The technique employed in this study uses differences in proton spin-spin relaxation times of polymer and oil phases to determine the amount of oil in the oil-extended rubber. The fact that the relaxation times of the polymer protons are much smaller than those of the oil proton is the criterion used to differentiate the signals originating from the two phases.
The NMR pulse was optimized using the oil-extended rubber with the highest oil content.
The oil-extended rubber was coagulated using salt acid.
But that was 60 years ago and there hasn't been much joint sharing among the tiremakers since; unless you count the lime they almost all abused General Tire's oil-extended rubber
patents in the early 1960s.