Rheological behaviour long-chain branching

Accordingly, siloxy-substituted complexes have been found to give polymers with rheological behaviour indicative of long-chain branching [44, 60, 61, 83, 84], but the relations between molar mass, PD and the low shear-rate rheological behaviour are distinctive to each catalyst [83]. 

We study here the case of a branched polyethylene (LDPE FN 1010), characterized by long chain branching, whose rheological behaviour has been previously described in Chapter II-l. Compared to linear LLDPE, it exhibits strain-hardening in elongational situations and higher values of first normal stress difference. 

On the other hand, a power law relaxation in rheology cannot be a sure indication for a gelation threshold. Self-similar relaxations has been associated with selfsimilar structures on the molecular and supermolecular level as well as for suspensions and emulsions (Winter and Mours 1997). Similarities between gelation and long-chain branching viscoelastic behaviour have been also discussed (Garcia-Franco et al. 2001). 

Romanini, D., Savadori, A., and Gianotti, G., Long chain branching in low density polyethylene. 2. Rheological behaviour of the polymers, Pofymer, 21,1092-1101 (1980). 

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