STUDY OF THE EFFECT OF ANNEALING, DRAW RATIO, AND MOISTURE UPON THE CRYSTALLINITY OF NATIVE AND COMMERCIAL GUTTA-PERCHA (TRANSPOLYISOPRENE) WITH DSC, DMTA, AND X-RAYS - DETERMINATION OF THE ACTIVATION-ENERGIES AT TG

The transitions occurring in gutta-percha (transpolyisoprene) below the melting point were determined with DMTA and DSC. A comparison of the results obtained with these two methods showed satisfactory agreement. The thermal properties of native and commercial gutta-percha samples (T(g) = 38 +/- 2-degrees-C and T(m) = 69 +/- 3-degrees-C) were investigated, both before and after annealing (at different times and temperatures), and at environments of different relative humidities. An increase in the draw ratio also proved to enhance the percentage crystallinity (% K) and improve the thermal stability (higher T(g)s and T(m)s) of gutta-percha. Finally, the activation energies DELTAE (33.9-40.2 kj/mo.1 X K) at glass transition temperature were determined and correlated to the percentage content (%) of the commercial gutta-percha samples in native gutta-percha.