Studies on the Effects of Hydrogenation on Peroxide Crosslinking and Rheological Characteristics of High Density Polyethylenes

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

EUROPEAN POLYMER JOURNAL

Año: 2008

0014-3057

The effects of hydrogenation of the terminal vinyl groups on peroxide modification and rheological properties of high-density polyethylene (HDPE) was investigated. The aim of the study was to determine exclusively, the effects of terminal vinyl groups on peroxide crosslinking and rheological properties of HDPE using one polymer type. This was achieved by hydrogenation of the terminal vinyl groups of a commercial HDPE to obtain an identical material from a structural point of view, differing only in the nature of the terminal unsaturations, and comparing its level of peroxide crosslinking with that of the original polymer. 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 increase 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.