Non-Isocyanate Carbamate Acrylates: Synthesis, Characterization, and Applications in UV 3D Printing

Abstract

In this paper, two synthetic routes for non-isocyanate carbamate acrylates (CAs) were explored. Four amino alcohols reacted with ethylene carbonate respectively forming carbamate alcohols. Additionally, carbamate amines were synthesized through the reaction of diethylene glycol with dimethyl carbonate, followed by the reaction of 4-methylcyclohexane-1,3-diamine. Five kinds of CAs were synthesized via oxa-Michael addition of carbamate alcohols and aza-Michael reactions of carbamate amines with neopentyl glycol diacrylate (NPGDA), respectively. The resulting intermediates and final CAs were characterized by electrospray ionization high-resolution mass spectrometry (ESI-HRMS), ¹H NMR, and FT-IR spectroscopy. The photopolymerization kinetics of the CAs were investigated using FT-IR spectroscopy. Under UV irradiation and initiation by 1 wt% 2-isopropylthioxanthone (ITX) for 30 s, the double bond conversion of the CAs synthesized by oxa-Michael addition were over 95%. The resulting CAs can be UV cured to form a transparent film with a gel content of 90%–95%, a hardness of 4–5 H, and a flexibility of 1 mm. A formulation consisting of 79 wt% CA2, 20 wt% NPGDA, and 1 wt% ITX was applied for 3D printing to produce various models with smooth surfaces, high precision, and excellent flexibility.