POLYPHENYLENE-SULFIDE PPS

PPS is a crystalline engineering plastic especially known for its high heat performance with heat deflection temperatures in excess of 260 °C. It has exceptional processability when injection moulded on conventional equipment. It also has outstanding dimensional stability and so is particularly suitable for precision moulding to severe tolerances. It can also be used as a replacement for high performance thermosets or metal, especially brass, in some applications. 

PPS is primarily used for surface mounted connectors and optical pick-up units but it is also replacing conventional materials in such applications as housings for mobile phones and other mobile information devices. New product grades include Ryton R-4-260 PPS from Chevron Phillips Chemical Co., which is a glass-filled PPS for electronics applications. Its properties include low flashing and low outgassing tendencies. 

Pol)rphenylene sulfide is an engineering polymer capable of use af elevafed femperafures. If has fhe following chemical sfrucfure  

PPS has a s)mimetrical, rigid backbone chain consisting of recurring para-substituted benzene rings and sulfur atoms. It is sold under the tradename of Ryton. Long-term exposure in air at 450°F (230°C) has no effect on the mechanical properties of PPS. 

PPS has exceptional chemical resistance. It is resistant to aqueous inorganic salts and bases and many inorganic solvents. Relatively few materials react with PPS at high temperatures. It can also be used under highly oxidizing conditions. 

Chlorinated solvents, some halegenated gases, and alkyl amines will attack PPS. It stress cracks in the presence of chlorinated solvents. 

Weak and strong alkalies have no effect. Refer to Table 2.31 for the compatibility of PPS with selected corrodents. Reference [1] provides a more detailed listing. 

The crystalline polymer, PPS (Ryton —Chevron Phillips Chemical Co., www.cpchem.com), has a high melting point (288 °C), outstanding chemical resistance, thermal stability, and fiammabifity resistance. It has no known solvents below 191—204 °C. The surface may be prepared as follows  

Wipe the faying surfaces with ethanol-soaked lint-free paper  

Clean off the dust with a stiff, bristled brush 

Polyphenylene-Sulfide (PPS) Developed in 1968, PPS was commercially introduced in 1973 (Ryton). This is a prominent engineering polymer, of the HT family, withstanding very high temperatures (arovmd 280 C). It is considered borderline between thermoplastic and thermosetting. Its basic stmcture consists of an aromatic core bonded to sulfur in the para-position. 

A = Excellent chemical resistance weight increase 3% or weight loss 0.5% and/or decrease in tensile stress at break 15% 

Butyl alcohol, n-butanol Butyl alcohol, n-butanol Calcium chloride, saturated Diesel 

Diesel oil Diethyl ether Ethanol Formic acid Freon, Frigen Frigen 113 

Elastic modulus (MPa) (tensile with 0.2% water content) 3312 n.a. 12420 

When blended with glass fibres and other fillers, PPS has a unique combination of properties including  

Automotive is the biggest market for PPS, accounting for over a half of total consumption. The main applications for PPS in automotive are electrical components such as cormectors, housings and coil formers, chemical pirmps, and car under-the-bonnet components such as brake systems, and electrical/electronic devices requiring high heat resistance, high dimensional stability, and corrosion resistance. 

Electrical electronics and industrial applications are also major markets for PPS. 

Weight Elong. Tensile strength Impact strength 

Resistant little or no change in weight small effect on mechanical properties generally suitable for practical use 

Fortron Hoechst Celanese Filler 40% Glass fiber 

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Fig. 11. Effect of polyolefin primers on bond strength of ethyl cyanoacrylate to plastics. All assemblies tested in accordance with ASTM D 4501 (block shear method). ETFE = ethylene tetrafluoroethylene copolymer LDPE = low-density polyethylene PFA = polyper-fluoroalkoxycthylene PBT = polybutylene terephthalate, PMP = polymethylpentene PPS = polyphenylene sulfide PP = polypropylene PS = polystyrene PTFE = polytetrafluoroethylene PU = polyurethane. From ref. [73].

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. 

Polyphenylene sulfide PPS is able to resist 450°F (232° C), and has good low temperature strength as well. It has low warpage, good dimensional stability, low mold shrinkage. Use includes hair dryers, cooking appliances, and critical under-the-hood automotive and military parts. 

PESA can be blended with various thermoplastics to alter or enhance their basic characteristics. Depending on the nature of thermoplastic, whether it is compatible with the polyamide block or with the soft ether or ester segments, the product is hard, nontacky or sticky, soft, and flexible. A small amount of PESA can be blended to engineering thermoplastics, e.g., polyethylene terepthalate (PET), polybutylene terepthalate (PBT), polypropylene oxide (PPO), polyphenylene sulfide (PPS), or poly-ether amide (PEI) for impact modification of the thermoplastic, whereas small amount of thermoplastic, e.g., nylon or PBT, can increase the hardness and flex modulus of PESA or PEE A [247]. 

Semi-aromatic PAs generally have a weak and slow absorption of water, a high rigidity, and are claimed to be more resistant to weathering and oils. For example, properties of polyphthalamides are intermediate between those of PA 66 and polyphenylene sulfide (PPS). 

Mat and continuous glass fibre reinforcements theoretically all the thermoplastics are usable in these forms, but up to now developments have concentrated on polypropylenes (PP), polyamides (PA) and thermoplastic polyesters (PET) fibre-reinforced PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. 

For the past 20 years, 1,4-dichlorobenzene has been used principally (35-55% of all uses) as a space deodorant for toilets and refuse containers, and as a fumigant for control of moths, molds, and mildews. A significant amount of 1,4-dichlorobenzene is exported (34%), with lesser amounts used in the production of polyphenylene sulfide (PPS) resin (approximately 27% of its total use), and as an intermediate in the production of other chemicals such as 1,2,4-trichlorobenzene (approximately 10%). Minor uses of 1,4-dichlorobenzene also include its use in the control of certain tree-boring insects and ants, and in the control of blue mold in tobacco seed beds (Chemical Marketing Reporter 1990 HSDB 1998). 

Production, Import/Export, Use, Release, and Disposal. Data on the production and uses of 1,4-dichlorobenzene in the United States are available (C EN 1995 Chemical Marketing Reporter 1990 HSDB 1998 IRPTC 1985 SRI 1996 TRI96 1998). Production has increased over the past decade and is projected to increase for the next several years due to an increased demand for 1,4-dichlorobenzene to be used in the production of polyphenylene sulfide (PPS) resins. Incineration is the recommended disposal method for 1,4-dichlorobenzene (HSDB 1998 IRPTC 1985). Disposal of this compound is controlled by... 

Nylon, polyacetal, polycarbonates, poly(2,6-dimethyl)phenylene oxide (PPO), polyimides, polyphenylene sulfide (PPS), polyphenylene sulfones, polyaryl sulfones, polyalkylene phthalates, and polyarylether ketones (PEEK) are stiff high-melting polymers which are classified as engineering plastics. The formulas for the repeating units of some of these engineering plastics are shown in Figure 1.15. 

Aromatic cyclic chains are more stable than aliphatic catenated carbon chains at elevated temperatures. Thus linear phenolic and melamine polymers are more stable at elevated temperatures than polyethylene, and the corresponding cross-linked polymers are even more stable. In spite of the presence of an oxygen or a sulfur atom in the backbones of polyphenylene oxide (PPO), polyphenylene sulfide (PPS), and polyphenylene sulfone, these polymers are... 

Aromatic polymers such as PS are readily attacked by chlorine bromine, concentrated sulfuric acid, and nitric acid. These reactions do not decrease the degree of polymerization of the polymers. Aromatic polymers with stiffening groups, such as PPO, polyarylsulfone, polyarylether ketone (PEEK), and polyphenylene sulfide (PPS), are more resistant to attack by corrosives than those with flexibilizing groups. 

Many semicompatible rubbery polymers are added to increase the impact resistance of other polymers, such as PS. Other comminuted resins, such as silicones or polyfluorocarbons, are added to increase the lubricity of other plastics. For example, a hot melt dispersion of polytetrafluoroethylene (ptfe) in polyphenylene sulfide (PPS) is used as a coating for antistick cookware. 

Polyphenylene sulfide (PPS) is a high-melting (290 C), injection-mold-able crystalline polymer with the following repeating unit ... 

High-performance polymers, such as polyphenylene sulfide (PPS) (Ry-ton), have excellent resistance to elevated temperatures, and this property can be enhanced by the incorporation of reinforcing fibers such as graphite fibers. 

Matrix materials for commercial composites are mainly liquid thermosetting resins such as polyesters, vinyl esters, epoxy resins, and bismaleimide resins. Thermoplastic composites are made from polyamides, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone, polyetherim-ide (PEI), and polyamide-imide (PAI). 

To illustrate this effect on colors, three single-pigment colors (blue, red, and yellow) were developed in three different resin systems. Blue and yellow were produced in acetal (POM), polyphenylene sulfide (PPS), and LCP. The red color was prepared in nylon 6,6, PPS, and LCP. The acetal and nylon resins are translucent while the PPS and LCP are opaque at the 3.2-mm sample thickness. In all three colors, the more translucent resins produced visually more brilliant, higher chroma colors than the more opaque resins with increased diffuse scattering. 

Many of the procedures used to prepare neutral CP precursors are commonly employed in the polymer industry. Hence, the polymerization methods of Ziegler-Natta, Friedel-Crafts, and nucleophilic displacements yield PA, PP, and polyphenylene sulfide (PPS), respectively. Other methods include Dields-Alder elimination, Wittig, and electrochemical coupling. The procedures used to prepare CPs in this vast arsenal are generally divided into two main categories chemical and electrochemical. 

There is a growing list of plastic materials capable of "meeting the challenge" in many applications involving hostile environments. Polyphenylene sulfide (PPS) is one of the leaders on this list and its environmental resistance has been studied extensively. This paper summarizes the performance characteristics of PPS in harsh environments. 

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