Page 208 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

Section 7.6 General Properties and Applicatrons of Thermop|ast|cs

period (e.g., bearings, cams, gears, bushings, and rollers), impellers, wear surfaces,
pipes, valves, shower heads, and housings.
Acrylics (such as PMMA) possess moderate strength, good optical properties,
and weather resistance. They are transparent (but can be made opaque), are generally
resistant to chemicals, and have good electrical resistance. Typical applications include
lenses, lighted signs, displays, window glazing, skylights, bubble tops, automotive
lenses, windshields, lighting fixtures, and furniture.
Acrylonitrile-butadiene-styrene (ABS) is rigid and dimensionally stable. It has
good impact, abrasion, and chemical resistance; good strength and toughness; good
low-temperature properties; and high electrical resistance. Typical applications include
pipes, fittings, chrome-plated plumbing supplies, helmets, tool handles, automotive
components, boat hulls, telephones, luggage, housing, appliances, refrigerator liners,
and decorative panels.
Cellulosics have a wide range of mechanical properties, depending on their com-
position. They can be made rigid, strong, and tough; however, they weather poorly
and are affected by heat and chemicals. Typical applications include tool handles,
pens, knobs, frames for eyeglasses, safety goggles, machine guards, helmets, tubing
and pipes, lighting fixtures, rigid containers, steering wheels, packaging film, signs,
billiard balls, toys, and decorative parts.
Fluorocarbons possess good resistance to high temperature [for example, a
melting point of 327°C for Teflon], chemicals, Weather, and electricity. They also
have unique nonadhesive properties and low friction. Typical applications include
linings for chemical-processing equipment, nonstick coatings for cookware, electri-
cal insulation for high-temperature wire and cable, gaskets, low-friction surfaces,
bearings, and seals.
Polyamides (from the words poly, amine, and carboxyl acid) are available in
two main types: nylons and arafnids:

° Nylons (a coined word) have good mechanical properties and abrasion resist-
ance. They are self-lubricating and resistant to most chemicals. All nylons are
/oygroscopic (absorb water); the moisture absorption reduces desirable mechan-
ical properties and increases part dimensions. Typical applications include
gears, bearings, bushings, rollers, fasteners, zippers, electrical parts, combs,
tubing, wear-resistant surfaces, guides, and surgical equipment.
' Aramids (aromatic polyamides) have very high tensile strength and stiffness.
Typical applications include fibers for reinforced plastics, bulletproof vests,
cables, and radial tires.

Polycarbonates are versatile. They have good mechanical and electrical proper-
ties, high impact resistance, and they can be made resistant to chemicals. Typical
applications include safety helmets, optical lenses, bullet-resistant window glazing,
signs, bottles, food-processing equipment, Windshields, load-bearing electrical com-
ponents, electrical insulators, medical apparatus, business machine components,
guards for machinery, and parts requiring dimensional stability.
Polyesters (thermoplastic polyesters; see also Section 7.7) have good mechani-
cal, electrical, and chemical properties; good abrasion resistance; and low friction.
Typical applications include gears, cams, rollers, load-bearing members, pumps, and
electromechanical components.
Polyethylenes possess good electrical and chemical properties; their mechanical
properties depend on composition and structure. Three major polyethylene classes
are: (1) lou/ density (LDPE), (2) /vig/9 density (HDPE), and (3) ultra/vig/v molecular
weight (UHMWPE). Typical applications for LDPE and HDPE are housewares,
bottles, garbage cans, ducts, bumpers, luggage, toys, tubing, bottles, and packaging