High-density polyethylene refractive index

Hinton and Rider extended the notion of c-slip to a study of homogeneous plastic deformation in cold-drawn high density polyethylene. They noted that the direction of maximum refractive index (which they labelled as the current c-axis) swung round towards the tensile axis during the tensile deformation of specimens cut at a range of angles 0 to the IDD. 

TABLE 13 Refractive index (w) and specific molar refrac-tivity of high-density polyethylene (Marlex 50)... 

In general, the refractive index of isotropic polyethylene samples tends to increase as the density increases. This is reasonable given that the refractive index of the relatively dense ciystallites is signiflcantly greater than that of the noncrystalline regions. Low density polyethylene typically has a refractive index of 1.51, while high density polyethylene has a refractive index of about 1.54. 

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