Rheological and thermal properties of purified raw natural rubber

Natural rubber (NR) is a very important raw material in the manufacture of many articles. Moreover, it is still irreplaceable in the manufacturing of heavy-duty vehicle tyres as well as items for both of medical and paramedical uses. The quality of a rubber product depends on properties of the raw rubber. Two raw NR grades were purified by dissolution and filtration. The rheological and thermal properties of the purified rubbers were studied. The results showed that filtered rubbers were more thermally stable than unfiltered rubbers. The effect of filtration on the glass transition temperature and the FTIR spectra was not much, indicating that no important bonds were broken or formed with dissolution and filtration. Both filtered and unfiltered samples were observed to be thermo-rheologically simple within the viscoelastic region. The temperature dependence of the shift factors was observed to fit well to the William, Landel and Ferry (WLF) with parameters (C1, C2) close to those typical for synthetic polyisoprene. Nevertheless, we observed slightly lower values for the filtered samples than the unfiltered samples. This was attributed to the removal of some gels during filtration.