Page 181 - Carrahers_Polymer_Chemistry,_Eighth_Edition

144 Carraher’s Polymer Chemistry

4. Cross-linked products are formed when the functionality of either reactant is greater than two.
Linear products are formed when the functionality of both reactants is two.
5. Condensation polymers tend to exist below their T at room temperature. They typically form
g
fairly ordered structures with lots of strong interactions between the various chains giving
strong materials with some, but not much, elongation when stretched. They are normally used
as fibers and plastics. They have high stress–strain ratios.

6. Condensation polymers include many of the materials referred to as synthetic or man-made
fi bers, including polyesters (especially poly(ethylene terephthalate) known as PET) and a vari-
ety of nylons (mainly nylon-66 and nylon 6).
7. A number of plastics are condensation polymers and include polyesters and nylons that are not
as highly oriented as the same materials in fiber form. Other plastics have been developed that

have outstanding heat stability, strength, or other properties that allows their wide use. These

plastics include PC, polyimides, PBI, polysulfides, polyethers, polysulfones, and polyketones.
8. PUs derived from reaction of diisocyanates and a variety of hydroxyl-containing materials form
the basis for foamed products and a variety of elastomeric materials.
9. Highly cross-linked condensation materials form the basis for a number of important adhesives
and bulk materials especially phenolic and amino plastics. Most of these products have formal-
dehyde as one of their starting reactants. These materials are thermosets that decompose before
melting so are more difficult to recycle than most condensation polymers that are thermoplas-

tics and do melt before decomposition.

10. Microfibers are simply fibers that are much thinner than typical fibers. They may be derived
from any fiber-producing material that is suitably treated to give thin fi bers.

GLOSSARY

Alkyds: Term originally used to describe oil-modified polyester, but now used for many poly-
ester plastics and coatings.
Allophanates: Reaction product of a urethane and an isocyanate.
Amino resins: Urea and MF resins.
Aramids: Aromatic polyamides.
A-stage: Linear prepolymer of phenol and formaldehyde.
Bakelite: Polymer produced by condensation of phenol and formaldehyde first by Leo

Baekeland.
Bifunctional: Molecule with two active functional groups.
Bisphenol A: 2,2’-Bis(4-hydroxphenol)propane.
B-stage: Advanced A-stage resin.
Carbamate: A urethane.
Carbamic acids: Unstable compounds that decompose spontaneously giving amines and car-
bon dioxide.
Carothers, W. H.: Inventor of nylon who also standardized much of the polymer nomenclature
we use today.
Carothers equation: DP = 1/(1–p)
n
Condensation reaction: Reaction in which two molecules react producing a third molecule and
a byproduct such as water.
Cyclization: Ring formation.
Dacron: Trade name for PET fi ber.
Drying: Cross-linking of an unsaturated polymer generally in the presence of oxygen.
Drying oil: An unsaturated oil like tung oil.
Engineering plastic: Plastics whose physical properties are good enough to permit their use as
structural materials; generally they can be cut, sawn, and drilled.

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