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Molecular, rheological, and thermal study of long‐chain branched polypropylene obtained by esterification of anhydride grafted polypropylene
Author(s) -
Guapacha Jorge,
Failla Marcelo D.,
Vallés Enrique M.,
Quinzani Lidia M.
Publication year - 2014
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.40357
Subject(s) - polypropylene , branching (polymer chemistry) , maleic anhydride , glycerol , crystallization , rheology , materials science , activation energy , polymer chemistry , fourier transform infrared spectroscopy , polymer , chemical engineering , chemistry , copolymer , organic chemistry , composite material , engineering
Long‐chain branched polypropylene was prepared using reaction in the molten state in the presence of glycerol and a linear polypropylene functionalized with maleic anhydride (PPg). The concentration of glycerol in the melt was varied in the range from 0.1 to 5 wt % to obtain different levels of branching. FTIR spectroscopy results indicate that the OH groups of glycerol react with the anhydrides on the PPg chains giving place to ester groups. The presence of long‐chain branches in the molecular structure of PPg was confirmed using multiple‐detection size‐exclusion chromatography and rheology. These techniques demonstrate that the level of branching increases with glycerol concentration and that the modification of PPg produces materials with a bimodal distribution of polymer species. Moreover, some of the highly modified materials display gel‐like behavior. The materials also display thermo‐rheological complexity and enhanced activation energy at low frequencies. The crystallization study shows that both the anhydride groups in PPg and the LCBs have opposite nucleating effects. PPg presents the largest activation energy of crystallization and its value decreases with the concentration of glycerol for a given level of crystallization. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131 , 40357.