The established CRYSTEX technique, based on separation of the polymer amorphous fraction (rubber) by temperature cycle plus
filtration inside of a stainless steel vessel, provides very precise results in the determination of the xylene solubles percentage,
also known as xylene extractables (XS), in polypropylene. The full automation of CRYSTEX makes it a very convenient alternative
to manual (ISO 6427, part B) or other methods used in the industry.
Table 1: Summary of results obtained in each single CRYSTEX analysis (different samples).
The addition of a capillary viscometer as well as special IR sensor, for ethylene content determination, to the CRYSTEX instrument
creates a very powerful tool for the analysis of polypropylene copolymers. A schematic diagram of such an instrument is presented
in Figure 1, together with the parameters being measured directly: Whole sample at high temperature after dissolution cycle
and amorphous fraction (rubber) at low temperature after crystallization. All information available from a single experiment
is summarized in Table 1 for a series of different samples.
The capillary viscometer implemented into the CRYSTEX makes it possible to obtain the intrinsic viscosity [η] of the original
sample as well as of the amorphous and crystalline components. Polymers in a very broad range of viscosity can be measured
providing good precision better than 0.7% RSD.
Specific sensors responding to the absorption bands of methyl and methylene groups in the MID-IR are used in order to analyse
the initial polymer as well as the amorphous phase providing composition information in terms of ethylene percent (C2%). Full
composition range is covered with the same calibration keeping a very good precision of less than 0.1% of ethylene, in the
A precise and robust apparatus has been made available to fully characterize PP copolymers. The intrinsic viscosity and ethylene
contents of the whole polymer and its amorphous and crystalline fractions can be determined, as well as the soluble fraction
percentage, which directly relates to xylene solubles, in a single analysis using a fully automated instrument under computer
control. Thus a very comprehensive characterization of PP is achieved with a single instrument requiring very little operator
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