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Long chain branched impact copolymer of polypropylene: Microstructure and rheology
Author(s) -
Chikhalikar Kalyani,
Deshpande Anushree,
Pol Harshawardhan,
Dhoble Deepa,
Jha Saroj,
Jadhav Kishor,
Mahajan Sunil,
Ahmad Zubair,
Kulkarni Surendra,
Gupta Surendra,
Lele Ashish
Publication year - 2015
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.23993
Subject(s) - materials science , rheology , polypropylene , differential scanning calorimetry , extrusion , copolymer , melt flow index , branching (polymer chemistry) , reactive extrusion , polymer , composite material , gel permeation chromatography , polymer chemistry , chemical engineering , thermodynamics , physics , engineering
A biphasic impact copolymer of polypropylene (ICP) was modified with peroxide by reactive extrusion process resulting in reduced melt flow index, improved melt strength, and higher die swell. The polymers were for the first time subjected to systematic rheological and microstructural characterization in an effort to understand their structure‐property relations. In shear rheological tests, the modified ICP displayed higher flow activation energy, reduced values of loss tangent and nearly equal frequency dependence of storage and loss modulli. The modified ICP also showed strain hardening behaviour in uniaxial extensional rheology and higher crystallization temperature in differential scanning calorimetry (DSC). All these are definitive indications of the presence of long chain branches (LCB). Fitting the rheological data of modified ICPs with the eXtended Pom Pom (XPP) model indicated the presence of LCB on the higher molecular weight fraction in the polymer, a result which was corroborated with multi‐detector high temperature gel permeation chromatography (HT‐GPC). More importantly, the matrix and rubber phases of the ICP were separately characterized for presence of long chain branching by rheology, DSC and HT‐GPC. The results indicate that while LCB existed in the matrix phase, microgels were present in both phases indicating that the reaction with peroxide occurred in both phases. POLYM. ENG. SCI., 55:1463–1474, 2015. © 2014 Society of Plastics Engineers