All the curves exhibit a
“U” shape, the upturn of the MooneyeRivlin plot could indicate the
interaction between the rubber and filler, and it could be used to
evaluate the limited extensibility of the polymer chains [28] and
the interfacial adherence between filler and rubber matrix [29].
Usually, the upturn occurs at a lowerl (corresponding to higherl1) in the curves indicates a stronger interfacial adherence be-tween the filler and rubber matrix [30,31].