Molecular Characterisation of Polymers: expertise description

In order to be able to correlate synthesis variables and process conditions with material and rheological properties, one needs to characterize the molecular structure and composition of the obtained polymers. In this respect as well polyolefins (PE, PP, EPDM) as engineering plastics (polyamiden, polyesters, polycarbonates) and polystyrene copolymers can be very well characterized. Following information can be obtained: molar mass distributions and moments, branching parameters and chemical composition as function of molar mass, and solution viscosity. These values are often used as product specifications. Also the amount of gel present in polymers can be determined. This can be important to optimize production processes and improve final product properties. Concerning fractionation, several other methods are available to seperate e.g. a blend of polymers or a mixture of particles and polymers. If necessary the fractions can be collected for further chemical composition or structure determination. This expertise is very important to improve new product development, process conditions, and product properties.

Techniques

Size Exclusion Chromatography (SEC)(=Gel Permeation Chromatography (GPC)) with a variety of hyphenated detectors: refractive index, evaporative mass detection, UV, viscosimetry, LC Transform -FTIR and mass spectrometry, Multi angle laser light scattering (MALLS)
Viscosimetry(Ubbelohde)
Light scattering
Temperature Rising Elution Fractionation (TREF)
Fractionation techniques: CXS (Cold Xylene Solubles), Holtrup (solvent/non-solvent)
Ultracentifugation, Osmometry, Oil Additive Tests

Application

Molecular mass distributions and moments (Mn, Mw, Mz, polydispersity) 
Structure information: stars, regular/random branching, hyperbranched, long or short chain branching, dendrimer-like.
Structural variations as function of molar mass. Chemical composition as function of molar mass and of mixtures/blends relative, specific and intrinsic viscosity in solution, Huggins constant fractionation of blends, gel/polymer, copolymers, low versus high molar mass.