TY - JOUR
T1 - The apparent activation energy and dynamic fragility of ancient ambers
AU - Zhao, Jing
AU - McKenna, Gregory B.
N1 - Funding Information:
The authors thank the National Science Foundation under award DMR-1207070 and the John R. Bradford endowment at Texas Tech University , each for partial support of this work. We also thank Y. P. Koh for his advice and comments, and Professor S.L. Simon for providing us access to her thermal analysis laboratory.
PY - 2014/4/25
Y1 - 2014/4/25
N2 - According to the literature, different types of materials have different glass transition temperature (Tg) dependences of apparent activation energy (Eg) and dynamic fragility (m). In previous work we found that for different ambers, there were different glass transition temperatures. These same samples provide an opportunity to study the Tg dependence of Eg and m for amber, which has not been reported previously in the literature. In this work, nine pieces of amber from different locations and having different ages were investigated by differential scanning calorimetry. Six cooling rates were used to provide the different thermal histories, and the corresponding limiting fictive temperatures were determined using Moynihan's area matching method. From the cooling rate dependence of the limiting fictive temperature both the apparent activation energy and dynamic fragility were calculated. We find that as glass transition temperature increases, both the apparent activation energy and dynamic fragility increase. The Tg dependence of m for amber shows a similar trend with temperature as do the metallic glass formers and compares favorably with the m-Tg dependence of other aromatic polymers.
AB - According to the literature, different types of materials have different glass transition temperature (Tg) dependences of apparent activation energy (Eg) and dynamic fragility (m). In previous work we found that for different ambers, there were different glass transition temperatures. These same samples provide an opportunity to study the Tg dependence of Eg and m for amber, which has not been reported previously in the literature. In this work, nine pieces of amber from different locations and having different ages were investigated by differential scanning calorimetry. Six cooling rates were used to provide the different thermal histories, and the corresponding limiting fictive temperatures were determined using Moynihan's area matching method. From the cooling rate dependence of the limiting fictive temperature both the apparent activation energy and dynamic fragility were calculated. We find that as glass transition temperature increases, both the apparent activation energy and dynamic fragility increase. The Tg dependence of m for amber shows a similar trend with temperature as do the metallic glass formers and compares favorably with the m-Tg dependence of other aromatic polymers.
KW - Amber
KW - Apparent activation energy
KW - Glass transition temperature
KW - dynamic fragility
UR - http://www.scopus.com/inward/record.url?scp=84898865614&partnerID=8YFLogxK
U2 - 10.1016/j.polymer.2014.03.004
DO - 10.1016/j.polymer.2014.03.004
M3 - Article
AN - SCOPUS:84898865614
SN - 0032-3861
VL - 55
SP - 2246
EP - 2253
JO - Polymer
JF - Polymer
IS - 9
ER -