Chemistry Reference
In-Depth Information
Synthesis and Characterization of Ethylene/Propylene
Copolymers in the Whole Composition Range
M
a
. Joaquina Caballero,
1
Inmaculada Suarez,
1
Baudilio Coto,
*
1
Rafael Van Grieken,
1
Benjamı´n Monrabal
2
Summary: The incorporation of comonomer molecules in the backbone of a homo-
polymer can influence the final properties of the material, decreasing its crystallinity
and the melting and glass transition temperatures, and increasing its impact
resistance and transparency. In the present work, ten ethylene/propylene copolymers
have been synthesized using a supported metallocene catalytic system covering the
whole composition range. Any desired composition was obtained by controlling the
feed composition during the reaction. These synthesized copolymers have been
characterized by different techniques in order to study the effect of the comonomer
incorporation onto their final properties. When the comonomer content is low, the
behaviour of the copolymer is similar to that of the corresponding homopolymer.
Nevertheless, if the comonomer content increases, the copolymer becomes more
amorphous (low crystallization temperature and soft XRD signals) and easily deform-
able, reaching a behaviour close to that corresponding to an elastomeric material. In
order to corroborate these results the samples have been characterized by TREF and
GPC-MALS. TREF analysis showed that copolymers containing less than 10% and more
than 80% of ethylene are semicrystalline, with elution temperatures typical of this
kind of polymers. Molecular weights are higher for homopolymers and they decrease
as the comonomer concentration increases, whereas the polydispersity index keeps
almost constant at the expected value for this kind of samples.
Keywords: ethylene/propylene copolymers; gel permeation chromatography (GPC);
metallocene supported catalysts; multiangle light scattering (MALS); temperature rising
elution fractionation (TREF)
Introduction
limited because PP toughness is low, espec-
ially at room and low temperatures.
[2]
This
is the reason why the copolymerization pro-
ducts of propylene with small amounts of
ethylene are of practical importance since
they allow to control the crystallization
processes.
[3]
The development of metallocene cata-
lyst technology has provided a rich set of
new copolymers materials with well-defined
microstructures.
In order to synthesize these products,
the combination of single site catalysts
with methylaluminoxane (MAO) as coca-
talyst for olefin polymerization throughout
the last two decades has been the subject
of intensive research, as a result of high
The thermoplastic polymer production with
elastomeric properties has been the focus
of scientists and manufacturers in the last
decade.
[1]
Polypropylene (PP) is a semi-
crystalline polymer widely used in packa-
ging, textile, and automobile industries
because of its good processability and pro-
perties. Nevertheless, its applications are
