Nascent morphology of polyethylene polymerized on flat model catalysts

• Published in: Polymer international 2004-07, Vol.53 (7), p.824-827
• Main Authors: Loos, J, Lemstra, PJ, van Kimmenade, EME, Niemantsverdriet, JW, Höhne, GWH, Thüne, PC
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; flat model catalysts; LVSEM; nascent morphology; Physicochemistry of polymers; Polymer industry, paints, wood; polymerization; properties; Technology of polymers
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.1564

The morphology and the thermal behavior of nascent polyethylene (PE) polymerized on flat models for the Phillips CrOx/SiO2 catalyst were investigated using low‐voltage scanning electron microscopy (LVSEM) and differential scanning calorimetry (DSC). Ethylene polymerizations were performed at 25 °C and 70 °C in gas phase. For the applied polymerization conditions, microscopy observations reveal that the formation of the macromolecules at the active catalyst sites, and their subsequent crystallization on the catalyst, result in homogeneous polymer layers having a thickness of the order of micrometers. The surface morphology of the nascent samples consists of spherical entities having a diameter 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 observed within the entire film. Thermal analysis of the samples shows that melting temperature and crystallinity of the nascent PE samples polymerized at 25 °C are noticeably higher than after melting and recrystallization. Samples polymerized at 70 °C, however, do not show these features. Copyright © 2004 Society of Chemical Industry