Presented at the 5th International Conference on Polyolefin Characterization (ICPC), 2014. Valencia, Spain.
Pilar del Hierro, Alberto Ortín, Benjamín Monrabal. Polymer Char, Valencia, Spain.
A new instrument for measuring the soluble/amorphous fraction in PP and PE resins (equivalent to the xylene solubles gravimetric method) has been developed, based on an automatic TREF (Temperature Rising Elution Fractionation) approach. The equipment is aimed at Quality Control laboratories in production plants, and can perform an analysis every 2 hours from a very representative sample of up to 4 grams of material.
The CRYSTEX QC does an automatic dissolution-crystallization-elution cycle using chlorinated solvent, combined with an infrared detector and a dual capillary viscometer, and no need of weighing, filtration or solvent handling. Besides the soluble fraction, the instrument also measures the ethylene content and intrinsic viscosity in both amorphous and crystalline fractions, as well as in the whole sample. The user only needs to put an approximate amount of 2-4 grams of sample in the equipment and the analysis proceeds automatically.
Optionally, a 42-vial autosampler is available, which works with 10 or 20 mL vials processing up to 400mg of material, allowing a large number of samples to be analyzed sequentially in an unattended manner.
A set of ethylene-propylene resins covering a broad range of amorphous fraction levels have been analyzed. Soluble fraction, intrinsic viscosity and ethylene content have been measured automatically by CRYSTEX QC, and the values obtained have been compared to the results applying standardized ISO methods. The correlations found were very good for all the parameters, while the precision of the CRYSTEX QC approach proved to be superior due to its full automation.