Nascent morphology of polyethylene polymerized on flat model catalysts

The morphol. and the thermal behavior of nascent polyethylene (PE) polymd. on flat models for the Phillips CrOx/SiO2 catalyst were investigated using low-voltage SEM (LVSEM) and differential scanning calorimetry (DSC). Ethylene polymns. were performed at 25 Deg and 70 Deg in gas phase. For the applied polymn. conditions, microscopy observations reveal that the formation of the macromols. at the active catalyst sites, and their subsequent crystn. on the catalyst, result in homogeneous polymer layers having a thickness of the order of micrometers. The surface morphol. of the nascent samples consists of spherical entities having a diam. less than one micrometer. Pillar-like objects form the internal structure of the PE films. Because these entities are only loosely connected, high porosity is obsd. within the entire film. Thermal anal. of the samples shows that melting temp. and crystallinity of the nascent PE samples polymd. at 25 DegC are noticeably higher than after melting and recrystn. Samples polymd. at 70 DegC, however, do not show these features. [on SciFinder (R)]