Page 610 - Carrahers_Polymer_Chemistry,_Eighth_Edition

18 Polymer Technology

Today, nearly 10,000 American companies are active in the general area of synthetic polymers.
Following is a brief description of these companies divided according to their function.

Manufacturers: There are more than 200 major manufacturers of general purpose polymers
and numerous other manufacturers of specialty polymers.
Processors: Some companies manufacture their own polymeric materials for subsequent pro-
cessing, but the majority purchases the necessary polymeric materials from other com-
panies. Processors may specialize in the use of selected polymers, such as nylons and
polycarbonates, or focus on particular techniques of processing, such as coatings, fi lms,
sheets, laminates, and bulk-molded and reinforced plastics.
Fabricators and Finishers: The majority of companies are involved in the fabrication and

finishing of polymers, that is, production of the end products for industrial and general
public consumption. Fabrication can be divided into three broad areas: machining, form-
ing, and fashioning. Machining includes grinding, sawing, screwing, and other techniques.
Forming includes molding and other methods of shaping and joining by welding, gluing,
screwing, and other techniques. Fashioning includes cutting, sewing, sheeting, and sealing.
Fabrication sequences vary with the polymeric material and desired end product.

While much classic polymer technology was developed without the benefit of science, modern
polymer technology and polymer science are closely associated. The technology of fi bers, elasto-
mers, coatings, composites, drug delivery, and plastics is discussed in this chapter.
Chemistry is moving center stage in many areas of medicine, biology, engineering, environmental
science, and physics. While solid-state physics is traditionally based on silicon, polymers offer a much
wider vista of opportunities for application and fine tuning those applications. Some areas are based

on single crystals that may be small in our sight, but are large when compared to individual molecules.
Even single silicon wafers with a minimum pattern dimension of 200 nm are on the order of ten times
the size of individual molecules. Eventually, electronic, photonic, and stress–strain behavior individuality
can be placed into single giant chains creating chains that behave as entire assemblies behave today.

18.1 POLYMER PROCESSING
Polymer processing can be defined as the process whereby raw materials are converted into products

of desired shape and properties. Thermoplastic resins are generally supplied as pellets, marbles, or
chips of varying sizes and they may contain some or all of the desired additives. When heated above
their T , thermoplastic materials soften and flow as viscous liquids that can be shaped using a vari-

g
ety of techniques and then cooled to “lock” in the micro and gross structure.

Thermosetting feedstocks are normally supplied as meltable and/or flowable prepolymer, oligomers,
or lightly or noncross-linked polymers that are subsequently cross-linked forming the thermoset article.
The processing operation can be divided into three general steps—preshaping, shaping, and
postshaping. In preshaping, the intent is to produce a material that can be shaped by application of
heat and/or pressure. Important considerations include the following:
• Handling of solids and liquids, including mixing, low, compaction, and packing
• Softening through application of heat and/or pressure
• Addition and mixing/dispersion of added materials

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