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Competition between chain scission and branching formation in the processing of high‐density polyethylene: Effect of processing parameters and of stabilizers
Author(s) -
Scaffaro R.,
La Mantia F.P.,
Botta L.,
Morreale M.,
Tz. Dintcheva N.,
Mariani P.
Publication year - 2009
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.21317
Subject(s) - branching (polymer chemistry) , bond cleavage , rheology , chain scission , materials science , polyethylene , polymer chemistry , stabilizer (aeronautics) , long chain , chemical engineering , polymer , polymer science , composite material , chemistry , organic chemistry , mechanical engineering , catalysis , engineering
Two samples of high‐density polyethylene with different molecular weight were processed in a batch mixer and the rheological and structural properties were investigated. In particular, the effect of different processing parameters and the eventual presence of different stabilizers were evaluated. Actually, two reactions may occur during processing: branching/crosslinking or chain scission. The results indicate that when the processing conditions promote a scarce mobility of the macromolecular chains (lower temperatures, lower mixing speed, and higher molecular weight), branching is more favored than chain scission. On increasing the mobility of the chain (higher temperature, higher mixing speed, and lower initial molecular weight), branching appears still the predominant reaction, but the chain scission becomes progressively more important. In both cases, no crosslinking occurs. The presence of stabilizers has different effects on the relative extent of branching or chain scission reactions depending on the kind and of the amount of stabilizer and on the processing condition adopted. The correct choice of a stabilizer system will, therefore, depend on the desired final structure. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers