Rolling and annealing of polyethylene

Abstract Modifications of microstructural and mechanical properties of polyethylene (PE) have been investigated by many authors, but nearly always on drawn polymers. Only a few papers deal with rolling of polymers. The aim of this work is to study the changes in morphological and mechanical properties due to cold-rolling, and the evolution of these same properties with thermal treatment after coldrolling. High density polyethylene (HDPE) with various rolling ratio (0—390%) is analyzed by X-ray diffraction and scanning electron microscopy (SEM). During cold-rolling, the crystalline lattice is partly transformed from orthorhombic to monoclinic structure. This transformation is reversible when the material is annealed one hour at 130°C. A great diminution of the size of the spherulites is observed during rolling. Mechanical properties are analyzed with tensile tests. The strain energy per unit volume is highly increased by rolling due to the raise of the number of links between crystalline and amorphous phas...