Polyethylene refractive index increments

Refractive index increments (dn/dc) were measured using the Chromatix KMX-16 differential refractometer and its heated cell at 145°C the values obtained are given in Table II. Refractive index Increments are essentially Identical for all the polyethylene types in a given solvent. 

A thermal treatment at 160°C for 1 hour has proved to be adequate for the removal of aggregates that persist at 145°C in TCB or ODCB solutions of polyethylene. Such a treatment enables one to obtain true solutions for use in SEC. Solution of polyethylene in aCN appears to be incomplete even after the 160 C treatment and aCN is therefore not recommended for use in SEC with polyethylene, despite the favorable specific refractive index Increment of its solutions. 

Table 3.2 Selected refractive index increments for polyethylene solution (for light scattering) ...

MGr (for polyethylene, for example) a slight increase of dielectric permeation at frequencies from 10 kHz to 60 MHz is observed s = 121 for non-radiated and s = 2.29 for polymer radiated by 640 kGr dose [163], This indicates the predominant influence of the anomalous dispersion curve run on the refractive index change n =/(/ ) and the possibility of at least one more part of increment and saturation tSn at high radiation doses of polymeric materials, isotactic PP, in particular, compared with doses indicated in this paragraph. 

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