In addition, a degree of loading with HAF carbon
black filler of 50 phr or more has resulted again
in a noticeable increase in the rate of variation of
M100 value with respect to irradiation dose. These
results may be attributed not only to the radiation
induced cross-linking as well as different interphase
linking but also to the role played by the carbon
black filler as a separate phase. In this respect and
under the limited extension of 100% elongation,
the HAF carbon black filler would be expected to
exist predominantly in its ‘‘structure’’ state, according
to which about 80 + 10 particles are closely bonded in its aggregated solid and separate form
[21]. Effective contribution to the M100 value of vulcanized
composites from this solid phase of filler
would then be expected when taking into consideration
that the tensile modulus parameter is additive
in character. The obtained results are in accord with
comparable results reported before for other rubber
composites [22].