Molecular, rheological, and thermal study of long-chain branched polypropylene obtained by esterification of anhydride grafted polypropylene

JORGE A. GUAPACHA; M. D. FAILLA; E.M. VALLÉS; L. M. QUINZANI

JOURNAL OF APPLIED POLYMER SCIENCE

JOHN WILEY & SONS INC

Lugar: New York; Año: 2014 p. 1 - 2

0021-8995

Long-chain branched polypropylenes were prepared by reactive modification in the molten state in the presence of glycerol. A polypropylene functionalized with ~0.7 wt% of maleic anhydride (PPg) was used as primary material. The esterification reaction between the maleic anhydride of PPg and the glycerol generates long-chain branched macromolecules. The molecular characterization as well as the rheological characterization of the synthesized polymers showed that the modification of PPg produces materials with a bimodal distribution of polymer species. The modified polymers exhibit enhanced low-frequency complex viscosity, increased dynamic moduli, and reduced phase angle, that may be associated new topological structures with longer relaxation times, which are attributed to molecules with LCB. The materials also display thermorheological complexity and enhanced activation energy at low frequencies. The comparison between the intrinsic viscosity of the branched samples with 0.1 % and 0.3% of crosslinking agent and the original polymer through the equation Mark-Houwink allows evaluating the level of branching. Non isothermal characterization by differential scanning calorimetry (DSC) shows the slight influence of the level of branches on the process crystallization and thermal parameters of modifies Pg?s.