Study On The Crosslink-Density And Dynamic Properties Of NR Compound And Vulcanizates

Some basic properties such as vulcanization process of the nature rubber (NR), the crosslink-density of the vulcanizates, and the dynamic properties of the NR compounds and vulcanizate were systematic investigated by employing the Nuclear Magnetic Resonance Crosslink-density spectrometer (NMR-CDS) and Rubber Processing Analyzer (RPA). The relationships of these properties with the curing system such as sulfur content, types and content of the accelerator, curing activator and curing temperature were studied, and some valuable rules were discovered.The NMR-CDS results showed that crosslink-density (XLD) of NR vulcanizates with the curing system of sulfur/benzothiazole sulfonamide/zinc oxide (ZnO)/Stearic acid (SA) was proportional to the dosage of sulfur and accelerator; the addition of the ZnO increased the XLD, but the SA showed little effect on XLD. The NMR-CDS results also showed that the XLD decrease when the curing temperature was too high. The relaxation parameter (T2) from the NMR-CDS decreased with the increase of the XLD.The dynamic properties of the specimen measured by RPA results showed that the influence of the different recipe components on the dynamic properties of the NR compound were similar when the mixing conditions kept constant. The dynamic modulus of the NR compound increased with increasing frequency and decreasing temperature, but the loss factor (tgδ) decreased; when the tear strains exceeded 28%, the dynamic modulus decreased sharply.The dependence of dynamic properties of NR vulcanizates on the tear frequency, tear strain and temperature varied with the XLD. For the vulcanizate with higher XLD, the dynamic properties slightly depended on the frequency, but highly depended on the strain; the storage modulus of the vulcanizate increased when the testing temperature increased.