A novel testing approach

freezing point depression of solvent in the swollen vulcanizate

is acquired to estimate the effect of crosslinking network structure

i.e. mesh size and crosslinks dispersion

on the mechanical properties of natural rubber vulcanizates cured by three different accelerator systems in details.No evident discrepancy is found in the crosslinking densities of vulcanizates cured with TU or STU or CZ only

indicating thiourea only accelerates vulcanization process and the sulfur atom of thiourea does not contribute to the sulfur crosslinking in the matrix.Results from freezing point depression tested by DSC measurements show that for solvent trapped within the crosslinking network of vulcanizates cured by STU its freezing point depression is the lowest and its full width at half maximum(FWHM) is the highest among the testing samples

indicating that the incorporation of STU facilitates the formation of a larger network mesh size and a more heterogeneous network in the vulcanizates.Furthermore

the total crystal index (CI) of all vulcanizates induced by stretching is almost the same

i.e.

the effect of total CI on the mechanical properties of vulcanizates can be ignored.By eliminating the effect of crosslinking density and CI on the mechanical properties of vulcanizates

the tensile strength of vulcanizates cured by STU reaches the maximum values

which could be originated from a larger network mesh size and a more heterogeneous network that favors the relaxation of stress and orientation of rubber molecules and crystallization under stretching.