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This contribution presents a survey on the influence of long chain branching on the linear viscoelastic properties. The aim of this article is to provide evidence that rheological testing is a potent tool for characterising polymers in the melts. The materials chosen are linear and slightly long- chain branched metallocene- catalysed polyethylene of narrow molecular mass distribution, as well as linear and highly long- chain branched polyethylene of broad molecular mass distribution, and other sample of the big family of polyolefin’s.

The linear viscoelastic flow properties are determined in shear creep and recovery experiments by means of a magnetic bearing torsional creep apparatus. The interest of this study consists in reviewing various experimental, theoretical and simulation results of the some viscoelastic properties. The samples with a slight degree of long- chain branching exhibit a surprisingly high zero shear-rate viscosity in comparison to linear one, whereas the highly branched polymers have a much lower viscosity compared to linear samples. Slightly branched polyethylene have got a higher steady- state compliance in comparison to linear products of similar polydispersity, whereas the highly branched polyethylene of broad molecular mass distribution exhibit a surprisingly low elasticity in comparison to linear broad molecular one. The same remarks are obtained for the other samples. The actual framework leads us to say that the number of branches is less important than the topology itself. Therefore, the position and architecture of the branches along the main polymer chain are the principal factors that control the material rheology.