Rheology of Flexible Homopolymers with Long-Chain Branching

Rheology of Flexible Homopolymers with Long-Chain Branching 

Mendelson et al. 1970). The Bueche theory predicts that the viscosity of branched flexible homopolymers is lower than that of linear homopolymers of the same The reduction of melt viscosity in the presence of long-chain branching may be attributed to (1) a reduction in relaxation times and (2) a reduction in chain entanglements or other interactions between polymer molecules in the bulk. It appears that the reduction in relaxation times may be related to g given in Eq. (6.40), and the reduction in chain entanglements or other interactions between polymer molecules may be related to E(g) given in Eq. (6.41). 

Another very important rheological property that is significant for the processing of LDPEs (for example, using the tubular film blowing process) is elongational viscosity 

For almost two decades following the early 1960s there had been relatively limited research activities on the rheology of branched flexible homopolymers. However, in 1988 McLeish (1988) extended the concept of the Doi-Edwards tube model, which had been developed for linear flexible homopolymers (see Chapter 4), to describe the dynamics of branched flexible homopolymers. Since then, during the past several years, other investigators (Blackwell et al. 2000 Bourrigaud et al. 2003, Inkson et al. 1999 McLeish and Larson 1998 McLeish et al. 1999 Shie et al. 2003 Verbeeten et al. 2001) have actively engaged in further development of this theory. Such efforts have 

We present here some experimental studies on the rheological behavior of branched flexible homopolymers. Our presentation follows the same spirit as that presented previously for linear flexible homopolymers fhaf is, we will use log versus log a and log G versus log G plots to discuss the effect of long-chain branching on the rheological behavior of flexible homopolymers. 

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