Thermal expansion behaviour of hydrostatically extruded linear polyethylene

The thermal expansion behaviour of a series of oriented linear polyethylenes has been measured over the temperature range –180 to + 70° C. With increasing deformation ratio the axial thermal expansion coefficient approaches that of the crystal unit cell, and the transverse expansion coefficient approaches that of the average in the crystal a- and b-axis directions. The implications of these results are discussed in terms of present understanding of the structure of these materials.