PPS Polyphenylene Sulphide

The selenium and tellurium analogues of PPS have also been synthesized and investigated [50]. As prepared, polyphenylene selenide (PPSe) and polyphenylene telluride (PPTe) are insulators with conductivities of less than 10 S m Exposure of PPSe to AsFs results in an insulator-to-conductor transformation, with a maximum conductivity in the range 0.1-1 S m being achieved. The thermal stability of PPSe is similar to that of PPS, while PPTe is decomposed by relatively mild conditions. 

Poly(sulphur nitride) is obtained as gold-coloured fibrous crystals from the solid-state polymerization of SN crystals. At room temperature its conductivity is in the region of 10 S m and this can be increased an order of magnitude by chemical modification with bromine. 

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Polyphenylene sulphide (PPS) (e.g. Ryton ) is a highly crystalline polymer with a melting point of 290 °C. It combines good mechanical properties with very high thermal and chemical resistance it is, moreover, self-extinguishing. It is, i.a., used as protective coating on metal surfaces. 

The theory has shown that an improvement of some 50% in mechanical properties should be produced by increasing fiber length from 0.3 mm to 2 mm. Several producers and specialist compounders of TPs have long fiber technology using nylons, polypropylenes, TP polyesters, and polyphenylene sulphide (PPS). 

Polyphenylenes The polyphenylene-based thermoplastics family includes polyphenylene ether (PPE), polyphenylene oxide (PPO), and polyphenylene sulphide (PPS). They have been one of the most successful groups introduced in the medium/higher range of cost/performance, with good heat stability and particularly good flammability properties. 

Examples of resins used include the nylon family (polyamide/PA), polypropylene (PP), polystyrene, and polyethylene. There continues to be growing applications for the higher-performance RTFs, such as polyphenylene sulphide (PPS) and polysulphone (PSU). Use is made of many other TPs (Chapter 3). 

The process can combine conventional glass fiber roving, aramid, or carbon fiber tows with TPs, most commonly polyethylene terephthalate (PET) and nylon (polyamide/PA). Other plastics used include polyphenylene sulphide (PPS), styrene-maleic anhydride (SMA), high-density polyethylene (HDPE), and polypropylene (PP). The TPs can take the form of pellets, chips, chunks, or shreds, and as the process uses hot-melt injection, no solvents or two-part systems are involved. Additives such as colorants and fillers can be used as required. 

The presence of moisture in the gas stream, which above 100 C will be present in the form of superheated steam, will also cause a rapid degradation of many fibres through hydrolysis, the rate of which is dependent on the actual gas temperature and its moisture content. Similarly, traces of acids in the gas stream can pose very serious risks to the filter fabric. Perhaps the most topical example is found in the combustion of fossil fuels. The sulphur that is present in the fuel oxidises in the combustion process to form SO, and in some cases, SO3 may also be liberated. The latter presents particular difficulties because, in the presence of moisture, sulphuric add will be formed. Hence, if the temperature in the collector were to be allowed to faU below the acid dew point, which could be in excess of 150°C, rapid degradation of the fibre could ensue. Polyaramid fibres are particularly sensitive to acid hydrolysis and, in situations where such an attack may occnr, more hydrolysis-resistant fibres, such as those produced from polyphenylene sulphide (PPS), would be preferred. On the debit side, PPS fibres cannot snstain continuous exposure to temperatures greater than 190 °C (or atmospheres with more than 15% oxygen), and where this is a major constraint, consideration would have to be given to more costly materials, such as polytetrafluoroethylene (PTFE). 

Another aromatic polymer within this family of thermoplastic polymers was the semi-crystalUne polymer polyphenylene sulphide (PPS), which offered better impact toughness and had a greater resistance to vacuum and thermal q cUng than its thermoplastic and thermosetting counterparts, Cogswell (1992). 

Thermoplastic materials which could be used in conjunction with silicone rubbers include nylons (polyamides), polybutylene terephthalate (PBT), polyphenylene sulphide (PPS) and polyethylene terephthalate (PET). 

Materials which may find favour in the future include polyphenylene sulphide (PPS) which has high temperature resistance and limited solvent sensitivity and polyether-ether ketone which has excellent temperature and solvent resistance, but, along with PPS, suffers from very high cost. 

Polyphenylene sulphide (PPS) was first produced in quantities that enabled its structure to be elucidated in 1948 but it was not until 1972 that the commercial exploitation of the material was begun by the Phillips Petroleum Company who named the product Ryton . As produced, it is a thermoplastic white powder, with a molecular structure based upon the repeat unit... 

Under high-humidity conditions, the chemical structure and low moisture absorption result in a very small dimensional change. Figure 7.10 shows very clearly both the small dimensional and weight changes for a glass-fibre-loaded LCP versus a glass-fibre-loaded polyphenylene sulphide (PPS) thermoplastic resin. 

Testing has taken place to compare LCPs with two materials used widely for electronic and telecommunications components glass-filled polyphenylene sulphide (PPS) and glass-reinforced polybutylene terephthalate (PBT). Over the temperature range 50-200 °C, the CTEs for the connectors made from the different plastics were 11 ppm/°C, for... 

Polyphenylene sulphides (PPS) are available in both thermosetting and thermoplastic versions depending on whether the polymer chain is branched or linear. This material is a white powder in its natural form but it can be formulated with fibrous fillers such as glass and asbestos and with mineral powders. 

High-performance engineering thermoplastics Fluoropolymers (PTFE, FEP, PVDF), liquid crystal polymers (LCP), polyphenylene oxides or ethers (PPO, PPE), aromatic polyketones (PEEK, PAEK), polyphenylene sulphides (PPS), polysulphones (PSU), polyether sulphones (PES), polyamideimides (PAI), polyetherimides (PEI), polyimides (TPI). 

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