Page 256 - Mechanical Engineer's Data Handbook

244 MECHANICAL ENGINEER'S DATA HANDBOOK

Polystyrene Polypropylene

This plastic is not very useful as an engineering This is a low density, hard, stiff, creep-resistant plastic
material, but used for toys, electrical insulation, refrig- with good resistance to chemicals, good wear resis-
erator linings, packaging and numerous commercial tance, low water absorption and of relatively low cost.
articles. It is available in unmodified form, in transpar- Produced as filaments, weaves and in many other
ent form and opaque colours, high-impact form and forms, polypropylene may be glass filled. It is used for
extra-high-impact form, as well as in a heat-resistant food and chemical containers, domestic appliances,
grade. It can be stabilized against ultraviolet radiation furniture, car parts, twine, toys, tubing, cable sheath,
and also made in expanded form. It is attacked by and bristles.
many chemicals and by ultraviolet light.
Polyphenylene sulphide
Polysulphone This is a high-temperature plastic useful up to 260 "C
with room temperature properties similar to those of
This has similar properties to nylon but they are nylon. It has good chemical resistance and is suitable
maintained up to 180 "C (120 "C for nylon). Its optical for structural components subject to heat. Glass filler
clarity is good and its moisture absorption lower than improves strength and heat resistance. Uses are similar
that of nylon. Applications are replacement for glass to those of nylon, but for high temperatures.
for medical needs and chemistry equipment, circuit
boards, and many electrical components. Polyphenylene oxide

Polyvinyl chloride (PVC) This is a rigid engineering plastic similar to polysul-
phone in uses. It can be injection moulded and has
This is one the most widely used of all plastics. With mechanical properties the same as those for nylon. It is
the resin mixed with stabilizers, lubricants, fillers, used for car parts, domestic appliances, and parts
pigments and plasticizers, a wide range of properties is requiring good dimensional stability.
possible from flexible to hard types, in transparent or
opaque-colour form. It is tough, strong, with good 6.13.2 Thermosets
resistance to chemicals, good low-temperature charac-
teristics and flame-retardant properties. It is used for Alkyds
electrical conduit and trunking, junction boxes, rain-
water pipes and gutters, decorative profile extrusions, There are two main groups of alkyds: diallylphthalate
tanks, guards, ducts, etc. (DAP) and diallylisophthalate (DIAP). These have
good dimensional stability and heat resistance (service
temperature 170 "C; intermittent use 260 "C), excellent
Polycarbonate electrical properties, good resistance to oils, fats and
most solvents, but restricted resistance to strong acids
This is tough thermoplastic with outstanding strength, and alkalis. The mechanical properties are improved
dimensional stability, and electrical properties, high by filling with glass or minerals. The main uses are for
heat distortion temperature and low temperature electrical components and encapsulation. A wide
resistance (down to - 100 "C). It is available in optical, range of colours and fast-curing grades are available.
translucent and opaque grades (many colours). Poly-
carbonates have good chemical resistance and Amino resins
weathering properties and can be stabilized against
ultraviolet radiation. They are used for injection These are based on formaldehyde with urea or
mouldings and blow extrusions for glazing panels, melamine formulated as coatings and adhesives for
helmets, face shields, dashboards, window cranks, and laminates, impregnated paper and textiles. Moulding
gears. Polycarbonate is an important engineering powder is compounded with fillers of cellulose and
plastic. wood flour, and extenders, etc. Composites with