We found that the addition of 1-octadecanol (OD) and octadecane (C18) to high-density polyethylene (HDPE) can modify the crystalline and amorphous phases of HDPE selectively. According to the dynamic mechanical analysis, OD was co-crystallized with the crystal phase of HDPE. It is interesting that OD promoted α-relaxation of HDPE at the higher temperatures than the melting point of OD. On the other hand, in HDPE blended with C18, it was suggested that C18 exists in the amorphous layer of HDPE and activates the relaxation of the amorphous chains of HDPE. Such selective modification of the supermolecular structure and mechanical property by the addition of olefin-like low-molecular-weight compounds becomes the fundamental knowledge of the roles of lubricants in the molding process of olefinic materials.
