1) The isothermal cure of the reactive natural rubber
compound (Table 1), of the primer (Chemosil 211) and of
the adhesive (Chemosil 425) were studied separately at
four different temperatures (130,140,150 and 160 C) for
each compound. For these experiments, the plates were
mounted on the rheometer which was preheated to the
desired temperature. A disk (B 20 mm) of the material
was then introduced for the measurement. In the case of
the rubber, the discs were cut from calendered sheets
(thickness 1 mm). For the primer and the adhesive, the
discs were cut from sheets obtained by pouring the
liquid suspensions onto siliconed paper and evaporating
the solvents. The resulting thicknesses of the discs were
typically 50 5 mm for the primer layer and 100 5 mm
for the adhesive layer.
2) The vulcanization bonding process was studied by
introducing the two multilayer setups shown in Fig. 2 in
the rheometer at 25 C. In both cases, the disposable
aluminum plates were previously washed with toluene
and were coated with two successive layers of primer
(z10 2 mm) and adhesive (z20 2 mm) using a paint
brush, and leaving enough time after each step for the
complete evaporation of the solvents (about 40 min. at
25 C for the primer and 15 min. at 25 C for the adhesive).
The thicknesses of the coated layers were
controlled using a coating thickness gauge (Surfix,
PHYNIX GmbH & Co.). After this preparation, the plates
were mounted in the rheometer and a disk of rubber cut
from calendered sheets placed between the plates. For
the reactive rubber (Fig. 2a), disks of 1 mm thickness
were used, while different thicknesses were used for the
non-reactive rubber (Fig. 2b). Rheological measurements
were conducted starting at 25 C, and submitting