The butyl rubber used in this study was Butyl grade 268 from
Exxon Mobil Chemical. Samples were prepared with three different
types of vulcanization systems (see Table 1) and reference
formulations were based on standards commonly used in tyre and
automotive industry. Isobutylene-based polymers employ a variety
of cure systems depending on requirements of the final cured
product.
Parts per hundred rubber (phr) is a measurement unit used in
the formulation of rubber compounds and refers to the amount of
a particular compound in relation to the total amount of rubber
used per 100 parts of rubber.
Admixtures were prepared in an open roll-mill, each roll of
40 kg capacity. The samples were cured in an electrically heated
HIDRAUL-MAQ, at 5 MPa pressure. Samples cured with sulfur and
donors were vulcanized at 170 1C for 15 min and the sample
cured with phenolic resin was vulcanized at 190 1C for 15 min.
Samples correspond to the same material before and after
radiation doses.