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
✍ Scribed by Ioannis Arvanitoyannis; Ioannis Kolokuris; John M. V. Blanshard; Colin Robinson
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 732 KB
- Volume
- 48
- Category
- Article
- ISSN
- 0021-8995
No coin nor oath required. For personal study only.
✦ Synopsis
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 ( Tg = 38 f 2°C and T,,, = 69 2 3OC) 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 Tfi and T,s) of gutta-percha. Finally, the activation energies AE (33.9-40.2 kj/mol X K ) at glass transition temperature were determined and correlated to the percentage content ( % ) of the commercial gutta-percha samples in native gutta-percha.