Page 209 - Manufacturing Engineering and Technology - Kalpakjian, Serope : Schmid, Steven R.

Chapter 7 Polymers: Structure, General Properties, and Applications
materials. UHMWPE is used in parts requiring high-impact toughness and resistance
to abrasive wear; examples include artificial knee and hip joints.
Polyimides have the structure of a thermoplastic, but the nonmelting charac-
teristic ofa thermoset. (See also Section 7.7.)
Polypropylenes have good mechanical, electrical, and chemical properties and
good resistance to tearing. Typical applications include automotive trim and compo-
nents, medical devices, appliance parts, wire insulation, TV cabinets, pipes, fittings,
drinking cups, dairy-product and juice containers, luggage, ropes, and weather
stripping.
Polystyrenes generally have average properties and are somewhat brittle, but
inexpensive. Typical applications include disposable containers; packaging; trays
for meats, cookies, and candy; foam insulation; appliances; automotive and radio/
TV components; housewares; and toys and furniture parts (as a substitute for
wood).
Polysulfones have excellent resistance to heat, water, and steam; they have
dielectric properties that remain virtually unaffected by humidity, are highly resist-
ant to some chemicals, but are attacked by organic solvents. Typical applications
include steam irons, coffeemakers, hot-water containers, medical equipment that
requires sterilization, power-tool and appliance housings, aircraft cabin interiors,
and electrical insulators.
Polyvinyl chloride (PVC) has a wide range of properties, is inexpensive and
water resistant, and can be made rigid or flexible. It is not suitable for applications
requiring strength and heat resistance. Rigid PVC is tough and hard; it is used for
signs and in the construction industry (for example, in pipes and conduits). Flexible
PVC is used in wire and cable coatings, in low-pressure flexible tubing and hose,
and in footwear, imitation leather, upholstery, records, gaskets, seals, trim, film,
sheet, and coatings.

7.7 General Properties and Applications
of Thermosetting Plastics

This section outlines the general characteristics and typical applications of the major
thermosetting plastics.
Alkyds (from al/eyl, meaning alcohol, and acid) possess good electrical insulat-
ing properties, impact resistance, dimensional stability, and low water absorption.
Typical applications are in electrical and electronic components.
Aminos have properties that depend on composition; generally, they are hard,
rigid, and resistant to abrasion, creep, and electrical arcing. Typical applications
include small-appliance housings, countertops, toilet seats, handles, and distributor
caps. Urea typically is used for electrical and electronic components; and melamine
for dinnerware.
Epoxies have excellent mechanical and electrical properties, good dimensional
stability, strong adhesive properties, and good resistance to heat and chemicals.
Typical applications include electrical components requiring mechanical strength
and high insulation, tools and dies, and adhesives. Fiber-reinforced epoxies have
excellent mechanical properties and are used in pressure vessels, rocket-motor cas-
ings, tanks, and similar structural components.
Phenolics are rigid (though brittle) and dimensionally stable, and they have
high resistance to heat, water, electricity, and chemicals. Typical applications include
knobs, handles, laminated panels, and telephones; bonding material to hold abrasive