Changes in the Chemical Structure and the Thermal/Physical Properties of Fluoropolymer Films Induced by Gamma Irradiation under Various Environments

This study was undertaken to explore the effect of heating on gutta-percha, analyzing the occurrence of endothermic peaks corresponding to the transformation that occurs in the crystalline structure of the polymer during thermal manipulation. This study also seeked to determine the temperature at which these peaks occur, causing a transformation from the beta- to the alpha-form, and from the alpha- to the amorphous phase. Eight nonstandardized gutta-percha points commercially available in Brazil (Konne, Tanari, Endopoint, Odous, Dentsply 0.04, Dentsply 0.06, Dentsply TP, Dentsply FM) and pure gutta-percha (control) were analysed using differential scanning calorimetry (DSC) and thermogravimetry analysis (TGA). The transition temperatures were determined and analysed. With the exception of Dentsply 0.04 and Dentsply 0.06, the majority of the products showed thermal behaviour typical of beta-gutta-percha, with two endothermic peaks, exhibiting two crystalline transformations upon heating from ambient temperature to 130°. Upon cooling and reheating, few samples presented two endothermic peaks. It was concluded that heating dental gutta-percha to 130°C causes changes to its chemical structure which permanently alter its physical properties.

Download Full-text

Comments on Thermal Physical Properties Testing Methods of Phase Change Materials

Advances in Mechanical Engineering ◽

10.1155/2013/695762 ◽

2013 ◽

Vol 5 ◽

pp. 695762 ◽

Cited By ~ 5

Author(s):

Jingchao Xie ◽

Yue Li ◽

Weilun Wang ◽

Song Pan ◽

Na Cui ◽

...

Keyword(s):

Physical Properties ◽

Phase Change ◽

Phase Change Materials ◽

Testing Methods ◽

Thermal Physical Properties

Download Full-text

Thermal-physical properties of nanoparticle-seeded nitrate molten salts

Renewable Energy ◽

10.1016/j.renene.2017.12.026 ◽

2018 ◽

Vol 120 ◽

pp. 275-288 ◽

Cited By ~ 35

Author(s):

Afrah Awad ◽

Helena Navarro ◽

Yulong Ding ◽

Dongsheng Wen

Keyword(s):

Physical Properties ◽

Molten Salts ◽

Thermal Physical Properties

Download Full-text

Oxidative Aging of Natural Rubber Vulcanizates. Part III. Crosslink Scission in Monosulfidic Networks

Rubber Chemistry and Technology ◽

10.5254/1.3539269 ◽

1969 ◽

Vol 42 (3) ◽

pp. 924-935 ◽

Cited By ~ 1

Author(s):

T. Colclough ◽

J. I. Cunneen ◽

G. M. C. Hrggins

Keyword(s):

Natural Rubber ◽

Physical Properties ◽

Chemical Structure ◽

Spectroscopic Methods ◽

Chemical Probes ◽

Conjugated Diene ◽

Strain Measurements ◽

Oxidative Aging ◽

Tert Butyl Hydroperoxide ◽

Natural Rubber Vulcanizates

Abstract A natural rubber vulcanizate containing almost entirely monosulfidic crosslinks was oxidized in oxygen and with tert-butyl hydroperoxide. The changes in physical properties due to oxidation were followed by stress—strain measurements, and the changes in chemical structure were investigated with chemical probes, and by spectroscopic methods. The results show that when the oxidized vulcanizates are heated at 75° C, the monosulfidic crosslinks are broken, that crosslinks containing two sulfur atoms are formed, and that conjugated diene and triene structures are introduced into the main polyisoprene chains.

Download Full-text