sulfide surface that forms next to a mold surface is more difficult to bond than a freshly abraided surface. This is possibly due to a different chemical surface structure that forms at high temperature when the resin is in contact with the metal mold surface. 

More recently, thermoplastics such as polyphenylene sulfide (PPS), polyether sulfone, and polyether ether ketone (PEEK) have entered the primary structures market in competition with thermosets. 

Thermoplastic matrices, is particularly attractive for automotive applications PP, for example, is economical, it can be processed quickly and can provide much better mechanical properties such as impact resistance, (i.e., bumpers, body panels [11]). PA are successfully applied in both under hood (i.e., inlet manifolds, radiator fans) and interiors (instrument panels, doors, front-end structures). For better temperature performance and mechanical properties, in some special application areas (motor racing sector, gearbox parts), polyether ether ketone and polyphenylene sulfide ( high performance thermoplastics ) are also used as matrices. 

Polyphenylene sulfide resins may have been made as byproducts in the research of Friedel and Crafts (1888) and later workers studying the preparation of diphenyl sulfide and related aromatic sulfur confounds. This early work has been reviewed and referenced in summaries by Lenz,(l) Gaylord ( ) and Smith. (2) However, it was not until 1948 that Macallum (4) prepared the resins by a method that defined their structure with reasonable certainty and yielded sufficient quantity to stu y some of their properties. 

Furthermore, the electrical properties can be adjusted by varying the matrix polymer and the filler distribution. Since the material concept allows for the use of almost any polymer matrix, the required material properties, for instance a high temperature resistance, can be provided by the use of polyphenylene sulfide (PPS) as a matrix polymer. The morphological structure, and thus the measured conductivity over the thickness, depend on the ratio of the melt temperatures and viscosities of both the polymer and metal alloy, whereas the passage conductivity is at a similarly high level of >4x10 S/m. 

Structural adhesives must have a glass transition temperature higher than the operating temperature to avoid a cohesively weak bond and possible creep problems. Modem engineering plastics, such as polyimide or polyphenylene sulfides, have very high glass transition temperatures. Most common adhesives have a relatively low glass transition temperature so that the weakest thermal link in the joint may often be the adhesive. 

Examples of polyphenylene sulhde blends not shown in other sections are listed in alphabetical order of the second polymer in the blend unless otherwise noted. Included in this section are polyphenylene sulfide blends not containing PA, PEST, or PO. When copolymer characterizatiOTi was not performed, the structure of the compatibilizing copolymer is inferred from the functionality location on each of the two polymers. In some cases, more than one type of compatibilizing copolymer may have formed. 

Figure P.17 General chemical structure of polyphenylene sulfide.

Polyphenylene sulfide is a partially crystalline polymer featuring an aromatic ring bridged by sulfur atoms in the 1,4-positions, as shown below. The form presented has the trade name of Ryton. Sample preparation of this material can be difficult, and the traditional KBr pellet method produces a poor-quality spectrum with Christiansen-type distortion (see Fig. 44b). A Csl pellet may be used instead to obtain an improved IR spectrum, suitable for quantitative analysis (see Fig. 44a). This polymer is usually used in conjunction with structural reinforcement additives, such as glass fibers or fillers such as PTFE (Teflon), and caution is necessary when attempting... 

The early chemical literature contains several references to materials either alleged or assumed to be polyphenylene sulfide. However, material characterization techniques in those early days were not as definitive as they are today. Consequently, structural assignments were not always completely accurate. Several of these references have been reviewed recently. a brief summary of these early investigations follows. 

He reported that polymers prepared in this manner generally contained more than one sulfur atom per repeat unit (x in the range 1.2-2.3). In addition the polymerization reaction was highly exothermic and difficult to control, even on a small scale.7 Certainly Macallum s work sparked an interest in polyphenylene sulfide (PPS) and triggered a series of investigations that eventually led to the commercial production of PPS. In 1954 Macallum sold his patents to Dow Chemical Co. where this polymerization scheme was studied further. However, the problems associated with the severe polymerization conditions and control of the exothermic reaction remained largely unsolved.9 Lenz and coworkers at Dow have studied the mechanism of the Macallum polymerizationlO and the structure of the polymer produced, ii The structure postulated consists of a crosslinked core to which are attached more or less extended, linear chains. 

Polyphenylene sulfide (PPS) has a rigid backbone chain consisting of recurring para-substituted benzene rings and sulfur atoms. The chemical structure is as follows ... 

S. Bahadur, C. Sunkara (2004) Effect of transfer film structure, composition and bonding on the tribological behaviour of polyphenylene sulfide filled with nano particles of TiOj, ZnO, CuO and SiC, Wear, to be published. 

In general, regularity in polymer structure and strong intermolecular forces favor high Tm values. Phenylene groups, such as those in polyphenylene, poly-p-phenylene oxide (PPO), and poly-p-phenylene sulfide (PPS), increase Tm values. 

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