Premium
Scission and crosslinking during oxidation of peroxide cured EPDM
Author(s) -
Landi V. R.,
Easterbrook E. K.
Publication year - 1978
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.760181503
Subject(s) - dicyclopentadiene , materials science , copolymer , peroxide , branching (polymer chemistry) , epdm rubber , polymer chemistry , bond cleavage , monomer , curing (chemistry) , polymer , ethylene , norbornene , radical , polymerization , softening point , composite material , catalysis , organic chemistry , chemistry , natural rubber
The chemorheology of polymers prepared by peroxide curing terpolymers of ethylene propylene and diene monomer (EPDM) was studied at 375°F in air. Measurements were conducted on terpolymers containing dicyclopentadiene (DCPD), ethylidene norbornene (ENB) or 1,4‐hexadiene (HD) and also on copolymers. Effects of the level of dicyclopentadiene were investigated. A linear relationship is found between crosslinks formed during oxidation and chain scissions. At low termonomer level and in copolymers, this relationship is linear only during the early stages of oxidation. Results are consistent with a kinetic model in which crosslinking sites and scissioning sites on the polymer compete for free radicals which propagate the oxidative chain reaction. Termonomer units apparently act primarily as crosslinking sites with the tendency to crosslink being substantially greater in DCPD than ENB and HD. The number of crosslinks per scission derived from stress relaxation correlates well with elongation to failure retained after air aging 3 days at 350°F. Adjustment of termonomer level can lead to a ratio of crosslinking to scission which strikes a balance between softening of copolymer and embrittlement of some terpolymers at elevated temperature.