Chemistry Reference
In-Depth Information
CHAPTER 9
Blends and Additives
9.1 BLENDS
Polymers are often blended together to obtain the desirable properties of each
component. It is more expedient to blend commercial polymers together than
to produce a new polymer. There are many commercial success stories based
upon this strategy, but it isn't necessarily true that properties are optimized.
Consider a handsome albeit lazy man married to a highly intelligent but
unattractive woman. They could have a beautiful intelligent baby if the baby
has the father's looks and the mother's brains. They could also have a baby
that is lazy and unattractive if the baby inherits the father's work ethic and the
mother's looks. So it can be with polymer blends. Much research is needed to
optimize a polymer blend. If one polymer is completely insoluble in the other
and there is no adhesion between the polymer domains, an article molded
from the blend can delaminate. For a good blend, one polymer is either
soluble in the other, a miscible blend, or if insoluble, an immiscible blend,
there needs to be good adhesion and dispersion of the polymer domains.
Polyphenylene oxide (PPO) is a high heat polyether made by oxidatively
coupling 2,6-xylenol. The polymer was invented by Allan Hay of General
Electric [1 - 3] and is the basis for the Noryl
®
product line.
CH
3
O
CH
3
x
PPO
PPO [4] is a high heat polymer and has a Tg of 208
∘
C. However, it is a
brittle polymer and is very difficult to process. By itself, it has limited com-
mercial value. However, PPO is miscible with polystyrene and addition of
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