Chemistry Reference
In-Depth Information
POLYPROPYLENE
CH
3
H
H
)
n
n
= 6000-20,000
(CH
2
CH
CC
CH
3
n
H
Special catalyst system (Ziegler-Natta) required
Three structures:
Isotactic
Syndiotactic
Atactic
Polypropylene was not developed until the 1950s when Ziegler and Natta
invented
coordination catalysts
. The structural difference between polyeth-
ylene and polypropylene is the methyl group in the propylene unit. Its
presence makes a difference because it makes possible three different poly-
mer structures:
Isotactic
, with all methyl groups in the same plane makes
the best plastic;
syndiotactic
, in which the methyl groups alternate in the
same plane; and
atactic
, with the methyl groups randomly in and out of the
plane is soft and rubbery. Polypropylene is used as film and in many structural
forms. It is also used as fibers for carpet manufacture and for thermal
clothing.
