Page 111 - Handbook of Plastics Technologies

THERMOPLASTICS

THERMOPLASTICS 2.51

may build up on the cylinder wall, yielding parts with black marks. Residual stresses may
be reduced by higher mold temperatures or by annealing. Extrusion and blow-molding
grades of polysulfones are higher molecular weight, with blow molding melt temperatures
in the range of 300 to 360°C and mold temperatures between 70 and 95°C.
The good heat resistance and electrical properties of polysulfones allows them to be
used in applications such as circuit boards and TV components. 352 Chemical and heat re-
sistance are important properties for automotive applications. Hair dryer components can
also be made from polysulfones. Polysulfones find application in ignition components and
structural foams. 353 Another important market for polysulfones is microwave cook-
ware. 354
2.2.27.1 Polyaryl Sulfone (PAS). This polymer differs from the other polysulfones in
the lack of any aliphatic groups in the chain. The lack of aliphatic groups gives this poly-
mer excellent oxidative stability, as the aliphatic groups are more susceptible to oxidative
degradation. 355 Polyaryl sulfones are stiff, strong, and tough polymers with very good
chemical resistance. Most fuels, lubricants, cleaning agents, and hydraulic fluids will not
affect the polymer. 356 However, methylene chloride, dimethyl acetamide, and dimethyl
formamide will dissolve the polymer. 357 The glass transition temperature of these poly-
mers is about 210°C, with a heat deflection temperature of 205°C at 1.82 MPa. 358 PAS
also has good hydrolytic stability. Polyarylsulfone is available in filled and reinforced
grades as well as both opaque and transparent versions. 359 This polymer finds application
in electrical applications for motor parts, connectors, and lamp housings. 360
The polymer can be injection molded, provided the cylinder and nozzle are capable of
reaching 425°C. 361 It may also be extruded. The polymer should be dried prior to process-
ing. Injection molding barrel temperatures should be 270 to 360°C at the rear, 295 to
390°C in the middle, and 300 to 395°C at the front. 362

2.2.27.2 Polyether Sulfone (PES). Polyether sulfone is a transparent polymer with high
temperature resistance and self-extinguishing properties. 363 It gives off little smoke when
burned. Polyether sulfone has the basic structure as shown in Fig. 2.39.

FIGURE 2.39 Structure of polyether sulfone.

Polyether sulfone has a T near 225°C and is dimensionally stable over a wide range of
g
364
temperatures. It can withstand long term use up to 200°C and can carry loads for long
365
times up to 180°C. Glass-fiber-reinforced grades are available for increased properties.
366
It is resistant to most chemicals with the exception of polar, aromatic hydrocarbons.
Polyether sulfone can be processed by injection molding, extrusion, blow molding or
367
thermoforming. It exhibits low mold shrinkage. For injection molding, barrel tempera-
368
tures of 340 to 380°C with melt temperatures of 360°C are recommended. Mold tem-
peratures should be in the range of 140 to 180°C. For thin-walled molding, higher
temperatures may be required. Unfilled PES can be extruded into sheets, rods, films, and
profiles.

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