Page 528 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)

508 Chapter 19 Plastics and Composite Materials: Forming and Shaping

incoming material blended with thermoplastic rubbers, polyvinyl chloride compounds, ABS,
f' from 170° to 230°C and for molding are up to 60°C. Dryness of the ma-
and nylon to obtain specific properties.
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The temperatures for elastomer extrusion are typically in the range
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junction with extrusion to impart greater strength. Examples of extruded
...:.;,;_ ,,, terials is important for product integrity. Reinforcements are used in con-
elastomer products are tubing, hoses, moldings, and inner tubes.
Injection-molded elastomer products cover a broad range of applications,
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such as numerous components for automobiles and appliances.
Rubber and some thermoplastic sheets are formed by the
FIGURE l9.20 Schematic illustration calendering process (Fig. 19.20), Wherein a Warm mass of the compound
of calendering. Sheets produced by this is fed into a series of rolls and is masticated. The thickness produced is
process subsequently are used in thermo- typically 0.3 to 1 mm, but can be made less by stretching the material. It
forming. The process also is used in the then is stripped off at speeds on the order of 2 rn/s to form a sheet, which
production of various elastomer and
may be as wide as 3 m. The calendered rubber then may be processed into
rubber products.

various products, such as tires and belts for machinery. The rubber or
thermoplastics also may be formed over both surfaces of a tape, paper,
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fabric, or various soft or rigid plastics, thus making them permanently laminated.

Roll surfaces may be textured to produce a rubber sheet with various patterns and

designs.
Discrete rubber products, such as gloves, are made by dipping a metal form
(such as in the shape of a hand for making gloves) repeatedly into a liquid compound
that adheres to the form. A typical compound is latex, which is a milklike sap obtained
from the inner bark of a tropical tree. The compound is then vulcanized (cross-linked),
usually in steam, and stripped from the form and becomes a discrete product.
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Processing Polymer-matrix Composites
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As described in Chapter 9, polymer-matrix composites (PMCS) (also called
reinforced plastics) are engineered materials with unique mechanical properties,
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especially high strength-to-Weight ratio, stiffness-to-weight ratio, fatigue strength,

creep resistance, and directional ro erties. Because of their com lex structure rein-
forced plastics require special methods to shape them into consumer and industrial
products (Fig. 1921).

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parts and structures, particularly over the long range of their
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service life, can be challenging because of the presence of two
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sponses to the methods of processing (Section 9.2).
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lg, plastics and the time and care required make the processing
The several steps involved in manufacturing reinforced
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costs very substantial, and generally, they are not competitive
With traditional materials and shapes. This situation has neces-
sitated the careful assessment and integration of design and
HGURE |9_2| ReinfOrCed_p1aStiC Components for manufacturing processes (concurrent engineering) in order
a Honda motorcycle. The parts shown are front to take advantages of the unique properties of these compos-
and rear forks, a rear swing arm, a vvheel, and ites. This is done While minimizing manufacturing costs and
brake disks. maintaining long-range product integrity, reliability, and pro-