Kelly Michael Robert, Kroyan Arpenik, Hallsteinsen Ingrid, Schnell Sondre Kvalvåg, Lein Hilde Lea
Department of Materials Science and Engineering, Norwegian University of Science and Technology, NTNU, Sem Sælands vei 12, 7034 Trondheim, Norway.
ACS Omega. 2024 Dec 11;9(51):50414-50426. doi: 10.1021/acsomega.4c07413. eCollection 2024 Dec 24.
In thermosetting epoxies, thermomechanical properties can be enhanced by conscious selection of curing agents. Full cross-linking leads to a maximum in the glass- transition temperature. However, the relation between the glass transition temperature and the epoxy matrix depends on several factors beyond the cross-linking degree, such as the molecular weight of the polymers, network organization, amount of branching, and the presence of hydrogen bonds. In this study, we investigated adding non- stoichiometric ratios of the epoxy resin Epikote 828 and the curing agent Jeffamine D230. The investigations were done through a combination of molecular dynamics simulations and experiments, primarily differential scanning calorimetry and nanoindentation. Reorganization of the network to fewer clusters with a higher degree of linearity overcomes the effect of cross-linking and leads to a reduction of glass-transition temperature with increasing concentrations of curing agent to epoxy. The elastic, shear, and compressive moduli remained constant. Hence, moderating the curing agent con- tent has the potential to improve thermal properties while maintaining mechanical properties for this epoxy system.
在热固性环氧树脂中，通过有意识地选择固化剂可以提高热机械性能。完全交联会使玻璃化转变温度达到最大值。然而，玻璃化转变温度与环氧基体之间的关系取决于交联度之外的几个因素，如聚合物的分子量、网络结构、支化量以及氢键的存在。在本研究中，我们研究了添加非化学计量比的环氧树脂Epikote 828和固化剂Jeffamine D230。研究通过分子动力学模拟和实验相结合的方式进行，主要是差示扫描量热法和纳米压痕法。网络重组为更少但线性度更高的簇，克服了交联的影响，并导致随着固化剂与环氧树脂浓度的增加，玻璃化转变温度降低。弹性模量、剪切模量和压缩模量保持不变。因此，调节固化剂含量有可能改善该环氧体系的热性能，同时保持其机械性能。
