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Branching degree and rheological response correlation in peroxide‐modified linear low‐density polyethylene
Author(s) -
Khonakdar Hossein Ali
Publication year - 2014
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.3314
Subject(s) - linear low density polyethylene , branching (polymer chemistry) , peroxide , molar mass distribution , molar mass , reptation , polymer chemistry , rheology , materials science , polyethylene , polymer , chemistry , organic chemistry , composite material
Correlations between rheological behavior and degree of long chain branching (LCB) of linear low‐density polyethylene (LLDPE) upon a peroxide (dicumyl peroxide [DCP]) modification process under various conditions are discussed in this paper. The gel content analysis revealed negligible insoluble crosslinked fraction implying that incorporation of DCP to LLDPE predominately leads to branching rather than crosslinking. The slight changes in average molecular weight and molecular weight distribution induced by peroxide modification under various conditions revealed that formation of low‐molecular‐weight fractions due to chain scission is also negligible. The changes in terminal, trans, and pendant double bonds concentration of the modified samples with different amounts of peroxide were well depicted by Fourier transform infrared spectroscopy. Considering insignificant changes in molecular weight and molecular weight distribution during peroxide modification, the deviation observed in zero‐shear‐rate viscosity (η 0 ) values of the modified LLDPE with that of power‐law equation related to the linear PEs could be reliably attributed to the presence of LCB in the peroxide modified samples. Increasing the DCP content at roughly constant molar mass led to increasing of η 0 values as a result of increased degree of LCB. The increase in η 0 values was ascribed to prolonged relaxation times of the polymer molecules due to the retarded reptation motion‐driven relaxation mechanism. Copyright © 2014 John Wiley & Sons, Ltd.