Determination of dn/dc values for ethylene-propylene copolymers

dn/dc values for polyethylene and polypropylene have been measured. The effect of wavelength was analyzed by including previously available data. The same experimental procedure was used for ethylene-propylene copolymers in the whole composition range. Effects of wavelength and copolymer composition on dn/dc values were simultaneously analyzed for the ethylene/propylene system and an equation was proposed to correlate all the experimental data. Standard deviation between experimental dn/dc values and those calculated by means of the proposed equation is similar to experimental uncertainty and, consequently, this equation can be used to extrapolate a confident value of dn/dc for a given wavelength and copolymer composition.