Aging behavior of a hot‐cured epoxy system
Aging behavior of a hot‐cured epoxy system
复制标题
热固化环氧体系的老化行为
DOI：
10.1002/app.22819
复制
发表时间：
2006
影响因子：
3
通讯作者：
W. Possart
中科院分区：
文献类型：
--
作者：
Davis Fata;W. Possart
采用DSC和IR衰减全反射光谱法研究了热固化环氧树脂体系（双酚A二缩水甘油醚（DGEBA）+双氰胺（DDA））在玻璃态下的热老化和水热老化。由于DDA从固体颗粒扩散到液体DGEBA基质中，固化产生含有低交联无定形区域的高度交联无定形基质。在完全固化后，网络具有相对低的分子移动性并且没有残留的反应性基团。热和水热加载在60°C下进行，远低于主要玻璃化转变温度（Tg 1 = 171°C）。这两种老化制度导致显着的化学和结构变化的玻璃状环氧树脂。它在低移动的基质内经历相对移动的链段的相分离，提供在108天老化内从Tg 2 = 86-114°C转变的第二玻璃化转变。这种相分离在加热到粘弹性状态时是可逆的。水热老化导致可逆和不可逆的塑化效果以及。在热老化时，未观察到化学变化，但水热老化会导致环氧体系发生显著的化学变化。这些修饰被确定为DDA的氰基产生的交联的部分降解，并对应于不可逆的塑化。固化的环氧树脂中的这些变化应该对粘合剂结合的机械性能产生影响。© 2005威利期刊有限公司应用聚合物科学杂志，2006年
The thermal and hydro-thermal aging of a hot-cured epoxy system (diglycidylether of bisphenol A (DGEBA) + dicyandiamide (DDA)) in the glassy state is revisited using DSC and IR attenuated total reflection spectroscopy. Because of the diffusion of DDA from the solid particles into the liquid DGEBA matrix, curing produces a highly crosslinked amorphous matrix that contains low crosslinked amorphous regions. After full curing, the network possesses a relatively low molecular mobility and no residual reactive groups. Thermal and hydro-thermal loading is performed at 60°C, well below the principal glass transition temperature (Tg1 = 171°C). Both aging regimes cause significant chemical and structural changes to the glassy epoxy. It undergoes a phase separation of relatively mobile segments inside the low mobile matrix, providing a second glass transition that shifts from Tg2 = 86–114°C within 108 days of aging. This phase separation is reversible on heating into the viscoelastic state. Hydro-thermal aging leads to a reversible and a nonreversible plasticizing effect as well. On thermal aging, no chemical changes are observed but hydro-thermal aging causes significant chemical modifications in the epoxy system. These modifications are identified as a partial degradation of crosslinks produced by the cyano groups of the DDA and correspond to the nonreversible plasticitation. These changes in the cured epoxy should exert an influence on the mechanical properties of an adhesive bond. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006