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Polypropylene (PP), the largest consuming plastics, strengthens
its role in the continuous expansions of applications by some innovative
developments. The recent developments on metallocene catalysis have
made some interesting products. For instance, the grades with excellent
organoleptic characteristics enhance the applications into packaging
of sensitive food products on account of very good migration resistance.
The syndiotactic PP with excellent impact characteristic is another
product that became a reality due to metallocene catalysis. These
new grades are now offered in North America by Atofina, Basell,
Dow, Exxon and Equistar.
A very interesting new development recently presented at ANTEC 2002
by the converter Procter & Gamble using Metallocene catalysis
is about PP homopolymer having elastomeric properties. These new
products named as EHPP: Elastomeric Homo PP have elongation as high
as 2000% and flexural modulus as low as 1 MPA. These new products
were developed by Procter & Gamble in collaboration with University
of Ulm, Germany. EHPP has been produced in the range from very low
molecular weight(28,000) to very high molecular weight(6million),
from very low isotacticity(15%) to moderate isotacticity level of
60%. These products therefore have almost no crystallinity(<2%)
to moderate crystallinity of about 25-30%. This new developments
exploits strength of metallocene catalysis for development of controlled
stereo irregularities or defects to teh level of 12.5% compared
to 2% for the conventional isotactic MPP. Procter & Gamble has
evaluated these EHPP as replacement of TPE with great success. These
new products are likely to be introduced in North America by 2003,
after Procter & Gamble licenses the technology to any existing
PP producer.
Another interesting joint development work of a converter Forbo-Novilun
of flooring in the Netherlands with Atofina is of insitu
polymerization of Acrylics with syndiotactic PP to produce a very
transparent product with excellent toughness and flexibility. This
product is aimed at the tough wear layer for floor coverings.
Basell, the global leader of PP has evaluated the
5th generation Z-N catalysts on its 2 plants in Italy and the Netherlands.
The 5th generation catalyst system called "succinates"
is expected to produce PP with very broad MWD (Molecular Weight
Distribution). The broader MWD has been responsible to achieve excellent
stiffness/impact balance in heterophasic PP copolymer. Additionally,
enhanced process ability of these grades could be the target applications
to enhance toughness and thereby increase its market.
Cornell University has developed a living polymerisation
process with polypropylene and ethylene in which syndiotactic PP
block polymer is coupled with EP rubber block using titanium catalyst
system. This research project funded by ExxonMobil could open up
entirely a new window of opportunity for PP. The initial product
developed by this process is quite flexible and would be an interesting
TPO with a wide array of potential applications.
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