Determination of polyolefin film properties from refractive index measurements

A technique is described for determining the density of polyolefin film from refractive index measurements. The procedure involves the measurement of the refractive indexes ( n x , n y , and n z ) along the three major axes of a film sample and conversion of the arithmetic average refractive index to a density value. The refractive index data are also used to calculate the per cent crystallinity and birefringence in the film.