The effect of vinyl concentration on the structural and rheological characteristics of peroxide modified high-density polyethylenes

AIREGUAMEN I. AIGBODION; JORGE A. RESSIA; ANDRÉS E. CIOLINO; MARCELO D. FAILLA; ENRIQUE M. VALLÉS

EUROPEAN POLYMER JOURNAL

Año: 2008

0014-3057

The effect of hydrogenation of the terminal vinyl groups on peroxide modification and rheological properties of high-density polyethylene (HDPE) was investigated. This was achieved by hydrogenating part of a commercial HDPE containing terminal vinyl groups to obtain two identical materials from a structural point of view, differing only in the nature of the terminal unsaturations.  Hydrogenated and unhydrogenated polymer samples were modified at 170oC with different amounts of organic peroxide ranging from 125–5,000 ppm. Changes in the molecular structure were determined by FTIR, SEC and rheological measurements. Hydrogenation of the terminal groups of the original polymer significantly reduced the rate of modification or crosslinking. Consumption of terminal vinyl groups of the unhydrogenated polymer increases linearly with the square root of the peroxide concentration. Dynamic viscosity and elasticity grow up with the level of peroxide modification. Unhydrogenated samples exhibit a rapid increase in viscosity and elastic modulus while their hydrogenated counterparts require about 500% of the amount of peroxide needed for the unhydrogenated sample to attain similar structural changes