Melt rheology of polyolefins

Rheology has a key position in polymer research, being an important link in the so-called 'chain of knowledge' reaching from the production of polymers to their end-use properties. A review of the melt rheology of polyolefins, which are the most widely used group of thermoplastic polymers today, is given in this paper both in terms of application and characterisation aspects. The materials are discussed according to their phase structures (single- and multi-phase polymers) and their chain structures (linear and branched). Aspects of the molar mass distribution, the chain structure and topology are discussed both from an experimental and theoretical point for the single-phase systems. For the technically more important types of multi-phase polymers like compounds and blends, the importance of rheological properties in the development of the phase structure is outlined as well as the possibility to use rheometry for structure investigations. In any case, the importance of considering the stress or strain history of a material sample in a rheological investigation is discussed. Finally, an outlook on the present and future developments in the field of polyolefins is given. (C) 2001 Elsevier Science Ltd. All rights reserved.