Polyolefins: Determination of Molecular Weight and Branching Structure by GPC/SEC

G. Heinzmann, B. Tartsch,
Viscotek, a Malvern Company

Polyethylene and Polypropylene are so-called Polyolefins. They are produced in large amounts every year. Depending on the process and catalyst used linear or branched polymers can be produced. In case of e. g. Polyethylene there are at least three polymer types: HDPE (High Density Polytheylene), LDPE (Low Density Polyethylene) and LLDPE (Linear Low Density Polytehylene). HDPE and LLDPE are made of linear or only slightly branched macromolecules with a high level of crystallinity. They form a dense structure in the final product. LDPE is made of highly branched molecules that form a final structure with low density due to a low degree of crystallinity. To analyse the different Polyethylene structures a High Temperature GPC/SEC-System is used with Triple Detection (Low Angle Light Scattering, Viscosity Detection and Refractive Index Detection). With such a system the molecular weight distribution and branching structure of polyolefins can be determined. Therefore it can easily be analysed what kind of structure a polyolefin sample has.

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