Isocyanate crosslinkers with blocking agents based on various amine derivatives were newly synthesized for automotive clearcoat applications. Amine-based blocking agents were prepared by varying the alkyl substituent attached on both sides of the main nitrogen atom (named DEA, DiPA, NtBEA, and NtBiA) to modify their deblocking feature in blocked isocyanates (BIs) and curing reaction under thermal curing conditions. Curing properties of clearcoats containing amine-based BIs were characterized at the normal curing temperature of 150°C and were compared with those by the commercialized BI, Desmodur® PL350. The dissociation ability of the amine-based BIs was interpreted using the density functional theory (DFT) simulation under their optimized geometric configurations. The urethane reaction between isocyanate group in BIs and hydroxyl group in a hydroxyl-functionalized polyol binder within clearcoats was confirmed from the OH stretching absorbance data via Fourier-transform infrared (FT-IR) spectrometer. The real-time cross-linking dynamics of various clearcoats with amine-based BIs were comprehensively investigated using rotational rheometer and rigid-body pendulum tester. The surface mechanical properties of fully-cured clearcoat films were measured by nano-indentation and nano-scratch testers to address the crosslinked network formation caused by amine-based BIs. It is demonstrated that the amine-based BIs could be favorably applied to thermal curing process of clearcoats, based on their reactivity and curing performance.

新合成了具有基于各种胺衍生物的封闭剂的异氰酸酯交联剂，用于汽车清漆应用。通过改变连接在主氮原子两侧的烷基取代基（分别命名为DEA，DiPA，NtBEA和NtBiA），以改变其在封端异氰酸酯（BIs）中的解封特性以及在热固化条件下的固化反应，来制备基于胺的封端剂。含有胺基BI的透明涂料的固化性能在150°C的正常固化温度下进行了表征，并与商用BI PL350进行了比较。在优化的几何构型下，使用密度泛函理论（DFT）模拟来解释基于胺的BI的解离能力。通过傅立叶变换红外（FT-IR）光谱仪从OH拉伸吸光度数据确定了BI中异氰酸酯基与透明涂料中羟基官能化多元醇粘合剂中的羟基之间的氨基甲酸酯反应。使用旋转流变仪和刚体摆锤测试仪全面研究了具有胺基BI的各种清漆的实时交联动力学。通过纳米压痕和纳米划痕测试仪测量完全固化的透明涂层膜的表面力学性能，以解决由胺基BI引起的交联网络形成。事实证明，基于胺的BI的反应性和固化性能，可以很好地应用于清漆的热固化过程。